The role of spin-orbit coupling for the superconducting state in Sr_2RuO_4

TL;DR

This paper investigates how spin-orbit coupling influences the superconducting pairing states in Sr_2RuO_4, demonstrating that it favors a chiral p-wave state based on band structure considerations.

Contribution

It shows how spin-orbit coupling lifts degeneracy among triplet pairing states in Sr_2RuO_4, favoring a specific chiral pairing state.

Findings

Spin-orbit coupling lifts degeneracy of triplet pairing states.

Chiral pairing state d(k) = z(k_x +/- i k_y) is favored.

Band structure considerations support the stability of the chiral state.

Abstract

The odd-parity spin-triplet Cooper pairing states show a six-fold degeneracy for a quasi-two-dimensional electron system. In this article we show how spin-orbit coupling can lift this degeneracy for Sr_2RuO_4 taking the band structure based on the three relevant t_{2g}-orbitals of the Ru-ions into account. The stabilized state depends on the relative strength of the pairing interaction. We show that under reasonable assumptions the chiral pairing state d(k) = z(k_x +/- i k_y) is favored against the others.