In electronic and photonic systems it is now well-established that non-trivial band-structures result in chiral edge states that are fully robust against scattering with disorder. In a recent work we introduced a theoretical scheme for topological polaritons in semiconductor microcavities and topological indirect-excitons in coupled quantum wells. The scheme is based on the spin-orbit coupling of exciton-polaritons or excitons in hexagonal lattice potentials and requires a magnetic field to break time-inversion symmetry. More recently, we have also considered the availability of nonlinearity in polariton systems and how it can lead to an interaction-induced mechanism of topological states. In a lattice of vortex-antivortex pairs we obtain a topological Bogoliubov spectrum, where fluctuations can propagate on top of a polariton condensate in topologically protected chiral edge modes. Remarkably, this mechanism of introducing topological behaviour no longer requires a magnetic field to break time reversal symmetry. Time reversal symmetry is rather broken locally by the choice of sign of phase winding in unit cells of the vortex-antivortex lattice.
The seminar is part of the mini-workshop on polaritonics hosted by the Polariton BEC Group.
Full program is found here: