Non-Hermitian topological exciton-polariton corner modes

Non-Hermitian topological corner modes can be formed in exciton-polariton lattices under nonresonant pumping. Signals propagating in the bulk of the system can travel around defects, which is not possible in one-dimensional topological lattices or two-dimensional lattices with Hermitian edge states. In the presence of nonlinear interactions, the system remains topological, as evidenced by the winding of the complex fluctuation spectrum. Finally, as all polariton states are localized, the system offers an opportunity for more accurate measurement of the polariton-polariton interaction strength as one can avoid condensing in a state with large overlap with the pump-induced exciton-reservoir.