cond-mat — Pith

0

cond-mat.mes-hall 2026-05-14 2 theorems

MoSe2/PdSe2 stack lifts A-exciton emission sixfold

Highly Efficient Exciton Modulation in MoSe₂/PdSe₂ Heterostructures

Interlayer coupling redirects excitons to raise room-temperature quantum yield from 1% to 6% without strain or doping.

abstract click to expand

Controlling exciton recombination in atomically thin semiconductors is central to their optoelectronic functionality, as the competition between radiative and non-radiative decay channels governs emission efficiency. Existing approaches, such as defect passivation, chemical doping, dielectric engineering, and strain tuning, primarily aim to suppress non-radiative losses. Here, we report a pronounced $\sim$6-fold enhancement of room-temperature A-exciton emission in a type-I MoSe$_2$/PdSe$_2$ van der Waals heterostructure, yielding a photoluminescence quantum yield of 6 %, compared to $\sim$1 % for as-exfoliated monolayer MoSe$_2$. This enhancement is accompanied by strong quenching of the B-exciton, consistent with interlayer electronic coupling that redistributes exciton populations toward the radiative A-exciton channel. Power- and temperature-dependent measurements reveal a suppression of exciton-exciton annihilation and a crossover to quenched emission at low temperature, indicating a redistribution of exciton relaxation pathways. Photoluminescence excitation spectroscopy further reveals a broadband enhancement spanning 450-725 nm, ruling out a resonance-specific mechanism. These results demonstrate that interlayer electronic coupling can be used as an efficient means to redirect exciton populations toward radiative channels, enhancing emission efficiency in two-dimensional semiconductors without chemical modification or strain.

0

cond-mat.quant-gas 2026-05-14 2 theorems

Monotiles yield unique polariton coherence patterns

Observation of an aperiodic polariton monotile

Single-tile aperiodic structures in microcavities produce six-fold Bragg peaks and synchronization unlike periodic or Penrose cases.

abstract click to expand

A plethora of unconventional localization phenomena and fractal features of linear spectrum observed in quasiperiodic structures have been accompanied by a long-standing quest for the geometrical elements and structures that permit tilings of the plane, but only in a non-periodic manner. Until 2024, it was believed that such quasiperiodic structures, or quasicrystals, could only be composed of at least two different tiles. Surprisingly, a newly discovered class of quasicrystals requires only one elementary monotile. However, its physical realization and study of propagating coherent excitations in this novel setting remained elusive. Here we optically sculpt aperiodic quasicrystals composed of "einstein" monotiles in an inorganic microcavity and observe nontrivial relative phases of the exciton-polariton condensates nonresonantly excited at the vertices of each monotile. Utilizing energy-resolved tomography in momentum-space, we reveal the formation of distinct Bragg peaks with six-fold symmetry and Dirac-like spectral fingerprints, intrinsic to the underlying graphene-like structure, while interferometric phase reconstruction shows a nontrivial synchronization pattern distinct from both periodic triangular lattices and Penrose quasicrystals. Our work demonstrates that monotiles can be converted into a programmable driven-dissipative artificial material, where long-range coherence coexists with enforced geometric aperiodicity, producing synchronization and spectral responses distinct from both periodic and conventional quasicrystalline tilings.

0

cond-mat.mes-hall 2026-05-14

Floquet systems quantize conductance to winding number via sideband sum

Quantized Transport in Floquet Topological Insulators

Numerical and analytic results show both longitudinal and Hall conductances reach exact multiples of e²/h only after all replica bands are,

abstract click to expand

We study quantum transport in a periodically driven (Floquet) topological system coupled to static fermionic reservoirs. Using the Floquet nonequilibrium Green's-function (NEGF) formalism we show, from exact numerics for a strip geometry, that the two-terminal (longitudinal) conductance is quantized as $|W_{\varepsilon}|\,e^2/h$, while the Hall (transverse) conductance is quantized as $W_{\varepsilon}\,e^2/h$, where $W_{\varepsilon}$ is the Floquet winding invariant associated with the quasienergy gap at $\varepsilon = 0$ or $\varepsilon = \Omega/2$. Quantization is achieved only after summing over the contribution of all Floquet sidebands. We provide an analytic understanding of this Floquet conductance sum rule, by considering the Hall conductance in the weak coupling limit. In that limit, we show that the Floquet Hall conductance gets contributions from the Floquet sidebands, which includes the signs of the velocities of the edge modes. Their sum yields exact quantization, as predicted by the Floquet sum rule. We find that in a wide range of parameter regime, the convergence is fast, making observation of the sum rule and Floquet winding numbers accessible to experiments.

0

cond-mat.soft 2026-05-13 1 theorem

Asymmetry tuning makes dielectric spheres interact as point charges at contact

Designing Coulombic Contact Interactions between Polarizable Particles through Asymmetry

Derived radius, charge, and permittivity ratios cancel polarization so many-body self-assembly matches pure Coulomb systems

abstract click to expand

Polarizable particle systems, including charged colloids, polarizable ions, biomolecular assemblies, and soft nanomaterials, can exhibit contact electrostatic interactions that depart strongly from Coulomb behavior when dielectric mismatch and geometric singularities amplify polarization effects. Here we use charged dielectric spheres as a model system and show that these polarization contributions can be canceled by jointly tuning size, charge, and dielectric asymmetries. By extending a recently developed image-charge formula to contacting dielectric spheres, we derive analytical conditions under which the contact interaction reduces to the bare Coulomb form. Accurate two-sphere calculations validate the resulting contact design rules with relative errors below $3\%$. Strikingly, many-body molecular dynamics simulations reveal that systems satisfying these two-body rules self-assemble into structures that closely match their pure Coulomb references. These results establish asymmetry as a route for turning electrostatic complexity into Coulombic simplicity at contact, with implications for controlled self-assembly and materials design.

0

cond-mat.mtrl-sci 2026-05-13 Recognition

Machine learning automates phase identification in powder diffraction

Automated multiphase identification and refinement in powder diffraction using mismatch-tolerant machine learning

RADAR-PD generates hypotheses from elemental constraints and refines them recursively for both X-ray and neutron data.

abstract click to expand

Powder diffraction is a primary structural characterization tool in materials science, yet automated phase identification remains a major bottleneck for autonomous discovery. Existing workflows rely heavily on search--match heuristics and manual Rietveld refinement, and broadly usable end-to-end automation is especially limited for neutron powder diffraction, where comparable tools are largely absent. Here we introduce RADAR-PD, a modality-aware machine learning framework for phase identification and quantification across both X-ray and neutron powder diffraction. RADAR-PD couples a mismatch-tolerant neural network operating on coarse momentum-transfer fingerprints with automated lattice nudging and physics-constrained Rietveld verification, enabling dominant-phase hypotheses to be generated from elemental constraints and secondary phases to be isolated recursively. On an experimental RRUFF PXRD benchmark, RADAR-PD outperforms DARA in recovering the reference phase. RADAR-PD further provides robust multiphase analysis on complex time-of-flight and constant-wavelength neutron datasets, addressing an important unmet need in automated neutron diffraction analysis. These results establish RADAR-PD as an auditable, instrument-agnostic framework for autonomous structural discovery.

0

cond-mat.quant-gas 2026-05-13 2 theorems

Strong interactions protect superradiance from dephasing in qubit arrays

Programmable Superradiance in an Interacting Qubit Array

Many-body eigenstates reshape decay pathways in a tunable waveguide system, keeping collective emission alive beyond the Dicke model.

abstract click to expand

When multiple quantum emitters couple to a common electromagnetic environment, interference in their collective radiative dynamics gives rise to superradiance and subradiance. In regimes where coherent interactions and collective dissipation compete, the microscopic many-body dynamics and quantum correlations among the emitters that underlie superradiance and subradiance are theoretically challenging and remain experimentally elusive, even though collective emission has been observed in many physical systems. Here, we realize a superconducting qubit array coupled to a common microwave waveguide that mediates collective dissipation, with simultaneous access to coherent interactions and microscopic measurements of many-body dynamics. Engineered qubit-waveguide couplings with tunable amplitude and phase enable control of collective interference and the resulting super- and subradiant states. Leveraging site-resolved control and readout, we directly observe the microscopic decay dynamics of multi-qubit states across different excitation manifolds and track the evolution of populations and tunable quantum correlations. We reveal collective decay in regimes beyond the ideal Dicke model, where strong qubit-qubit interactions stabilize superradiance and subradiance against local dephasing and reshape decay pathways through spatially and spectrally structured many-body eigenstates. Our results establish a flexible platform for exploring collective phenomena in many-body quantum optics and driven-dissipative approaches to robust quantum information processing.

0

cond-mat.mtrl-sci 2026-05-13 Recognition

Equivariant framework builds n-dependent Hamiltonians for magnets

Equivariant Space Group and Hamiltonian for Collinear Magnetic Systems

Symmetry construction for collinear systems enables topological pumping studies and ab-initio modeling of orientation effects

abstract click to expand

Condensed matter physics increasingly focuses on exploiting the magnetic order parameter orientation n as a tuning knob for properties of collinear magnetic materials, but a general method for constructing effective Hamiltonians with explicit n-dependence has been lacking. Here, we develop a symmetry-based framework, built on the equivariant space group, for constructing such Hamiltonians, termed equivariant magnetic Hamiltonians (EMHs). The resulting EMH lives in a higher-dimensional k-n space and exhibits unconventional symmetry actions and topological features. Using a 1D ferromagnetic chain and a 3D antiferromagnet as examples, we demonstrate that explicit n-dependence in EMHs enables the study of magnetic-dynamics-driven topological pumping, including even-integer charge pumping and a second-Chern-number-induced quantized pumping of surface anomalous Hall conductivity. Beyond model systems, we incorporate the framework into first-principles calculations to construct ab-initio EMHs that accurately capture the n-dependent band structures of real materials. The approach can also be generalized to non-collinear magnetic systems. Our work establishes a general framework for constructing EMHs and for exploring the rich physics arising from magnetic anisotropy and magnetic dynamics.

0

cond-mat.soft 2026-05-13 Recognition

Embryo junction wiggles follow inverse-square law

Fluctuation spectra of embryonic cell-cell interfaces reveal inverse-square scaling

Spatial and temporal spectra match tension-dominated membrane models even in actively reshaping tissue.

abstract click to expand

Tissue-scale shape changes are driven by ensembles of intracellular forces. However measuring force in these contexts remains a difficult challenge. Here we perform spectral analysis of transverse fluctuations of cell-cell junctions in \emph{Xenopus} embryonic tissue explants undergoing convergent extension. We developed an image analysis pipeline to extract fluctuation amplitude profiles $u(x,t)$ from time-lapse confocal movies and computed two-dimensional spatiotemporal power spectra. We observe power-law scaling of mean-squared fluctuation power spectra consistent with $\langle u_q^2 \rangle \sim q^{-2}$ and $\langle u_f^2 \rangle \sim f^{-2}$. The spatial scaling agrees with predictions from the Helfrich Hamiltonian, and the temporal scaling agrees with overdamped dynamics of a fluctuating membrane, both in the tension-dominated regime. Pharmacological reduction of actomyosin contractility (via low-dose blebbistatin or latrunculin B) did not significantly alter either scaling exponent. Our results provide an early empirical characterization of junction fluctuation spectra in an actively shape-changing tissue. Simple tension-dominated membrane models appear sufficient to describe transverse junction dynamics despite their active and coupled nature. This work establishes a quantitative baseline for future studies of tension-bearing tissues and motivates the development of physical models specific to multicellular systems.

0

cond-mat.soft 2026-05-13 2 theorems

Onsager principle derives drop dynamics on uneven surfaces

Variational approach to droplet motion on uneven solid surfaces, including contact line dynamics and evaporation

Equations for contact-line motion and evaporation follow from free-energy variation in the overdamped limit

abstract click to expand

We show how dynamical equations for liquid films and drops on uneven surfaces, including contact line dynamics and evaporation/condensation effects, may be formulated as a variational dynamics, generated via Onsager's variational principle. The theory applies in the isothermal overdamped-dynamics limit. We apply this general approach to obtain several well-known results on contact line dynamics and to study drops pinning and sliding on inclined corrugated surfaces. This approach constructs the dynamical equations starting from the free energy of the system and therefore has the advantage that it naturally incorporates the correct equilibrium properties.

0

cond-mat.supr-con 2026-05-13 Recognition

Damping peaks below Tc from Andreev states in c-axis YBCO/LSMO

Anomalous spin-pumping behavior of half-metallic ferromagnet/d-wave superconductor heterostructures

Interface states dominate spin pumping when proximity to the half-metal locally suppresses the d-wave order parameter.

abstract click to expand

Spin-pumping experiments in superconductor/ferromagnet heterostructures, which probe spin-sinking by the superconductor, have revealed a variety of complex behaviors. Most studies have focused on conventional s-wave superconductors combined with metallic or insulating ferromagnets. Here, we study a d-wave superconductor paired with a half-metallic ferromagnet, in epitaxial YBa2Cu3O7-d/La0.7Sr0.3MnO3 heterostructures with two crystalline orientations: one in which YBCO is c-axis oriented, and the other in which YBCO grows along the (103) direction. Using ferromagnetic resonance (FMR), we probe the temperature-dependent Gilbert damping coefficient {\alpha}. For (103) heterostructures, {\alpha}(T) initially decreases below Tc, but then increases at lower temperatures, exceeding normal-state levels. This behavior can be understood in terms of the opening of the superconducting gap and spin transport via nodal quasiparticles, which dominate when the ab-plane of YBCO is exposed at the interface. In stark contrast, c-axis heterostructures exhibit a pronounced enhancement of {\alpha}(T) below Tc, peaking at 0.65-0.7Tc before decaying. This anomaly suggests the dominance of interface-bound Andreev states, arising from a locally suppressed superconducting order parameter due to proximity effects with the half-metallic LSMO.

0

cond-mat.mes-hall 2026-05-13 Recognition

Screw dislocation splits optical shifts in GaAs quantum wire

Optical Response of a screw dislocated GaAs Quantum Wire: Temperature and Pressure Effects

The dislocation parameter redshifts one transition while blueshifting the other; temperature and pressure further tune positions and heights

abstract click to expand

We investigate the influence of a screw dislocation, characterized by the dislocation parameter, on the optical response of a parabolic GaAs cylindrical quantum wire under the combined effects of temperature, hydrostatic pressure, and the axial magnetic field. Using a torsion-modified metric together with pressure- and temperature-dependent material properties, namely the effective mass and dielectric permittivity, we obtain exact solutions of the Schr\"odinger equation in terms of Whittaker functions. The screw dislocation introduces a $k_z$-dependent coupling that breaks the symmetry between the angular momentum states $m$ and $-m$ and modifies the centrifugal term in the effective potential. Based on the resulting eigenstates, we evaluate the linear and third-order nonlinear optical absorption coefficients, as well as the corresponding refractive index changes, for the dipole-allowed transitions $m = 0 \to +1$ and $m = 0 \to -1$. Our results show that increasing the dislocation parameter produces a pronounced redshift and suppresses the resonance amplitude for the $m = 0 \to +1$ transition, whereas the $m = 0 \to -1$ transition exhibits a blueshift accompanied by peak enhancement. We further find that increasing temperature shifts the resonances toward higher photon energies and enhances their amplitudes, while hydrostatic pressure causes a redshift and reduces the peak intensity for both transitions. In addition, the magnetic field strengthens the optical response and induces a blueshift for the $m = 0 \to +1$ transition, whereas the opposite behavior is obtained for the $m = 0 \to -1$ transition. We have also examined the behavior of the refractive index changes, which exhibit analogous asymmetric dependence on the dislocation parameter.

0

cond-mat.stat-mech 2026-05-13 Recognition

Analytic formulas quantify link fluctuations in extensible chains

Link length and energy fluctuations in extensible freely jointed chains

Asymptotically exact expressions give means, spreads, and distributions of lengths and energies under force.

abstract click to expand

The freely jointed chain is often applied to model the thermodynamics of single polymer chains, but the traditional formulation of the model lacks internal energy changes due to bond stretching. For this reason, the extensible freely jointed chain model includes a potential energy function, typically harmonic, that governs the length of each link in the chain. Among the other quantities of interest that are subject to thermal fluctuations, these link lengths and energies too fluctuate about their ensemble average values. Since a plethora of models for polymer chains and networks incorporate chain dissociation as a function of either link length or energy, these fluctuations are crucial to understand and quantify. Motivated by this fact, fluctuations in link length and energy are analyzed within a freely jointed chain under an applied force. These fluctuations are quantified through their average values, standard deviations, and probability distributions. Across all values, asymptotically correct analytic relations and their less ergonomic exact counterparts are introduced. The asymptotic relations are verified to be accurate through direct comparison and to be correct within transcendentally small terms through error analysis. In certain cases, the fluctuations are shown to be approximately normally distributed. Hereafter, model components predicated on link length or energy ought to account for these fluctuations.

0

cond-mat.mtrl-sci 2026-05-13 2 theorems

Fixed electronic shape plus recoil kernel fits graphene spectra to 8 keV

Graphene lattice recoil in hard X-ray photoemission: Experiment and Theory

Convolution of low-energy intrinsic response with photon-energy-dependent phonon kernel reproduces line shapes and centroid shifts without a

abstract click to expand

Hard-x-ray C 1s photoemission from monolayer graphene probes a regime in which nuclear recoil and intrinsic electronic asymmetry contribute on comparable energy scales to the observed spectral line shape. Here we combine experiment and modeling over the photon-energy range 0.8 keV--8 keV to resolve this interplay quantitatively. A graphene-specific implementation of the Fujikawa--Takata cumulant formalism, based on an anisotropic vibrational density of states constrained by first-principles phonon calculations, captures the expected recoil scaling with photon energy and emission geometry but fails to reproduce the pronounced asymmetric tails of the measured spectra. To overcome this limitation, we introduce an explicit electronic convolution model in which an intrinsic, photon-energy-independent electronic line shape extracted from near-recoilless 0.8 keV data is convolved with a phonon recoil kernel carrying the full dependence on photon energy and emission angle. This approach reproduces both the measured line-shape evolution and the observed centroid shifts across the explored energy range without refitting the spectra at higher photon energies. The results show that recoil in graphene cannot be described by a baseline treatment in which the phonon recoil kernel is combined only with symmetric lifetime broadening, but must be treated together with the intrinsic many-body electronic response of the C 1s line.

0

cond-mat.quant-gas 2026-05-13 Recognition

Interference peaks survive and strengthen in 1D Mott insulator

The wave nature of a Mott insulator

One-dimensional lattice gases show growing coherence as the system becomes more insulating, so interference no longer marks superfluidity.

abstract click to expand

Quantum phases of matter are routinely identified by coherence features, with interference patterns being one of the most directly observable quantities. In lattices, the superfluid-to-Mott-insulator (SF-MI) transition is commonly viewed as a change from wave-like coherence to particle-like localization: interference peaks are taken as a hallmark of superfluidity, whereas their disappearance is used to diagnose insulating behavior. Here, we challenge this picture for one-dimensional (1D) strongly interacting gases subject to a lattice potential. We realize a gapped Mott insulator through pinning in a shallow lattice and find that pronounced interference peaks persist deep in the insulating regime. Strikingly, the interference becomes stronger as the Mott fraction increases, demonstrating that a certain degree of coherence still exists in the insulator state. Measurements of the one-body correlation function reveal an oscillatory, exponentially decaying coherence pattern across several lattice sites, in quantitative agreement with quantum Monte Carlo (QMC) simulations. Our work shows that interference does not uniquely diagnose superfluidity and it exposes the unexpected wave nature of a 1D Mott insulator.

0

cond-mat.mes-hall 2026-05-13 1 theorem

Magnon polaritons form in 30-nm Cr2Ge2Te6 flakes

Magnon polaritons in a van der Waals ferromagnet coupled to a superconducting resonator

Coupling to a superconducting resonator produces avoided crossings whose strength scales with the square root of thickness.

abstract click to expand

Achieving magnon-photon hybridization in the microwave regime is essential for integrating magnetic excitations with superconducting circuits. While this has been extensively demonstrated in bulk magnetic systems, realizing it in two-dimensional van der Waals materials remains challenging due to their reduced magnetic volume and increased dissipation. Here, magnon-photon hybridization is observed in exfoliated flakes of the van der Waals ferromagnet Cr$_2$Ge$_2$Te$_6$, with thicknesses down to 30 nm. The resulting magnon polaritons-hybrid excitations of cavity photons and magnons-are evidenced by reproducible avoided crossings across six devices, enabled by a low-impedance superconducting resonator design. The coupling strength follows the expected square-root dependence on thickness, and extrapolation of this scaling indicates that hybridization in the monolayer limit is within reach.

0

cond-mat.supr-con 2026-05-13 2 theorems

Phase slips destroy long-range order in FeSe

Phase-slip residual-order spin state in FeSe

A narrow manifold of defects in a stripe background reproduces both observed spin-fluctuation types.

abstract click to expand

Clarifying the magnetic ground state is essential for analysing unconventional superconductivity, because microscopic magnetic order provides one of the basic starting assumptions for spin-fluctuation pairing theories. FeSe exhibits pronounced stripe- and Neel-type spin fluctuations yet lacks static long-range order, posing a long-standing puzzle. By combining PBE and r2SCAN mixed exchange-correlation calculations with spectrally weighted simulations of the static spin structure factor S(q), we show that FeSe is not governed by a single magnetic configuration but by a nearly degenerate manifold of phase-slip defects embedded in a stripe background. We term this state a residual-order spin state (ROSS): a spin state that retains local stripe-like antiferromagnetic correlations but loses long-range phase coherence because of phase slips. Multiple slip configurations are compressed into an exceptionally narrow energy window. Non-local magneto-elastic coupling redistributes domain-wall formation energy through the lattice, whereas competing magnetic interactions truncate the real-space coherence length to an optimal scale of about ten moments. Weighted superpositions of these slip states reproduce the momentum-space line shapes of both stripe- and Neel-type spin fluctuations observed by inelastic neutron scattering, providing a microscopic basis for superconductivity models built on spin fluctuations.

0

cond-mat.mtrl-sci 2026-05-13 2 theorems

Ordering sets magnetism in FePt Janus particles

Ordering governs magnetic tunability in FePt-based Janus particles independent of curvature

Coercivity holds steady across 3-10 micrometer sizes while ordering changes alter reversal, giving a clear size boundary for geometry-driven

abstract click to expand

Magnetic Janus particles enable remote actuation in biomedical, microfluidic, and materials applications. While curvature-driven magnetic effects are well known at the nanoscale, their influence on magnetization reversal in micrometer-sized particles is still unclear. In this work, we combine experiments and micromagnetic simulations to study curvature-dependent magnetism in FePt-coated Janus particles with diameters ranging from 3-10 microm, and extend the analysis to 1-20 microm through simulations. Structural and crystallographic characterization confirms continuous FePt coatings with near-equiatomic composition and partial L1_0 ordering. Magnetometry measurements show nearly unchanged hysteresis behavior across particle sizes, with coercivity remaining approximately constant m_0Hc = 1.13 +/- 0.05 T, pooled n = 8). Statistical analysis reveals no significant dependence of coercivity or remanence on particle diameter (p = 0.61 for Hc and p = 0.85 for Mr/Ms). To explain these results, we introduce FunMaP, an open-source micromagnetic simulation framework that enables direct comparison between experiments and idealized FePt caps. Simulations confirm that curvature has little effect on magnetization reversal at micrometer scales, consistent with a locally planar magnetic limit where the exchange length is much smaller than the particle radius. In contrast, differences in chemical ordering strongly affect hysteresis shape and coercivity. These findings demonstrate that magnetic behavior in micrometer-scale FePt Janus particles is governed mainly by material ordering rather than curvature. This work establishes a quantitative boundary for curvature-dependent magnetism and provides design guidelines for programmable magnetic micro-systems.

0

cond-mat.mes-hall 2026-05-13 Recognition

Bilayer graphene dots show 0.5-0.9 neV/√Hz charge noise

Probing charge noise in bilayer graphene quantum dots by Landau-Zener-St\"uckelberg-Majorana spectroscopy

LZSM spectroscopy finds thermal or phonon sources dominate over two-level fluctuators and match silicon and III-V levels.

abstract click to expand

Charge noise is an important factor limiting qubit coherence and relaxation in solid-state devices. In bilayer graphene (BLG) quantum dots, recently established as a promising platform for spin- and valley-based qubits, both the origin and magnitude of charge noise remain largely unexplored. Here, we investigate high-frequency charge noise using Landau-Zener-St\"uckelberg-Majorana (LZSM) interference spectroscopy. We study a single-particle charge qubit formed in a BLG double quantum dot at frequencies between 5 and 10 GHz and extract a noise spectral density $S_\varepsilon$ on the order of 0.5-0.9 neV$/\sqrt{\mathrm{Hz}}$. This is comparable to values reported for III-V semiconductor platforms and silicon. From the temperature and frequency dependence of the charge qubit decoherence, we conclude that thermal (Johnson) noise or electron-phonon coupling dominates over two-level fluctuators.

0

cond-mat.mtrl-sci 2026-05-13 Recognition

S-doping shifts few-layer graphene from linear to flat bands

Engineering few-layer graphene by S-doping: from sustaining linear dispersion to flat bands

Specific sulfur placements in one to four layers open gaps or flatten bands near the Fermi level, allowing tuning between metallic and flat,

abstract click to expand

Motivated by the technological relevance of S-doped few-layer graphene (FLG) in battery applications and in the oxygen reduction reaction, we systematically explore the effect of basal plane S-doping on the electronic properties of mono-, bi-, and four-layer graphene, using first-principles calculations with van der Waals corrections. In the monolayer we find a variety of effects ranging from a sustained Dirac cone with localized impurity bands away from the Fermi level in thiophenic doping (2V1S) to a band gap opening of 0.4 eV and flat bands close to the Fermi-level in graphitic doping (1V1S) and an additional $n$-type doping together with spin-polarization, when three S-atoms are adsorbed in a four-site vacancy (4V3S). Incorporation in FLG leads to modification of the Dirac cone into a set of hyperbolic touching bands in 2V1S; reduction (bilayer) and closing of the band gap with additional hyperbolic touching bands in conjunction with the flat band at the Fermi level in 1V1S and 4V3S and a reduction of spin polarization in the latter. Overall, S-doping enables design of the band structure and tuning the electronic behavior of FLG from metallic to insulating and from linear dispersive to flat bands that makes S-doped FLG a promising material for versatile technological applications.

0

cond-mat.mtrl-sci 2026-05-13 1 theorem

Machine learning turns XPCS data into grain boundary kinetics

Probing Non-Equilibrium Grain Boundary Dynamics with XPCS and Domain-Adaptive Machine Learning

Domain-adaptive models trained on simulations extract diffusivity, stiffness and concentration from experimental fluctuation maps.

abstract click to expand

Grain-boundary (GB) dynamics control the stability, mechanical, and functional response of nanocrystalline materials, but direct experimental access to their slow non-equilibrium motion has been limited. Here we establish X-ray photon correlation spectroscopy (XPCS), combined with domain-adaptive machine learning, as a quantitative probe of GB dynamics. Temperature- and grain-size-dependent two-time XPCS measurements in nanocrystalline silicon reveal pronounced departures from time-translation invariance, showing that GB relaxation can remain far from equilibrium over experimental timescales. However, direct extraction of quantitative physical information from these high-dimensional, noisy fluctuation maps faces a significant challenge. To overcome this barrier, we develop a semi-supervised learning framework that transfers physical parameter labels from continuum simulations to unlabeled experimental XPCS maps through domain-adaptive representation alignment. This AI-augmented approach enables the extraction of key kinetic parameters, including bulk diffusivity, GB stiffness, and effective GB concentration, directly from experimental XPCS measurements. Our results show how machine learning can transform indirect fluctuation signals into quantitative materials dynamics, providing a general route to study non-equilibrium defect motion in solids.

0

cond-mat.soft 2026-05-13 1 theorem

Two-grain bridges supply 85% of capillary pressure in wet grains

Morphology-resolved stress contributions in sheared wet granular materials

Morphology tracking during shear shows complex clusters add little to cohesion, allowing parameter-free friction prediction

abstract click to expand

Three-dimensional X-ray microtomography, coupled to rheometric measurements, enables a morphology-resolved reconstruction of capillary stresses at the grain scale in unsaturated wet granular materials. Liquid domains are automatically classified into capillary bridges, dimers, trimers, and larger clusters, and their spatial organization is tracked as a function of shear deformation and liquid content. We show that shear localization governs the redistribution of the liquid phase: capillary bridges remain uniformly distributed throughout the sample, while higher-order morphologies accumulate preferentially near the lower boundary of the shear-zone through a shear-driven coalescence mechanism. Despite this spatial localization, simple two-grain bridges generate the dominant contribution to the isotropic capillary pressure, accounting for nearly 85\% of the total at liquid-to-solid volume ratio $\epsilon = 0.05$, whereas more complex liquid clusters contribute only weakly to the overall cohesion. Incorporating the morphology-resolved capillary pressure into an effective-stress framework qualitatively reproduces the macroscopic friction coefficient across the full range of investigated liquid contents, without adjustable parameters. These results establish a predictive micro--macro link between liquid morphology and the rheology of wet granular materials.

0

cond-mat.mes-hall 2026-05-13 2 theorems

Bistable flows in electron fluid yield S-shaped I-V curves

Flow bistability in non-Newtonian electron fluid

Two coexisting steady states in narrow channels of non-Newtonian 2D conductors produce voltage-dependent current switching and hysteresis.

abstract click to expand

Modern two dimensional conductors with low defect densities and strong electron-electron scattering are favorable platforms for formation of a viscous fluid of conduction electrons. Electric properties of these systems are determined by the hydrodynamic regime of charge transport distinguished by many experimental signatures: a decrease in sample resistance with increasing temperature (the Ghurzhi effect), strong negative magnetoresistance and others. Here we consider the flow of 2D electron fluid in the nonlinear regime characterized by non-Newtonian viscosity which depends on spatial gradients of hydrodynamic velocity. We derive a simplified version of the dynamic equations for the non-Newtonian electron fluid and consider the specific underlying mechanism associated with local electron heating. Recent works have demonstrated that this may be one of the main mechanisms for nonlinearity in 2D electron fluids. We show that in a certain range of parameters, the two steady-state flow configurations coexist for the narrow channel geometry, and this bistability leads to an S-shaped current-voltage characteristic. By solving the derived time-dependent dynamic equations, we trace the transient response to a step variation of the longitudinal voltage and demonstrate how the current switching and hysteresis occur in samples with the non-Newtonian electron fluid.

1 0

0

cond-mat.stat-mech 2026-05-13 2 theorems

Diameter dynamics create ultrastable glasses

Identifying the relevant parameters in design strategies for stable glasses

New methods that reach extreme hyperuniformity and local order without size changes produce no stability gain, implicating preparation time-

abstract click to expand

A glass is conventionally obtained by cooling a bulk supercooled liquid through its glass transition temperature. The discovery of ultrastable glasses prepared using physical vapor deposition, together with the recent multiplication of numerical algorithms created to increase the stability of glasses, demonstrates the existence of a variety of strategies for designing glasses with different physical properties. This raises a broader question: which parameters most strongly govern the enhancement of glass stability? Existing computational strategies often produce highly stable glasses by optimizing certain physical properties through dynamical changes in particle diameters. We challenge the idea that these physical quantities are causally responsible for glass stability and suggest instead that diameter dynamics is the principal source of enhanced stability. To support our view, we introduce computational methods to optimize physical quantities without changing the particle diameters. Using the examples of enhanced hyperuniformity at large scale and local ordering at small scale, we design glass configurations with highly optimized values compared to bulk equilibrium states. However, these glasses do not show enhanced stability. The proposed physical quantities are correlated with glass stability, but are not causally responsible for ultrastability. These findings indicate that design rules for stable glasses should be reinterpreted in terms of the dynamical processes that generate stability, rather than the optimized physical quantities they target.

0

cond-mat.soft 2026-05-13 Recognition

Flux limit at surface corrects diffusivity error in elastomers

Following the thread: surface and bulk solvent migration in silicone elastomers from local volumetric swelling

Local 3D volume tracking shows solvent entry is rate-limited at the interface, fixing an order-of-magnitude underestimate from bulk models.

abstract click to expand

Poroelastic materials, consisting of a permeable solid matrix infiltrated with fluid, are ubiquitous in natural and engineering contexts. In poroelastic polymer solids, the elastic matrix swells to equilibrium when immersed in a solvent bath; thus, the network elasticity couples to the solvent transport. Despite the ubiquity and importance of poroelastic theory in describing phenomena as diverse as earthquakes and biological tissues, there is a paucity of experimental data that probe the local network response to controlled stress and solvent boundary conditions. Here, we first probe the baseline diffusion kinetics of a polymeric solvent during free swelling of a polydimethylsiloxane (PDMS) network with well-characterized silicone oils. In situ 3D spatiotemporal measurements identify a flux-limited interfacial boundary condition, contradicting the canonical fully drained assumption. This correction eliminates an order-of-magnitude underestimation of diffusivity in standard bulk analysis. The swelling equilibrium is accurately captured by a Flory-Rehner theory that requires modification to include the effective finite extensibility of the filled network. Solvent migration is then studied using a bending configuration for three material preparations: as-prepared, mobile-phase-free, and fully swollen in silicone oils. The as-prepared and mobile-phase-free beams show no discernible volumetric change or force relaxation, whereas local in situ measurements directly resolve tensile-side dilation and compressive-side contraction, yielding the effective diffusivities in agreement with the force-relaxation data. These measurements rigorously benchmark solvent diffusivity in polymer networks, underscoring the importance of unambiguous interfacial boundary conditions and shedding light on mechanics and engineering across poroelastic polymers and geomaterials.

0

cond-mat.soft 2026-05-13 2 theorems

Cell divisions suppress avalanches in tissue rearrangements

Cell divisions suppress dynamical correlations in solid tissues

They fluidize tissues below yield stress yet limit long-range correlated events through a finite energy budget, unlike passive solids.

abstract click to expand

Developing tissues often maintain mechanical coherence while continuously remodeling through cellular processes such as cell divisions and rearrangements. In this way, they are an example of amorphous solids. In passive amorphous solids, local rearrangements can trigger one another through long-ranged elastic interactions, leading to system-spanning avalanches near yielding. Whether similar collective dynamics should be expected in living tissues is unclear, because cell divisions generate stress and remodeling events independently of local mechanical stability. Here, we address this question using a two-dimensional elastoplastic model in which cell divisions are treated as active plastic events. We find that while cell divisions fluidize the tissue below the passive yield stress, but preserve the marginal stability in the quasistatic limit. However, they also strongly suppress the system-spanning avalanches of cell rearrangements, in constrast with the expected behavior in passive amorphous solids. Finally, we show that the avalanche supression originates from the energy balance in the system. Namely, the energy injected by cell divisions allows for shear flow below the yield stress, but also provides a finite budget for rearrangements. These results suggest that proliferating tissues display the structural hallmarks of marginal amorphous solids while exhibiting much shorter-ranged correlations in dynamics, compared to passive amorphous solids.

0

cond-mat.mtrl-sci 2026-05-13 Recognition

Thermal history tunes cold crystallization energy in 10OS5

Competing crystallization pathways and cold crystallization kinetics in 10OS5 liquid crystal

Different cooling rates create glass or metastable crystals that release varying heat on reheating for potential storage use.

abstract click to expand

The liquid crystalline 4-pentylphenyl-4'-decyloxythiobenzoate is investigated in various temperature programs for determination of crystallization kinetics and glassforming properties. The Avrami model, Augis-Bennett method and isoconversional method are used. Cooling at the 25-30 K/min rate results in formation of the glass of the tilted smectic Y phase with the herring-bone order within layers. Slower cooling leads to the partial or total (2 K/min) crystallization of the metastable Cr2 phase, which during subsequent heating or annealing in a proper temperature transforms to another Cr1 phase. Heating from the vitrified smectic Y leads to cold crystallization of the pure Cr1 phase or the Cr1/Cr2 mix. Both Cr1 and Cr2 are conformationally disordered crystal phases, which is indicated both by the melting entropy values and the dielectric spectra. The results demonstrate that the energy released during cold crystallization can be tuned by thermal history, highlighting 10OS5 as a candidate for thermal energy storage applications.

0

cond-mat.mtrl-sci 2026-05-13 2 theorems

AFM dissipation detects sub-band mobilities in SrTiO3 2DEG

Mechanical detection of sub-band mobilities of two-dimensional electron gas on reduced SrTiO₃(001) surface

Peaks tied to quantum capacitance follow Kohler's rule under magnetic fields to yield per-sub-band mobilities

abstract click to expand

The two-dimensional electron gas (2DEG) in reduced strontium titanate offers a versatile platform for oxide electronics, yet its dissipation mechanisms under field driven charge fluctuations remain poorly understood. Here, we combine low-temperature atomic force microscopy with scanning tunnelling spectroscopy to probe the force and dissipation responses of a mechanical oscillator interacting with the STO 2DEG. The observation of Rydberg like image potential states by tunnelling experiments confirm the 2DEG formation, while dissipation spectroscopy reveals bias-dependent peaks linked to local electrostatic gating and charge redistribution within the 2DEG energy sub-bands. These features are quantitatively explained by variations in quantum capacitance as carrier density is tuned by electric fields. Under magnetic fields, dissipation peaks obey the Kohler's rule, allowing extraction of carrier mobilities in each sub-band. Our results establish a non-invasive AFM - based methodology for quantifying energy losses in quantum oxides, providing new insights into charge dynamics relevant for spintronic applications.

0

cond-mat.mtrl-sci 2026-05-13 1 theorem

Alternating layers raise impact energy dissipation by over 50%

Enhanced Impact Mitigation via 3D-Multilayered Material Architectures

Mass-matched monolithic and octet lattice stacks outperform uniform architectures by localizing failure and controlling wave propagation in

abstract click to expand

Materials designed by nature commonly exhibit functional grading and laminated structures, particularly when intended for enhanced impact protection. Synthetic materials have also found success in exploiting this concept with fully dense but spatially varying architectures, as is the case with advanced fiber-based composites. In the lightweight materials space, porous architected materials have shown benefits for extreme impact mitigation, proving to be advantageous in dissipating large amounts of energy per unit mass, but rarely harness the benefits of layering or functional grading in designs. Here, a design paradigm for lightweight multilayered materials towards high impact-mitigation efficacy is demonstrated, showing that the use of alternating monolithic and beam-based architectures leads to enhanced and predictable responses under extreme conditions. These layered, mass-equivalent `heterostructures' with different ordering and proportions of octet and monolithic layers outperform single-architecture lattices on a mass-normalized energy dissipation basis by >50% when subjected to supersonic microparticle impact. Through analysis that combines wave-propagation analysis, nonlinear finite element simulations, and post-impact crater reconstruction, layer-by-layer mechanical properties are mapped to crater formation and energy dissipation behaviors. This heterostructure design framework offers a simple approach towards tuning failure and impact resistance of materials for protective applications from Whipple shields to sports equipment.

0

cond-mat.mtrl-sci 2026-05-13 Recognition

Two quantum materials deliver 4-volt magnesium cathodes

Discovery of High-Voltage Magnesium-Ion Cathodes using Machine Learning and First-Principles Calculations

Screening 917 topological candidates with a neural network and DFT yields stable materials at 3.66 V and 4.06 V average voltage.

abstract click to expand

Developing high-performance cathode materials for magnesium-ion batteries (MIBs) remains challenging because Mg$^{2+}$ ions move slowly, and conventional materials exhibit low voltage outputs. In this study, machine learning and first-principles calculations were combined to investigate topological quantum materials (TQMs) as a new class of cathode candidates. A modified crystal graph convolutional neural network (mCGCNN) was used to screen 917 Mg-containing TQMs, identifying a small subset of materials with predicted voltages above 3 V and high volumetric capacities. Among these, Mg$_2$VO$_4$ and Mg$_6$MnO$_8$ were selected for detailed density functional theory (DFT) analysis. Formation energy and convex-hull calculations indicate that Mg$_x$VO$_4$ exhibits a fully stable magnesiation pathway, whereas Mg$_x$MnO$_8$ demonstrates minor metastability at intermediate compositions. The calculated voltage profiles yield average voltages of 3.66 V for Mg$_2$VO$_4$ and 4.06 V for Mg$_6$MnO$_8$, in good agreement with machine learning predictions. Electronic structure analysis, supported by Wannier interpolation, confirms that both materials are semiconducting, with valence bands dominated by O $2p$ states and conduction bands by transition-metal $d$ states, indicating a charge-transfer redox mechanism. Compared to conventional Mg cathodes, these TQMs exhibit higher voltages and competitive capacities, underscoring their potential for next-generation multivalent batteries. This study demonstrates that integrating machine learning with first-principles calculations offers an efficient approach for discovering and understanding novel cathode materials.

0

cond-mat.str-el 2026-05-13 2 theorems

CDW hotspots block cyclotron orbits to create linear magnetoresistance

H-linear magnetoresistance in NbSe₂ due to impeded cyclotron motion

Scattering sinks from charge-density-wave order in NbSe2 match transport data and suppress quantum oscillations

abstract click to expand

Linear magnetoresistance (LMR) is a widespread phenomenon observed in a host of quantum materials ranging from semiconductor nanostructures to quantum critical and strange metals. While multiple scenarios to explain LMR have been proposed, a complete understanding of the phenomenon remains elusive. Indeed, it is highly likely that the origin of LMR depends on the specific electronic state. Here, we report a study of the impact of disorder on the form of the magnetoresistance of the prototypical charge-density-wave (CDW) compound 2$H$-NbSe$_2$. The magnetoresistance is shown to exhibit strong qualitative and quantitative agreement with Boltzmann transport analysis incorporating impeded cyclotron motion (ICM). We identify the source of ICM in 2$H$-NbSe$_2$ as strong scattering sinks where the CDW order connects the high temperature Fermi cylinders. Such unusual "hotspots" provide an explanation for the observed LMR as well as for the long-unexplained absence of quantum oscillations inside the charge ordered state in 2$H$-NbSe$_2$. These findings provide strong evidence that ICM generates LMR in certain correlated metals.

0

cond-mat.str-el 2026-05-13 2 theorems

Stretched lattice material acts as dipolar paramagnet without ordering

Magnetism and spin dynamics of Na₅Yb(MoO₄)₄: A weakly interacting rare-earth stretched diamond lattice

Large Yb ion separations suppress exchange, leaving dipolar forces and single-ion effects to control dynamics down to 50 mK.

abstract click to expand

We report a comprehensive investigation of the structural and magnetic properties of Na$_5$Yb(MoO$_4$)$_4$, a member of the stretched diamond magnetic lattice family. Neutron powder diffraction at 3.3~K confirms that the compound crystallizes in the tetragonal \textit{I4$_1$/a} space group, with a large interatomic separation of 6.33~\AA{} between magnetic Yb ions forming a three-dimensional stretched diamond framework. Magnetic susceptibility and specific heat measurements reveal no evidence of long-range magnetic order down to 60~mK. The low-temperature magnetic behavior is governed by an effective $J_{\mathrm{eff}} = 1/2$ Kramers doublet ground state, well separated from excited crystal-field levels, arising from the distorted dodecahedral oxygen coordination of Yb$^{3+}$. Density functional theory calculations within the DFT+$U$ framework indicate that exchange interactions between Yb ions are negligibly small, consistent with the long O--Mo--O super-superexchange pathways. The temperature dependence of the specific heat exhibits signatures of gapped spin excitations, most likely originating from long-range dipolar correlations and further shaped by weak exchange interactions together with the strong single-ion anisotropy of the Yb moments. Muon spin relaxation measurements reveal persistent low-energy spin dynamics, indicating that dipolar correlations remain dynamic and are insufficient to stabilize static magnetic order down to 50~mK. These results identify Na$_5$Yb(MoO$_4$)$_4$ as a rare example of a dipolar quantum paramagnet in which single-ion physics and long-range dipolar interactions dominate, while exchange interactions are suppressed to the millikelvin energy scale.

0

cond-mat.stat-mech 2026-05-13 2 theorems

Fermion thermodynamics reduces to classical particles with built-in attractions

Statistical Potential for Identical Fermions: Emergent Attraction and Pauli Crystal Formation

A collective statistical potential turns attractive for N greater than two and places its minima exactly at Pauli-crystal sites.

abstract click to expand

We show that the thermodynamics of $N$ identical fermions maps onto that of distinguishable particles governed by a collective statistical potential -- the microscopic origin of degeneracy pressure. Known to be purely repulsive for ${N=2}$, this potential develops attractive contributions for ${N\geq 3}$. Its minima coincide with Pauli crystal configurations, providing the energetic origin of these structures. For large $N$, the dominant force is attractive on inner shells and repulsive on outer ones -- not of two-body origin. The global minimum undergoes discrete melting transitions at specific temperatures.

0

cond-mat.str-el 2026-05-13 2 theorems

Kitaev interactions stabilize vortex lattice in GeCo2O4

Emergent Vortex Ordering in a Multiflavor Pyrochlore-Lattice Compound GeCo₂O₄

Neutron scattering and regression analysis show how these couplings plus frustration produce the emergent order in the multiflavor compound.

abstract click to expand

Entangled spin and orbital degrees of freedom provide a multiflavor route to novel magnetic states inaccessible in conventional spin systems. Here, we report the experimental identification of an emergent vortex lattice in the multiflavor pyrochlore-lattice compound GeCo$_2$O$_4$. By combining comprehensive neutron scattering experiments with a regularized regression framework, we identify substantial Kitaev interactions among the nearest-neighboring Co$^{2+}$ pseudospins, which cooperate with geometric frustration to stabilize the vortex order. These results reveal an unexpected route to vortex-lattice order in a three-dimensional Kitaev-frustrated magnet and demonstrate a regularized protocol for Hamiltonian determination in frustrated quantum materials.

0

cond-mat.mtrl-sci 2026-05-13 Recognition

Vacancies stabilize N-N complexes that trap carriers deep in Ga2O3 gap

Vacancy-Enhanced N-N Bonding and Deep Level Complex Defect Formation in β-Ga₂O₃

DFT results show these stable defects introduce localized states from N and O p-orbitals, limiting transport and favoring semi-insulating Ga

abstract click to expand

The formation and electronic properties of nitrogen-related defect complexes in $\beta-Ga_2O_3$ are investigated using first-principles calculations. Starting from the energetically favorable $N_{i9}-N_{OI}$ configuration, nitrogen atoms exhibit a strong tendency toward co-localization, leading to reduced $N-N$ separation. However, analysis of bond lengths and electron localization function shows that these configurations do not fully attain molecular $N_{2}$ character. The role of intrinsic defects is further examined by introducing oxygen and gallium vacancies. Vacancy-assisted configurations enhance local lattice relaxation and further decrease the $N-N$ distance. Formation energy calculations indicate that several vacancy-assisted complexes are thermodynamically favorable, while binding energy analysis confirms their stability against dissociation. Despite this, the density of states analysis reveals that all configurations introduce localized electronic states within the band gap. These states originate primarily from hybridized $N$-$2p$ and $O$-$2p$ orbitals and remain energetically separated from the band edges. Spin density analysis further confirms strong localization. Overall, these defect complexes act as deep trapping centers, limiting carrier transport in $\beta-Ga_2O_3$ and thereby promoting semi-insulating behavior and current blocking characteristics.

0

cond-mat.mtrl-sci 2026-05-13 2 theorems

Simulations map rod geometry and grain tilt to higher Alnico coercivity

Tailoring the material properties, nanostructure and grain alignment of Alnico magnets through micromagnetic simulations

Finite-element runs on exchange-decoupled rods plus a trained regressor reveal concrete trends for improving rare-earth-free magnets.

abstract click to expand

Alnico magnets have gained renewed interest in the search for rare-earth free permanent magnets due to their high thermal stability and magnetisation. However, the limited coercivity of these shape-anisotropy-based alloys constrains their performance. Starting from a reference Alnico sample, we realised a finite elements micromagnetic study of exchange-decoupled rods by varying their dimensions and interrod spacing across those observed experimentally. We computed the hysteresis properties by progressing from micromagnetic simulations of a small number of rods within the magnetostatic field of their neighbours to large systems treated statistically based on the distribution of orientations of the grains. We compared the coercivity of an isolated rod with that of the exchange-decoupled system to highlight the effect of magnetostatic interactions. We computed analytically the stray field acting on a single rod as a consequence of its surrounding rods in order to confirm the scaling of the coercivity with the packing fraction p. We explored how intrinsic material properties influence magnetic behaviour by examining materials with different magnetocrystalline anisotropy constants and saturation polarisation values. Results from several hundred simulations were used to train a multi-layer perceptron regressor and predict the magnetic properties as function of the dimensions of the rods, interrod spacing and orientation of the grains. With this approach, we highlight the underlying trends by which nanoscale structuring, intrinsic material properties and grain alignment can be tailored to improve the magnetic properties of Alnico alloys.

0

cond-mat.str-el 2026-05-13 2 theorems

y1=0.1 splits Curie from Curie-Weiss in 2D AF quantum criticality

Staggered spin susceptibility at a two-dimensional antiferromagnetic quantum critical point

Zero-point fluctuations produce simple 1/T susceptibility only for weak mode-mode coupling at the critical point.

abstract click to expand

We report on the finite temperature staggered spin susceptibility $\chi(Q)$ as a function of the mode-mode coupling constant $y_1$ in the self-consistent renormalization theory of two-dimensional antiferromagnetic spin fluctuations with zero-point quantum fluctuations just at the quantum critical point ($y_0$ = 0). We find that the value $y_1$ = 0.1 is a criterion to classify the effect of the zero-point spin fluctuations on the temperature dependence of $\chi(Q)$ into a Curie law for weak $y_1 < $ 0.1 and a Curie-Weiss type or a power law type for strong $y_1 > $ 0.1.

0

cond-mat.supr-con 2026-05-13 2 theorems

LaFeAsO shows mismatched nematic Weiss temperatures

Nematicity in LaFeAsO single crystals studied by elastoresistance, high-resolution thermal expansion and shear-modulus measurements

Elastoresistivity and shear modulus yield different divergence points, unlike in BaFe2As2 and contrary to Landau theory.

abstract click to expand

Nematicity in LaFeAsO single crystals is studied by means of high-resolution thermal expansion, shear modulus, and elastoresistivity measurements. A softening of the shear modulus $C_{\rm 66}$ towards the structural phase transition at $T_{\rm S}$ is observed. In addition, a similar Curie-Weiss-like divergence of the nematic susceptibilities is found in the temperature dependence of both $\chi^{sh}$ and $\chi^{er}$, which are deduced from the shear modulus (sh) and the elastoresistivity (er) studies, respectively. These observations provide evidence for an electronic origin of nematicity in LaFeAsO. The characteristic energy of the coupling between the lattice and the electronic degrees of freedom is deduced to $\sim$30~K. The comparison to corresponding measurements on BaFe$_2$As$_2$ single crystals reveals a very similar temperature dependence of the shear modulus but yields contrasting results for $\chi^{er}$ : In BaFe$_2$As$_2$, $\chi^{er}$ diverges similarly as the uncoupled nematicity deduced from the shear modulus data as it is expected from the underlying Landau theory. In contrast, the Weiss temperatures of $\chi^{er}$ and $\chi^{sh}$ are significantly different in LaFeAsO. This difference is at odds with the commonly anticipated theories of resistivity anisotropy and electronic nematicity in iron pnictides.

0

cond-mat.mes-hall 2026-05-13 1 theorem

Edge states appear in hexagonal chains below critical hopping ratio

Topological edge states of the hexagonal linear chain

The topological phase of the one-dimensional model produces exponentially localized boundary states only when one hopping amplitude is the

abstract click to expand

We study the eigenspectrum properties of a one-dimensional molecular chain composed of hexagonal unit cells. The system features two alternating hopping parameters, resulting in a rich energy spectrum with both dispersive and flat bands. By analyzing the model under periodic and open boundary conditions, we identify two insulating phases separated by a gap-closing transition controlled by the ratio of hopping amplitudes. In the topological phase, realized when the hopping ratio falls below a critical value, edge states emerge that are exponentially localized at the boundaries of finite chains.

0

cond-mat.other 2026-05-13 Recognition

Trap engineering pushes organic photodetector EQE above 1100%

Enhanced Photomultiplication Effect by Synergistic Integration of Hole-Blocking Layers and Trap Engineering in PM-OPDs

Isolated 0.5 wt% hole traps and blocking layers deliver high gain, 4x10^12 Jones detectivity, and 22 kHz speed at low dark current.

abstract click to expand

Photomultiplication-type organic photodetectors (PM-OPDs) promise exceptional sensitivity for weak-light detection but typically suffer from a gain-bandwidth trade-off where high external quantum efficiency (EQE) incurs large dark current and slow response times. Here, we demonstrate a fully vacuum-deposited PM-OPD architecture that mitigates these limitations by integrating hole-blocking layers low-stoichiometry molecular trap engineering. We isolate discrete trapping sites that maximize positive space-charge accumulation by introducing m-MTDATA as a dedicated hole-trapping site at a low concentration (0.5 wt\%) into a BDP-OMe:C60 bulk heterojunction. This engineered charge confinement triggers efficient field-assisted electron injection from the anode while remaining strictly below the threshold for localized percolation, effectively decoupling the photocurrent multiplication mechanism from trap-mediated dark current shunts. Consequently, the optimized device achieves a peak EQE exceeding 1100% at a reverse bias of -4 V. The optimized device exhibits a specific detectivity of 4x10^{12} Jones under -2 V reverse bias along with a cutoff frequency (f-3dB) of 22 kHz.

0

cond-mat.quant-gas 2026-05-13 2 theorems

Symmetry fixes universal C=3 speed limit in Bose gas

Universal Speed Limit in a Far-from-Equilibrium Bose Gas: Symmetry and Dynamical Decoherence

The amplitude of coherence spreading is predicted parameter-free once an emergent symmetry enforces conserved current and decoherence cuts a

abstract click to expand

Predicting universal transport coefficients in far-from-equilibrium quantum systems remains a fundamental challenge. A paradigmatic example is the non-thermal fixed point (NTFP) of isolated Bose gases, where coherence spreads as $\ell^2(t) = C\hbar t/m$ with a universal constant $C$. While the scaling exponent $z=2$ is well established, the amplitude $C$ has remained elusive because the underlying particle cascade $n(k)\sim k^{-4}$ leads to a divergent kinetic energy, threatening the very existence of a constant speed limit. Here we resolve this paradox and present the first analytical, parameter-free prediction of a universal amplitude $C$. A deep interplay between symmetry and dissipation is uncovered. The emergent weak U(1) symmetry at the NTFP enforces a conserved total current, forcing the low-energy phase dynamics to obey a diffusive Langevin equation with noise entering as the divergence of a stochastic current. This structure, combined with dynamical decoherence of high-momentum modes, yields a universal power-law momentum distribution $\tilde{f}(v)\sim(1+v^2)^{-3}$ (with $v=k\ell$) that naturally regularizes the ultraviolet divergence. From this, a parameter-free geometric baseline $C=3$ is obtained, independent of microscopic details. The experimental value $C=3.4(3)$ [Martirosyan et al., Nature 647, 608 (2025)] is then shown to be quantitatively consistent with universal logarithmic corrections arising from a marginally irrelevant coupling at the fixed point. A new paradigm is thus established for predicting transport coefficients in strongly correlated non-equilibrium systems: symmetry constraints determine the low-energy effective theory, dynamical decoherence provides a natural ultraviolet completion, and scaling analysis delivers testable predictions moving beyond scaling exponents to quantitative amplitude prediction.

0

cond-mat.stat-mech 2026-05-13 2 theorems

Non-reciprocity fades at criticality for n>=4 conserved systems

Critical Dynamics of Non-Reciprocally Coupled Conserved Systems

One-loop RG identifies a fixed point where large-scale dynamics obey detailed balance despite microscopic non-reciprocal couplings.

abstract click to expand

Non-reciprocal systems have been shown to sustain time-dependent patterns, most prominently travelling waves. The transition into these time-dependent states generally breaks time-translational invariance, representing a clear deviation from equilibrium dynamics. Though common implementations of non-reciprocity lead to such phenomenology, these spatio-temporal patterns are absent in other models. In the same vein, the ensuing scaling behaviour also depends on the precise way non-reciprocity is implemented. To better understand the effects of different non-reciprocal interactions, we study the critical conserved dynamics of non-reciprocally coupled spin systems. Specifically, we consider the dynamics of two $n$-component order parameter fields $\boldsymbol{\phi}_i$ with $i \in\{1,2\}$. Unlike the common implementations of non-reciprocal interactions, we introduce the non-reciprocity solely through the non-linear interaction between the distinct species. Using the field-theoretic renormalisation group (RG) procedure, we perform a one-loop analysis and show that at one-loop level, the critical behaviour depends on the microscopic value of certain quantities. Using the flow functions, we elucidate the behaviour of the fixed points for different bare microscopic values. We also show that for $n \geq 4$, there is a fixed point where the ensuing critical dynamics asymptotically obey detailed-balance, implying the emergent dynamics are agnostic to the microscopic non-reciprocity on large scales. Finally, we show that the conserved dynamics reduces the number of independent scaling exponents, mimicking the effect of a standard fluctuation-dissipation relation.

0

cond-mat.quant-gas 2026-05-13 Recognition

Spinor BEC solitons show sine-Gordon collision shifts

Observation of sine-Gordon-like solitons in a spinor Bose-Einstein condensate

Tunable velocities produce elastic interactions whose phase offset matches simulations, creating a controllable platform for integrable wave

abstract click to expand

We experimentally generate sine-Gordon-like solitons in a spin-1 spinor Bose-Einstein condensate (BEC) utilizing a robust and reproducible local phase-imprinting scheme. We find that the soliton velocity can be tuned by the effective quadratic Zeeman shift. This enables the investigation of controlled soliton interactions, in which we observe the characteristic elastic collision behavior of the integrable sine-Gordon model. The spatial displacement -- the so-called phase shift -- between incoming and outgoing solitons, the signature of their pairwise interaction, is found to be in quantitative agreement with numerical spin-1 simulations within the error bars. These results establish spinor BECs as a highly controllable experimental platform for studying aspects of the dynamics of sine-Gordon-like models.

0

cond-mat.mtrl-sci 2026-05-13 2 theorems

Fe3Sn2 susceptibility isotherms collapse at isosbestic points

Universality of magnetic susceptibility in the conical state of kagome ferromagnet Fe₃Sn₂

DMS data reveal quadratic temperature corrections and stripe-to-bubble domain evolution in the conical state near 0.6 T

abstract click to expand

We report universal behavior of the differential magnetic susceptibility (DMS) in the conical phase that mediates the spin-reorientation (SR) transition of the kagome ferromagnet Fe$_3$Sn$_2$. Within the SR temperature range, the DMS isotherms exhibit extremely narrow crossing regions, forming isosbestic points. Using an isosbestic-invariance analysis, we show that the isotherms collapse onto a single temperature-independent curve, revealing quadratic-in-temperature corrections to the susceptibility. Complementary field-dependent magnetic-force-microscopy measurements uncover evolution of spin textures from stripe-like domains at low fields to isolated bubble-like domains near the isosbestic field ($\sim 0.6$~T), a behavior not previously reported in bulk Fe$_3$Sn$_2$ within the conical state. These findings point to a universal mechanism for the emergence of complex magnetic textures near isosbestic points, driven by the competition between magnetocrystalline anisotropy, dipolar interactions, and external magnetic field.

0

cond-mat.str-el 2026-05-13 1 theorem

In-gap states mirror spin excitations in doped Kitaev models

Relationship between doping-induced in-gap states and spin excitations in Kitaev-Hubbard models

Dispersions of charge in-gap states in chains and ladders match spin gaps, Jordan-Wigner modes, and Z2 vison gaps.

abstract click to expand

We investigate the connection between doping-induced in-gap states and underlying spin excitations in Mott insulators by employing cluster perturbation theory on one-dimensional (1D) and quasi-1D Kitaev-Hubbard models. By manipulating Kitaev-like hopping terms ($t^{\prime}$) that selectively control spin anisotropies in the strong-coupling limit, we establish a direct correspondence between the kinetic dispersion of the in-gap states and the spin excitation spectra. Specifically, in the Z chain, in-gap states evolve from a gapless dispersion to a gapped flat band as the system transitions from the Heisenberg to the Ising model, exhibiting a gap scaling of $2t^{\prime 2}/U$ that matches the Ising spin gap. In the XY chain, the in-gap states split into a dispersive and a flat branch at the Kitaev limit, perfectly mirroring the Jordan-Wigner fermionic spectrum. For the two-leg ladder, we observe an emergent broad continuum of in-gap states that reflects the fractionalization of spin excitations, accompanied by a gap manifesting the presence of topological $Z_2$ visons. Our results establish a robust correspondence between charge and spin dynamics in doped Mott insulators and demonstrate that in-gap states can serve as a probe of exotic quantum spin phenomena, including fractionalization and topological excitations, offering a new pathway to investigate spin liquids via spectroscopic probes of charge excitations.

0

cond-mat.str-el 2026-05-13 2 theorems

Moiré fractional insulators host optically active exciton-roton mode

Exciton-roton mode in moir\'e fractional Chern insulators

Hybridization with interband transitions gives the mode a roton minimum and light response, enabling optical detection of zero-field FCI集体ex

abstract click to expand

Moir\'e fractional Chern insulators (FCIs) are a novel class of quantum matter that realizes fractional quantum Hall (FQH) physics in zero magnetic field and provides a platform for exploring unconventional collective excitations. Here we show that hybridization between the magneto-roton and moir\'e interband excitations gives rise to an exciton-roton mode absent in continuum FQH systems in the long-wavelength limit. Using exact diagonalization and a variational Bethe-Salpeter equation for twisted MoTe$_2$, we demonstrate that this hybridization is controlled by the quantum geometry and yields a mode that combines excitonic optical response with the characteristic FCI roton minimum. The resulting exciton-roton remains low-lying, with excitation energy below the interband transition, and acquires optical activity, leading to a double-peak spectroscopic signature. These results identify optical spectroscopy as a direct probe of collective excitations in moir\'e FCIs.

0

cond-mat.str-el 2026-05-13 2 theorems

Multi-layer verification certifies exact diagonalization results

CERTIFY-ED: A Multi-Layer Verification Framework for Exact Diagonalization of Quantum Many-Body Systems

CERTIFY-ED runs three LAPACK paths and thirteen validations across sixteen models, emitting tamper-evident certificates with 10^{-15} level

abstract click to expand

Exact diagonalization (ED) is a workhorse technique in computational quantum many-body physics, but published ED results are rarely accompanied by machine-checkable evidence of their numerical correctness. The community typically relies on the implicit trust chain LAPACK $\to$ user code $\to$ result, with at most informal agreement against another package treated as confirmation. We argue that this practice is inadequate for a method whose output frequently underpins theoretical claims, and we present \textsc{certify-ed}, a verification framework designed to be used \emph{alongside} existing ED packages (QuSpin, XDiag, ALPS) rather than as a replacement for them. The framework consists of (i) a multi-oracle eigensolver that runs three independent LAPACK paths and reports their pairwise disagreement, (ii) thirteen logically independent validation layers covering algebraic invariants, analytic limits, alternative algorithms, arbitrary-precision reference computation, conservation laws, dynamical consistency, and finite-size scaling, and (iii) tamper-evident SHA-256 hashed certificates that downstream consumers can verify. The framework also ships an error-injection layer that confirms the entire pipeline detects six injected error classes. Running on sixteen physics models from one-dimensional spin chains to two-dimensional Kitaev honeycomb clusters, our reference implementation passes 53 of 53 unit tests and 81 of 81 individual validation tests in under thirty seconds, with maximum disagreement against QuSpin of $1.6\times 10^{-14}$ across 320 eigenvalue comparisons, and agreement with 50-digit \texttt{mpmath} reference values to $1.6\times 10^{-15}$. The package is released under the MIT license on Zenodo and Github

0

cond-mat.mes-hall 2026-05-13 2 theorems

Laser sidebands suppress WSe2 barrier tunneling

Laser-assisted tunneling in a static tungsten diselenide WSe₂ barrier

Floquet interference and energy shifts overcome Klein tunneling and enable dynamic transport control.

abstract click to expand

We study the tunneling effect of Dirac fermions in a monolayer WSe$_2$ subjected to a static electrostatic barrier and irradiated by a linearly polarized laser field. Within the Floquet formalism, the time-periodic driving is incorporated to derive analytical wave functions across the three regions of the system. By enforcing continuity conditions at the interfaces, we obtain the transmission and reflection coefficients, which are then used to evaluate the conductance via the B\"uttiker approach. Our results reveal that the laser field induces a rich Floquet sideband structure, whose number and strength increase with the driving parameter $\alpha$. This leads to a significant suppression of transmission and provides an efficient mechanism to overcome Klein tunneling. Moreover, increasing the width of the irradiated region enhances the interaction between fermions and the external field, resulting in energy renormalization and the formation of Stark-like confined states. The interaction between several Floquet channels creates strong interference effects, which reduce the transmitted current even further. The results demonstrate that light-matter interaction allows for the dynamic control of quantum transport in WSe$_2$ materials. This technology allows for the development of new optoelectronic devices, including tunable quantum filters and light-controlled nanoscale transistors.

1 0

0

cond-mat.mtrl-sci 2026-05-13 Recognition

Ti-based glass sets new specific strength record at 13% strain

Synergistic improvement of specific strength and plasticity achieved in Ti-based metallic glass designed based on quasicrystal structure

Al microalloying inherits quasicrystal short-range order to break the strength-plasticity trade-off

abstract click to expand

Achieving a balance between low density, high strength, and good ductility remains a major challenge in the development of structural materials. Ti-based bulk metallic glasses (BMGs) have attracted considerable attention due to their exceptionally high specific strength. However, the intrinsic strength-plasticity trade-off has hindered their practical applications. Based on a quasicrystal-derived structural heredity and minor-element microalloying, this work realizes a synergistic enhancement of specific strength and plasticity in Ti-based BMGs. The resulting ((Ti_{40}Zr_{40}Ni_{20})_{72}Be_{28})_{97}Al_{3} BMGs demonstrate an ultrahigh specific strength of 5.34 \times 10^5 \text{ N}\cdot\text{m}\cdot\text{kg}^{-1}, establishing a new record for Ti-based BMGs, along with a plastic strain of 13\%, breaking through the traditional strength-plasticity limitation of BMGs. Structural analyses show that Al microalloying effectively inherits and modulates the short-range order derived from quasicrystalline structures, thereby achieving an observed synergistic enhancement in both strength and plasticity. This work provides new insights into composition design and lightweight structural applications of Ti-based BMGs.

0

cond-mat.mtrl-sci 2026-05-13 2 theorems

Descriptors from theory identify new inorganic electrides

Theory and Discovery of Electrides

The framework explains why electrons localize in interstices and applies to high-pressure and organic cases as well.

abstract click to expand

Electrides are materials with electrons localized at interstitial regions of the crystal lattice and have been identified as promising candidates for a variety of applications, including catalysis, electron emission, and superconductivity. We present a theoretical framework for the origin of interstitial electrons in electrides. We demonstrate that this theory can explain electride-like behavior in prototypical electrides, and we use it to develop descriptors for the high-throughput discovery of new inorganic electride candidates from first principles. We also show that the same concepts can explain electride-like behavior in other classes of material, including high-pressure electrides and organic electrides and, more broadly, provide an alternative understanding of F-center defects and solvated electrons.

0

cond-mat.soft 2026-05-13 1 theorem

Hydrogel permeability collapses to master curve with PEGDA surface

Nanostructure of PEGDA-PEG hydrogel membranes and how it controls their permeability

Scaling as volume over surface reveals thin water films between facetted polymer domains control flow.

abstract click to expand

The spacial heterogeneity of hydrogels composed of PEGDA and added polymer chains is expected to play a crucial role on their transport properties which can be exploited in filtration or tissue engineering. However little is known about the arrangement of the polymer chains in the matrix and the length scales of these heterogeneities. Here we combine solid-state NMR and Small Angle Neutron Scattering to unravel the structure and dynamics of PEGDA hydrogels containing added PEG chains of various concentrations. Our results show that the samples present heterogeneities in both the PEGDA and PEG concentrations and suggest that the PEG chains entangle with the PEGDA network. When plotting the sample permeability, K, as a function the specific surface of the PEGDA heterogeneities we obtain a master curve, showing that the heterogeneity of the PEGDA matrix controls the permeability of the sample. Moreover the scaling K ___ V/S suggests a structure composed of facetted PEGDA/PEG heterogeneities separated by a network of aqueous thin and flattened films in which the water can permeate.

0

cond-mat.soft 2026-05-13 2 theorems

Second hole alters wrinkle nucleation and spread in tensed sheets

Tensional wrinkling of thin elastic sheets with two circular holes

Bipolar stress analysis and floating-film experiments show hole separation sets threshold, sites, orientation and extent under tension.

abstract click to expand

A paradigm for the study of wrinkling in elastic sheet is the Lam\'{e} configuration, in which azimuthal wrinkles form in an annular sheet subjected to tensile loads at both edges. Since wrinkles are spatially extended, this instability provides a mechanism for stress transmission over long distances. A natural extension of this problem is wrinkling in sheets with multiple holes or broken symmetry. Here, we investigate tension-induced wrinkling in thin elastic sheets containing two circular holes by combining analytical modeling and experiments. The pre-buckled state is solved analytically using bipolar coordinates, enabling identification of the wrinkling threshold as a function of the distance between the two holes. Near-threshold wrinkling and interactions between wrinkles are analyzed, and we validate our theoretical predictions against experimental observations obtained through video imaging of spin-coated polystyrene sheets floating on liquid surfaces with controlled surface tension. Our results demonstrate that geometric symmetry breaking, such as the presence of a second hole, strongly influences wrinkle nucleation, orientation, and spatial extent. Beyond mechanics, these findings might provide a simple mechanism for cellular mechanosensing, where force transmission is amplified by mechanical instabilities.

0

cond-mat.quant-gas 2026-05-13 2 theorems

Vortex in dipolar droplet generates spontaneous magnetization

Barnett effect in rotating spinor dipolar quantum droplets

The cloud then rotates rigidly under magnetic field as mechanical Larmor precession; opposite-chirality pairs bind stably.

abstract click to expand

We propose releasing the spin degree of freedom to stabilize the vortex state in self-bound droplets of dipolar Bose-Einstein condensates. When a vortex is embedded into the droplet, spontaneous magnetization arises in the axial direction via a mechanism similar to the Barnett effect; that is, the orbital angular momentum is transferred to the spin angular momentum. When an external magnetic field is applied to the spontaneously magnetized droplet, the entire atomic cloud starts to rotate without changing its shape, which can be regarded as mechanical Larmor precession of a macroscopic object. A chirally different pair of droplets can form a stable bound state because of the attractive interaction between the spontaneously magnetized droplets.

0

cond-mat.str-el 2026-05-13 2 theorems

Altermagnons switch from selective damping to deformed coherence at MIT

Altermagnons at the metal-insulator transition

Chirality-dependent lifetimes vanish while branches stay coherent but strongly reshaped in the insulating phase.

abstract click to expand

By means of slave-boson theory for the Hubbard model on the checkerboard lattice, we calculate dynamical altermagnetic spin susceptibilities from the metallic to the Mott-insulating regime. We track magnon dispersion and lifetime renormalization, allowing us to uncover a crossover from a chirality-selective dissipation of magnon modes to coherent yet strongly deformed chiral magnon branches across the metal insulator transition. Our formalism lends itself to a quantitative description of collective spin dynamics in correlated altermagnets.

0

cond-mat.soft 2026-05-13 2 theorems

Acoustic force quantifies single-condensate viscoelasticity

Tracer-free Contactless Acoustic Microrheometry Quantifies Viscoelastic Spectrum of Phase-separated Condensates

Contactless measurements on microscale droplets yield shear-modulus spectra from 0.01 to 10 Hz, validated on dextran and applied to nucleic酸

abstract click to expand

The rheology of phase-separated condensates plays a central role in applications spanning advanced materials design and cellular processes, yet quantitative characterization of their viscoelasticity remains challenging due to the limitations of existing microrheological methods that require tracer particles or mechanical contact. Here, we establish tracer-free and contactless acoustic microrheometry as a versatile platform for quantifying the frequency-dependent complex shear modulus of single microscale condensates over 0.01-10 Hz. Using spatiotemporally controlled acoustic radiation force generated within a micro-acoustic resonator, this method deforms condensates for creep-recovery and oscillatory viscoelastic measurements. Quantitative validation using dextran condensates in a polyethylene-glycol continuous phase successfully captures their size- and frequency-dependent mechanical responses, while application to nucleic-acid condensates reveals salt-dependent internal viscoelastic changes at single-condensate resolution. By enabling quantitative dissection of condensate mechanics without invasive probes, acoustic microrheometry provides a broadly applicable framework for investigating phase-separated condensates across materials science, soft matter physics, biology, and beyond.

0

cond-mat.mes-hall 2026-05-13 2 theorems

Free fermion classification reduces to graded algebra decomposition

The Algebra of Free Fermions: Classifying Spaces, Hamiltonians, and Computation

Encoding symmetries in a Z2-graded algebra turns the problem into a representation extension that yields both classification and explicit 0D

abstract click to expand

Research on topological phases of matter is a core field in modern condensed matter physics. Free fermion systems, such as topological insulators and superconductors, have been studied using the "Tenfold Way" and K-theory. Building on Kitaev's idea of $\Omega$-spectrum and classifying space, as well as Freed-Moore's K-theory, this work demonstrates that free fermionic systems form a genuine $G$-$\Omega$-spectrum and clarifies its connection to several distinct classification schemes appearing in the physical literature. By introducing the $\mathbb{Z}_2$-graded algebra $A_{\mathrm{sym}}^V$, the classification problem for systems with general symmetries, including antilinear symmetries, antisymmetries, projective representations, and point group symmetries, is turned into an extension problem in representation theory. To solve this, a computational method for the $\mathbb{Z}_2$-graded Wedderburn-Artin decomposition of $A_{\mathrm{sym}}^V$ is developed. This decomposition not only yields a classification but also enables the explicit construction of the corresponding Dirac Hamiltonian. Furthermore, a GAP programming package has been developed to automate these calculations.

0

cond-mat.mtrl-sci 2026-05-13 Recognition

ML surrogates cut lattice thermal conductivity prediction costs by orders of magnitude

Fast and Accurate Prediction of Lattice Thermal Conductivity via Machine Learning Surrogates

Benchmarks show MLIP models excel inside known ranges while deep networks like ALiEGNN handle unseen low-conductivity materials better.

abstract click to expand

The appearance of generative models has opened vast chemical spaces in the design of functional materials. Although machine learning interatomic potentials (MLIPs) have substantially accelerated phonon calculations, high-fidelity prediction of lattice thermal conductivity \k{appa}lat still requires accurate treatment of anharmonic interactions, which remains a key challenge for existing potentials across novel chemical spaces. To address this challenge, we present a comprehensive benchmark of 15 surrogate models for predicting \k{appa}lat using the Phonix database, which contains 6,966 entries with anharmonic phonon properties derived from first-principles calculations. Firstly, We categorize these surrogate models into three distinct groups: Physical-informed feature descriptors combined with ML models, end-to-end deep neural networks, and pre-trained MLIP-embeddings combined with ML models. By evaluating model performance across random, space-group disjoint (testing generalization to unseen crystal symmetries), and Out-Of-Distribution splits (OOD dataset that testing extrapolation to property regimes beyond the training range) based on \k{appa}lat, we probe both interpolation and exploration capabilities. Our results reveal that MLIP-embedded models excel in interpolation within well-sampled regions, deep neural network models especially ALiEGNN demonstrate superior robustness in OOD regimes critical for discovering novel low-\k{appa}lat. Additionally, we find a systematic degradation in performance when the structural representation is reduced. Although surrogate models exhibit lower accuracy than direct simulations using first-principles calculation, they reduce computational costs by orders of magnitude, enabling efficient high-throughput screening of thermoelectric materials with minimal loss in generative design workflows.

0

cond-mat.quant-gas 2026-05-13 1 theorem

Lattice shaking maps interband Berry connections in atoms

Interband Berry connection measurement in the optical honeycomb lattice

Excitation strength under modulation reveals geometric features like Dirac strings in the honeycomb lattice band structure.

abstract click to expand

The geometry of Bloch bands affects many physical properties of crystalline solids and other spatially periodic systems. Direct experimental determination of such geometry is an active area of research. In this work, we focus on the fundamental connection between optical excitations and the relative geometry of pairs of Bloch bands, as characterized by the interband Berry connection. We simulate the response of electrons in solids to optical excitation by the response of ultracold fermionic atoms in optical lattices to periodic modulation of the lattice position. The strength of resonant excitation between bands, measured at each quasimomentum and for various lattice-shaking polarizations, directly maps out the interband Berry connection. We apply this method to the optical honeycomb lattice, driving excitations between the ground $n=1$ band and the excited $n'=\{2,3,4\}$ bands. We observe transparency lines of quasimomenta at which the response to excitation of specific polarization is zero. Further, the interband Berry connection between bands 1 and 3 shows irreducible Dirac strings connecting the $K$ and $K'$ points in the Brillouin zone, lines along which the interband Berry connection abruptly changes orientation. Our work establishes optical response as a powerful tool for characterizing geometrical and topological properties of band structure.

0

cond-mat.str-el 2026-05-13 1 theorem

Pressure raises Curie temperature in Y2NiIrO6 to 240 K

Outstanding TC Enhancement in 5d-3d Y2NiIrO6 by Compression

Bond and angle compression strengthens 5d-3d exchange while rock-salt order prevents frustration.

abstract click to expand

Understanding and predicting the properties of 5d compounds critically depend on the identification of the superexchange interactions from which their magnetism emerges. The study of pressure effects on double perovskites Y2NiIrO6 (YNIO) provide deep insight toward this goal. At ambient pressure, YNIO is a ferrimagnetic insulator with the Ir4+-5d Jeff = 1/2 Mott-insulating state. Under the physical pressure up to 17 GPa, the compound exhibits concurrent compression on Ni/Ir-O bond lengths and Ni-O-Ir bond angles, leading to increase of the Curie temperature from 192 to 240 K. In contrary, external pressure increases distanced Ir-Ir interaction and in turn induces magnetic frustration in Sr2IrO4/Sr3Ir2O7 due to the extended 5d orbitals. In YNIO, the rock-salt ordered Ni-Ir naturally blocks extended superexchange beyond the nearest neighbor, and in turn suppresses such magnetic frustration. Moreover, the orthogonal Ni eg-Ir t2g pathway in YNIO is robust under lattice distortion, while the superexchange is weakened by bond bending in La2NiMnO6 with a similar half-filed eg-t2g configuration. Our findings establish a framework for elucidating the mechanism of 5d-3d superexchange and guides bond-engineered magnetism in iridate-related systems.

0

cond-mat.supr-con 2026-05-13 2 theorems

Superconducting pairings induce Euler topology on honeycomb lattices

Euler Topology in Superconducting Honeycomb Lattices

s-wave and f-wave states produce mirror-protected helical modes at domain walls and non-Abelian Dirac-node braiding under anisotropy.

abstract click to expand

Electronic bands in systems with space-time inversion (IST) symmetry can host nontrivial Euler topology. Here, we investigate the band topology of IST-symmetric superconducting honeycomb lattices and demonstrate that s-wave spin-singlet (SWSS) and f-wave spin-triplet (FWST) superconducting pairings give rise to valley-Euler and Euler superconductors, respectively. We find that Euler topology in both pairing states gives rise to mirror-symmetry-protected helical domain-wall modes. Furthermore, we show that Euler topology in the FWST state induces non-Abelian braiding of Dirac nodes in momentum space when anisotropic hopping is introduced. Our work establishes superconducting electronic instabilities as a natural route to realizing nontrivial Euler band topology in Dirac materials.

0

cond-mat.supr-con 2026-05-13 1 theorem

Strain stabilizes superconductivity in nickelate films at ambient pressure

Experimental Progress in Ambient-Pressure Superconducting Bilayer Nickelate Films

Bilayer films now permit transport, spectroscopy, and device studies without high-pressure setups.

abstract click to expand

Bilayer Ruddlesden-Popper nickelates display superconductivity near 80 K under high pressure, establishing a new nickelate platform for studying unconventional high-temperature superconductivity. The recent stabilization of superconducting RA3Ni2O7 (RA = rare earth or alkaline earth) films at ambient pressure has changed the experimental landscape: epitaxial strain can reproduce key structural ingredients of the high-pressure phase while making transport, spectroscopy, microscopy, and device-oriented measurements directly accessible. This Review summarizes the experimental progress on ambient-pressure superconducting bilayer nickelate films, with emphasis on synthesis routes, oxygen stoichiometry, substrate-induced strain, normal-state transport, superconducting properties, doping phase diagrams, and momentum-resolved electronic structure. We highlight several issues that remain unsettled, including the reproducibility of phase-pure ultrathin films, the microscopic origin of the two-step superconducting transition, the role of oxygen defects and substrate-derived doping, the position of the Ni 3dz2-derived {\gamma} band, and the pairing symmetry. We close by outlining experimental directions that could establish a more quantitative link among crystal structure, orbital reconstruction, and superconductivity in bilayer nickelate films.

0

cond-mat.mtrl-sci 2026-05-13 2 theorems

G0W0 in numerical atomic orbitals matches plane-wave accuracy

G⁰W⁰ implementation based on the pseudopotential and numerical-atomic-orbital basis-set framework: Algorithms and benchmarks

A compressed resolution-of-identity scheme and analytic small-q treatment enable efficient large-system simulations with established code

abstract click to expand

The $GW$ method delivers substantially improved accuracy in electronic band structure calculations over conventional Kohn-Sham density functional theory (KS-DFT) by explicitly incorporating the electron self-energy effect beyond mean-field approximations. Despite many existing implementations, a periodic $GW$ implementation within the framework of numerical atomic orbitals (NAO) combined with the pseudopotential (PP) scheme has not been reported. This is urgently needed given the increasing popularity of the NAO-PP framework in KS-DFT calculations and its importance for the development of machine-learning electronic-structure approaches. In this work, we present an efficient NAO-PP-based $G^0W^0$ computational framework by interfacing the first-principles software package ABACUS with LibRPA -- a library for performing low-scaling random-phase approximation and $GW$ calculations based on NAOs. Our approach employs the localized resolution of identity (LRI) technique with a novel compression scheme, significantly improving both computational efficiency and numerical stability. In addition, an analytic treatment of the small-q limit of the microscopic dielectric function reduces the need for dense q-point sampling. Furthermore, we propose a practical strategy to select a suitable KS-DFT pseudopotential prior to $G^0W^0$ calculations by examining the frequency-dependent macroscopic dielectric function. Systematic benchmarks validate the effectiveness of our compression scheme and real-space tensor filtering strategies, demonstrating both high accuracy and significant computational efficiency gains. Comparisons with established $G^0W^0$ implementations show excellent agreement in band structures and band gaps, confirming ABACUS+LibRPA as a reliable and efficient platform for large-scale $G^0W^0$ simulations.

0

cond-mat.soft 2026-05-13 2 theorems

Minimal two-network model explains double-network toughness

Defect screening and load transfer in minimal hard-soft double networks

Load transfer screens defects in the hard network, producing universal failure-strain scaling and delocalized damage.

abstract click to expand

Double network (DN) materials exhibit anomalous strength and toughness that far exceed the sum of their constituents. While widely exploited, the fundamental physical mechanisms underlying this synergy remain elusive. Here, we show that a minimal three-dimensional model of two coupled, disordered linear-elastic networks is sufficient to capture the essential physics of DN nonlinear mechanics. The model reproduces the full suite of unique mechanical behaviors, including yielding, necking, strain hardening, and the brittle-to-ductile transition. Mechanical contrast between the hard and soft networks drives inter-network load transfer, which screens defects and suppresses stress concentrations in the hard network. By defining a stress-concentration factor, K_sc, we find that the hard-network failure strain scales universally as 1/K_sc, directly bridging microscopic defect screening to macroscopic yielding. We further show that complete defect screening triggers the shift from localized necking to delocalized damage. Furthermore, the stable necking plateau is identified as an energetic selection governed by the balance between potential energy release and irreversible dissipation. These findings reveal that a simple linear-elastic framework can account for the rich nonlinear landscape of DN materials, providing a general principle for designing next-generation tough solids.

0

cond-mat.soft 2026-05-13 Recognition

Model separates soft elasticity from viscoelasticity in LCEs

Thermoviscoelasticity of polydomain liquid crystal elastomers regulated by soft elasticity

Rate-independent mesogen reorientation sets the limiting stretch while polymer relaxation adds rate dependence and residual buildup, all erc

abstract click to expand

Liquid crystal elastomers (LCEs) are elastomeric networks with rod-like mesogens that reorient under load. In polydomain LCEs, this reorientation drives a polydomain-to-monodomain transition that produces a soft-elastic plateau. Coupling between this soft elasticity and polymer-network viscoelasticity yields a path-dependent thermoviscoelastic response, central to applications in damping, impact protection, and tough adhesives. However, the physics governing this response under complex thermomechanical histories remains insufficiently studied. We present a combined experimental and theoretical study of polydomain LCEs under three uniaxial protocols: single-cycle loading-unloading, stress-free recovery from various pre-stretches, and multi-cycle loading with progressively increasing amplitude. We develop a finite-deformation constitutive model combining two parallel mechanisms: rate-independent, temperature-dependent soft elasticity from mesogen reorientation, and time- and temperature-dependent viscoelasticity. With a single parameter set, the model quantitatively reproduces all three protocols and resolves each mechanism's contribution. A temperature-dependent soft-elastic limit governs the low-rate response and the long-time recovered stretch, while viscoelasticity controls the rate-dependent deviation and the cycle-wise accumulation of residual stretch away from this limit. A thermal recovery test above the nematic-isotropic transition confirms that all hysteresis and residual deformation are reversible, ruling out irreversible damage. The framework provides mechanistic understanding and a predictive basis for designing polydomain LCE components under complex thermomechanical histories.

0

cond-mat.soft 2026-05-13 Recognition

Polarization modulation is sinusoidal in one antiferroelectric nematic but soliton-like in

Landau theory applied to antiferroelectric ordering in ferroelectric nematic liquid crystals

In the antiferroelectric phase the polarization modulation is reasonably well approximated by a simple sinusoid in DIO, whereas in FNLC919…

abstract click to expand

The polarization and density modulation associated with antiferroelectric ordering is studied experimentally as a function of temperature in two ferroelectric nematic liquid crystals, the prototypical single compound (DIO) and a commercial mixture (FNLC919). The modulation wavenumber qA is determined by small angle X-ray diffraction from the weak smectic-like density wave (wavenumber qS = 2qA) that accompanies the polarization modulation. Results for qS and the saturated value of the polarization are analyzed in terms of Landau theory previously developed to describe the para-/antiferro-/feroelectric sequence of phase transitions in solid ferroelectrics. The analysis indicates that the polarization modulation is reasonably well approximated by a simple sinusoid in the antiferroelectric phase of DIO, whereas in FNLC919 the modulation develops a strongly soliton-like profile (with sharply decreasing wavenumber) close to the antiferro- to ferrolectric transition.

0

cond-mat.supr-con 2026-05-13 2 theorems

Superconductivity boosts CDW phase coherence in cuprates

Superconductivity Reinforces Charge-Density-Wave Phase Coherence across Cuprates

Across multiple families, phase coherence grows below Tc with no peak broadening and precise wave-vector locking, even in disordered samples

abstract click to expand

For decades, superconductivity in high-Tc cuprates has been viewed as a competitor that suppresses charge-density-wave (CDW) order by reducing its amplitude and spatial extent. Here, we show that this picture is incomplete, as superconductivity is accompanied by a systematic enhancement of CDW phase coherence across multiple cuprate families. Using resonant soft x-ray scattering combined with a coherence-sensitive momentum-profile analysis, we uncover a BCS-like growth of phase coherence below Tc, which phenomenologically manifests as the absence of CDW peak broadening and near-perfect wave-vector locking. This enhancement remains visible even in a disorder-dominated regime created by long-term crystal aging and follows a common trend when compared with published data on Bi-, Hg-, Y-, and Nd-based cuprates. These results indicate that superconductivity reshapes CDW order in two distinct ways, suppressing its amplitude while strengthening its phase coherence, and reveal an additional phase-level interplay with lattice coupling in high-Tc cuprates.

0

cond-mat.supr-con 2026-05-13 1 theorem

PtPb4 shows symmetry-broken superconductivity with Majorana-like zero modes

Discovery of a nonsymmorphic superconductor with spontaneous rotational symmetry breaking and nontrivial zero modes

Anisotropic resistivity and persistent vortex zero states in this nonsymmorphic compound suggest a new route to topological states.

abstract click to expand

Topological superconductivity has attracted great interest due to its fundamental significance for realizing Majorana quasiparticles and fault-tolerant quantum computation. Nonsymmorphic superconductors, with symmetry-protected nontrivial electronic structures, offer a promising route to exotic topological superconducting states, yet experimental realizations remain scarce. Here we identify nonsymmorphic compound PtPb4 as a robust platform hosting superconductivity with spontaneous rotational symmetry breaking and nontrivial zero-energy modes. PtPb4 crystallizes in a frustrated Shastry-Sutherland lattice and exhibits nontrivial band topology. By combining in-plane and out-of-plane resistivity measurements, pronounced twofold anisotropy is observed in both the superconducting state and the upper critical field, evidencing spontaneous rotational symmetry breaking. Scanning tunneling microscopy/spectroscopy further reveal twofold-symmetric magnetic vortices, providing direct real-space evidence for the symmetry-broken superconducting state. Notably, a robust zero-energy vortex bound state emerges and persists without spatial splitting over extended distances, consistent with the characteristics expected for Majorana bound state. These findings uncover an exotic superconducting state in PtPb4 and establish a promising platform for exploring topological superconductivity and superconducting quantum devices.

0

cond-mat.soft 2026-05-12 2 theorems

Active stresses broaden pores and thicken bundles in actin networks

Mechanics of heterogeneous fiber networks

Raising motor concentration increases local elastic modulus and lengthens the range of strain propagation at network heterogeneity scales.

abstract click to expand

Internally generated active stresses drive soft materials into architectures inaccessible to thermal self-assembly. We use a microtubule-based active fluid to assemble and irreversibly restructure actin-fascin networks. Subsequently, we probe the mesoscale mechanics of such networks by combining active microrheology with fluorescence imaging of the strain field around the probe. Increasing motor concentration broadens the pore-size distribution and thickens load-bearing bundles, raising the mean local elastic modulus and its spatial variability. Displacement fields of actively-processed networks propagate over longer range when compared to unprocessed networks. At large strains, both networks strain soften and plastically restructure. The combined microrheology and strain-imaging approach show that tunable active stresses reprogram the structure and viscoelastic response of fiber networks at the scale of their structural heterogeneity.

0

cond-mat.soft 2026-05-12 Recognition

Partially wet states limited to specific contact angles and curvatures

Existent condition of partially wet state in capillary tubes

Energy minimization shows corner films exist only in a bounded region of parameter space for square tubes.

abstract click to expand

We develop a theory that predicts the equilibrium states of a fluid contained in a capillary which has corners. Each section of the tube can take three states: completely wet state where the tube section is completely occupied by the fluid, partially wet state where only the corners are occupied by the fluid known as corner film or finger, and completely dry state. We calculate the phase diagram of these states for a square tube with rounded corners. It is shown that the partially wet state can exist only in a certain region in the parameter space spanned by the equilibrium contact angle and the corner curvature.

0

cond-mat.stat-mech 2026-05-12 2 theorems

Percolation threshold drops faster near 3D in fractional lattices

Random-h Fractional-Dimensional Lattices Reveal Endpoint-Compressed Percolation Activation between Two and Three Dimensions

High-resolution scans show activation compresses at the three-dimensional endpoint while mass and coordination evolve independently.

abstract click to expand

Non-integer dimensionality is central to fractal and complex systems, yet it is rarely represented as an explicit lattice on which classical statistical-mechanical models can be directly simulated. Here we introduce random-h fractional dimension (RhFD), a constructive lattice framework in which fractional-dimensional environments are generated by stochastic activation of local connectivity, h. In the 2D-to-3D interval, RhFD lattices are formed by recursively growing out-of-plane sites from a square base with probability \r{ho}h. Using quenched site-percolation simulations, we show that the construction recovers the integer-dimensional endpoints and yields a robust crossover in which the percolation threshold decreases from the 2D regime toward the 3D regime. The crossover is not a uniform interpolation: high-resolution scans reveal endpoint-compressed activation, with -dpc/d\r{ho}h increasing toward \r{ho}h = 1. Mass dimension increases with \r{ho}h, whereas the coordination descriptor first decreases as sparse protrusions form and then rises sharply when a dense 3D backbone emerges. RhFD provides an explicit lattice substrate for fractional-dimensional statistical mechanics and shows that geometric mass, local coordination, and critical connectivity can decouple during dimensional crossover.

0

cond-mat.str-el 2026-05-12 Recognition

Unbiased large-N fixes vestigial order ambiguity

Unbiased large-N approach to competing vestigial orders of density-wave and superconducting instabilities

Respecting Fierz identities among composite operators yields unique interactions and parameter regions without stable vestigial phases.

abstract click to expand

When a primary order breaks multiple symmetries, partially ordered phases that only break a subset of those symmetries, known as vestigial phases, may onset at a higher temperature. This concept has been applied to a wide range of systems, including iron pnictides, cuprates, van der Waals antiferromagnets, doped topological insulators, and twisted bilayer graphene. In general, a multi-component primary order parameter (OP) supports multiple vestigial channels, each described by a quadratic (or higher-order) composite OP. However, the standard large-$N$ approach to the Ginzburg-Landau action of the primary OP has an intrinsic ambiguity in how one decouples the composite OPs, leading to situations in which one can seemingly enhance or eliminate altogether any vestigial instability. Here, we show that this ambiguity is a direct consequence of redundancy relations, such as Fierz identities, that relate different composite OPs, reflecting the fact that different vestigial channels interfere with each other and thus cannot be treated separately. To resolve this ambiguity, we propose an unbiased large-$N$ approach that respects both the redundancy relations and the underlying symmetry-group structure, and that gives unique values for the effective interactions of all vestigial channels. Our analysis reveals the generic existence of regions in the parameter space of quartic Landau coefficients where no vestigial order is stable, in contrast to the standard large-$N$ approach, but in agreement with weak-coupling and variational approaches. We illustrate our results by analyzing the vestigial orders of charge-density waves, spin-density waves, and multi-component superconductors in tetragonal, hexagonal, and cubic systems, respectively, revealing the presence of exotic vestigial phases describing spin-quadrupolar, charge-$4e$ superconducting, and altermagnetic orders.

0

cond-mat.mes-hall 2026-05-12 2 theorems

Antiferromagnetism emerges in MoSe2 quantum Hall states

Optical signatures of antiferromagnetic correlations in a strongly interacting quantum Hall MoSe2 monolayer

Valley Landau level crossings broaden at low fillings, revealing interactions that favor an unpolarized ground state over conventional ferom

abstract click to expand

Strong magnetic fields quench the kinetic energy of electrons, leading to the formation of flat energy bands, known as Landau levels (LLs). In this situation, even weak interactions can drive the emergence of various ordered phases. The simplest of such phases is a quantum Hall ferromagnet, where a spontaneous spin polarization emerges when LLs with opposite spins cross. The presence of strong electron-electron interaction at zero field changes this picture and makes the resulting states much harder to predict. Here we use magneto-optical spectroscopy to reveal quantum Hall states with unconventional correlations favouring an unpolarized state in the strongly correlated electron liquid in a MoSe2 monolayer. The oscillations of the exciton polaron energies as a function of perpendicular magnetic field and electron density demonstrate the emergence of LLs in a correlated electron liquid and density-dependent crossings between LLs of opposite valleys. On lowering the LL filling factor, where interactions within LLs are stronger, the crossings systematically broaden, indicating an increase in the Zeeman energy required to fully polarize the valley-degenerate LLs. These observations are shown to be consistent with antiferromagnetic interactions between LL electrons, favouring a ground state with zero valley polarization, and are therefore inconsistent with conventional quantum Hall ferromagnetism. This discovery demonstrates a qualitatively distinct form of quantum Hall magnetism in a strongly correlated electron liquid, establishing an anchoring point for understanding spin-unpolarized fractional and ordered states of correlated electrons driven by magnetic field.

0

cond-mat.quant-gas 2026-05-12 2 theorems

One mode drives both slowing and giant response in photon condensate

Giant critical response in a driven-dissipative quantum gas

Fluctuations slow and weak pumps amplify maximally at the same condensate size of 1250, set by a shared weakly damped mode.

abstract click to expand

Systems close to a phase transition turn weak perturbations into large responses. At equilibrium, this amplification is closely linked to criticality: fluctuations grow, dynamics slow, and a common soft mode controls the response. Whether this correspondence survives in driven-dissipative quantum systems, sustained by continuous pumping and loss away from thermal equilibrium, remains an open question. Here we show experimentally that it does. In a room-temperature semiconductor photon Bose-Einstein condensate, the critical slowing of spontaneous intensity fluctuations and the amplification of weak pump perturbations are measured independently. Both peak at the same condensate population, $\bar{n}_c = 1250$, where the dimensionless slowing factor and susceptibility reach the same value, $\bar{n}_c/2 = 625$. A single weakly damped collective photon-reservoir mode governs both effects. This fluctuation-response correspondence in a finite open quantum gas establishes critical susceptibility as a measurable dynamical signature of condensation, with peak gain set by system size.

0

cond-mat.supr-con 2026-05-12 2 theorems

Embedding method tracks superconducting proximity over hundreds of nanometers

First-principles real-space embedding theory of the superconducting proximity effect

Real-space dynamical embedding with normal and anomalous self-energies predicts spectral functions in mesoscopic heterostructures without厚sl

abstract click to expand

When a superconductor is placed in contact with a normal material, Cooper pairs penetrate the latter and induce superconductivity via the proximity effect. Despite its central role in quantum materials, superconducting devices and topological platforms, a predictive first-principles description of the proximity effect at realistic interfaces has remained computationally prohibitive so far. Here, we fill this gap by developing a Green's-function framework based on real-space dynamical embedding that enables first-principles simulations of superconducting proximity in mesoscopic systems. We show that the proximity effect admits a transparent diagrammatic formulation in terms of normal and anomalous embedding self-energies, which disentangle and quantify the distinct renormalization mechanisms generated by coupling to a superconducting bath. By combining this formalism with recursive schemes, we compute local spectral functions and proximity lengths extending over hundreds of nanometers into the bulk without resorting to thick interface slabs. We deploy the approach on tight-binding models (Qi-Hughes-Zhang and Fu-Kane-Mele), where we analyze mixed-parity superconductivity in topological insulators proximitized by $s$-wave superconductors, and on first-principles simulations of NbSe$_2$/CrBr$_3$ heterostructures based on density-functional theory and maximally-localized Wannier functions, the latter enabling direct comparison with scanning tunneling spectroscopy experiments. Our work provides a scalable and conceptually unified framework that bridges microscopic electronic structure and mesoscale proximity physics, enabling predictive atomistic simulations of superconducting interfaces.

0

cond-mat.mes-hall 2026-05-12 2 theorems

Magnetic field induces tunable hyperbolic polaritons in semimetals

Magnetic-field-tunable cyclotron hyperbolic polaritons

Cyclotron motion creates dielectric anisotropy below resonance that supports field-controlled modes observable by terahertz imaging.

abstract click to expand

Hyperbolic polaritons are conventionally associated with structural anisotropy or phononic Reststrahlen bands. Here, we predict a new class of hyperbolic polaritons arising from magnetic-field-induced cyclotron motion of charge carriers. When a perpendicular magnetic field is applied to high-mobility semimetals, the cyclotron response drives the in-plane dielectric function from metallic- to insulating-like below the cyclotron resonance frequency, while the out-of-plane response remains metallic. This anisotropy creates a hyperbolic dielectric environment that supports field-tunable hyperbolic polaritons. We develop a comprehensive theoretical framework incorporating coupling to other collective excitations and show that these modes can be directly visualized in real space via terahertz near-field nanoscopy. Our work identifies cyclotron motion as a new route to hyperbolic polaritons and establishes a versatile platform for magnetically programmable nanophotonics.

0

cond-mat.mtrl-sci 2026-05-12 2 theorems

Periodic defects open band gap in graphene only for multiples of three

Symmetry Guided Band-Gap Opening via Periodic Topological Defects in Graphene

Zone folding merges Dirac points when supercell size N is a multiple of three, producing larger tunable gaps with flower defects.

abstract click to expand

Graphene lacks an intrinsic band-gap, which limits its use in electronic applications. Here we demonstrate that periodic arrays of topological defects can open and control a band-gap in a predictable manner governed by defect spacing and lattice symmetry. Using first-principles density functional theory calculations supported by tight-binding models, we investigate graphene superlattices containing Stone-Wales and flower-like defects over a range of $N \times N$ periodicities, where $N$ determines the defect separation. We show that band-gap opening occurs only when translation symmetry is reduced in a specific way: for supercells with $N$ a multiple of three, Brillouin-zone folding brings the Dirac cones at $K$ and $K'$ to the same momentum in the reduced Brillouin zone. In particular, flower-like defect superlattices produce larger and tunable band-gaps, whose magnitude decreases systematically with increasing defect separation and approaches zero in the dilute-defect limit. These results establish a predictive framework for band-gap engineering in defect-patterned graphene and clarify the microscopic mechanism underlying gap formation in periodically reconstructed lattices.

0

cond-mat.mtrl-sci 2026-05-12 2 theorems

Dual doping yields 11 GPa hardness in nanocrystalline nickel

Synergistic doping of the grain interior and grain boundary alters deformation mechanisms and enables extreme strength in nanocrystalline Ni-Cr-Y alloys

Cr inside grains and Y at boundaries suppress sliding and rotation while grain size stays fixed.

abstract click to expand

Solid solution addition and grain boundary segregation have been independently shown to enhance the strength of nanocrystalline alloys. In the present study, the synergy between these two effects is investigated in nanocrystalline Ni-Cr-Y sputtered films through systematic variation of alloying element contents with grain size kept constant. Cr is introduced into a solid solution and serves to strengthen the lattice, while Y segregates to the grain boundaries to stabilize these features. Nanoindentation is used to probe hardness, with unexpected trends and very high values observed. Cr additions led to nanocrystalline solid solution strengthening, yet saturation was observed at higher concentrations due to the emergence of grain boundary dominated processes, as evidenced by pile-up morphologies containing slip steps and grain rotation. Y segregated to the grain boundaries, enhancing boundary-mediated strengthening by pinning the dislocations and suppressing dislocation emission, grain boundary sliding, and grain rotation processes. With increasing Y concentration, the nanocrystalline solid solution strengthening effect induced by Cr addition becomes weaker. This phenomenon can be attributed to a reduced dislocation bowing distance caused by dopant pinning. Most notably, the strongest ternary Ni-Cr-Y alloy exhibited a hardness of 11.0 GPa, among the highest hardness values reported for single-phase Ni-based alloys. These findings highlight how tuning grain and grain boundary chemistry offers a viable strategy to control dislocation mechanics and improve the strength of nanocrystalline metals.

0

cond-mat.mes-hall 2026-05-12 2 theorems

Zigzag edges define four classes of graphitic quadrupole insulators

Bound States in Second-order Topological Graphitic Structures

Domain intersections produce protected massless corner states; smoother walls add massive states with angular momentum.

abstract click to expand

Quadrupole insulators are a class of second-order topological insulators (SOTIs) that host zero-dimensional corner states within a two-dimensional bulk. Despite their unique properties, their realization in electronic systems on realistic material platforms remains rare. In this work, we present a general design principle to obtain quadrupole insulators based on two-dimensional graphitic structures. By engineering the positions and connections of zigzag edges, we identify four topological classes of graphitic structures. We show that topologically protected massless corner state emerge at the intersection of domains belonging to different topological classes. Crucially, by tuning the smoothness of the domain wall, we further demonstrate the appearance of additional massive localized states with non-zero angular momentum. Our results provide a practical framework for realizing experimentally accessible SOTIs and uncover the coexistence of both massless and massive bound states in two dimensions.

0

cond-mat.quant-gas 2026-05-12 Recognition

DMRG and pairing models unify BCS-BEC crossover in trapped 1D Fermi chains

BCS-BEC crossover in trapped one-dimensional Fermi-Hubbard chains: entanglement and correlation signatures from DMRG and effective-pairing theory

Conditioned correlations distinguish regimes where insulating and superfluid regions coexist under harmonic confinement.

abstract click to expand

Confined ultracold atoms in optical lattices provide a versatile platform for simulating lattice models of strongly correlated quantum systems, where pairing phenomena and superfluid phases can be explored under controlled conditions. While the crossover between the Bardeen-Cooper-Schrieffer (BCS) phase and the Bose-Einstein condensation (BEC) is well understood in homogeneous systems, spatial confinement breaks translational symmetry and reshapes correlation patterns, making the BCS-BEC identification in trapped geometries challenging and allowing unconventional phases to emerge with no direct analog in homogeneous systems. Here we present a characterization of the BCS-BEC crossover in harmonically confined one-dimensional Fermi-Hubbard chains. Our analysis combines Density Matrix Renormalization Group (DMRG) simulations and entanglement-based diagnostics with effective models describing the formation of tightly bound fermion pairs. This combined approach enables a detailed understanding of how the interplay between interactions and confinement reshapes the crossover, leading to insulating regions coexisting with persistent superfluid correlations. Within this framework, we further introduce conditioned correlation functions whose power-law decay allows a clear distinction between BCS-like and BEC-like regimes. The consistency between the effective descriptions and the numerical DMRG results yields a unified picture of the crossover in harmonically confined geometries.

0

cond-mat.stat-mech 2026-05-12 2 theorems

FRG treats noise-to-signal ratio as temperature for anomaly detection

Field Theory of Data: Anomaly Detection via the Functional Renormalization Group. The 2D Ising Model as a Benchmark

In the 2D Ising benchmark the method locates critical thresholds with under 4% error by mapping detection to RG flows near the Marchenko-Pa

abstract click to expand

We establish a correspondence between anomaly detection in high-noise regimes and the renormalization group flow of non-equilibrium field theories. We provide a physical grounding for this framework by proving that the detection of phase transitions in interacting non-equilibrium systems maps to the study of an effective equilibrium field theory near its Gaussian fixed point, which we identify with the universal Marchenko-Pastur distribution. Applying the Functional Renormalization Group to the two-dimensional Model A, we demonstrate that the noise-to-signal ratio acts as a physical temperature, where the signal emerges as ordered domains within a thermalized background of fluctuations. Using the exact Onsager solution as a benchmark, we show that this approach identifies critical thresholds with an error below 4%, significantly outperforming standard information-theoretic metrics such as the Kullback-Leibler divergence. Our results provide a universal strategy for resolving structures in complex datasets near criticality, bridging the gap between statistical mechanics and statistical inference.

0

cond-mat.mes-hall 2026-05-12 1 theorem

Photon momentum breaks symmetry to enable bulk photocurrents in PdTe

Photon Momentum Enabled Symmetry Breaking and Nonlinear Photocurrents in the Centrosymmetric Dirac Semimetal PdTe

Thickness-dependent measurements show the helicity-dependent response originates in the centrosymmetric bulk rather than surfaces.

abstract click to expand

In centrosymmetric Dirac semimetals, second order nonlinear photocurrents are forbidden by the coexistence of time-reversal and inversion symmetries. Here, we demonstrate that finite photon momentum transfer acts as a dynamic symmetry breaking mechanism in PdTe, enabling nonlinear optical responses that are nominally forbidden in the centrosymmetric bulk. Through polarization sensitive measurements, we resolve distinct contributions from the circular photogalvanic effect (CPGE), geometric shift currents, and photon drag mediated processes. We show that the helicity dependent current vanishes at normal incidence and reverses sign with the angle of incidence, reflecting the coupling between photons and spin polarized surface states. Crucially, thickness dependent analysis reveals that the helicity dependent photocurrent component C scales with film thickness, establishing a robust bulk contribution enabled by momentum transfer. This confirms that incident photons provide the directional axis required to probe interband quantum geometry, rather than the response originating solely from surface states or strain. Our results demonstrate that optical excitation can dynamically reduce the effective symmetry of the system, enabling access to quantum geometric tensors and establishing PdTe as a promising platform for exploring nonequilibrium dynamics governed by photon momentum in high symmetry topological materials.

0