Non-Hermitian topological mobility edges and transport in photonic quantum walks

TL;DR

This paper explores topological mobility edges in non-Hermitian quasicrystals, revealing how different origins of non-Hermiticity affect transport properties, demonstrated through photonic quantum walks in synthetic lattices.

Contribution

It uncovers the topological nature of mobility edges in non-Hermitian systems and links their origin to distinct transport phenomena in photonic quantum walks.

Findings

Mobility edges exhibit topological structures in the complex energy plane.

Different non-Hermitian origins lead to distinct winding numbers and transport behaviors.

Ballistic transport occurs with asymmetric hopping, while pseudo localization appears with complex potential phases.

Abstract

In non-Hermitian quasicrystals, mobility edges (ME) separating localized and extended states in complex energy plane can arise as a result of non-Hermitian terms in the Hamiltonian. Such ME are of topological nature, i.e. the energies of localized and extended states exhibit distinct topological structures in the complex energy plane. However, depending on the origin of non-Hermiticity, i.e. asymmetry of hopping amplitudes or complexification of the incommensurate potential phase, different winding numbers are introduced, corresponding to different transport features in the bulk of the lattice: while ballistic transport is allowed in the former case, pseudo dynamical localization is observed in the latter case. The results are illustrated by considering non-Hermitian photonic quantum walks in synthetic mesh lattices.