Magnetic Control of the Non-Hermitian Skin Effect in Two-Dimensional Lattices

TL;DR

This paper develops a theoretical framework to understand how magnetic and synthetic gauge fields influence the non-Hermitian skin effect in two-dimensional lattices, revealing suppression mechanisms and the fragility of the effect.

Contribution

It introduces a non-Hermitian extension of the Harper--Hofstadter model to analyze magnetic control of the NHSE, highlighting distinct physical mechanisms for suppression.

Findings

Magnetic fields suppress the geometric skin effect in reciprocal models.

Skin localization can persist in nonreciprocal systems despite magnetic fields.

The geometry-dependent skin effect is fragile against weak magnetic fields.

Abstract

The non-Hermitian skin effect (NHSE) -- the anomalous boundary accumulation of an extensive number of bulk modes -- has emerged as a hallmark of non-Hermitian physics, with broad implications for transport, sensing, and topological classification. A central open question is how magnetic or synthetic gauge fields influence this boundary phenomenon. Here, we develop a theoretical framework for magnetic control of the NHSE along line boundaries in two-dimensional single-band lattices. Using a non-Hermitian extension of the anisotropic Harper--Hofstadter model as a representative example, we show that magnetic fields suppress the geometric skin effect in reciprocal models, whereas skin localization can persist in nonreciprocal systems. The analysis disentangles the interplay of flux, nonreciprocity, and boundary geometry, revealing that magnetic fields mitigate or suppress the NHSE through distinct physical mechanisms -- such as bulk localization via Landau or Anderson physics, or the restoration of effective reciprocity. In particular, the geometry-dependent skin effect in reciprocal systems is found to be fragile against even weak magnetic fields.