Superconductivity of bilayer two-orbital Hubbard model for La$_{3}$Ni$_{2}$O$_{7}$ under high pressure

TL;DR

This study combines DFT and DMRG to explore how pressure affects superconductivity in La$_{3}$Ni$_{2}$O$_{7}$, revealing a transition from superconducting to Luttinger liquid states as pressure increases.

Contribution

It provides a detailed quantum phase diagram of a bilayer two-orbital Hubbard model under pressure, linking theoretical predictions with experimental observations of pressure-dependent superconductivity.

Findings

Superconductivity weakens with increasing pressure.

Transition from superconducting to Luttinger liquid state above 80 GPa.

Interaction-to-hopping ratio influences superconductivity weakening.

Abstract

By combining density functional theory (DFT) and density matrix renormalization group calculations, we investigate the unusual pressure dependence of superconducting transition temperature ($T_c$) in the nickelate superconductor La$_{3}$Ni$_{2}$O$_{7}$. Using the hopping integrals and on-site potentials obtained by fitting the DFT band structures, we map a quantum phase diagram of a bilayer two-orbital Hubbard model with increasing pressure in a ladder geometry, which has an intermediate Hubbard repulsion and a Hund's coupling. Near $3/8$ filling, we find a strong spin density wave order, which at $3/8$ filling shows a real-space spin pattern similar to the spin-charge stripe order along a lattice direction. At $21/64$ filling, we find a superconducting phase with interlayer superconductivity (SC) in both the $d_{z^2}$ and $d_{x^2-y^2}$ orbitals, as well as in-plane SC in the $d_{z^2}$ orbital. Intriguingly, the SC is weakened with increasing pressure and transits to a Luttinger liquid above $80$ GPa, which qualitatively agrees with the experimental observations of decreasing $T_c$ with increasing pressure and a transition to Fermi liquid above $80$ GPa in La$_{3}$Ni$_{2}$O$_{7}$. Through a comparative study, we further show that the ratio of interaction to hopping integral, which reduces moderately with increasing pressure, may play a dominant role in the weakening of SC. Our results of this experimentally relevant model not only find a robust SC through suppressing the competing spin density wave order, but also give new insight into the unusual pressure dependence of SC in La$_{3}$Ni$_{2}$O$_{7}$.