Topology of multipartite non-Hermitian one-dimensional systems

The multipartite non-Hermitian Su-Schrieffer-Heeger model is explored as a prototypical example of onedimensional systems with several sublattice sites for unveiling intriguing insulating and metallic phases with no Hermitian counterparts. These phases are characterized by composite cyclic loops of multiple complex-energy bands encircling single or multiple exceptional points (EPs) on the parametric space of real and imaginary energy. We show the topology of these composite loops is similar to well-known topological objects like M??bius strips and Penrose triangles, and can be quantified by a nonadiabatic cyclic geometric phase which includes contributions only from the participating bands. We analytically derive a complete phase diagram with the phase boundaries of the model. We further examine the connection between encircling of multiple EPs by complex energy bands on parametric space and associated topology.

Automated summary

The multipartite non-Hermitian Su-Schrieffer-Heeger model is investigated as a representative example of one-dimensional systems with multiple sublattice sites, revealing intriguing insulating and metallic phases with no Hermitian counterparts. The topology of these composite loops, characterized by multiple complex-energy bands encircling exceptional points on the parametric space, resembles well-known topological objects and can be quantified by a nonadiabatic cyclic geometric phase involving only the participating bands.