Non-Hermitian Floquet invisibility

TL;DR

This paper demonstrates that non-Hermitian Floquet systems can achieve wave invisibility across a spectral band by manipulating complex site potentials and modulation frequencies, with potential applications in wave control.

Contribution

It introduces a method to realize Floquet invisibility in a non-Hermitian lattice through harmonic modulation of site potentials, extending the concept of wave cloaking.

Findings

Invisibility occurs within a spectral band limited by a spectral singularity.

Full-band invisibility is achieved when the singularity is at the Brillouin zone edge.

Invisibility persists with multiple oscillating impurities.

Abstract

Wave transport and scattering in open systems can be profoundly affected by non- Hermitian dynamics. In this work we consider wave scattering in a one-dimensional tight-binding lattice with a low-frequency harmonically-vibrating complex site potential. Floquet scattering is shown to be suppressed in a range of the spectral lattice band, which is limited by a singularity in the spectral transmission/reflection amplitudes for inelastic scattering channels. Invisibility over the entire spectral band is found when the singularity is pushed at the edge of the Brillouin zone, which requires a modulation frequency larger than the width of the tight-binding lattice band. Remarkably, invisibility is found to persist for multiple oscillating lattice impurities.