Topological phases in one-dimensional nonreciprocal superlattices

Abstract

Non-Hermitian topological systems have been shown to exhibit many interesting properties. However, due to the presence of complex energy spectra and non-Hermitian skin effect (NHSE), the topological edge states will be dynamically unstable and unresolvable from the bulk states which are also localized at the boundaries. Here we propose a one-dimensional nonreciprocal superlattice model in which topological phases are solely induced by the modulated asymmetric hopping amplitude. Most importantly, we can obtain robust real energy spectra, and in the meanwhile, eliminate the NHSE both in the commensurate and incommensurate lattices by tuning the modulation. Thus the topological zero and nonzero energy edge states are stable and distinguishable from the bulk states, which would definitely facilitate the experimental identifications of non-Hermitian topological phases. We further propose a practical scheme to realize this nonreciprocal model by exploiting electrical circuits.