Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors. arXiv submission processing window: times are unavailable (UTC).

1. Superconductivity in bilayer La$_3$Ni$_2$O$_7$: A review focusing on the strong-coupling Hund’s rule assisted pairing mechanism

Summary: The high-temperature superconductivity in bilayer La₃Ni₂O₇ originates from its unique two-orbital bilayer electronic structure, where the 3d_z² orbital is nearly half-filled and localized, generating strong interlayer antiferromagnetic exchange via the inner apical oxygen 2p_z orbital, while the 3d_x²-y² orbital is approximately quarter-filled and highly itinerant. Under strong coupling, Hund’s rule coupling aligns the spins of the two orbitals on the same nickel site, effectively transferring the interlayer antiferromagnetic exchange to the itinerant 3d_x²-y² orbital, forming an effective coupling J⊥. This mechanism can be simplified into a strong-coupling bilayer t-J-J⊥ model for the 3d_x²-y² band, where J⊥ drives electrons to form interlayer Cooper pairs, realizing extended s-wave pairing superconductivity with high critical temperature. Meanwhile, the strongly localized 3d_z² electrons tend to form interlayer ladder singlets; due to the lack of phase coherence, these singlets do not directly participate in the superconducting condensation but instead give rise to a pseudogap phase. This review systematically elaborates on this strong-coupling Hund’s rule assisted pairing theory, providing a unified framework for understanding the mechanism of high-temperature superconductivity in this system.