Stochasticity-induced non-Hermitian skin criticality

TL;DR

This paper uncovers a new type of non-Hermitian skin criticality driven by stochastic disorder in 2D lattices, revealing how disorder can enhance state amplification through feedback loops, with implications for non-Hermitian sensing.

Contribution

It introduces a novel disorder-induced non-Hermitian skin criticality mechanism, analytically predicts scaling behavior, and demonstrates its general applicability to non-Hermitian lattices.

Findings

Stronger disorder can enhance state amplification.

Analytical critical GBZ accurately predicts scaling.

Disorder-induced feedback loops cause anomalous spectra.

Abstract

Typically, scaling up the size of a system does not change the shape of its energy spectrum, other than making it denser. Exceptions, however, occur in the new phenomenon of non-Hermitian skin criticality, where closely competing generalized Brillouin zone (GBZ) solutions for non-Hermitian state accumulation give rise to anomalously scaling complex spectra. In this work, we discover that such non-Hermitian criticality can generically emerge from stochasticity in the lattice bond orientation, a surprising phenomenon only possible in 2D or beyond. Marked by system size-dependent amplification rate, it can be physically traced to the proliferation of feedback loops arising from excess local non-Hermitian skin effect (NHSE) accumulation induced by structural disorder. While weak disorder weakens the amplification as intuitively anticipated, stronger disorder enigmatically strengthens the amplification almost universally, scaling distinctly from conventional critical system. By representing cascades of local excess NHSE as ensembles of effectively coupled chains, we analytically derived a critical GBZ that predicts how state amplification scales with the system size and disorder strength, highly consistent with empirical observations. Our new mechanism for disordered-facilitated amplification applies generically to structurally perturbed non-Hermitian lattices with broken reciprocity, and would likely find applications in non-Hermitian sensing through various experimentally mature meta-material platforms.