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A Tunable Atomic and Molecular Quantum Gas in Optical Lattices
Optical lattices, constructed by the interference pattern of laser beams, provide a periodic potential for ultracold particles. Cold atoms/molecules in optical lattices can therefore simulate electrons in condensed matter systems. Novel features of the optical lattices include
Formation and condensation of composite bosons by pairing fermionic atoms open the door to the exploration of superfluidity in different regimes. In the strong-coupling limit, atoms form short ranged molecules, which undergo Bose-Einstein condensation (BEC) at low temperatures. In the weak-coupling regime, Cooper-pairing of atoms occurs in the Bardeen-Cooper-Schrieffer (BCS) state. In the crossover regime, the two types of superfluid smoothly connect to a “resonance superfluid”, for which a universal behaviour is predicted.
I propose to study ultracold atomic and molecular gases in an optical lattice potential, which can simulates general condensed matter systems and introduces novel quantum phases with long range correlation. For an interacting Fermi gas in a weak optical lattice potential, a d-wave pairing phase and an anti-ferromagnetic phase are expected to exist , which could provide new perspectives to high-Tc superconductivity. In a strong confining lattice with a few atoms or molecules localized in each lattice site, reactive scattering processes at ultralow temperatures can be realized with a full control over the internal and external degrees of freedom.
There are three primary goals of this work:
One example would be the formation of atomic trimers or quadrumers by pairing the dimers and/or the atoms in optical lattices. Possible schemes to induce the pairing will be investigated. By lowering the lattice potential, the bosonic quadrumers can possibly undergo Bose-Einstein condensation and the fermionic trimers can possibly be Cooper paired at low temperatures. The realization of the above pairing processes will provide a common testing ground for the studies of chemical physics, few-body physics and condensed matter physics.
 W.H. Hofstetter, J.I. Cirac, P.Zoller, E. Demler and M.D. Lukin, Phys. Rev. Lett. 89, 220407 (2002)
Related: cesium experiment.