title: Observation of long-lived polariton states in semiconductor microcavities across the parametric threshold.
abstract: The excitation spectrum around the pump-only stationary state of a polariton optical parametric oscillator in semiconductor microcavities is investigated by time-resolved photoluminescence. The response to a weak pulsed perturbation in the vicinity of the idler mode is directly related to the lifetime of the elementary excitations. A dramatic increase of the lifetime is observed for a pump intensity approaching and exceeding the optical parametric oscillator threshold. The observations can be explained in terms of a critical slowing down of the dynamics upon approaching the threshold and the following appearance of a soft Goldstone mode in the spectrum.
authors.affiliation: Departamento Física de Materiales, Universidad Autonóma de Madrid, 28049 Madrid, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Ballarini
authors.forename: D
authors.initials: D
authors.lastname: Sanvitto
authors.forename: A
authors.initials: A
authors.lastname: Amo
authors.forename: L
authors.initials: L
authors.lastname: Viña
authors.forename: M
authors.initials: M
authors.lastname: Wouters
authors.forename: I
authors.initials: I
authors.lastname: Carusotto
authors.forename: A
authors.initials: A
authors.lastname: Lemaitre
authors.forename: J
authors.initials: J
authors.lastname: Bloch