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SUMMARY:Tunable quantum gases in optical lattices: ground state molecules 
 and strongly-interacting 1D systems - Hanns-Christoph Naegerl (University 
 of Innsbruck)
DTSTART:20100503T143000Z
DTEND:20100503T160000Z
UID:TALK22402@talks.cam.ac.uk
CONTACT:6270
DESCRIPTION:I will report on several of our recent experiments with tunabl
 e quantum \ngases in optical lattices. In the first experiment\, we produc
 e ultracold \nand dense samples of rovibrational ground state (RGS) molecu
 les near \nquantum degeneracy. We first associate dimer molecules out of a
  \nlattice-based Mott-insulator state loaded from an atomic BEC and then \
 ncoherently transfer the molecules to the RGS by a multiphoton STIRAP \npr
 ocess. With an overall efficiency of 50%\, we prepare a molecular \nquantu
 m gas state in which every second site of an optical lattice is \noccupied
  with a RGS molecule [1]. We expect that\, with further \noptimization of 
 the transfer procedure\, a BEC of RGS molecules is possible.\n\nIn the sec
 ond experiment\, we prepare an exotic many-body\, \nhighly-correlated quan
 tum state in 1D geometry known as the \nsuper-Tonks-Girardeau (sTG) gas. I
 n contrast to the well-known case of \nthe Tonks-Girardeau (TG) gas\, inte
 ractions are strongly attractive for \nthe sTG gas. The question thus aris
 es whether this state exists at all \nand how it can be accessed\, as attr
 active interactions give rise to a \nfamily of  more deeply bound states. 
 We observe a confinement-induced \nresonance that allows us to first enter
  deeply into the TG regime and \nfrom there to cross over into the sTG reg
 ime\, which we find to be \nsurprisingly stable. We analyze the crossover 
 in terms of the collective \nmode frequencies of the 1D system and in term
 s of the energy and \nparticle loss [2].\n\nIn the third experiment\, we o
 bserve the superfluid-to-Mott-insulator \n(SF-MI) phase transition for a s
 trongly-interacting 1D gas. For \nsufficiently strong interactions\, the i
 nsulating state is induced by an \narbitrarily week lattice\, in striking 
 contrast to the SF-MI transition \nobserved for weakly-interacting 3D gase
 s. We map out the phase diagram \nand find that our measurements agree wel
 l with a quantum-field \ndescription of the transition based on the well-k
 nown sine-Gordon model. \n\n[1] Quantum gas of rovibronic ground-state mol
 ecules in an optical \nlattice\, J.G. Danzl et al.\, to appear in Nature P
 hysics\, arXiv:0909.4700 \n(2009).\n[2] Realization of an Excited\, Strong
 ly Correlated Quantum Gas Phase\, E. \nHaller et al.\, Science 325\, 1224 
 (2009).\n\n
LOCATION:Rutherford building\, Seminar Room B
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