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Electronic structure of compressively strained thin film La$_2$PrNi$_2$O$_7$

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arxiv 2504.16372 v2 pith:7UXTQTOX submitted 2025-04-23 cond-mat.supr-con cond-mat.mtrl-sci

Bai Yang Wang , Yong Zhong , Sebastien Abadi , Yidi Liu , Yijun Yu , Xiaoliang Zhang , Yi-Ming Wu , Ruohan Wang
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Jiarui Li Yaoju Tarn Eun Kyo Ko Vivek Thampy Makoto Hashimoto Donghui Lu Young S. Lee Thomas P. Devereaux Chunjing Jia Harold Y. Hwang Zhi-Xun Shen
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classification cond-mat.supr-concond-mat.mtrl-sci
keywords filmsbandstrainedcompressivelypressureresultssuperconductivitythin
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abstract

The discovery of superconductivity in the bulk nickelates under high pressure is a major advance in physics. The recent observation of superconductivity at ambient pressure in compressively strained bilayer nickelate thin films has now enabled direct characterization of the superconducting phase through angle resolved photoemission spectroscopy (ARPES). Here we present an in-situ ARPES study of compressively strained La$_2$PrNi$_2$O$_7$ films grown by oxide molecular beam epitaxy, and the ozone treated counterparts with an onset T$_c$ of 40 K, supplemented with results from pulsed laser deposition films with similar T$_c$. We resolve a systematic strain-driven electronic band shift with respect to that of bulk crystals, in qualitative agreement with density functional theory (DFT) calculations. However, the strongly renormalized flat 3$d_{z2}$ band shifts a factor of 5-10 smaller than anticipated by DFT. Furthermore, it stays ~70 meV below the Fermi level, contradicting the expectation that superconductivity results from the high density of states of this band at the Fermi level. We also observed a non-trivial k$_z$ dispersion of the cuprate-like 3$d_{x2-y2}$ band. Combined with results from both X-ray diffraction and DFT, we suggest that the strained films are under ~5 GPa effective pressure, considerably larger than the na\"ive expectation from the DFT relaxed structure. Finally, the ~70 meV energy position is intriguingly close to the collective mode coupling more prominently seen in thin films, in the energy range of both oxygen related phonons and the maximum of the spin excitation spectrum.

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Cited by 11 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Superconducting gap structure and bosonic mode in La2PrNi2O7 thin films at ambient pressure

    cond-mat.supr-con 2025-06 conditional novelty 8.0 of 10

    Tunneling spectra on La2PrNi2O7 thin films reveal a dominant anisotropic s-wave gap near 19 meV, a smaller gap of 6-8 meV, and a bosonic mode at about 30 meV, pointing to s± pairing.

  2. Doping evolution of spin excitations in La$_{3-x}$Sr$_{x}$Ni$_2$O$_7$/SrLaAlO$_4$ superconducting thin films

    cond-mat.supr-con 2026-03 conditional novelty 7.0 of 10

    Spin excitations persist with nearly unchanged exchange energy through the superconducting dome of Sr-doped La3Ni2O7 films, then collapse into a damped continuum when superconductivity is lost at x=0.38.

  3. LA-CaRe-CNN: Cascading Refinement CNN for Left Atrial Scar Segmentation

    eess.IV 2025-08 conditional novelty 7.0 of 10

    In a model of La3Ni2O7, two different superconducting pairing mechanisms coexist and switch dominance with doping, explaining experiments with and without a gamma band.

  4. Triplon-mediated pairing and the superconducting gap structure in bilayer nickelates

    cond-mat.str-el 2026-02 conditional novelty 6.0 of 10

    Interlayer singlet-triplet excitations (triplons) mediate an interband s± superconducting pairing that explains the larger α-band gap and its anisotropy in bilayer nickelates.

  5. Superexchanges and Charge Transfer in the La$_3$Ni$_2$O$_7$ Thin Films

    cond-mat.supr-con 2025-11 conditional novelty 6.0 of 10

    In La3Ni2O7 thin films, the interlayer d3z2-r2 antiferromagnetic coupling is about 27% weaker than in bulk, in-plane coupling is nearly unchanged, and hole/electron doping is particle-hole asymmetric.

  6. Role of correlations in Ruddlesden-Popper bilayer nickelates under compressive strain

    cond-mat.str-el 2025-08 conditional novelty 6.0 of 10

    At -2% compressive strain, dynamic electron correlations make a dz2-derived flat band cross the Fermi level in bilayer La3Ni2O7, creating an extra Fermi pocket absent in static DFT+U; at -3% the pocket disappears.

  7. Pairing symmetry and superconductivity in La$_3$Ni$_2$O$_7$ thin films

    cond-mat.supr-con 2025-06 conditional novelty 6.0 of 10

    RMFT on the bilayer two-orbital t-J model predicts s±-wave pairing in La3Ni2O7 thin films, with a nodeless beta pocket and Tc near 60 K, plus an inter-orbital d-wave channel that reinforces the dominant pairing.

  8. Theoretical study on ambient pressure superconductivity in La$_3$Ni$_2$O$_7$ thin films : structural analysis, model construction, and robustness of $s\pm$-wave pairing

    cond-mat.supr-con 2025-06 unverdicted novelty 6.0 of 10

    s±-wave pairing remains robust in La3Ni2O7 thin-film models under FLEX, but reduced Tc is reproduced only when using the experimental structure's small interlayer hopping.

  9. Filling and Interlayer Superexchange Control Superconductivity in La$_3$Ni$_2$O$_7$

    cond-mat.supr-con 2026-03 unverdicted novelty 5.0 of 10

    The superconducting T_c of La3Ni2O7 is controlled by the d_x2-y2 orbital filling and the interlayer magnetic exchange J_perp, so clean electron doping should raise T_c.

  10. Compressive Strain Turns $s^{\pm}$ into $d$-Wave Pairing in One-unit-cell La$_3$Ni$_2$O$_7$ Thin Film Via Substrate-Induced Hole Doping

    cond-mat.supr-con 2025-12 conditional novelty 5.0 of 10

    Hole doping drives the pairing in strained 1-unit-cell La3Ni2O7 films from weak/nonexistent to a d_x2-y2 (then d_xy) wave, through intra-layer spin fluctuations within the γ pocket.

  11. Recent progress in nickelate superconductors

    cond-mat.supr-con 2025-09 conditional novelty 2.0 of 10

    A comprehensive review of nickelate superconductors that surveys the 112, 327, and 43(10) families and frames the key open questions about their pairing mechanisms.

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