Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity

TL;DR

This paper investigates the low temperature electronic properties of Sr_2RuO_4, revealing its orbital-singlet spin-triplet superconducting state with specific anisotropic and fluctuation characteristics, consistent with experimental observations.

Contribution

It introduces a theoretical model predicting an orbital-singlet spin-triplet superconducting order parameter with specific anisotropy and fluctuation features in Sr_2RuO_4.

Findings

Superconducting order parameter is orbital-singlet spin-triplet.

Spatial anisotropy of the order parameter is 7%.

Temperature dependencies match experimental data.

Abstract

The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx} orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized description of the in-plane electron correlations the superconducting order parameter is found to be a orbital-singlet spin-triplet with two spatial components. The spatial anisotropy is 7%. The different components of the order parameter give rise to two-dimensional gapless fluctuations. The phase transition is of third order. The temperature dependence of the pair density, specific heat, NQR, Knight shift, and susceptibility are in agreement with experimental results.