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SUMMARY:Bose-Einstein condensation of semiconductor excitons: 50 years lat
 er\, at last! - Prof. Francois Dubin\, Institut des NanoSciences de Paris
DTSTART:20170612T131500Z
DTEND:20170612T141500Z
UID:TALK72959@talks.cam.ac.uk
CONTACT:Dr Joanna Waldie
DESCRIPTION:Semiconductor excitons constitute model composite bosons made 
 of two fermions\, an electron and a hole bound by Coulomb attraction. The 
 excitons bosonic character is therefore dominant in a dilute regime so tha
 t it was envisioned already 50 years ago that excitons undergo Bose-Einste
 in condensation under accessible experimental conditions.\n \nThis talk em
 phasises the experimental and theoretical barriers that have prevented the
  demonstration of exciton condensation\, prior to our recent works. As pre
 dicted by Combescot et al\, I will show that a condensate of excitons is m
 ade by a dominant fraction of lowest energy and optically inactive exciton
 s\, coherently coupled to a weak population of higher energy and optically
  bright ones. The latter part allows detecting quantum statistical signatu
 res of the four-component condensate\, such as macroscopic spatial coheren
 ce below a critical temperature of about 1 Kelvin. As expected\, I will sh
 ow that quantised vortices emerge in the quantum regime\, unveiling a supe
 rfluid character. All together\, our experiments reveal a novel type of qu
 antum gas completing atomic systems\, but also superconductors and liquid 
 helium.
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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