Competition between d-wave superconductivity and magnetism in uniaxially strained Sr2RuO4

TL;DR

This study uses functional renormalization group methods on a realistic model of Sr2RuO4 to analyze how uniaxial strain influences its superconducting and magnetic properties, revealing a dominant d-wave pairing and strain-enhanced critical temperature.

Contribution

It provides the first detailed theoretical analysis of strain effects on Sr2RuO4's superconductivity using a realistic model with spin-orbit coupling and density functional theory inputs.

Findings

Dominant d_{x^2-y^2} superconducting state identified

Critical temperature increases under uniaxial strain

Competition between superconductivity and spin-density wave explored

Abstract

The pairing symmetry of Sr$_2$RuO$_4$ is a long-standing fundamental question in the physics of superconducting materials with strong electronic correlations. We use the functional renormalization group to investigate the behavior of superconductivity under uniaxial strain in a two-dimensional realistic model of Sr$_2$RuO$_4$ obtained with density functional theory and incorporating the effect of spin-orbit coupling. We find a dominant $d_{x^2-y^2}$ superconductor mostly hosted by the $d_{xy}$-orbital, with no other closely competing superconducting state. Within this framework we reproduce the experimentally observed enhancement of the critical temperature under strain and propose a simple mechanism driven by the density of states to explain our findings. We also investigate the competition between superconductivity and spin-density wave ordering as a function of interaction strength. By comparing theory and experiment, we discuss constraints on a possible degenerate partner of the $d_{x^2-y^2}$ superconducting state.