Exceptional point induced lasing dynamics in a non-Hermitian system

TL;DR

This paper demonstrates that a finite non-Hermitian SSH model at an exceptional point can serve as a laser medium, producing stationary emission throughout the system, revealing new lasing dynamics distinct from spectral singularity mechanisms.

Contribution

It introduces a novel laser mechanism in finite non-Hermitian systems at exceptional points, expanding understanding of non-Hermitian lasing beyond spectral singularities.

Findings

Finite non-Hermitian SSH system acts as an active laser medium at threshold.

Stationary particle emission can occur anywhere in the system.

Interference effects between wave packets lead to unique phenomena.

Abstract

Non-Hermitian systems exhibit many peculiar dynamic behaviors which never showed up in Hermitian systems. The existence of spectral singularity (SS) for a non-Hermitian scattering center provides a lasing mechanism in the context of quantum mechanics. In this paper we show exactly that a finite system at exceptional point (EP) can also provide an alternative laser solution. We investigate the dynamics of non-Hermitian Su-Schrieffer-Heeger (SSH) model around EP, based on the analysis of parity-time (PT ) and chiral-time (CT ) symmetries of the Hamiltonian. In contrast to the SS lasing mechanism for an infinite system, such an SSH chain acts as an active laser medium at threshold, within which a stationary particle emission can be fired anywhere, rather than a specific location at the non-Hermitian scattering center only. In addition, some relevant peculiar phenomena arising from interference between wave packets are revealed based on the analytical solutions.