A brief review of hybrid skin-topological effect

TL;DR

This review discusses the hybrid skin-topological effect in non-Hermitian systems, highlighting its mechanisms, theoretical developments, and experimental realizations across various physical platforms.

Contribution

It provides a comprehensive overview of HSTE, including realization methods, related theoretical concepts, and recent experimental demonstrations, advancing understanding of non-Hermitian topological states.

Findings

HSTE supports skin-localized edge states and extended bulk states.

Realizations include electric circuits, photonic crystals, and active matter.

Theoretical links to higher-order skin effects and PT symmetry.

Abstract

The finding of non-Hermitian skin effect has revolutionized our understanding of non-Hermitian topological phases, where the usual bulk-boundary correspondence is broken and new topological phases specific to non-Hermitian system are uncovered. Hybrid skin-topological effect (HSTE) is a class of newly discovered non-Hermitian topological states that simultaneously supports skin-localized topological edge states and extended bulk states. Here we provide a brief review of HSTE, starting from different mechanics that have been used to realize HSTE, including non-reciprocal couplings, onsite gain/loss, and non-Euclidean lattice geometries. We also review some theoretical developments closely related to the HSTE, including the concept of higher-order non-Hermitian skin effect, parity-time symmetry engineering, and non-Hermitian chiral skin effect. Finally, we summarize recent experimental exploration of HSTE, including its realization in electric circuits systems, non-Hermitian photonic crystals, and active matter systems. We hope this review can make the concept of hybrid-skin effect clearer and inspire new finding of non-Hermitian topological states in higher dimensional systems.