Topology of an anti-parity-time symmetric non-Hermitian Su-Schrieffer-Heeger model

Abstract

We propose an anti-parity-time (anti-PT) symmetric non-Hermitian Su-Schrieffer-Heeger (SSH) model, where the large non-Hermiticity constructively creates nontrivial topology and greatly expands the topological phase. In the anti-PT-symmetric SSH model, the gain and loss are alternatively arranged in pairs under the inversion symmetry. The appearance of the degenerate point at the center of the Brillouin zone determines the topological phase transition, whereas the exceptional points unaffect the band topology. The large non-Hermiticity leads to unbalanced wave-function distribution in the broken anti-PT-symmetric phase and induces the nontrivial topology. Our findings can be verified through introducing dissipations in every other two sites of the standard SSH model even in its trivial phase where the nontrivial topology is solely induced by the dissipations.