Topological Monomodes in non-Hermitian Systems

E. Slootman, W. Cherifi, L. Eek, R. Arouca, M. Bourennane, C. Morais Smith

Published 2023-04-12Version 1

We show theoretically and experimentally the existence of topological monomodes in non-Hermitian systems created by loss engineering. This challenges the idea that edge states always come in pairs in $\mathbb{Z}_2$ symmetry-protected topological systems. We theoretically show the existence of a monomode in a non-Hermitian 1D and 2D SSH models. Furthermore, we classify the systems in terms of the (non-Hermitian) symmetries that are present and calculate the corresponding topological invariant. To corroborate the theory, we present experiments in photonic lattices in which a monomode is observed in a non-Hermitian 1D SSH chain.