Scaling laws for non-Hermitian skin effect with long-range couplings

TL;DR

This paper explores how long-range couplings in non-Hermitian systems influence the non-Hermitian skin effect and quantum entanglement, revealing a transition from scale-free to localized states and subextensive entanglement scaling.

Contribution

It demonstrates that long-range couplings fundamentally alter NHSE behavior and entanglement scaling, providing new insights into non-Hermitian physics with nonlocal interactions.

Findings

Long-range couplings induce scale-free skin modes at $ ext{alpha}=0$.

Increasing $ ext{alpha}$ causes a spectral transition and localization crossover.

Entanglement entropy scales subextensively due to nonlocality and complex spectrum.

Abstract

Recent years have witnessed a surge of research on the non-Hermitian skin effect (NHSE) in one-dimensional lattices with finite-range couplings. In this work, we show that the long-range couplings that decay as $1/l^{\alpha}$ at distance $l$ can fundamentally modify the behavior of NHSE and the scaling of quantum entanglement in the presence of nonreciprocity. At $\alpha=0$, the nonlocality of couplings gives rise to the scale-free skin modes, whose localization length is proportional to the system size. Increasing the exponent $\alpha$ drives a complex-to-real spectral transition and a crossover from a scale-free to constant localization length. Furthermore, the scaling of nonequilibrium steady-state entanglement entropy exhibits a subextensive law due to the nonlocality and the complex spectrum, in contrast to an area law arising from NHSE. Our results provide a theoretical understanding on the interplay between long-range couplings and non-Hermiticity.