Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session H02: Atoms in Optical Lattices I |
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Chair: Trey Porto, National Institute of Standards and Technology Room: Grand A |
Wednesday, May 30, 2018 8:00AM - 8:12AM |
H02.00001: Band and correlated insulators of cold fermions in a mesoscopic lattice Martin Lebrat, Pjotrs Gri\v{s}ins, Dominik Husmann, Samuel H\"{a}usler, Laura Corman, Thierry Giamarchi, Jean-Philippe Brantut, Tilman Esslinger Conductance is one of the simplest measurable quantities revealing the conducting or insulating nature of a physical system, and yet an intricate non-local property sensitive to quantum interferences and interactions at a microscopic level. In our cold-atom setup, such a conductance measurement can be performed by connecting two macroscopic reservoirs of ultracold fermions to a smaller structure engineered by light potentials, and probing the current created by a atom number difference between the reservoirs. We report on the transport of degenerate Lithium-6 atoms through a structure tailored in a bottom-up approach: Using a Digital Micromirror Device to project up to nine consecutive scatterers inside a one-dimensional constriction, a lattice can be formed one site at a time. We observe the emergence of a band gap, originating from interferences among the scatterers. The coherent character of transport can be investigated by independently changing the lattice length and the temperature. The presence of a gap is robust against strongly attractive interparticle interactions and hints at the existence of a Luther-Emery liquid, a novel phase distinctive of the one-dimensional character of the underlying wire. [Preview Abstract] |
Wednesday, May 30, 2018 8:12AM - 8:24AM |
H02.00002: Exploration of a Floquet phase diagram in a driven optical lattice Kevin Singh, Kurt Fujiwara, Zachary Geiger, Mikhail Lipatov, David Weld Ultracold atoms in modulated optical lattices provide an ideal test bed for exploring the response of many-body quantum systems to strong driving. The stabilization or destabilization of new states of matter by variation of drive parameters can be encapsulated in Floquet phase diagrams; these maps of system properties as a function of drive parameters can be viewed as a nonequilibrium generalization of thermodynamic phase diagrams. We report on experimental exploration of a Floquet phase diagram using ultracold bosonic lithium in a strongly-driven optical lattice. As the drive frequency and amplitude are tuned into previously unexplored regions, we observe a sharp transition line between stable and unstable behavior. We explore the effect of Feshbach-tunable interactions and variable tunneling on the properties of this Floquet phase diagram, and compare the results to classical and quantum theories. [Preview Abstract] |
Wednesday, May 30, 2018 8:24AM - 8:36AM |
H02.00003: Quantum state engineering of a Hubbard system with ultracold fermions Geoffrey Ji, Christie Chiu, Muqing Xu, Anton Mazurenko, Daniel Greif, Markus Greiner Accessing new regimes in quantum simulation requires development of new techniques for quantum state preparation. We demonstrate quantum state engineering of a strongly-correlated many-body state of the two-component repulsive Fermi-Hubbard model on a square lattice. Our scheme makes use of an ultra-low entropy doublon band insulator created through entropy redistribution. After isolating the band insulator, we change the underlying potential to expand it into a half-filled system. The final many-body state realized shows strong antiferromagnetic correlations and a temperature below the exchange energy. We observe an increase in entropy, which we find is likely caused by many-body physics during the expansion process. Finally, we investigate possible means of improving the adiabaticity of the scheme. This technique is promising for low-temperature studies of cold-atom-based lattice models. [Preview Abstract] |
Wednesday, May 30, 2018 8:36AM - 8:48AM |
H02.00004: Beating the diffraction limit: an optical lattice of sub-wavelength barriers Yang Wang, Sarthak Subhankar, Przemyslaw Bienias, Mateusz Lkacki, Tsz-chun Tsui, Mikhail Baranov, Alexey Gorshkov, Peter Zoller, James Porto, Steven Rolston We report on the creation of a conservative optical lattice for cold atoms with sub-wavelength features well below the diffraction limit of the light. To achieve this, we use the nonlinear optical response of three-level atoms in spatially dependent dark states. The geometric gauge potential of atoms in this spatially dependent dark state provides a conservative potential with ultra-narrow barriers, physically realizing a Kronig-Penney potential. We demonstrate optical lattices with barrier widths less than $\lambda/50$, study the band structure and dissipation mechanisms, and compare experimental findings with theory. The potential is generalizable to higher dimensions and different geometries, allowing, for example, nearly perfect box traps, narrow tunnel junctions for atomtronics applications, and dynamically generated lattices with subwavelength spacings. [Preview Abstract] |
Wednesday, May 30, 2018 8:48AM - 9:00AM |
H02.00005: Observation of the Sliding Phase in $^8^7$Rb A Dewan, M. E. W Reed, Z. S Smith, S. L Rolston We present observations of the sliding phase in disordered ultracold $^{87}$Rb. For systems with \emph{a,b,c} axis, and 1D disorder along \emph{c}-axis, the sliding phase is when ``\emph{c}-axis superfluid response disappears, while the system remains superfluid in the \emph{a} and \emph{b} directions'' \footnote{ David Pekker \emph{et} \emph{al.}, \textbf{Phys. Rev Lett.}, 105:085302, 2010}. We generate the sliding phase potential using a disordered optical lattice generated by our high-bandwidth arbitrary lattice apparatus. Our findings show three phase crossover regimes at distinct temperatures, which compares favourably to theoretical predictions$^($\footnote{Ibid.}$^,$\footnote{Priyanka Mohan \emph{et} \emph{al.}, \textbf{Phys. Rev Lett.}, 105:085301, 2010}$^,$\footnote{Nicolas Laflorencie, \textbf{EPL}, 99, 2012}$^)$. In addition, we present data suggesting the presence of a Griffiths phase. [Preview Abstract] |
Wednesday, May 30, 2018 9:00AM - 9:12AM |
H02.00006: Realization of Dirac semi-metal bands in a two-dimensional optical lattice with spin-orbit coupling Bo Song, Chengdong He, Zejian Ren, Elnur Hajiyev, Qianhang Cai, Xiong-Jun Liu, Gyu-Boong Jo Spin-orbit coupling is a key mechanism to induce exotic band structures and gives rise to topological phases. In this talk, we will report our experimental realization of spin-obit coupling in a two-dimensional (2D) optical lattice, and the observation of tunable 2D Dirac semimetal band structures. We highlight the tunability of band topology in our system by showing the band inversion, manipulating the asymmetry of semimetal bands and tuning the dimensionality. Furthermore, we probe the Dirac point by monitoring the time-averaged momentum-resolved spin texture after the quench from the trivial to the Dirac semimetal bands. Our work demonstrated here provides an experimental platform to explore novel topological phases of matter for cold atoms. [Preview Abstract] |
Wednesday, May 30, 2018 9:12AM - 9:24AM |
H02.00007: High precision multi-band spectroscopy of ultracold atoms in optical lattices Benno Rem, Nick Flaeschner, Matthias Tarnowski, Dominik Vogel, Klaus Sengstock, Christof Weitenberg Spectroscopic tools are fundamental for the understanding of complex quantum systems. Here we demonstrate high-precision multi-band spectroscopy in a graphene-like lattice using ultracold fermionic atoms. From the measured band structure, we characterize the underlying lattice potential with a relative error of $1.2\cdot10^{-3}$. Such a precise characterization of complex lattice potentials is an important step towards precision measurements of quantum many-body systems. Furthermore, we explain the excitation strengths into the different bands with a model and experimentally study their dependency on the symmetry of the perturbation operator. This insight suggests the excitation strengths as a suitable observable for interaction effects on the eigenstates. [Preview Abstract] |
Wednesday, May 30, 2018 9:24AM - 9:36AM |
H02.00008: Site-Resolved Microscopy of a Photonic Mott Insulator Ruichao Ma, Clai Owens, Brendan Saxberg, David Schuster, Jonathan Simon Superconducting circuits have emerged as a competitive platform for realizing a practical quantum computer, satisfying the challenges of controllability, long coherence and strong interactions between individual systems. In this work, we apply this well-developed toolbox to a different problem: the exploration of strongly correlated phases of photonic quantum matter. The qubits of the quantum circuit become the sites of a Bose Hubbard lattice - their anharmonicity provides the on-site photon-photon interaction, couplings between them generates inter-site tunneling, while multiplexed qubit readout provides time- and site- resolved microscopy of the Bose Hubbard system. We further develop a new method for dissipative preparation and stabilization of incompressible phases of matter, achieved through reservoir engineering. We characterize our Bose-Hubbard system through coherent lattice dynamics including quantum random walks, and then connect it to the dissipative stabilizer to realize and investigate a Mott insulator of photons. These experiments demonstrate the power of superconducting circuits for studying strongly correlated physics, and with the recently demonstrated low-loss microwave Chern insulators could point the way to topological many-body states of photons. [Preview Abstract] |
Wednesday, May 30, 2018 9:36AM - 9:48AM |
H02.00009: Dicke model simulation via cavity-assisted Raman transitions Zhiqiang Zhang, Chern Hui Lee, Ravi Kumar, Kyle Arnold, Stuart Masson, Arne Grimsmo, Scott Parkins, Murray Barrett The Dicke model is of fundamental importance in quantum mechanics for understanding the collective behaviour of atoms coupled to a single electromagnetic mode. Here, we demonstrate a Dicke-model simulation using cavity-assisted Raman transitions in a configuration using counter-propagating laser beams. The observations indicate that motional effects should be included to fully account for the results and these results are contrasted with the experiments using single-beam and co-propagating configurations. A theoretical description is given that accounts for the beam geometries used in the experiments and indicates the potential role of motional effects. In particular a model is given that highlights the influence of Doppler broadening on the observed thresholds. [Preview Abstract] |
Wednesday, May 30, 2018 9:48AM - 10:00AM |
H02.00010: Self-adapted Floquet Dynamics of Ultracold Bosons in a Cavity Xi-Wang Luo, Chuanwei Zhang Floquet dynamics of a quantum system subject to periodic modulations of system parameters provide a powerful tool for engineering new quantum matter with exotic properties. While system dynamics are significantly altered, the periodic modulation itself is usually induced externally and independent of Floquet dynamics. Here we propose a new type of Floquet physics for a Bose-Einstein condensate (BEC) subject to a shaken lattice generated inside a cavity, where the shaken lattice and atomic Floquet bands are mutually dependent, resulting in self-adapted Floquet dynamics. In particular, the shaken lattice induces Floquet quasi-energy bands for the BEC, whose back action leads to a self-adapted dynamical normal-superradiant phase transition for the shaken lattice. Such self-adapted Floquet dynamics show two surprising and unique features: \textit{i}) the normal-superradiant phase transition possesses a hysteresis even without atom interactions; \textit{ii}) the dynamical atom-cavity steady state could exist at free energy maxima. The atom interactions strongly affect the phase transition of the BEC from zero to finite momenta. Our results provide a powerful platform for exploring self-adapted Floquet dynamics, which may open an avenue for engineering novel quantum materials. [Preview Abstract] |
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