NonHermitian Topological Phases in a Hermitian Modified Bosonic Kitaev Chain

Abstract: We present a modification to the bosonic Kitaev chain that, despite being Hermitian, supports both nonHermitian skin effect and nontrivial topological edge modes in its excitation Hamiltonian. We establish an exact mapping between the excitation Hamiltonian of our system and a nonHermitian Su-Schrieffer-Heeger (SSH) model, which allows for a completely analytical characterization of its topology. In particular, topological phase transition points separating a topologically trivial and nontrivial regime were identified analytically by the appropriate winding number invariant and the presence of zero energy modes. Similarly to the regular bosonic Kitaev chain, the nonHermitian skin effect and some (but not all) topological edge modes are quickly destroyed at nonzero bosonic onsite potential (harmonic oscillator frequency). Remarkably, however, disorder partially recovers some of these features. This work thus demonstrates the potential of a modified bosonic Kitaev chain as a platform to generate rich nonHermitian topological phenomena from a completely Hermitian system's perspective. Lastly, we suggest a possible experimental realization of the model, which could allow for total control over the parameter space.