Species-specific optical lattices

Abstract

We examine single-frequency optical schemes for species-selective trapping of ultracold alkali-metal atoms. Independently addressing the elements of a binary mixture enables the creation of an optical lattice for one atomic species with little or no effect on the other. We analyze a ``tune-in'' scheme, using near-resonant detuning to create a strong potential for one specific element. A ``tune-out'' scheme is also developed, in which the trapping wavelength is chosen to lie between two strong transitions of an alkali-metal atom such that the induced dipole moment is zero for that species but is nonzero for any other. We compare these schemes by examining the trap depths and heating rates associated with both. We find that the tune-in scheme is preferable for $\mathrm{Li}\text{\ensuremath{-}}\mathrm{Na}$, $\mathrm{Li}\text{\ensuremath{-}}\mathrm{K}$, and $\mathrm{K}\text{\ensuremath{-}}\mathrm{Na}$ mixtures, while the tune-out scheme is preferable for $\mathrm{Li}\text{\ensuremath{-}}\mathrm{Cs}$, $\mathrm{K}\text{\ensuremath{-}}\mathrm{Rb}$, $\mathrm{Rb}\text{\ensuremath{-}}\mathrm{Cs}$, $\mathrm{K}\text{\ensuremath{-}}\mathrm{Cs}$, and $^{39}\mathrm{K}\text{\ensuremath{-}}^{40}\mathrm{K}$ mixtures. Several applications of species-selective optical lattices are explored, including the creation of a lattice for a single species in the presence of a phononlike background, the tuning of relative effective mass, and the isothermal increase of phase-space density.