title: Spontaneous and triggered vortices in polariton optical-parametric-oscillator superfluids.
abstract: We study nonequilibrium polariton superfluids in the optical-parametric-oscillator regime by using a Gross-Pitaevskii equation with pumping and decay. We identify a regime above the optical-parametric-oscillator threshold, where the system undergoes spontaneous symmetry breaking and is unstable towards vortex formation without any rotating drive. Stable vortex solutions differ from metastable ones; the latter can persist but can be triggered only externally. Both spontaneous and triggered vortices are characterized by a generalized healing length, specified by the optical-parametric-oscillator parameters only.
authors.affiliation: Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid 28049, Spain. francesca.marchetti@uam.es
authors.forename: F M
authors.initials: FM
authors.lastname: Marchetti
authors.forename: M H
authors.initials: MH
authors.lastname: Szymańska
authors.forename: C
authors.initials: C
authors.lastname: Tejedor
authors.forename: D M
authors.initials: DM
authors.lastname: Whittaker