Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session N2: Optical Lattices |
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Chair: Brian DeMarco, University of Illinois Room: 200B |
Thursday, June 6, 2013 10:30AM - 10:42AM |
N2.00001: Formation and decay of Bose Einstein condensates in an excited band of a double-well optical lattice Saurabh Paul, Eite Tiesinga We investigate the formation of a Bose Einstein condensate in the P-band of a double well optical lattice [1]. The lattice traps the atoms in two dimensions while confinement in the third direction is provided by a weak harmonic trap. We estimate the band structure using a tight binding(TB) model, using local simple harmonic oscillator functions. We are interested in the case when the ground s-orbital of shallow wells and the excited p-orbital of adjacent deep wells is tuned to resonance, varying the onsite energy real time. A numerical estimate of the band structure using a plane wave basis, and comparison of the tunneling parameters with that of the TB model shows that the TB model is not a good approximation for higher bands. We estimate the life time of the condensate, using TB wave functions for the four lower bands and numerical estimates for higher bands. The life time is mainly dominated by a two body collision aided decay process to the ground band. Corrections involve simultaneous transitions to the ground and other excited bands, which become progressively important with increasing lattice depth. \\[4pt] [1] G. Wirth et al., Nature Physics doi:10.1038/nphys1857 [Preview Abstract] |
Thursday, June 6, 2013 10:42AM - 10:54AM |
N2.00002: Experiments with single atoms laser-cooled to their 3D ground state in an optical tweezer Adam Kaufman, Brian Lester, Cindy Regal We present our recent work in which we have cooled a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. We spectroscopically measure a total ground state occupation of 90$\%$ and observe coherent control of the spin-motional quantum state. Building on these results, we plan to investigate using an array of traps created by our high-NA lens as an avenue towards bottom-up quantum simulation. By combining a dynamically controlled double-well potential with Raman assisted tunneling, we will look to realize the principle ingredients of Bose-Hubbard physics, namely on-site interactions and complex tunneling amplitudes. [Preview Abstract] |
Thursday, June 6, 2013 10:54AM - 11:06AM |
N2.00003: First-order transition and hysteresis phenomena of Bose-Bose mixtures in an optical lattice Daisuke Yamamoto, Takeshi Ozaki, Carlos Sa de Melo, Ippei Danshita We study the superfluid-Mott insulator transition in Bose-Bose mixtures loaded into an optical lattice applying the self-consistent mean-field theory to the two-component Bose-Hubbard model. It is known that the transition in this system with repulsive inter-component interaction can be of first order near the tip of the Mott lobes at even filling factors. Assuming equal hoppings and equal intra-component interactions for both components, we first discuss the metastability of the superfluid and Mott insulator phases with two bosons per site at zero temperature. We find that the hysteresis region is wide enough to be detected in the experiments with tuning the ratio of the hopping and the intra-component interaction. We also discuss the effects of finite temperatures and anisotropy between the two components in consideration of the actual experimental situation. [Preview Abstract] |
Thursday, June 6, 2013 11:06AM - 11:18AM |
N2.00004: Disordered Hubbard Model with Ultracold Atoms William McGehee, Stanimir Kondov, Brian DeMarco We report a measurement of a metal-to-insulator transition in the disordered Fermi Hubbard model (DFHM). The DFHM is the subject of intense research in condensed matter physics due to its applicability to strongly correlated electronic systems. We realize the model using ultracold $^{40}K$ atoms in an optical lattice superimposed with a speckle light field. We find that the disorder induces an Anderson-like transition for a range of atom-atom interaction strengths in qualitative agreement with theory predictions. [Preview Abstract] |
Thursday, June 6, 2013 11:18AM - 11:30AM |
N2.00005: Ultracold atoms in an optical lattice one millimeter from air Dylan Jervis, Graham Edge, Stefan Trotzky, David McKay, Joseph Thywissen Over the past decade, ultracold atoms in optical lattices have shown to be versatile systems able to realize canonical Hamiltonians of condensed matter. High-resolution in-situ imaging of ultracold clouds has furthermore enabled thermometry, equation of state measurements, direct measurement of fluctuations, and unprecedented control. We report on microscopy of ultracold bosons and fermions in a novel configuration where the atoms are harmonically trapped 800 microns away from a 200 micron-thick vacuum window. This window also serves as a retro-reflecting mirror for an optical lattice, into which the atoms can be loaded. Two additional transverse standing waves complete the three-dimensional lattice setup. In free space, we have shown that laser cooling with 405 nm light, on the open 4S$_{1/2}$-5P$_{3/2}$ transition, allows for temperatures below the Doppler temperature of the 4S$_{1/2}$-4P$_{3/2}$ cycling transition at 767 nm. Microscopy with 405 nm light furthermore reduces the diffraction limit of in-situ imaging. [Preview Abstract] |
Thursday, June 6, 2013 11:30AM - 11:42AM |
N2.00006: Decoherence and heating of fermions in optical lattices Saubhik Sarkar, Stephan Langer, Johannes Schachenmayer, Andrew J. Daley A key challenge in current experiments with ultracold fermionic atoms in optical lattices is to reach sufficiently low temperatures in order to explore many interesting quantum phases, including magnetically ordered states. Incoherent scattering of light from the lasers that form the lattices can contribute significantly to the heating, which competes with processes cooling the system into these states. We study the robustness of the magnetically ordered many-body states to this mechanism, deriving a many-body master equation for two-component fermions and investigating how the heating is influenced by choices in the atomic physics as well as parameters of the many-body Hamiltonian. Specifically, we show that for alkaline earth atoms these states can be particularly robust in a far-detuned optical lattice, as direct decoherence of spin states is strongly suppressed, and the decoherence rate for the many-body state becomes proportional to the probability of virtual double-occupations in the Mott Insulator state. [Preview Abstract] |
Thursday, June 6, 2013 11:42AM - 11:54AM |
N2.00007: Superfluidity and Mott transitions of repulsively interacting three-component fermionic atoms in an optical lattice Kensuke Inaba, Sei-ichiro Suga We investigated the superfluidity and the Mott transition of repulsively interacting three-component (color) fermionic atoms in an optical lattice [1]. We found that the characteristic Mott transition occurs even at non-integer half filling, when the interaction strengths are strongly anisotropic: the atoms of two of the three colors form the pair to avoid the strongest interaction; as a result, the paired Mott transition occurs because of the effective filling being an integer. We found that a superfluid state appears close to the Mott phase, because the effective attractive interaction is mediated by the density fluctuations of the unpaired atoms. We will discuss the analogical superfluidity and Mott transitions seen in condensed matter.\\[4pt] [1] K. Inaba and S. Suga, Phys. Rev. Lett. 108, 255301 (2012). [Preview Abstract] |
Thursday, June 6, 2013 11:54AM - 12:06PM |
N2.00008: Quantum phases of quadrupolar Fermi gases in optical lattices Satyan Bhongale, Ludwig Mathey, Erhai Zhao, Susanne Yellin, Mikhail Lemeshko We introduce a new platform for quantum simulation of many-body systems based on nonspherical atoms or molecules with zero dipole moment but possessing a significant value of electric quadrupole moment. We consider a quadrupolar Fermi gas trapped in a 2D square optical lattice, and show that the peculiar symmetry and broad tunability of the quadrupole-quadrupole interaction results in a rich phase diagram encompassing unconventional BCS and charge density wave phases, and opens up a perspective to create topological superfluid. Quadrupolar species, such as metastable alkaline-earth atoms and homonuclear molecules, are stable against chemical reactions and collapse and are readily available in experiment at high densities. [Preview Abstract] |
Thursday, June 6, 2013 12:06PM - 12:18PM |
N2.00009: Collective many-body effects in ultracold gases in an optical cavity Mark Lee, Janne Ruostekoski In free space atoms in dense or degenerate gases exhibit a cooperative response to light scattering, resulting in collective linewidths and shifts which depend not only upon the properties of the individual atoms but also the quantum statistical properties of the gas. For ultra-cold gases trapped within optical cavities the picture is substantially altered by the discrete nature of the cavity mode to which the atoms couple, and by the scattered light mediating long range atom-atom interactions. We derive a formalism to describe many-body collective effects on light scattering in the cavity, and compare the results of simple models to stochastic calculations. The results include both spatial variation of the atom density due to light induced potentials and quantum correlation properties. [Preview Abstract] |
Thursday, June 6, 2013 12:18PM - 12:30PM |
N2.00010: Controlled manipulation of light by cooperative response of atoms in an optical lattice Stewart Jenkins, Janne Ruostekoski We show that atoms in an optical lattice can respond cooperatively to incident light [1]. Such a cooperative response can be employed to precisely control and manipulate light on the subwavelength scale. As an illustration, we consider an optical lattice whose atoms are in a Mott-insulator state with precisely one atom per lattice site. The cooperative response of the atoms originates from strong dipole-dipole interactions mediated by scattered electromagnetic fields. As a result of these interactions, the atoms exhibit collective modes of electronic excitation distributed over the lattice. By tailoring the spatial phase profile of the incident light, one can address specific linear combinations of these modes. We demonstrate how the cooperative response can be used to produce optical excitations at isolated sites in the lattice. \\[4pt] [1] S. D. Jenkins and J. Ruostekoski, Phys. Rev. A \textbf{86} 031602(R) (2012). [Preview Abstract] |
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