Engineering skin effect across a junction of Hermitian and non-Hermitian lattice

TL;DR

This paper investigates how connecting non-Hermitian and Hermitian lattices affects the localization of eigenstates, revealing boundary-condition-dependent phenomena like edge localization, mobility edges, and scale-invariant phases.

Contribution

It introduces a novel system combining Hermitian and non-Hermitian lattices, demonstrating boundary-dependent effects on localization and spectrum, including the emergence of mobility edges.

Findings

Localized states at the junction under OBC

Mobility edges separate localized and delocalized states

Scale-invariant localized phase under PBC

Abstract

We study a system where the two edges of a non-Hermitian lattice with asymmetric nearest-neighbor hopping are connected with two Hermitian lattices with symmetric nearest-neighbor hopping. In the absence of those Hermitian lattices, the majority of the eigenstates of the system will be localized at the edges, the phenomena known as the non-Hermitian skin effect. We show that once we connect it with the Hermitian lattices, for open boundary conditions (OBC), the localized states exist at the junction of the non-Hermitian and Hermitian lattice; moreover, the spectrum shows mobility edges that separate delocalized and localized states. On the contrary, mobility edges vanish for periodic boundary conditions (PBC), and the delocalized phase turns into a scale-invariant localized phase, where the localized states are still peaked at the junctions. We also find that if the connected Hermitian lattices are thermodynamically large, in OBC, most of the states become delocalized, while in PBC, the system still shows the scale-invariant localized phase.