Recently, the bilayer perovskite nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ has been reported to exhibit high-temperature superconductivity near 80 K under a moderate pressure of about 14 GPa. To investigate the underlying pairing mechanism and symmetry in this complex system, we propose and analyze a mixed spin-1 and spin-$\frac{1}{2}$ bilayer $t\text{−}J$ model in the strong-coupling regime. This model explicitly incorporates the crucial role of strong Hund's coupling, which favors the formation of local spin-triplet states from the two on-site $E_g$ orbital electrons at half-filling. We further investigate the model using both slave-particle mean-field theory and the density matrix renormalization-group method. Our simulation results reveal that the dominant pairing channel is the interlayer one in the $3d_{x^2-y^2}$ orbital. Hund's coupling is shown to enhance superconductivity within a reasonable physical range. Moreover, electron doping strengthens superconductivity by increasing carrier density; in contrast, hole doping weakens superconductivity. These findings offer critical insights into the unconventional superconductivity of pressurized ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ and underline the important role of orbital-selective behavior and Hund's rule.

Close

PrevNext

View figure in article

• Pairing mechanisms
• Superconductivity
• High-temperature superconductors
• Unconventional superconductors
• Density matrix renormalization group
• Mean field theory
• Slave bosons
• t-J model