Kondo effect in a parity-time-symmetric non-Hermitian Hamiltonian

TL;DR

This paper explores how non-Hermitian, parity-time symmetric effects influence the Kondo effect in quantum impurity systems, revealing a critical coupling threshold and phases with suppressed conductance.

Contribution

It introduces a generalized non-Hermitian Anderson model with PT symmetry and analyzes the persistence and suppression of the Kondo effect using renormalization group methods.

Findings

Kondo effect persists below a critical non-Hermitian coupling.

Spontaneous PT symmetry breaking suppresses the Kondo effect.

Low-energy behavior varies with PT symmetry phase.

Abstract

The combination of non-Hermitian physics and strong correlations can give rise to new effects in open quantum many-body systems with balanced gain and loss. We propose a generalized Anderson impurity model that includes non-Hermitian hopping terms between an embedded quantum dot and two wires. These non-Hermitian hopping terms respect a parity-time ($\mathcal{PT}$) symmetry. In the regime of a singly occupied localized state, we map the problem to a $\mathcal{PT}$-symmetric Kondo model and study the effects of the interactions using a perturbative renormalization group approach. We find that the Kondo effect persists if the couplings are below a critical value that corresponds to an exceptional point of the non-Hermitian Kondo interaction. On the other hand, in the regime of spontaneously broken $\mathcal{PT}$ symmetry, the Kondo effect is suppressed and the low-energy properties are governed by a local-moment fixed point with vanishing conductance.