Breakdown of the Meissner effect at the zero exceptional point in non-Hermitian two-band BCS model

TL;DR

This paper investigates how the Meissner effect in a non-Hermitian two-band BCS model breaks down at the exceptional point, revealing novel symmetry-breaking phenomena in complex superconducting systems.

Contribution

It derives a complex Ginzburg-Landau model from a non-Hermitian BCS model and analyzes the breakdown of the Meissner effect at the exceptional point.

Findings

Meissner effect breaks down at the exceptional point

Gap parameters remain finite at the breakdown

Analogous to the Higgs mechanism in complex field theory

Abstract

The spontaneous symmetry breaking of a continuous symmetry in complex field theory at the exceptional point of the parameter space is known to exhibit interesting phenomena, such as the breakdown of a Higgs mechanism. In this work, we derive the complex Ginzburg-Landau model from a non-Hermitian two-band BCS model via path integral and investigate its spontaneous symmetry breaking. We find that analog to the Higgs mechanism, the Meissner effect of the complex Ginzburg-Landau model also breaks down at the exceptional point while the gap parameters stay finite.