Disorder-Driven Topological Localization Transitions in Floquet Non-Hermitian Systems

Abstract Incorporating disorder, Floquet driving, or non-Hermiticity into topological physics—individually or pairwise—has unveiled a diverse set of novel topological phases beyond the conventional paradigm. However, their collective interplay in shaping topology constitutes a daunting, uncharted frontier. In this Letter, we explore, both theoretically and experimentally, topological localization transitions in disordered Floquet non-Hermitian systems. Implemented on a highly reconfigurable acoustic metamaterial platform, our study reveals two fundamental phenomena that expose the intertwined physical landscape forged by this tripartite synergy. First, we observe a disorder-driven, sequential line-gap topological transition as disorder grows, evidenced by a relocation of topological edge modes from the π-gap to 0-gap. Second, we uncover a concurrent skin-Anderson crossover governed by a point-gap topological transition, where the increased disorder dramatically suppresses the non-Hermitian skin effect through its interplay with Anderson localization. These findings establish disorder as a powerful, unified knob for controlling both line-gap and point-gap topology in Floquet non-Hermitian settings.