Skin-effect localization and maximal-order exceptional points in reciprocal Floquet lattices
摘要
In systems exhibiting the non-Hermitian skin effect (NHSE), higher-order exceptional points (EPs) exhibit unique characteristics making them invaluable for enhanced lasing and sensing operations. When these critical degeneracies reach a maximal order, equal to the system size N, they induce a collapse of the spectrum, not only into a singular eigenstate but also a singular point in physical space. To date, NHSE EPs of maximal order have been predicted in nonreciprocal systems, such as the Hatano-Nelson lattice, where this collapse occurs in the limit of infinite anisotropy. Challenging this perspective, we demonstrate that reciprocal Floquet systems are capable of exhibiting skin localization of arbitrary strength—ranging from mild localization, to the extreme regime of maximal-order exceptional points. By employing