Mikhail Lukin

PROBING NEW KINDS OF SUPERFLUIDITY OF ULTRA-COLD ATOMS
Personnel: theoretical: M. Lukin (PI), Caspar van der Wal (postdoc)
We showed theoretically that confinement of cold fermionic atoms in optical lattices can be used to dramatically increase the transition temperature to a superfluid state and thus maek ti readily observable under current experimental conditions. Depending upon carefully controlled parameters, a transition to a superfluid state of Cooper pairs, antiferromagnetic states or more exotic d-wave pairing states can be induced and probed. The results of proposed experiments can provide a critical insihgt into the origin of high-temperature superconductivity in cuprates.

We are currently exploring the techniques for detecting superfluid properties of fermions near critcial temperature.

PROBING QUANTUM MAGNETISM AND EXOTIC PHASES OF ULTRACOLD ATOMS IN OPTICAL LATTICES
We proposed a technique that allows to induce and control strong interaction between spin states of neighboring atoms in an optical lattice. We showed that the properties of spin exchange interactions, such as magnitude, sign, and anisotropy can be designed by adjusting the optical potentials. We showed that this technique can be used to efficiently 'engineer' quantum spin systems with desired propeties, for specific examples ranging from scalable quantum computation to probing a model with complex topological order that supports exotic anyonic excitations. We are also investigating the quantum states resulting from melting non-trival spin phases.

We are curently exploring the techniques for spectoscopic detection and manipulation of exotic states. In particular, we developed a theory for probing high-order coherence of matter waves, which can provide unambiguous signatures for such states.

MESOSCOPIC PHENOMENA IN ULTRA-COLD ATOMS
We demonstrated theoretically a possibility to form large (mesoscopic) molecular ions in an ultracold degenerate bosonic gas doped with charged impurities. We showed that the polarization potentials produced by ionic impurities are capable of capturing thousands of atoms into loosley bound states. We described the spontaneous dynamics of formation of these hollow molecular ions via photon emission and suggest an optical technique for coherent stimulation of free atoms into a specific bound state. The resulting clusters can be accurately manipulated with external electric fields.

SUPERFLUIDITY IN DISORDERED POTENTIALS
We are also investigating the origin and implication of condensate fragmentation in microfabricated atom traps and waveguides. We have shown theoretically that the fragmentation originates from the small fluctuations in shape of current carrying wires. Our theortical analysis provides a first principle explanation of the recent experimental results. We further explore the possibilities of studying the so-called bose-glass phase in the regime of strong disorder.