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arXiv · 2307.10144

The s$^\pm$-Wave Pairing and the Destructive Role of Apical-Oxygen Deficiencies in La$_3$Ni$_2$O$_7$ Under Pressure

Yu-Bo Liu·Jia-Wei Mei·Fei Ye·Wei-Qiang Chen·Fan Yang
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Abstract

Recently, the bilayer perovskite nickelate La$_3$Ni$_2$O$_7$ has been reported to show evidence of high-temperature superconductivity (SC) under a moderate pressure of about 14 GPa. To investigate the superconducting mechanism, pairing symmetry, and the role of apical-oxygen deficiencies in this material, we perform a random-phase-approximation based study on a bilayer model consisting of the $d_{x^2-y^2}$ and $d_{3z^2-r^2}$ orbitals of Ni atoms in both the pristine crystal and the crystal with apical-oxygen deficiencies. Our analysis reveals an $s^{\pm}$-wave pairing symmetry driven by spin fluctuations. The crucial role of pressure lies in that it induces the emergence of the $γ$-pocket, which is involved in the strongest Fermi-surface nesting. We further found the emergence of local moments in the vicinity of apical-oxygen deficiencies, which significantly suppresses the $T_c$. Therefore, it is possible to significantly enhance the $T_c$ by eliminating oxygen deficiencies during the synthesis of the samples.

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Yu-Bo Liu, Jia-Wei Mei, Fei Ye, Wei-Qiang Chen, Fan Yang. 2023-11-03. The s$^\pm$-Wave Pairing and the Destructive Role of Apical-Oxygen Deficiencies in La$_3$Ni$_2$O$_7$ Under Pressure. https://doi.org/10.1103/physrevlett.131.236002

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