Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session N2: Optical Lattices |
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Chair: Ken O'Hara, Penn State University Room: Grand Ballroom GF |
Thursday, June 7, 2012 10:30AM - 10:42AM |
N2.00001: Investigation of the Fermi-Hubbard model with $^{6}$Li in an optical lattice Russell A. Hart, Pedro M. Duarte, Tsung-Lin Yang, Randy G. Hulet We present our results on investigation of the physics of the Fermi-Hubbard model using an ultracold gas of $^{6}$Li loaded into an optical lattice. We use all-optical methods to efficiently cool and load the lattice beginning with laser cooling on the $2S_{1/2}\rightarrow 2P_{3/2}$ transition and then further cooling using the narrow $2S_{1/2}\rightarrow 3P_{3/2}$ transition to T $\sim$ 59 $\mu$K.\footnote{P. M. Duarte et al., Phys. Rev. A \textbf{84}, 061406 (2011).} The second stage of laser cooling greatly enhances loading to an optical dipole trap where a two spin state mixture of atoms is evaporatively cooled to degeneracy. We then adiabatically load $\sim$$10^{6}$ degenerate fermions into a 3D optical lattice formed by three orthogonal standing waves of 1064 nm light. Overlapped with each of the three lattice beams is a non-retroreflected beam at 532 nm. This light cancels the harmonic trapping caused by the lattice beams, which extends the number of lattice sites over which a N\'eel phase can exist and facilitates evaporative cooling in the lattice. We investigate the possibility of observing antiferromagnetic ordering of spins in the lattice using Bragg scattering of light.\footnote{T. A. Corcovilos et al., Phys. Rev. A \textbf{81}, 013415 (2010).} [Preview Abstract] |
Thursday, June 7, 2012 10:42AM - 10:54AM |
N2.00002: Dual Mott Insulator in a Spin-Dependent Optical Lattice Hirokazu Miyake, Georgios Siviloglou, Colin Kennedy, David Weld, David Pritchard, Wolfgang Ketterle A major goal of the field of ultracold atoms is the realization of quantum magnetism. It has been theoretically proposed that for a two-component system in an optical lattice, one can emulate the Heisenberg Hamiltonian and observe phases such as XY-ferromagnetism and anti-ferromagnetism by controlling the spin-exchange constants. Towards this goal, we have developed a spin-dependent optical lattice for bosonic $^{87}$Rb atoms that allows us to tune the inter-species interaction energy. In particular, we have studied its effect on the superfluid-to-Mott insulator transition. [Preview Abstract] |
Thursday, June 7, 2012 10:54AM - 11:06AM |
N2.00003: First order SF-MI transition in the Bose-Hubbard model with tunable three-body onsite interaction Barbara Capogrosso-Sansone, Arghavan Safavi-Naini, Javier von Stecher, Seth Rittenhouse Ultra-cold atoms in optical lattices have allowed for exploration of quantum effects beyond the superfluid to Mott insulator transition. Moreover, many-body interactions might give rise to new intriguing phenomena. In this work we study how the presence of an onsite, tunable, $3$-body interaction term affects the many-body physics of the two-dimensional Bose Hubbard model. The 3-body interaction can be tuned by coupling the triply occupied states to a trapped universal trimer. We present mean field results which we compare with Monte Carlo calculations. We find that, as the $3$-body interaction strength increases, the $n=3$ Mott lobe grows larger at the expense of the neighboring lobes and phase transitions from superfluid to Mott insulator become of first order. Our studies at finite temperature show that these transitions remains of first order at temperatures of order of the hopping. [Preview Abstract] |
Thursday, June 7, 2012 11:06AM - 11:18AM |
N2.00004: Degenerate gases of strontium in optical lattices Simon Stellmer, Benjamin Pasquiou, Rudolf Grimm, Florian Schreck Ultracold strontium atoms are subject to active research due to properties not present for alkali atoms. Our recent achievements of quantum degeneracy of all existing bosonic and fermionic isotopes allow for a wide variety of experiments. Insensitivity to external fluctuations, long lifetime metastable states, and decoupling of the nuclear spin from the electronic state make strontium an ideal candidate for quantum computation processes. This system can also be used to implement quantum simulation of many-body effects: strontium atoms exhibit SU(\textit{N}) symmetry, as their collisional properties are spin-independent, and can therefore be used to study SU(\textit{N}) magnetism effects, such as the implementation of the Kondo lattice model or the observation of spin liquids. Here we report on the improved production of degenerate gases of all strontium isotopes. Moreover, we report on the creation of various doubly-degenerate Bose-Bose and Bose-Fermi mixtures of strontium isotopes. We present the adiabatic loading of strontium BEC in a 3D optical lattice into the Mott insulator regime. We also report on the loading of degenerate multi-component Fermi seas of up to 10 spin states in optical lattices, and observe the appearance of the Mott insulator regime for these systems. [Preview Abstract] |
Thursday, June 7, 2012 11:18AM - 11:30AM |
N2.00005: Reservoir-assisted band decay of ultracold atoms in a spin-dependent optical lattice David Chen, David McKay, Carolyn Meldgin, Brian DeMarco We report measurements of reservoir-assisted decay of atoms in excited bands in a cubic, spin-dependent optical lattice. We adiabatically load a 87Rb BEC in a mixture of mF=0 and mF=-1 states into a 3D lattice. Atoms in the mF=-1 state experience a strong lattice potential. On the contrary, atoms in the mF=0 state form a harmonically trapped superfluid reservoir since they do not interact with the lattice. We transfer atoms in the mF=-1 state to the first excited band using stimulated Raman transitions, and we measure the decay rate to the ground band induced by collisions with the reservoir. [Preview Abstract] |
Thursday, June 7, 2012 11:30AM - 11:42AM |
N2.00006: Bose-Einstein Condensation in the second band of an optical lattice, a tight binding analysis and numerical estimate of its formation and decay 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, by 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 reveals that the TB model is not a good approximation for higher bands. In the TB limit, we estimate the life time of the condensate, which is mainly dominated by a two body collision aided decay process to the ground band. Numerically, we find corrections to this, where simultaneous transitions to the ground and an excited band also contributes to the decay of the condensate. \\[4pt] [1] G. Wirth et al., Nature Physics doi:10.1038/nphys1857 [Preview Abstract] |
Thursday, June 7, 2012 11:42AM - 11:54AM |
N2.00007: Sub-wavelength Resonance Imaging and Robust Addressing of Atoms in an Optical Lattice Enrique Montano, Jae Hoon Lee, Poul Jessen, Ivan Deutsch We demonstrate a resonance imaging protocol for optical lattices that enables robust preparation and single qubit addressing of atoms with sub-wavelength resolution in 1D. Our setup consists of a 3D optical lattice, and a superimposed long-period 1D ``superlattice'' that creates a position dependent shift of the transition frequency between two spin states in the ground manifold. We show that isolated planes of atoms can be prepared by flipping resonant spins with a microwave pulse and removing the remaining non-resonant spins. Consecutive microwave pulses in a translated superlattice allow us to image these planes with a resolution better than 200 nm. We show that composite pulse techniques can reduce the sensitivity of the addressing to small variations in the relative position and intensity of the lattices. Furthermore, with this technique, we show that we are able to perform independent unitaries (single qubit quantum gates) on adjacent lattice sites with a single composite pulse. Finally, we perform randomized benchmarking, similar to that done by Olmschenk et al., to measure the error per randomized computational gate for these numerically generated composite pulses. [Preview Abstract] |
Thursday, June 7, 2012 11:54AM - 12:06PM |
N2.00008: Preparation of two-particle total hyperfine spin-singlets via spin-changing interactions Sungkit Yip, Chao-Chun Huang, Ming-Shien Chang For (hyperfine-)spin-1 or spin-2 bosons in a one-dimensional optical lattice in the regime of one particle per site, we have shown [1] that there is a large (interaction) parameter regime where the system has dimerized ground states. Using a period-two superlattice, these dimerized states can be adiabatically transformed to a collection of singlet pairs, or vice versa. Here we describe, starting from two hyperfine spin-1 or 2 particles both with m{\_}F = 0, how spin-changing dynamics under the influence of spin dependent interaction and quadratic Zeeman field can generate two-particle singlets, thus allow us to in principle create these exotic dimerized states. These spin-1 or 2 singlet pairs may also have quantum information science applications. \\[4pt] [1] Pochung Chen,et al, Phys. Rev. A 85, 011601(R) (2012) [Preview Abstract] |
Thursday, June 7, 2012 12:06PM - 12:18PM |
N2.00009: Strongly interacting fermions in a 1D optical lattice Ariel Sommer, Lawrence Cheuk, Mark Ku, Waseem Bakr, Tarik Yefsah, Martin Zwierlein Strongly correlated fermions in an array of two-dimensional planes coupled via tunneling serve as an important model system for high-temperature superconductors and layered organic conductors. We realize this model using ultracold fermionic $^6$Li atoms in a one-dimensional optical lattice near a Feshbach resonance. The depth of the lattice controls the interlayer coupling, and tunes the system between three and two dimensions. Pairing between fermions is studied using radio-frequency spectroscopy. The binding energy of fermion pairs is determined along the dimensional crossover and for different interaction strengths through the BEC-BCS crossover. [Preview Abstract] |
Thursday, June 7, 2012 12:18PM - 12:30PM |
N2.00010: Instabilities of Spin-polarized Fermions in Optical Lattice Chen Yen Lai, Chuntai Shi, Shan-Wen Tsai We study a two species fermion mixture with different populations on a square lattice, which can be modeled by a Hubbard Hamiltonian with on-site inter-species interaction. Such a model can be realized in a cold atom system with fermionic atoms in two different hyperfine states loaded on an optical lattice, and with interaction strength that can be tuned by an external magnetic field. When one of the fermion species is close to half-filling, the system is highly affected by lattice effects. We find several correlated phases for this system, including spin density wave state, d-wave charge density wave state, and p-wave superfluid state for the minority species. We study this system using a functional renormalization group method, determining its phase diagram and providing an estimate for the critical temperature of each phase. These phases emerge from a combination of interaction, population imbalance, and lattice effects. Lattice effects in particular lead to a much richer phase diagram than that of a imbalanced mixture of fermionic gas. [Preview Abstract] |
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