Electronic structure and disorder effect of La₃Ni₂O₇ superconductor

Determining the electronic structure of La₃Ni₂O₇ is an essential step towards uncovering its superconducting mechanism. It is widely believed that the bilayer apical oxygens play an important role in the bilayer La₃Ni₂O₇ electronic structure. Applying the hybrid exchange–correlation functionals, we obtain a more accurate electronic structure of La₃Ni₂O₇ at its high-pressure phase, where the bonding d_z² band is below the Fermi level owing to the apical oxygen. The symmetry properties of this electronic structure and its corresponding tight-binding model are further analyzed. We find that the antisymmetric part is highly entangled, leading to a minimal nearly degenerate two-orbital model. Then, the apical oxygen vacancies effect is studied using the dynamical cluster approximation. This disorder effect strongly destroys the antisymmetric β Fermi surface, leading to the possible disappearance of superconductivity.