The Effect of Carrier Doping and Thickness on the Electronic Structures of La₃Ni₂O₇ Thin Films

The discovery of high-temperature superconductivity in bilayer nickelate La_3Ni_2O_7 under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure. Recently, the realization of superconductivity in compressively strained La_3Ni_2O_7 thin films grown on the SrLaAlO_4 substrates, with a T_\rm c exceeding 40 K, represents a significant step toward this goal. Here, we investigate the influence of film thickness and carrier doping on the electronic structure of La_3Ni_2O_7 thin films, ranging from 0.5 to 3 unit cells, using first-principles calculations. For a 2 unit-cell film with an optimal doping concentration of 0.3 hole per formula unit (0.15 hole/Ni), the Ni-d_z^2 interlayer bonding state crosses the Fermi level, resulting in the formation of \gamma pockets at the Fermi surface. These findings align with angle-resolved photoemission spectroscopy experimental data. Our results provide theoretical validation for the recent experimental discovery of ambient-pressure superconductivity in La_3Ni_2O_7 thin films and underscore the significant impact of film thickness and carrier doping on electronic property modulation.