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Center for Excitonics
Seminar Series Announcement
Tuesday, May 10, 2011
3:00 PM
RLE Conference Room: 36-428
Speaker: Benoît Deveaud-Plédran, Ecole Polytechnique Fédérale de Lausanne
Bose-Einstein condensates of polaritons: Vortices and superfluidity
Abstract The idea of a possible Bose Eintein condensation in the solid
state has been explored since the beginning of the sixties with the hope to
get transition temperatures much more accessible than the temperatures
needed for the condensation of atomic vapors (less than 1µK for Rubidium).
The advantage in solids is that people are trying to condense excitons (an
electron-hole pair in a semiconductor) with a mass similar to that of an
electron, i.e. four orders of magnitude less than a rubidium atom. The price
to pay is the disorder inherent to any real solid state system as well as
the limited lifetime of the quasiparticles. We are using exciton
polaritons, quasiparticles made one half for excitons and one half from a
confined photon. Polaritons are bosons with a mass five orders of magnitude
lighter than an electron. Then, condensation at temperatures of the order of
300 K has been observed. The price to pay is the incredibly short lifetime
of the polaritons : one picosecond. During this talk, I will detail our
studies on the physical properties of polariton condensates. In particular,
I will focus on the evidence for superfluidity through the observation of
quantized vortices. I will show their time resolved behavior, and show the
first direct evidence for half quantized vortices, a specialty of spinor
condensates.
Bio Benoit Deveaud-Plédran is a full professor in Physics at the Ecole
Polytechnique Fédérale de Lausanne having received his Physics Engineering
degree from the Ecole Polytechnique, Paris in 1974, his Masters degree in
Optoelectronics from Rennes University in 1977, and his PhD from Grenoble
University in 1984. Amongst his many awards and recognitions are the 1985
Young Researcher Award from Paris' Ministry of Defense, the 2004 Best
Teacher Award from EPFL, and the 2009 Outstanding Referee Award from
Physical Review Letters. He is a specialist in the optical spectroscopy of
semiconductors with a particular dedication to ultrafast and coherent
optical spectroscopy. Over the last few years his team has expanded the
understanding of coherent optical spectroscopy by developing a whole
ensemble of actively stabilized interferometers, able to perform spectral
interferometry as well as a profound understanding of the physics of
semiconductor microcavities.
Light refreshments will be served
The Center for Excitonics is an Energy Frontier Research Center funded by
the U.S. Department of Energy, Office of Science and Office of Basic
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