Condensed Matter Physics Seminar

2 p.m., Thursday, April 29, 2004
Room 1201, Physics Building

 Mott insulator to superfluid transition of ultracold atoms near a Feshbach resonance

Krishnendu Sengupta

(Physics Department, Yale University)

Abstract:  We study ultracold bosonic atoms in an optical lattice near a Feshbach resonance using an extended Hubbard model. We find that such a system has three possible ground states: a) Mott insulator b) molecular condensate (MC) and c)atomic and molecular condenstate (AC+MC). The transiiton between these phases can be induced by varying the depth of the optical lattice potential and/or by changing the magnetic field which determines the proximity of the system to the resonance. We obtain the phase diagram as a function of these parameters within mean-field theory. We find that the superfluid-Mott insulator transition may become first order in certain regions of the phase diagram. We also show that the Mott phases with even or odd total number of atoms and molecules per site behave differently as we approach the superfluid-insulator transition point. In particular, the even Mott phases exhibit a reentrant behavior (MC-insulator-AC+MC) as we vary the magnetic field through the transition at a fixed optical lattice depth and total density.  We also discuss the experimental implications of our results.
Host:  Yakovenko
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