The fate of Wannier-Stark localization and skin effect in periodically driven non-Hermitian quasiperiodic lattices

TL;DR

This paper explores how periodic driving influences localization and skin effects in non-Hermitian quasiperiodic lattices, revealing new phases, mobility edges, and multifractal skin states driven by time-dependent electric fields.

Contribution

It demonstrates the emergence of novel non-trivial phases and multifractal skin states due to periodic driving in non-Hermitian quasiperiodic systems, extending understanding beyond static cases.

Findings

Periodic drive induces new phases with mobility edges.

Electric field driving can restore skin effects under open boundary conditions.

Skin states become multifractal under periodic driving.

Abstract

The eigenstates of one-dimensional Hermitian and non-Hermitian tight-binding systems (in the presence/absence of quasiperiodic potential) and an external electric field undergo complete localization with equally spaced eigenenergies, known as the Wannier-Stark (WS) localization. In this work, we demonstrate that when the electric field is slowly modulated with time, new non-trivial phases with multiple mobility edges emerge in place of WS localized phase, which persists up to a certain strength of the non-Hermiticity. On the other hand, for a large driving frequency, we retrieve the usual sharp delocalization-localization transition to the usual (no WS) localized phase, similar to the static non-Hermitian Aubry-Andr\'e-Harper type without any electric field. This vanishing of WS localization can be attributed solely to the time-periodic drive and occurs irrespective of the non-Hermiticity. Interestingly, under the open boundary condition (OBC), we find that contrary to the undriven systems where an external electric field destroys the SE completely, the SE appears in certain regime of the parameter space when the electric field is temporally driven. This appearance of SE is closely related to the absence of extended unitarity. In addition, in the presence of the drive, the skin states are found to be multifractal, contrary to its usual nature in such non-Hermitian systems. An in-depth understanding about the behavior of the states in the driven system is established from the long-time dynamics of an initial excitation.