Effects of non-magnetic impurities on spin-fluctuations induced superconductivity

TL;DR

This paper investigates how non-magnetic impurities influence the phase diagram of interacting electrons with a flat Fermi surface, revealing transitions from SDW to d-wave superconductivity and then to a random antiferromagnetic state as nesting worsens.

Contribution

It introduces a renormalization group approach to analyze impurity effects on phase transitions in a flat Fermi surface system, highlighting the impact on critical temperature and phase stability.

Findings

Critical temperature decreases with increasing impurity concentration.

Phase transitions from SDW to d-wave superconductivity to RAF occur with worsening nesting.

Impurity-induced pair breaking is most effective near maximal superconducting critical temperature.

Abstract

We study the effects of non-magnetic impurities on the phase diagram of a system of interacting electrons with a flat Fermi surface. The one-loop Wilsonian renormalization group flow of the angle dependent diffusion function $D(\theta_1,\theta_2,\theta_3)$ and interaction $U(\theta_1,\theta_2,\theta_3)$ determines the critical temperature and the nature of the low temperature state. As the imperfect nesting increases the critical temperature decreases and the low temperature phase changes from the spin-density wave (SDW) to the d-wave superconductivity (dSC) and finally, for bad nesting, to the random antiferromagnetic state (RAF). Both SDW and dSC phases are affected by disorder. The pair breaking depends on the imperfect nesting and is the most efficient when the critical temperature for superconductivity is maximal.