Topological semimetal phase and dynamical characterization in a non-Hermitian two-leg ladder model

Abstract

We show the phase transition between the trivial and the topological semimetal phases in a non-Hermitian two-leg ladder model. We find that, the topological properties of this special model can be captured by a equivalent model with chiral symmetry in which the equivalent model owns the pure imaginary nonreciprocal intercell and long-range hopping simultaneously. Based on the equivalent model, we reveal that the system possesses the gapless topological semimetal phase induced by four exceptional points, which is different from the general topological semimetal phase usually owning two exceptional points. Significantly, we demonstrate that the system has the distinct transmission behaviors within the trivial and topological semimetal phases, leading the phase transition between trivial and topological semimetal phases and the boundary between left and right non-Hermitian skin effects can both be characterized dynamically via the propagation speed of the evolved initial state. Our investigation further supplies the contents on a topological semismetal phase in the non-Hermitian two-leg ladder model and may provide a possible tool to visualize the phase transition of the topological semimetal phase.