title: Effect of interactions on vortices in a nonequilibrium polariton condensate.
abstract: We demonstrate the creation of vortices in a macroscopically occupied polariton state formed in a semiconductor microcavity. A weak external laser beam carrying orbital angular momentum (OAM) is used to imprint a vortex on the condensate arising from the polariton optical parametric oscillator (OPO). The vortex core radius is found to decrease with increasing pump power, and is determined by polariton-polariton interactions. As a result of OAM conservation in the parametric scattering process, the excitation consists of a vortex in the signal and a corresponding antivortex in the idler of the OPO. The experimental results are in good agreement with a theoretical model of a vortex in the polariton OPO.
authors.affiliation: Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, United Kingdom.
authors.forename: D N
authors.initials: DN
authors.lastname: Krizhanovskii
authors.forename: D M
authors.initials: DM
authors.lastname: Whittaker
authors.forename: R A
authors.initials: RA
authors.lastname: Bradley
authors.forename: K
authors.initials: K
authors.lastname: Guda
authors.forename: D
authors.initials: D
authors.lastname: Sarkar
authors.forename: D
authors.initials: D
authors.lastname: Sanvitto
authors.forename: L
authors.initials: L
authors.lastname: Vina
authors.forename: E
authors.initials: E
authors.lastname: Cerda
authors.forename: P
authors.initials: P
authors.lastname: Santos
authors.forename: K
authors.initials: K
authors.lastname: Biermann
authors.forename: R
authors.initials: R
authors.lastname: Hey
authors.forename: M S
authors.initials: MS
authors.lastname: Skolnick