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SUMMARY:Probing many-body physics with cold atoms: The Higgs boson and qua
 ntum hexatic order.  - Georg Bruun\, Aarhus University
DTSTART:20140528T130000Z
DTEND:20140528T140000Z
UID:TALK52764@talks.cam.ac.uk
CONTACT:Dr G Moller
DESCRIPTION:n this talk\, I describe how cold atoms can be used to test tw
 o phenomena which play a key role in our description of quantum many-body 
 physics. \n\nThe first is the Higgs mode\, which plays a fundamental role 
 for our understanding of both low and high energy physics\, giving element
 ary particles their mass and leading to collective modes in condensed matt
 er and nuclear systems. The Higgs mode has been observed in a limited numb
 er of table-top systems\, where it however is characterised by a short lif
 etime due to decay into a continuum of modes. A major goal which has remai
 ned elusive so far\, is therefore to realise a long-lived Higgs mode in a 
 controllable system. Here\, we show how an undamped Higgs mode can be obse
 rved unambiguously in a Fermi gas in a two-dimensional trap\, close to a q
 uantum phase transition between a normal and a superfluid phase. The secon
 d phenomena is the hexatic phase\, which is a phase in between a liquid an
 d a crystal. We show how such a phase can be realised in the quantum regim
 e for the first time\, using a two-dimensional gas of dipolar molecules. W
 e derive approximate phase diagrams using a pair of Lindemann criteria\, s
 uitably adapted to deal with effects of thermal fluctuations in two dimens
 ions.  The hexatic phase is predicted to survive down to very low temperat
 ures.
LOCATION:Ryle Seminar Room no. 930\, Rutherford Building\, Cavendish Labor
 atory
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