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

Abstract

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