摘要
The recent discovery of superconductivity in pressurized bilayer nickelate La_(3)Ni_(2)O_(7) has triggered tremendous research interest.However,the experimentally observed oxygen deficiency implies that obtaining perfect stoichiometric single crystals is still challenging.The influence of oxygen deficiency on physical properties remains unexplained.Here,we construct a chemical potential phase diagram to characterize the stability of La_(3)Ni_(2)O_(7).The narrow stable region explains the difficulty of synthesizing pure samples.First,oxygen defect studies reveal that the interlayer apical oxygen vacancy has the highest defect concentrations and is responsible for oxygen deficiency.Second,unfolding band structures show as the oxygen-deficient variant increases,Ni 3d_(z^(2)) bands shift toward a lower energy position under the Fermi level at Γ point,which is adverse to the metallization of Ni 3d_(z^(2)) bands.Third,high-pressure calculations indicate that oxygen vacancy would destroy the hybridization of interlayer Ni 3d_(z^(2)) orbitals,and the larger the oxygen deficiency,the higher the pressure needed to metalize the Ni 3d_(z^(2))bands.Thus,the oxygen deficiency would suppress the emergence of superconductivity in La_(3)Ni_(2)O_(7–δ).Our results elucidate the mechanism of oxygen deficiency for superconductivity in La_(3)Ni_(2)O_(7–δ) and provide instructive guidance to the experimental research.
基金
supported by the Key Research and Development Program of China(Grant No.2023YFA1406301)
the National Natural Science Foundation of China(Grant No.12274061)
the Sichuan Science and Technology Program(Grant No.2024ZYD0164)。
