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SUMMARY:Superfluidity of a non-equilibrium polariton condensate - Dr Jonat
 han Keeling\, University of St Andrews
DTSTART:20110519T131500Z
DTEND:20110519T144500Z
UID:TALK31284@talks.cam.ac.uk
CONTACT:Joe Bhaseen
DESCRIPTION:Microcavity polaritons are a system that can show coherence in
  a strongly-coupled light matter system at low temperatures. As such\, the
 y connect both to Bose-Einstein condensation and also to lasing\, and they
  currently provoke a number of questions about what properties such a non-
 equilibrium superfluid might have. Some aspects of superfluidity\, such as
  the observation of quantised vortices\, and some experiments on scatterin
 g from defects have been studied experimentally. Theoretically\, the effec
 ts of finite particle lifetime on the excitation spectrum has been discuss
 ed\, and some of its consequences for superfluidity have been examined. Ho
 wever\, the superfluid density of the non-equilibrium polariton condensate
  has not previously been calculated.  I will present an approach to calcul
 ating superfluid density\, revealing how the polariton system can show a s
 uperfluid response despite not having a linear excitation spectrum.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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