Observation of long-lived polariton states in semiconductor microcavities across the parametric threshold.
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.
Ballarini
D
D
Departamento Física de Materiales, Universidad Autonóma de Madrid, 28049 Madrid, Spain.
Sanvitto
D
D
Amo
A
A
Viña
L
L
Wouters
M
M
Carusotto
I
I
Lemaitre
A
A
Bloch
J
J