Coexistence of topological Anderson insulator and multifractal critical phase in a non-Hermitian quasicrystal

TL;DR

This paper explores a non-Hermitian quasicrystal model where topology, disorder, and non-Hermiticity interplay, revealing a coexistence of topological Anderson insulator and multifractal critical phases with exact phase boundaries.

Contribution

It introduces a non-Hermitian Su-Schrieffer-Heeger model with quasiperiodic modulation, uncovering new phase coexistences and analytical phase boundaries.

Findings

Quasiperiodic modulation enhances topological regimes.

Induces a non-Hermitian topological Anderson insulator phase.

Reveals coexistence of TAI and multifractal critical phases.

Abstract

The interplay of topology, disorder, and non-Hermiticity gives rise to phenomena beyond the conventional classification of quantum phases. We propose a one-dimensional non-Hermitian Su-Schrieffer-Heeger model with quasiperiodically modulated nonreciprocal intracell hopping. We show that quasiperiodic modulation can substantially enhance the topological regime and, remarkably, induce a non-Hermitian topological Anderson insulator (TAI) phase. Beyond the topological transition, increasing nonreciprocity drives a cascade of localization transitions in which all bulk eigenstates evolve from extended to multifractal critical and ultimately to localized states. Strikingly, the extended-to-critical transition coincides exactly with a real-complex spectral transition. We establish complete phase diagrams and derive exact analytical boundaries for both topological and localization transitions, uncovering an unanticipated coexistence of TAI and multifractal critical phases. Finally, we propose a feasible implementation in topolectrical circuits. Our results reveal a new paradigm for studying the cooperative effects of topology, quasiperiodicity, and non-Hermiticity.