Non-Hermitian Chiral Edge Modes With Complex Fermi Velocity

TL;DR

This paper investigates non-Hermitian chiral edge modes with complex Fermi velocities, revealing their unique spectral properties and localization behaviors, which could influence future studies on topological materials and non-equilibrium transport phenomena.

Contribution

It introduces a novel non-Hermitian skin effect induced by local dissipation in chiral edge modes with complex Fermi velocities, expanding understanding of NH topological systems.

Findings

Complex spectra form straight lines in topological materials.

Chirality separates modes with positive and negative energies.

Localized modes differ at boundaries of 2D topological systems.

Abstract

Recently, much attention has been paid to uncovering the influence of dissipation on a quantum system, particularly on how the non-Hermitian (NH) terms modify the band topology of topological materials and reshape the profile of the wavefunctions of a system (or the NH skin effect). In this paper, a specific NH skin effect that induced by local dissipation is studied for chiral edge modes, in which the NH term corresponds to the local imaginary Fermi velocity of the chiral edge modes. By solving the NH Schr\"{o}dinger equation of the non-Hermitian chiral edge modes (nhCEs) with complex Fermi velocity, we uncovered the remarkable complex spectra and the wavefunctions of the nhCEs. We find that the complex spectra of these modes is a straight line in the topological materials, and its chirality can separates the modes with positive energy from those with negative energy, in which they are localized at different positions. We also studied the nhCEs at the boundary of 2-dimensional (2D) topological materials, the 2D $p$-wave superconductor and the Qi-Wu-Zhang model, in which the general law of nhCEs was verified. We expect that our findings will pave the way for researching the transport properties of the chiral edge modes in the non-equilibrium context.