Observation of the Exceptional Skin Effect on a Non-Hermitian Flat band
Abstract
Flat band and non-Hermitian are both significant conceptions in modern physics. In this study, we delve into the behaviours of flat bands in non-Hermitian systems, focusing on the interplay between the flat band and its dispersive counterparts, investigating the exceptional points (EPs) formed by them together, and the non-Hermitian skin effect (NHSE) on the flat band correspondingly generated, which we name as the exceptional skin effect (ESE). Employing non-Hermitian flat band under chiral/sublattice symmetry, where energy remains highly degenerate, we explore their unique properties. Unlike traditional NHSE which requires the enclosing of a non-zero area in the Bloch complex energy spectrum, the ESE on flat band can be generated with a Bloch complex energy spectrum consisting of one single point, i.e. enclosing no area. By analytically tuning non-Hermitian parameters, changes in the complex energy spectrum and Riemann surfaces are observed, revealing the formation of EPs through the hybridization of flat and dispersive bands while maintaining the dimension of the Hilbert subspace. Additionally, the wave functions of flat band exhibit ESE in specific parameter regions, contrary to the existing frameworks. Experimental validation is conducted using an elastic wave system with actively modulated non-Hermitian parameters, showcasing the impact on flat-band states and confirming the formation of ESE due to flat band-dispersive bands hybridization and correspondingly formed EPs. These results offer novel insights into non-Hermitian physics and present potential directions for further researches and applications in this field.
Keywords
Cite
@article{arxiv.2412.19034,
title = {Observation of the Exceptional Skin Effect on a Non-Hermitian Flat band},
author = {Dongyi Wang and Ruoyang Zhang and Chinghua Lee and Kun Ding and Guancong Ma},
journal= {arXiv preprint arXiv:2412.19034},
year = {2025}
}
Comments
There's an error in Fig.1 (d), (g), (h) where the Es employed in the analytical calculations is 10 while the real Es in experiment is 10.6. Also, the authors did not reach a consensus on the official release of the manuscript. All the authors demand the withdrawal of the paper