# Disorder-induced exceptional points and nodal lines in Dirac superconductors

## TL;DR

This paper investigates how disorder affects quasiparticle spectra in Dirac superconductors, revealing the emergence of non-Hermitian features like Fermi arcs and exceptional lines, which depend on system dimensionality.

## Contribution

It introduces the concept of disorder-induced non-Hermitian phenomena in Dirac superconductors, showing the formation of Fermi arcs and exceptional lines in different dimensions.

## Key findings

- Disorder transforms nodes into Fermi arcs or areas bounded by exceptional points or lines.
- In 2D, a Fermi arc bounded by exceptional points can be realized.
- In 3D, supercurrents and disorder create Fermi surfaces bounded by exceptional lines.

## Abstract

We consider the effect of disorder on the spectrum of quasiparticles in the point-node and nodal-line superconductors. Due to the anisotropic dispersion of quasiparticles disorder scattering may render the Hamiltonian describing these excitations non-Hermitian. Depending on the dimensionality of the system, we show that the nodes in the spectrum are replaced by Fermi arcs or Fermi areas bounded by exceptional points or exceptional lines, respectively. These features are illustrated by first considering a model of a proximity-induced superconductor in an anisotropic two-dimensional (2D) Dirac semimetal, where a Fermi arc in the gap bounded by exceptional points can be realized. We next show that the interplay between disorder and supercurrents can give rise to a 2D Fermi surface bounded by exceptional lines in three-dimensional (3D) nodal superconductors.