Wave Delocalization from Clustering in Two-Dimensional Non-Hermitian Disordered Lattices

Abstract

Localization appears in a variety of phenomena in disordered systems, including a complete halt of electron transport, light localization in photonic structures, and sound localization in elastic networks. This universality stems from a fundamental wave-mechanical phenomenon: the interference between multiple scattering paths. Therefore, the common trend of localization, which is further enhanced by increasing the degree of disorder, is maintained in most wave systems. Here, the presence of delocalization behaviors induced by non-Hermitian disorder is demonstrated in two-dimensional systems, as opposed to the typical disorder-induced localization. A random checkerboard structure that consists of photonic amplifying and dissipating elements is examined as an order-to-disorder generalization of a parity-time-symmetric system. In this non-Hermitian disordered system, we show that the relationship between localization and disorder dramatically changes upon the control of contrast between material phases, even exhibiting a disorder-induced delocalization in the low-contrast regime. This counterintuitive phenomenon originates from the disorder-induced clustering of non-Hermitian material phases, which leads to the unbroken condition of parity-time symmetry. This finding will provide new insight into the multifaceted role of disorder extended by non-Hermitian physics.