Scientific Report - BEC

Ultracold gases in optical lattices 50and to explore exotic quantum phases.Unitary Fermi gas in a 1D optical latticeFirst experiments with Fermi superfluids in one-dimensional (1D) optical lattices [14]have focused on the study of the critical velocity along the crossover and revealed thatsuperfluidity is particularly robust at unitarity. It is also well known that a periodicpotential favors the formation of molecules in a two-component Fermi gas [15], providingan effective shift of the resonance and bound states in the two-body problemeven at unitarity. A major problem is to understand the consequences of the molecularformation in the superfluid phase. Moreover, for large laser intensities, the lattice isexpected to give rise to 2D effects. In [16] we investigated these properties by usinga mean-field theory based on the Bogoliubov – de Gennes (BdG) equations. By numericallysolving the BdG equations, we have first calculated the equation of state, thecompressibility and the effective mass of the unitary Fermi gas in the lattice. The resultshave been used to obtain interesting predictions for observable quantities such asthe sound velocity, the frequency of collective modes, and the density profile of trappedgases in typical experimental configurations. We have shown that the inclusion of a 1Doptical lattice, by favoring the formation of molecular configurations and by inducinga band structure in the quasiparticle spectrum, has profound consequences on all thesequantities.[1] O. Morsch and M. K. Oberthaler, Rev. Mod. Phys. 78, 179 (2006).[2] G. Roati, M. Zaccanti, C. D’Errico, J. Catani, M. Modugno, A. Simoni, M. Inguscio,and G. Modugno, Phys. Rev. Lett. 99, 010403 (2007).[3] G. Barontini and M. Modugno, Phys. Rev. A 76, 041601(R) (2007).[4] B. Wu and Q. Niu, Phys. Rev. A 64, 061603(R) (2001).[5] L. Fallani, L. De Sarlo, J. E. Lye, M. Modugno, R. Saers, C. Fort, and M. Inguscio,Phys. Rev. Lett. 93, 140406 (2004).[6] L. Fallani,F. S. Cataliotti, J. Catani, C. Fort, M. Modugno, M. Zawada, and M.Inguscio, Phys. Rev. Lett. 91, 240405 (2003).[7] B. Eiermann et al., Phys. Rev. Lett. 91, 060402 (2003).