Mixed higher-order topology: boundary non-Hermitian skin effect induced by a Floquet bulk

Abstract

We show that anomalous Floquet topological insulators generate intrinsic, non-Hermitian topology on their boundary. As a consequence, removing a boundary hopping from the time-evolution operator stops the propagation of chiral edge modes, leading to a non-Hermitian skin effect. This does not occur in Floquet Chern insulators, however, in which boundary modes continue propagating. The non-Hermitian skin effect on the boundary is a consequence of the nontrivial topology of the bulk Floquet operator, which we show by designing a real-space topological invariant. Our work introduces a form of `mixed' higher-order topology, providing a bridge between research on periodically-driven systems and the study of non-Hermiticity. It suggests that periodic driving, which has already been demonstrated in a wide range of experiments, may be used to generate non-Hermitian skin effects.

Published version

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Cited by in corpus (16)

• Topological Non-Hermitian skin effect
• Hermitian Bulk -- Non-Hermitian Boundary Correspondence
• Observation of non-Hermitian topology in a multi-terminal quantum Hall device
• Universal platform of point-gap topological phases from topological materials
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• Real-space topological localizer index to fully characterize the dislocation skin effect
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• Dimensional crossover of class D real-space topological invariants