Pair correlations in the two-orbital t-J ladder model for the bilayer nickelates

The recent discovery of high-temperature superconductivity in the bilayer nickelates, e.g., La3Ni2O7 [1] calls for a theory of superconductivity, where the central focus of the pairing mechanism is the elucidation of the roles of two eg (dx^2-y^2 and dz^2) orbitals in the strongly correlated bilayer. To address this issue, we investigate the superconducting pair correlations in a two-orbital t-J ladder model for La3Ni2O7 by employing the density matrix renormalization group (DMRG) method [2]. Our calculations demonstrate that interchain-intraorbital pair correlations exhibit slow power-law decays, comparable to quasi-long-range superconducting order, and this tendency is further encouraged by Hund's coupling. In addition, we find the growth of interorbital (between dx^2-y^2 and dz^2) pair correlations even in the absence of apparent pairing glues. Our findings suggest a perspective on the cooperative contribution of hybridized two orbitals to superconductivity in the bilayer nickelates.

[1] H. Sun et al., Nature 621, 493 (2023) [2] M. Kakoi et al., Phys. Rev. B 109, L201124 (2024)