Edge-controlled non-Hermitian skin effect in the modified Haldane model

TL;DR

This paper explores how edge-specific gain and loss in a modified Haldane model induce and control non-Hermitian skin effects, revealing a nonlocal antichiral skin effect and the role of $ ext{PT}$ symmetry.

Contribution

It introduces a novel edge-controlled mechanism for inducing and manipulating non-Hermitian skin effects in antichiral topological systems.

Findings

Edge gain/loss induces skin effects in antichiral systems.

Nonlocal skin effect occurs in narrow ribbons with asymmetric edge dissipation.

Bulk skin modes depend on $ ext{PT}$ symmetry breaking.

Abstract

The hybrid skin-topological effect (HSTE) arises from the interplay between the non-Hermitian skin modes and topologically protected edge states. Here, we investigate the HSTE associated with antichiral edge states in a modified Haldane nanoribbon with gain and loss applied exclusively at the zigzag edges. We show that in antichiral systems, the HSTE originates from an imbalance of effective gain and loss between edge states and counter-propagating bulk modes, revealing a mechanism distinct from that in conventional chiral systems. Remarkably, in sufficiently narrow ribbons, gain or loss applied to only one edge induces a skin effect in the states localized at the opposite edge, demonstrating a non-Hermitian nonlocal antichiral skin effect. We further show that edge-localized dissipation can induce bulk skin modes only when $\mathcal{PT}$ symmetry is broken, while the bulk non-Hermitian skin effect is strictly forbidden in the $\mathcal{PT}$-symmetric regime. By tuning the gain and loss applied solely at the edges, both the emergence and localization direction of bulk skin modes can be controlled. Our results establish a symmetry-based mechanism for controlling non-Hermitian skin effects via edge dissipation in antichiral systems.