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

TL;DR

This paper introduces an anti-PT symmetric non-Hermitian SSH model where large non-Hermiticity induces nontrivial topology, expanding topological phases and revealing new phase transition mechanisms unaffected by exceptional points.

Contribution

It proposes a novel anti-PT symmetric SSH model demonstrating how non-Hermiticity can create and expand topological phases, with potential experimental verification through dissipation engineering.

Findings

Non-Hermiticity constructively creates nontrivial topology.

Degenerate points determine topological phase transitions.

Dissipation alone can induce nontrivial topology in trivial phases.

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 degenerate point at the center of the Brillouin zone determines the topological phase transition, while the exceptional points unaffect the band topology. The large non-Hermiticity leads to unbalanced wavefunction distribution in the broken anti-PT -symmetric phase and induces the nontrivial topology. Our findings can be verified through introducing dissipations in every another two sites of the standard SSH model even in its trivial phase, where the nontrivial topology is solely induced by the dissipations.