Perturbation theory analysis of the strain-dependent superconducting phase diagram for Sr$_2$RuO$_4$

TL;DR

This paper uses FLEX to analyze how strain affects the superconducting phase diagram of Sr$_2$RuO$_4$, supporting the idea that a $d_{x^2-y^2}$ singlet pairing state explains its superconducting behavior.

Contribution

It applies FLEX to model the strain-dependent phase diagram of Sr$_2$RuO$_4$, reproducing its key features and supporting the $d_{x^2-y^2}$ pairing hypothesis.

Findings

Reproduces the strain-dependent phase diagram of Sr$_2$RuO$_4$

Supports the $d_{x^2-y^2}$ singlet pairing as a key superconducting state

Aligns theoretical results with experimental observations

Abstract

Previously, it was shown that a superconducting state dominated by singlet $d_{x^2-y^2}$ intra-band pairs emerges from the fluctuation exchange approximation (FLEX) applied to a realistic model for Sr$_2$RuO$_4$, a result that is increasingly in alignment with experimental data. Here we apply FLEX to model the strain-dependent phase diagram of Sr$_2$RuO$_4$ and show that we are able to reproduce its unusual features. This adds weight to the argument that a predominantly $d_{x^2-y^2}$ singlet pairing state represents a reasonable starting point for describing the superconducting properties of Sr$_2$RuO$_4$.