Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session G9: Optical Lattices and Quantum Magnetism 
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Chair: Randall Hulet, Rice University Room: 556AB 
Wednesday, May 25, 2016 8:00AM  8:12AM 
G9.00001: Lattice dynamics in Bosonic $^7$Li Huiyao Y. Chen, Minwoo Jung, Jacob Rabinowitz, Ivaylo S. Madjarov, Hil F. H. Cheung, Yogesh Sharad Patil, Mukund Vengalattore The light mass and strong spindependent interactions in $^7$Li make it an attractive candidate to study Bosonic quantum magnetism and lattice dynamics in regimes where rapid dynamics is favored, e.g. percolative transport and entropy segregation. Such studies require large ensembles of quantum degenerate $^7$Li atoms which has proved to be a technical challenge. We describe our ongoing efforts to overcome this challenge using Raman sideband cooling (RSC). In addition to enabling the rapid production of large degenerate gases, RSC is also a very powerful means of local control of lattice gas dynamics [1]. Extending this to a spinful $^7$Li Bose gas will also enable studies of transport and defect dynamics in F=1 lattice gases. \\[4pt] [1] Y. S. Patil et al., PRL 115, 140402 (2015) [Preview Abstract] 
Wednesday, May 25, 2016 8:12AM  8:24AM 
G9.00002: The influence of lattice geometry on antiferromagnetic correlations and their dynamics in the FermiHubbard model Gregor Jotzu, Daniel Greif, Michael Messer, R\'{e}mi Desbuqois, Frederik G\"{o}rg, Tilman Esslinger It is well known that in the thermodynamic limit, quantum effects hinder the formation of true longrange order in lower dimensions. However, on shorter lengthscales correlations can actually be enhanced by reducing the connectivity of a lattice. Here we report on the observation of antiferromagnetic correlations of ultracold fermions in a variety of optical lattice geometries that are well described by the Hubbard model, including dimers, 1D chains, ladders, isolated and coupled honeycomb planes, as well as square and cubic lattices. The dependence of total correlations and their distribution on the specific geometry is experimentally probed by measuring the spin correlator along different lattice tunnelling bonds. We study distinct geometries as well as continuous crossovers between them, and find a strong dependence on the specific configuration. By dynamically changing the lattice geometry and studying the timeevolution of the system, we determine the time required for the formation and redistribution of spin correlations. Timescales ranging from a sudden quench of the lattice geometry to an adiabatic evolution are probed. [Preview Abstract] 
Wednesday, May 25, 2016 8:24AM  8:36AM 
G9.00003: Detection of antiferromagnetic order by cooling atoms in an optical lattice TsungLin Yang, Rafael Teles, Kaden Hazzard, Randall Hulet We have realized the FermiHubbard model with fermionic $^{6}$Li atoms in a threedimensional compensated optical lattice. \footnote{R. A. Hart, P. M. Duarte et al., Nature 519, 211214 (2015).} The compensated optical lattice has provided low enough temperatures to produce shortrange antiferromagnetic (AF) spin correlations, which we detect via Bragg scattering of light. Previously, we reached temperatures down to 1.4 times that of the AFM phase transition, more than a factor of 2 below temperatures obtained previously in 3D optical lattices with fermions. In order to further reduce the entropy in the compensated lattice, we implement an entropy conduit  which is a single blue detuned laser beam with a waist size smaller than the overall atomic sample size. This repulsive narrow potential provides a conductive metallic path between the low entropy core and the edges of the atomic sample where atoms may be evaporated. In addition, the entropy conduit may store entropy, thus further lowering the entropy in the core. We will report on the status of these efforts to further cool atoms in the optical lattice. [Preview Abstract] 
Wednesday, May 25, 2016 8:36AM  8:48AM 
G9.00004: Firstorder superfluid to Mottinsulator phase transitions in spinor condensates Zihe Chen, Jie Jiang, Lichao Zhao, Shengtao Wang, Tao Tang, Luming Duan, Yingmei Liu We observe evidence of firstorder superfluid to Mottinsulator quantum phase transitions in a latticeconfined antiferromagnetic spinor BoseEinstein condensate. The observed signatures include hysteresis effect, significant heatings across the phase transitions, and evolutions of spin populations due to the formation of spin singlets in the Mottinsulator phase. The nature of the phase transitions is found to strongly depend on the ratio of the quadratic Zeeman energy to the spindependent interaction. Our observations are qualitatively understood by the mean field theory, and in addition suggest tuning the quadratic Zeeman energy is a new approach to realize superfluid to Mottinsulator phase transitions. [Preview Abstract] 
Wednesday, May 25, 2016 8:48AM  9:00AM 
G9.00005: Fermionic superfluidity with repulsive alkalineearth atoms in optical superlattices Leonid Isaev, Ana Maria Rey We propose a novel route to superfluidity in fermionic alkalineearth atoms with repulsive interactions, that uses local kineticenergy fluctuations as a "pairing glue" between the fermions. We exploit different polarizabilities of electronic ${}^1 S_0$ ($g$) and ${}^3 P_0$ ($e$) states of the atoms to confine the $e$ and $g$ species in different optical superlattices. For example, in a onedimensional case the $e$lattice can be implemented as an array of weaklycoupled doublewells (DWs) with large intraDW tunneling, and contain one localized $e$atom in each DW to avoid losses due to $e$$e$ collisions. On the contrary, the shallow $g$lattice has a large bandwidth and an arbitrary filling. We consider a nuclearspin polarized system and demonstrate how kineticenergy fluctuations of the localized $e$atoms mediate an attractive interaction between the $g$fermions, thus leading to a $p$wave superfluid. We derive a lowenergy model and determine the stability of this state against chargedensity wave formation and phase separation. Our results can be tested with ${\rm Yb}$ or ${\rm Sr}$ fermionic atoms and have a direct relevance for the physics of hightemperature superconductor materials. [Preview Abstract] 
Wednesday, May 25, 2016 9:00AM  9:12AM 
G9.00006: Measurement of the Equation of State of the TwoDimensional Hubbard Model Luke Miller, Eugenio Cocchi, Jan Drewes, Marco Koschorreck, Daniel Pertot, Ferdinand Brennecke, Michael Koehl The subtle interplay between kinetic energy, interactions and dimensionality challenges our comprehension of stronglycorrelated physics observed, for example, in the solid state. In this quest, the Hubbard model has emerged as a conceptually simple, yet rich model describing such physics. Here we present an experimental determination of the equation of state of the repulsive twodimensional Hubbard model over a broad range of interactions, $0 \leq U/t \leq 20$, and temperatures, down to $k_{B}T/t = 0.63(2)$ using highresolution imaging of ultracold fermionic atoms in optical lattices. We show density profiles, compressibilities and double occupancies over the whole doping range, and hence our results constitute benchmarks for stateoftheart theoretical approaches. [Preview Abstract] 

G9.00007: ABSTRACT WITHDRAWN 
Wednesday, May 25, 2016 9:24AM  9:36AM 
G9.00008: Observation of Nonlinear Looped Band Structure of BoseEinstein condensates in an optical lattice Elizabeth Goldschmidt, Silvio Koller, Roger Brown, Robert Wyllie, Ryan Wilson, Trey Porto We study experimentally the stability of excited, interacting states of bosons in a doublewell optical lattice in regimes where the nonlinear interactions are expected to induce ``swallowtail'' looped band structure. By carefully preparing different initial coherent states and observing their subsequent decay, we observe distinct decay rates, which provide direct evidence for multivalued band structure. The double well lattice both stabilizes the looped band structure and allows for dynamic preparation of different initial states, including states within the loop structure. We confirm our state preparation procedure with dynamic GrossPitaevskii calculations. The excited loop states are found to be more stable than dynamically unstable ground states, but decay faster than expected based on a meanfield stability calculation, indicating the importance of correlations beyond a meanfield description. [Preview Abstract] 
Wednesday, May 25, 2016 9:36AM  9:48AM 
G9.00009: Quantum memory effects in noninteracting coldatom systems: Hysteresis loop and lattice transformation Chihchun Chien, Mekena Metcalf, Chenyen Lai Memory effects are observable in magnetization, rechargeable batteries, and many systems exhibiting historydependent states. Quantum memory effects are observable, for instance, in atomic superfluids [1]. A counterintuitive question is whether quantum memory effects can exist in noninteracting systems. Here we present two examples of coldatom systems demonstrating memory effects in noninteracting systems. The first example is a ringshaped potential loaded with noninteracting fermions. An artificial vector potential drives a current and with a tunable dissipative background, the current lags behind the driving and exhibits hysteresis loops. The dissipative energy can be controlled by the coupling between the fermions and the background. In the second example, cold atoms loaded in a tunable optical lattice transformed from the triangular to the kagome geometry. The kagome lattice supports a flatband consisting of degenerate localized states. Quantum memory effects are observable after a lattice transformation as the steadystate density depends on the rate of the transformation [2]. The versatility of memory effects in coldatom systems promises novel applications in atomtronics. [1] S. Eckel et al., Nature 506, 200 (2014). [2] C. Y. Lai and C. C. Chien, arXiv:1510.08978. [Preview Abstract] 
Wednesday, May 25, 2016 9:48AM  10:00AM 
G9.00010: Quench Dynamics of Quasi2D Antiferromagnetic Spinor Condensates Seji Kang, Sang Won Seo, Joon Hyun Kim, Yongil Shin We report on the quench dynamics of quasi2D antiferromagnetic spin1 BoseEinstein condensates, where we prepare a highly oblate condensate in the easyaxis polar phase with a positive quadratic Zeeman energy, q\textgreater 0 and quench the condensate to the eaxyplane polar phase by suddenly changing q to negative. The initial instability is caused by transverse magnons as expected in a meanfield Bogoliubov theory and then, spin turbulence is generated and relaxed, leading to creation of topological defects such as halfquantum vortices. We characterize the quench dynamics by measuring the temporal evolution of the spin populations and the spatial distribution of magnetization. The scaling behavior of the quench dynamics will be discussed in terms of initial instability, spin wave generation, and defect formation. [Preview Abstract] 
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