Self-Doped Molecular Mott Insulator for Bilayer High-Temperature Superconducting La₃Ni₂O₇

Recent discovery of high-temperature superconductivity in bilayer nickelate La₃Ni₂O₇(LNO) has stimulated intensive research into its correlation and superconductivity. Since doping a Mott insulator is one central role for realizing a high-temperature superconductor, it’s crucial to establish the Mott limit of the bilayer system. In this work, we propose La₃Ni₂O₇ to be a self-doped Mott insulator, whose molecular Mott limit is formed by two nearly degenerate anti-symmetric d_x²-y² and d_z² orbitals. Partial occupation of the higher-energy symmetric d_x²-y² orbital leads to self-doping, which may be responsible for high-temperature superconductivity in La₃Ni₂O₇. The proposed scenario is further demonstrated by solving the local electronic states using exact diagonalization at realistic parameters. The superconducting pairing symmetry is also analyzed using renormalized mean filed theory.