Using Disorder to Identify Bogoliubov Fermi-Surface States

TL;DR

This paper proposes that the presence of a Bogoliubov Fermi-surface in superconductors can be identified by how physical properties depend on disorder, notably through a linear residual density of states, aiding experimental detection.

Contribution

It introduces a disorder-based criterion to identify Bogoliubov Fermi-surface states in superconductors, supported by theoretical analysis of their stability and optical properties.

Findings

Residual density of states varies linearly with disorder in BG-FS

Supercurrent remains stable against impurities in BG-FS

Optical conductivity shows Drude-like behavior in BG-FS

Abstract

We argue that a superconducting state with a Fermi-surface of Bogoliubov quasiparticles, a Bogoliubov Fermi-surface (BG-FS), can be identified by the dependence of physical quantities on disorder. In particular, we show that a linear dependence of the residual density of states at weak disorder distinguishes a BG-FS state from other nodal superconducting states. We further demonstrate the stability of supercurrent against impurities and a characteristic Drude-like behavior of the optical conductivity. Our results can be directly applied to electron irradiation experiments on candidate materials of BG-FSs, including Sr$_2$RuO$_4$, FeSe$_{1-x}$S$_x$, and UBe$_{13}$.