Non-Hermitian chiral anomalies

TL;DR

This paper investigates the existence and nature of chiral anomalies in non-Hermitian systems, revealing novel anomalous conservation laws that differ from Hermitian systems, with implications for experimental realizations.

Contribution

It provides a unified framework to calculate anomalous responses in non-Hermitian systems, uncovering new anomalous terms in chiral currents not present in Hermitian counterparts.

Findings

Non-Hermitian systems exhibit unique anomalous conservation laws.

Derived novel anomalous terms in chiral currents.

Results applicable to experimental systems with non-Hermitian Hamiltonians.

Abstract

The chiral anomaly underlies a broad number of phenomena, from enhanced electronic transport in topological metals to anomalous currents in the quark-gluon plasma. The discovery of topological states of matter in non-Hermitian systems -- effective descriptions of dissipative systems -- raises the question of whether there are anomalous conservation laws that remain unaccounted for. To answer this question, we consider both $1+1$ and $3+1$ dimensions, presenting a unified formulation to calculate anomalous responses in Hermitianized, anti-Hermitianized and non-Hermitian systems of massless electrons with complex Fermi velocities coupled to non-Hermitian gauge fields. Our results indicate that the quantum conservation laws of chiral currents of non-Hermitian systems are not related to those in Hermitianized and anti-Hermitianized systems, as would be expected classically, due to novel anomalous terms that we derive. These may have implications for a broad class of emerging experimental systems that realize non-Hermitian Hamiltonians.