Bridging the gap between topological non-Hermitian physics and open quantum systems

Authors: Gomez-Leon, Alvaro; Ramos, Tomas; Gonzalez-Tudela, Alejandro; Porras, Diego

Journal: PHYSICAL REVIEW A

Publication date: 2022/07/25

DOI: 10.1103/PhysRevA.106.L011501

Abstract: We relate observables in open quantum systems with the topology of non-Hermitian models using the Keldysh path-integral method. This allows to extract an effective Hamiltonian from the Green’s function which contains all the relevant topological information and produces omega-dependent topological invariants, linked to the response functions at a given frequency. Then, we show how to detect a transition between different topological phases by measuring the response to local perturbations. Our formalism is exemplified in a one-dimensional Hatano-Nelson model, highlighting the difference between the bosonic and the fermionic case.