标题： 高压La$_3$Ni$_2$O$_7$中配对机制的强耦合极限研究 显示英文标题

标题： A Strong-Coupling-Limit Study on the Pairing Mechanism in the Pressurized La$_3$Ni$_2$O$_7$

摘要： 近日，报道了双层钙钛矿镍酸镧 La$_3$Ni$_2$O$_7$在约$14$GPa 的适度压力下，在接近$80$K 的高温下表现出超导性。 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 $t$-$J$ 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 onsite $E_g$ 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 dominate pairing channel is the interlayer one in the $3d_{x^2-y^2}$ orbital. The 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. 这些发现为加压下 La$_3$Ni$_2$O$_7$的非常规超导性提供了重要的见解，并强调了轨道选择性和洪德规则的重要作用。 显示英文摘要

摘要： Recently, the bilayer perovskite nickelate La$_3$Ni$_2$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 $t$-$J$ 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 onsite $E_g$ 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 dominate pairing channel is the interlayer one in the $3d_{x^2-y^2}$ orbital. The 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 La$_3$Ni$_2$O$_7$ and underline the important role of orbital-selective behavior and Hund's rule.