Topological phase in a Kitaev chain with spatially separated pairing processes

Abstract

The dynamic balance between pair creation and annihilation processes takes a crucial role to the topological superconductivity in the Kitaev model. Here we study the effect of spatial separation of creation and annihilation terms, i.e., sources and drains of pair are arranged alternatively. In this regard, a non-Hermitian Hamiltonian is naturally considered, which may possess complex energy branches. However, when the Bardeen-Cooper-Schrieffer pair excitation is only considered, the spectrum in such a subspace is fully real. In particular, the Zak phases extracted from the pair wave function are quantized and therefore able to characterize the different phases regardless of the breaking of time-reversal symmetry. For open chain system, the corresponding Majorana lattice is investigated. We find that although there are complex modes, all the edge modes have zero energy and obey the bulk-boundary correspondence. This results in the Kramer-type degeneracy of both the real and complex levels as a signature of the topologically nontrivial phase.