Manipulating Spectral Windings and Skin Modes through Nonconservative Couplings

TL;DR

This paper reveals how nonconservative couplings can induce and control the non-Hermitian skin effect and spectral windings, enabling new ways to manipulate wave localization and nonreciprocal energy flow in non-Hermitian systems.

Contribution

It introduces a method to manipulate spectral windings and skin modes via nonconservative couplings, expanding understanding of non-Hermitian topological effects.

Findings

Different spectral windings can be achieved, including identical, opposite, and twisted.

Unipolar and bipolar non-Hermitian skin effects are observed with distinct eigenmode localizations.

Spectral phases are linked to nonreciprocal transmission properties.

Abstract

The discovery of the non-Hermitian skin effect (NHSE) has revolutionized our understanding of wave propagation in non-Hermitian systems, highlighting unexpected localization effects beyond conventional theories. Here, we discover that NHSE, accompanied by multitype spectral phases, can be induced by manipulating nonconservative couplings. By characterizing the spectra through the windings of the energy bands, we demonstrate that band structures with identical, opposite, and even twisted windings can be achieved. These inequivalent types of spectra originate from the multichannel interference resulting from the interplay between conservative and nonconservative couplings. Associated with the multitype spectra, unipolar and bipolar NHSE with different eigenmode localizations can be observed. Additionally, our findings link the nonreciprocal transmission properties of the system to multiple spectral phases, indicating a connection with the skin modes. This paper paves new pathways for investigating non-Hermitian topological effects and manipulating nonreciprocal energy flow.