Spin triplet superconductivity in Sr2RuO4

TL;DR

This paper investigates the superconducting state of Sr2RuO4 using a three-band model, revealing a complex order parameter with nodal structures that align well with experimental observations, advancing understanding of triplet superconductivity.

Contribution

It introduces a detailed three-dimensional three-band model to describe the superconducting order parameter in Sr2RuO4, explaining experimental data and analyzing stability against disorder.

Findings

Identified a complex order parameter with line or point nodes on specific Fermi surface sheets.

The model's predictions match experimental measurements of specific heat, penetration depth, and thermal conductivity.

Analyzed the stability of the superconducting state under disorder and varying interactions.

Abstract

Sr2RuO4 is at present the best candidate for being a superconducting analogue of the triplet superfluidity in ^3He. This material is a good (albeit correlated) Fermi liquid in the normal state and an exotic superconductor below Tc. The mechanism of superconductivity and symmetry of the order parameter are the main puzzling issues of on-going research. Here we present the results of our search for a viable description of the superconducting state realised in this material. Our calculations are based on a three-dimensional effective three-band model with a realistic band structure. We have found a state with non-zero order parameter on each of the three sheets of the Fermi surface. The corresponding gap in the quasi-particle spectrum has line or point nodes on the alpha and beta sheets and is complex with no nodes on the gamma sheet. This state describes remarkably well a number of existing experiments including power low temperature dependence of the specific heat, penetration depth, thermal conductivity etc. The stability of the state with respect to disorder and different interaction parameters are also analyzed briefly.