TOPOLOGICAL CHARACTERIZATION AND LOCALIZATION BEHAVIOR IN NON-HERMITIAN SYSTEM

Abstract

In this dissertation, we are motivated to study the topological characterization and localization behavior in non-Hermitian systems. In the first project, we investigate the topological characterization of the multiband non-Hermitian systems using Majorana’s stellar representation. In the second project, we study the competition between the localization power of the topological edge states and the non-Hermitian skin effect and realize the delocalization of the topological edge states. In the third project, by continuing the concept of delocalized topological modes, we explore its application on topological lasing, where the lasing output can be significantly enhanced. In the fourth project, we discover an exotic phenomenon where the direction of the non-Hermitian skin effect can be reversed by coupling two non-Hermitian chains with the same preferred direction of the non-Hermitian skin effect. The physics behind such a phenomenon is found to be a destructive interference between two coupled chains.