Hopf Bifurcation of Nonlinear Non-Hermitian Skin Effect

TL;DR

This paper uncovers how nonlinearity induces a Hopf bifurcation in the non-Hermitian skin effect, leading to destabilization of skin states and emergence of delocalized states with complex dynamics.

Contribution

It introduces the concept of Hopf bifurcation in nonlinear non-Hermitian systems and demonstrates its effects on skin states and phase space dynamics.

Findings

Nonlinearity destabilizes skin states.

Hopf bifurcation leads to delocalized limit cycle states.

Critical skin effect occurs at bifurcation point.

Abstract

The non-Hermitian skin effect, nonreciprocity-induced anomalous localization of an extensive number of eigenstates, represents a hallmark of non-Hermitian topological systems with no analogs in Hermitian systems. Despite its significance across various open classical and quantum systems, the influence of nonlinearity has remained largely unclear. Here, we reveal the Hopf bifurcation of the nonlinear skin effect as a critical phenomenon unique to nonlinear non-Hermitian systems. We demonstrate that nonlinearity destabilizes skin states and instead gives rise to the emergence of delocalized states associated with limit cycles in phase space. We also uncover the algebraically localized critical skin effect precisely at the Hopf bifurcation point. We illustrate these behavior in a nonlinear extension of the Hatano-Nelson model in both continuum and lattice. Our work shows a significant role of nonlinearity in the skin effect and uncovers rich phenomena arising from the interplay between non-Hermiticity and nonlinearity.