Enhancement of Second-Order Non-Hermitian Skin Effect by Magnetic Fields

TL;DR

This paper reveals that magnetic fields can enhance and induce the second-order non-Hermitian skin effect, contrasting with their suppressive effect on the first-order skin effect, and explores the topological origins of this phenomenon.

Contribution

It demonstrates that magnetic fields can robustly enhance and induce second-order skin effects in non-Hermitian systems, revealing new magnetic field behaviors and topological mechanisms.

Findings

Magnetic fields can enhance the second-order skin effect.

Magnetic fields can induce SOSE in trivial non-Hermitian systems.

Magnetic fields can transition systems from hybrid to pure SOSE.

Abstract

The non-Hermitian skin effect is a unique phenomenon in which an extensive number of eigenstates are localized at the boundaries of a non-Hermitian system. Recent studies show that the non-Hermitian skin effect is significantly suppressed by magnetic fields. In contrast, we demonstrate that the second-order skin effect (SOSE) is robust and can even be enhanced by magnetic fields. Remarkably, SOSE can also be induced by magnetic fields from a trivial non-Hermitian system that does not experience any skin effect at zero field. These properties are intimately related to to the persistence and emergence of topological line gaps in the complex energy spectrum in presence of magnetic fields. Moreover, we show that a magnetic field can drive a non-Hermitian system from a hybrid skin effect, where the first-order skin effect and SOSE coexist, to pure SOSE. Our results describe a qualitatively new magnetic field behavior of the non-Hermitian skin effect.