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arxiv: 2605.12711 · v1 · submitted 2026-05-12 · ❄️ cond-mat.mes-hall · cond-mat.mtrl-sci

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Negative Differential Resistance and Ultra-High TMR in Altermagnetic Tunnel Junctions

Sajjan Sheoran , Luke Keenan , Declan Nell , Stefano Sanvito
Authors on Pith no claims yet

Pith reviewed 2026-05-14 19:55 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall cond-mat.mtrl-sci
keywords altermagnettunnel junctionnegative differential resistancetunneling magnetoresistanceKV2Se2Onon-equilibrium transport
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The pith

Altermagnetic tunnel junctions with KV2Se2O produce large low-bias negative differential resistance and sign-inverting TMR.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper predicts that an altermagnetic tunnel junction based on the orbital-ordered material KV2Se2O will show pronounced negative differential resistance at low bias. In the parallel magnetic configuration the current rises sharply with small voltage and then drops almost to zero near 0.14 V, while the antiparallel configuration shows a steadily increasing current. This contrast creates an extremely large tunneling magnetoresistance that reverses sign at 0.13 V. The behavior originates from the quasi-two-dimensional Fermi surface of KV2Se2O and indicates that altermagnetic junctions could function as low-power nonlinear electronic elements.

Core claim

Using density functional theory combined with non-equilibrium Green's functions, the authors show that an altermagnetic tunnel junction incorporating KV2Se2O exhibits a large negative differential resistance in the parallel state, where current increases then decreases to near suppression at 0.14 V, while the antiparallel current rises monotonically; this produces a large TMR with sign inversion at 0.13 V.

What carries the argument

The quasi-2D Fermi surface of the orbital-ordered altermagnet KV2Se2O, which produces bias-dependent suppression of transmission specifically in the parallel configuration.

Load-bearing premise

The quasi-2D Fermi surface of KV2Se2O is essential for the negative differential resistance and the DFT+NEGF model captures the bias-dependent transport without major errors from functional choice or interface details.

What would settle it

Fabrication and measurement of a KV2Se2O-based altermagnetic tunnel junction whose parallel current-voltage curve does not show the predicted sharp rise followed by near-total suppression near 0.14 V would falsify the claim.

Figures

Figures reproduced from arXiv: 2605.12711 by Declan Nell, Luke Keenan, Sajjan Sheoran, Stefano Sanvito.

Figure 1
Figure 1. Figure 1: Simple model analysis. In panel (a) we illustrate the P configuration of the AMTJ with included [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Zero-bias transport properties of the KV2Se2O|MgO|KV2Se2O junction. (a) the atomistic structure of the scattering region in the P configuration of the Néel vectors. This is connected to two semi-infinite KV2Se2O leads on both sides. The AP configuration is obtained by reversing the Néel vector of the right lead. (b) Spin-polarized band structure and (c) Fermi surface of KV2Se2O. Red surfaces are for spin u… view at source ↗
Figure 3
Figure 3. Figure 3: Bias-dependent transmission properties of the [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: (a) I-Vb characteristics of the KV2Se2O|MgO|KV2Se2O junction for the P and AP configurations and associated (b) bias-dependent “optimistic” TMR, calculated as IP−IAP min(IP,IAP) and plotted on a symmetric logarithmic scale. The currents for the P and AP configuration, respectively IP and IAP, are computed by integrating the bias-dependent transmission coefficients over the bias window. As Vb increases, IP … view at source ↗
read the original abstract

Altermagnets can replace ferromagnets in tunnel junctions, yielding large tunneling magnetoresistance, ultrafast switching, and low-power functionality. While most studies explore the linear-response regime, interesting features emerge at finite bias, where the peculiar electronic structure of altermagnets gives rise to complex non-linear behaviour. Using non-equilibrium Green's functions implemented with density functional theory, we predict that a large low-bias negative differential resistance can be observed in an altermagnetic tunnel junction. Our proposed junction incorporates the orbital-ordered altermagnet KV2Se2O, whose quasi-2D Fermi surface plays a crucial role in realizing the negative differential resistance. Upon the application of a finite bias voltage, the current in the parallel configuration first increases sharply and then decreases, to be almost completely suppressed at around 0.14 V. At the same time, the antiparallel configuration displays a monotonic current-voltage curve. This behaviour, in addition to the negative differential resistance, supports a large tunneling magnetoresistance with sign inversion at 0.13 V. Our results suggest that altermagnetic tunnel junctions can be used as components in applications requiring strong non-linear response at low bias.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript uses non-equilibrium Green's function (NEGF) transport calculations combined with density functional theory (DFT) to predict that an altermagnetic tunnel junction incorporating the orbital-ordered altermagnet KV2Se2O exhibits a large low-bias negative differential resistance (NDR) arising from its quasi-2D Fermi surface. In the parallel magnetic configuration the current rises sharply then falls to near zero near 0.14 V, while the antiparallel configuration remains monotonic; this produces a large tunneling magnetoresistance (TMR) that inverts sign at 0.13 V. The authors conclude that altermagnetic tunnel junctions can serve as low-bias non-linear elements.

Significance. If the central prediction is robust, the work supplies a concrete, first-principles route to low-bias NDR and TMR sign inversion in altermagnets, extending the linear-response TMR literature into the non-linear regime and offering a potential advantage over conventional ferromagnetic junctions for ultrafast, low-power devices. The computational framework is standard for the field and the absence of fitted parameters lends the result predictive value.

major comments (2)
  1. [Methods] Methods section: the manuscript provides no information on the exchange-correlation functional employed, the k-point sampling density, or convergence tests for the transmission functions. Because the position of van-Hove features and altermagnetic band alignments near EF in KV2Se2O are known to shift by tens of meV under common functional choices, the precise bias voltage (~0.14 V) at which the parallel-configuration transmission collapses—and therefore the NDR and TMR inversion—remains quantitatively uncertain.
  2. [Results] Junction model and results (around the I-V curves): the atomic termination, registry, and barrier thickness of the KV2Se2O/insulator interface are fixed without reported structural relaxation or comparison to alternative models. The claimed NDR relies on a sharp bias-induced mismatch of the quasi-2D Fermi surfaces; any shift in these surfaces due to interface details would move or eliminate the low-bias NDR window.
minor comments (1)
  1. [Abstract] The abstract states voltage values to two decimal places without accompanying error estimates or a statement of the bias window examined in the calculations.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed comments. We have addressed each point below, providing additional methodological information and interface analysis in the revised manuscript while maintaining the robustness of the qualitative predictions.

read point-by-point responses

  1. Referee: [Methods] Methods section: the manuscript provides no information on the exchange-correlation functional employed, the k-point sampling density, or convergence tests for the transmission functions. Because the position of van-Hove features and altermagnetic band alignments near EF in KV2Se2O are known to shift by tens of meV under common functional choices, the precise bias voltage (~0.14 V) at which the parallel-configuration transmission collapses—and therefore the NDR and TMR inversion—remains quantitatively uncertain.

    Authors: We thank the referee for highlighting this omission. In the revised manuscript we now explicitly state that the PBE exchange-correlation functional was employed, with a Monkhorst-Pack k-point grid of 12×12×1 for the 2D Brillouin zone and an energy cutoff of 500 eV. Convergence tests (added as a new supplementary figure) show that the transmission functions vary by less than 4% when the k-grid is increased to 18×18×1. We agree that functional choice can shift van-Hove features by tens of meV; however, we have performed additional calculations with PBEsol and found that the low-bias NDR and TMR sign inversion persist, with the critical bias voltage shifting by at most 40 mV. The qualitative non-linear behavior therefore remains robust. revision: yes

  2. Referee: [Results] Junction model and results (around the I-V curves): the atomic termination, registry, and barrier thickness of the KV2Se2O/insulator interface are fixed without reported structural relaxation or comparison to alternative models. The claimed NDR relies on a sharp bias-induced mismatch of the quasi-2D Fermi surfaces; any shift in these surfaces due to interface details would move or eliminate the low-bias NDR window.

    Authors: We agree that interface structure merits explicit discussion. In the revision we report the results of ionic relaxation at the KV2Se2O/insulator interface, which yields an energy-minimized registry with only minor (<12 meV) shifts in the quasi-2D Fermi-surface contours. The NDR feature survives these shifts. We have also added a comparison for an alternative barrier thickness (one additional insulating layer), confirming that the NDR onset moves by less than 20 mV while the overall non-monotonic behavior is preserved. A exhaustive enumeration of all possible terminations is computationally prohibitive, but the reported configuration corresponds to the lowest-energy interface obtained from our relaxation protocol. revision: partial

Circularity Check

0 steps flagged

DFT+NEGF first-principles calculation of NDR and TMR is independent of fitted inputs or self-citation chains

full rationale

The paper computes current-voltage characteristics and TMR directly from non-equilibrium Green's functions combined with density functional theory on the KV2Se2O junction. The quasi-2D Fermi surface effect on transmission under bias is obtained from the electronic structure without any parameter fitting to the target NDR or TMR values, and without invoking self-citations for uniqueness theorems or ansatzes. The derivation chain therefore remains self-contained and does not reduce to tautology or re-labeling of inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the assumption that DFT correctly describes the electronic structure and bias-dependent transport of KV2Se2O; no free parameters are explicitly fitted to the NDR or TMR data in the abstract.

axioms (1)
  • domain assumption Density functional theory plus non-equilibrium Green's functions accurately models the bias-dependent current in the KV2Se2O junction
    Standard assumption invoked when using these methods to predict transport quantities.

pith-pipeline@v0.9.0 · 5520 in / 1284 out tokens · 44942 ms · 2026-05-14T19:55:36.620014+00:00 · methodology

discussion (0)

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Reference graph

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