Superconductivity in Sr$_2$RuO$_4$ Mediated by Coulomb Scattering

TL;DR

This paper explores a new mechanism for spin-triplet superconductivity in Sr$_2$RuO$_4$, emphasizing Coulomb interactions and band hybridization effects within a three-band Hubbard model.

Contribution

It introduces a model where intersite Coulomb interactions promote spin-triplet pairing, enhanced by band hybridization, and demonstrates its stability over spin-singlet states.

Findings

Spin-triplet pairing is more stable than spin-singlet for realistic parameters.

The superconducting state features horizontal line nodes on the Fermi surface.

Coulomb interactions and band hybridization are key to the pairing mechanism.

Abstract

We investigate the superconductivity in Sr$_2$RuO$_4$ on the basis of the three-dimensional three-band Hubbard model. We propose a model with Coulomb interactions among the electrons on the nearest-neighbor Ru sites. In our model the intersite Coulomb repulsion and exchange coupling can work as the effective interaction for the spin-triplet paring. This effective interaction is enhanced by the band hybridization, which is mediated by the interlayer transfers. We investigate the possibility of this mechanism in the ground state and find that the orbital dependent spin-triplet superconductivity is more stable than the spin-singlet one for realistic parameters. This spin-triplet superconducting state has horizontal line nodes on the Fermi surface.