Self-sustained emission in semi-infinite non-Hermitian systems at the exceptional point

TL;DR

This paper investigates semi-infinite non-Hermitian systems at the exceptional point, revealing universal persistent emission and reflectionless absorption phenomena independent of symmetry, through analysis of a finite cluster coupled to a lead.

Contribution

It demonstrates that such systems can have a full real spectrum and exhibit universal dynamical behaviors without symmetry constraints.

Findings

Full real spectrum achieved without symmetry requirements

Unidirectional plane wave at the exceptional point

Persistent emission and reflectionless absorption observed

Abstract

Complex potential and non-Hermitian hopping amplitude are building blocks of a non-Hermitian quantum network. Appropriate configuration, such as PT-symmetric distribution, can lead to the full real spectrum. To investigate the underlying mechanism of this phenomenon, we study the phase diagram of a semi-infinite non-Hermitian system. It consists of a finite non-Hermitian cluster and a semi-infinite lead. Based on the analysis of the solution of the concrete systems, it is shown that it can have the full real spectrum without any requirements on the symmetry and the wave function within the lead becomes a unidirectional plane wave at the exceptional point. This universal dynamical behavior is demonstrated as the persistent emission and reflectionless absorption of wave packets in the typical non-Hermitian systems containing the complex on-site potential and non-Hermitian hopping amplitude.