Anderson Delocalization in Strongly Coupled Disordered Non-Hermitian Chains

TL;DR

This paper demonstrates that in strongly coupled disordered non-Hermitian chains, Anderson delocalization can be induced, restoring the non-Hermitian skin effect even under strong disorder, with experimental verification via electrical circuits.

Contribution

It reveals a novel transition to Anderson delocalization in coupled disordered non-Hermitian chains driven by engineered disorder correlations and inter-chain coupling.

Findings

Delocalization occurs once inter-chain coupling exceeds a threshold.

Re-emergence of the non-Hermitian skin effect independent of disorder strength.

Experimental observation of the effect in electrical circuit analogs.

Abstract

Disorder and non-Hermitian effects together can upend how waves localize. In a 1D disordered chain, the non-Hermitian skin effect (NHSE) can induce Anderson delocalization, defying the usual rule that disorder in low dimensions always localizes states. While weak disorder leaves the NHSE intact, strong disorder restores Anderson localization. Here, we study a surprising twist: coupling a strongly disordered Hatano-Nelson chain to a disordered Hermitian chain with their disorder anti-symmetrically correlated. Strikingly, once the inter-chain coupling exceeds a threshold, the system undergoes Anderson delocalization irrespective of disorder strength, reinstating the NHSE with no Hermitian counterpart. This transition arises from the interplay of non-reciprocal hopping, inter-chain coupling, and engineered disorder correlations, and is captured by a real-space winding number. To confirm this, we build an electrical-circuit analog and directly observe the re-emergent NHSE via voltage measurements. Our work uncovers unexplored and experimentally accessible physics at the crossroads of non-Hermiticity and disorder.