Percolation-induced PT symmetry breaking

TL;DR

This paper explores how percolation transitions influence PT symmetry breaking in non-Hermitian topological systems through a novel topologically guided gain mechanism, revealing new dynamical behaviors.

Contribution

It introduces a new mechanism of topologically guided gain and demonstrates how percolation transitions can induce PT symmetry breaking in non-Hermitian topological systems.

Findings

Percolation transitions drive the edge spectrum from real to complex.

Topologically guided gain causes irreversible growth in large topological islands.

Interlayer tunneling feedback leads to novel dynamical effects.

Abstract

We propose a new avenue in which percolation, which has been much associated with critical phase transitions, can also dictate the asymptotic dynamics of non-Hermitian systems by breaking PT symmetry. Central to it is our newly-designed mechanism of topologically guided gain, where chiral edge wavepackets in a topological system experience non-Hermitian gain or loss based on how they are topologically steered. For sufficiently wide topological islands, this leads to irreversible growth due to positive feedback from interlayer tunneling. As such, a percolation transition that merges small topological islands into larger ones also drives the edge spectrum across a real to complex transition. Our discovery showcases intriguing dynamical consequences from the triple interplay of chiral topology, directed gain and interlayer tunneling, and suggests new routes for the topology to be harnessed in the control of feedback systems.