Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session S33: Focus Session: Artificial Gauge Fields and Systems with Long Range Interactions II |
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Sponsoring Units: DAMOP Chair: Chuangwei Zhang, University of Texas, Dallas Room: 706 |
Thursday, March 6, 2014 8:00AM - 8:12AM |
S33.00001: Realization of the Harper Hamiltonian with Artificial Gauge Fields in Optical Lattices Hirokazu Miyake, Georgios Siviloglou, Colin Kennedy, William Cody Burton, Wolfgang Ketterle Systems of charged particles in magnetic fields have led to many discoveries in science--such as the integer and fractional quantum Hall effects--and have become important paradigms of quantum many-body physics. We have proposed and implemented a scheme which realizes the Harper Hamiltonian, a lattice model for charged particles in magnetic fields, whose energy spectrum is the fractal Hofstadter butterfly. We experimentally realize this Hamiltonian for ultracold, charge neutral bosonic particles of $^{87}$Rb in a two-dimensional optical lattice by creating an artificial gauge field using laser-assisted tunneling and a potential energy gradient provided by gravity. Laser-assisted tunneling processes are characterized by studying the expansion of the atoms in the lattice. Furthermore, this scheme can be extended to realize spin-orbit coupling and the spin Hall effect for neutral atoms in optical lattices by modifying the motion of atoms in a spin-dependent way by laser recoil and Zeeman shifts created with a magnetic field gradient. Major advantages of our scheme are that it does not rely on near-resonant laser light to couple different spin states and should work even for fermionic particles. Our work is a step towards studying novel topological phenomena with ultracold atoms. [Preview Abstract] |
Thursday, March 6, 2014 8:12AM - 8:24AM |
S33.00002: Synthetic gauge fields in quantum gases of dysprosium Hui Zhai, Benjamin Lev To the toolbox of quantum gas-based many-body physics, highly magnetic atoms offer large, possibly non-perturbative, long-range dipolar interactions concomitant with extraordinarily large SU(2) spinors and novel atomic structure. We report on our recent proposal [1] to create a diversity of exotic quantum many-body phases--non-Abelian quantum magnets, high-spin quantum Hall states--using the unusual properties of dysprosium under the influence of large light-induced gauge fields, both Abelian and non-Abelian, to generate large synthetic magnetic fields and spin-orbit coupling. We will describe recent experimental progress as well as new results on the collisional properties of quantum dipolar Bose and Fermi gases of Dy, recently produced in our laboratory for the first time [2,3], including Feshbach resonance spectra [4]. \\[4pt] [1] X. Cui, B. Lian, T.-L. Ho, B. Lev, and H. Zhai, Synthetic Gauge Field with Highly Magnetic Lanthanide Atoms, PRA 88, 011601(R) (2013). \\[0pt] [2] M. Lu, N. Burdick, S. Youn, and B. Lev, A Strongly Dipolar Bose-Einstein Condensate of Dysprosium, PRL 107, 190401 (2011). \\[0pt] [3] M. Lu, N. Burdick, and B. Lev, Quantum Degenerate Dipolar Fermi Gas, PRL, 108, 215301 (2012).\\[0pt] [4] N. Burdick, K. Baumann, M. Lu, and B. Lev, to be published. [Preview Abstract] |
Thursday, March 6, 2014 8:24AM - 8:36AM |
S33.00003: Bosons with Artificial Gauge Fields and Mott Physics on the Honeycomb Lattice Ivana Vidanovic, Alexandru Petrescu, Karyn Le Hur, Walter Hofstetter We study bosons in the tight-binding model on the honeycomb lattice introduced by Haldane. We analyze the ground state topology and quasiparticle properties in the Mott phase by applying bosonic dynamical mean field theory, strong-coupling perturbation theory, exact diagonalization and numerical evaluations of sample Hall conductivity. The phase diagram also contains two different superfluid phases. The quasiparticle dynamics, number fluctuations, and local currents are measurable in cold atom experiments. [Preview Abstract] |
Thursday, March 6, 2014 8:36AM - 8:48AM |
S33.00004: Topological states in photonic systems Mohammad Hafezi, Sunil Mittal, Prabin Adhikari, Jingyun Fan, Alan Migdall, Jacob Taylor Topological features -- global properties which are not discernible locally -- emerge in systems from magnets to fractional quantum Hall systems. The best known examples are quantum Hall effects, where insensitivity to local properties manifests itself as conductance through edge states that is insensitive to defects and disorder. In this talk, I demonstrate how similar physics can be observed for photons; specifically, how various quantum Hall Hamiltonians can be simulated with linear optical elements. I report the first observation of topological photonic edge state using silicon-on-insulator technology. Furthermore, I discuss the prospect of measuring integer topological invariants, the addition of optical non-linearity and the possibility of implementing fractional quantum Hall states of photons, in both optical and circuit-QED systems. [Preview Abstract] |
Thursday, March 6, 2014 8:48AM - 9:00AM |
S33.00005: Site-resolved detection of current fluctuations Florian Marquardt, Stefan Kessler Two recent developments have significantly expanded the toolbox for ultracold atoms in optical lattices: Site-resolved single-atom detection and the generation of artificial gauge fields. We propose a scheme for site-resolved detection of local current operators [arXiv:1309.3890]. This will allow to measure spatial correlations in fluctuating current patterns and the full counting statistics of local currents. We illustrate the possibilities via numerical simulations for interacting systems of ultracold atoms, with and without an artificial magnetic field. [Preview Abstract] |
Thursday, March 6, 2014 9:00AM - 9:12AM |
S33.00006: Ultracold atoms in a cavity: synthetic gauge fields and cavity-mediated long-range interactions Farokh Mivehvar, David Feder The collective coupling of ultracold neutral atoms to electromagnetic fields in cavity QED results in cavity-mediated long-range atom-atom interactions, paving the way for the realization of strongly correlated states and collective phenomena. That said, quantum Hall and topological insulator states are not directly accessible in these environments because they require the coupling of the particles' center-of-mass motion to external magnetic fields and to internal spin degrees of freedom, respectively. In this work, we show that coupling three-level atoms to two counter-propagating ring-cavity modes in the $\Lambda$ scheme can give rise to synthetic spin-orbit interactions and large synthetic magnetic fields. In the presence of an additional optical lattice, the Hamiltonian in the weak-coupling regime corresponds to an effective spin-orbit coupled Hubbard model for the atoms in the first Bloch band, including a variety of long-range atom-atom interactions. The eigenstates of this model are explored for various choices of the parameters. [Preview Abstract] |
Thursday, March 6, 2014 9:12AM - 9:48AM |
S33.00007: Experimental investigation of spin-orbit coupled BECs Invited Speaker: Peter Engels Ultracold atomic gases provide a powerful tool to study the physics of artificial gauge fields and complex Hamiltonians. In this context, the implementation of spin-orbit coupling is an advancement that is currently met with great interest, both theoretically and experimentally. In our lab we have implemented spin-orbit coupling by using a Raman dressing scheme. Our recent experiments with spin-orbit coupled Bose-Einstein Condensates (BECs) include the observation of quantum quench dynamics and Zitterbewegung, upper spin-orbit band dynamics, and an analogy for the Dicke type phase transition. Furthermore, in our experiments we have studied the physics arising from a combination of spin-orbit coupling and a moving optical lattice: by measuring atom loss due to modulational instability in a system composed of a spin-orbit coupled BEC loaded into a moving optical lattice, the dispersion relation of this system can be investigated. This investigation of the band structure is corroborated by matching theoretical results. I will report on the current status of our ongoing investigations. [Preview Abstract] |
Thursday, March 6, 2014 9:48AM - 10:00AM |
S33.00008: Evidence of Dirac Monopoles in a Spin-1 Bose-Einstein Condensate Michael Ray, Emmi Ruokokoski, Saugat Kandel, Mikko M\"{o}tt\"{o}nen, David Hall Isolated magnetic poles (monopoles) have not yet been observed, although there are good theoretical reasons for thinking that they may exist --- and profound implications if they do. The first successful theoretical description of a magnetic monopole consistent with quantum mechanics was formulated by Dirac [1], but may be applied more generally to quantum-mechanical systems in the presence of gauge potentials. We describe the successful experimental creation of Dirac monopoles in a \emph{synthetic} magnetic field in the context of a dilute-gas Bose-Einstein condensate. The existence of a monopole is inferred from direct observations of a vortex line that terminates inside the condensate, which evidence is supported by excellent agreement between experiment and numerical simulations. [1] P.A.M. Dirac, Proc. R. Soc. Lond. A \textbf{133}, 60 (1932). [Preview Abstract] |
Thursday, March 6, 2014 10:00AM - 10:12AM |
S33.00009: Spin-orbit coupling induced FFLO-like superfluidity and skyrmion-like polarization textures in trapped Fermi gases Menderes Iskin We study the interplay between the Zeeman field and spin-orbit coupling (SOC) in harmonically trapped Fermi gases loaded into a two-dimensional single-band tight-binding optical lattice. Using the Bogoliubov-de Gennes theory, we find that the Zeeman field combined with a Rashba SOC gives rise to $(i)$ Fulde-Ferrell-like superfluidity and $(ii)$ skyrmion-like polarization textures near the edges of the system. The effects of interaction, temperature, SOC anisotropy and Zeeman field anisotropy on the superfluid ground state and polarization textures will also be discussed. [Preview Abstract] |
Thursday, March 6, 2014 10:12AM - 10:24AM |
S33.00010: Spin Transport in Spin Orbit Coupled Bose Einstein Condensates Robert Niffenegger, Abraham Olson, Chuan-Hsun Li, Yong Chen We study spin transport induced by synthetic spin-dependent electric fields in spin-orbit coupled (SOC) Bose Einstein Condensates (BECs). The 1D SOC is created with counter propagating Raman lasers which couple hyperfine spins ($m_F=-1$ and 0, of F=1) and momentum states of $^{87}Rb$, allowing us to engineer spin dependent vector potentials. Quickly lowering the Raman laser intensity (spin-orbit Raman coupling) splits the spin vector potentials in opposite directions and applies opposite synthetic electric fields to the two dressed spin BECs. We allow them to oscillate in opposite directions within the optical trap (exhibiting a spin dipole mode) and measure their momentum after time of flight. The oscillations damp when the spin BECs collide and the damping increases as the Raman coupling is increased, possibly related to the Raman coupling dressing and increasing the effective spin interactions. Over longer time scales, thermalization accompanies the damping of the bare spins' oscillations. However, with Raman coupling, the overdamped dressed spins' oscillations are accompanied by rich excitations in the BEC but less thermalization. Our experiments may provide new insights for understanding and controlling spin transport and spin decoherence in atomtronic or spintronic devices. [Preview Abstract] |
Thursday, March 6, 2014 10:24AM - 10:36AM |
S33.00011: Quantum quasicrystals and other exotic states of spin-orbit coupled dipolar bosons Sarang Gopalakrishnan, Ryan Wilson, Brandon Anderson, Benjamin Lev, Charles Clark, Ivar Martin, Eugene Demler We study dipolar Bose gases in which the bosons experience a Rashba spin-orbit coupling. We show that the degenerate dispersion minimum due to the spin-orbit coupling, combined with the long-range dipolar interaction, can stabilize a rich phase diagram including a number of exotic phases, such as a quantum quasicrystal [1] (in the quasi-2D limit) and a meron state [2] (in the 3D limit), as one tunes the strength of the dipolar interaction and the spin-orbit coupling. We discuss specific level schemes for exploring this phase diagram using ultracold dysprosium. [1] S. Gopalakrishnan, I. Martin, and E.A. Demler, Phys. Rev. Lett. 111, 185304 (2013) [2] R.M. Wilson, B.M. Anderson, and C.W. Clark, Phys. Rev. Lett. 111, 185303 (2013) [Preview Abstract] |
Thursday, March 6, 2014 10:36AM - 10:48AM |
S33.00012: Observing Topological Chiral Orders in 2D Optical Lattices without Spin-orbit Coupling Xiong-Jun Liu, Zheng-Xin Liu, K.T. Law, W. Vincent Liu, T.K. Ng We propose to observe topological chiral orders with cold atoms without spin-orbit coupling in a two-dimensional optical lattice directly based on the recent experiments which use Raman beams to induce the hopping between nearest-neighbor sites. In the simplest case with s-orbital model, the chiral Chern insulating phases are predicted in the single-particle regime. Moreover, by considering a spin-1/2 system, we predict that the chiral spin liquid phase may exist in the interacting regime. This work proposes realistic cold atom platforms to observe topological chiral orders in the experiment. [Preview Abstract] |
Thursday, March 6, 2014 10:48AM - 11:00AM |
S33.00013: Magnetically generated spin-orbit coupling for ultracold atoms Brandon Anderson, Ian Spielman, Gediminas Juzeli\={u}nas We present a new technique for producing two and three dimensional Rashba-type spin-orbit coupling for ultra cold atoms without involving light. The method relies on a sequence of pulsed inhomogeneous magnetic fields imprinting suitable phase gradients on the atoms. For sufficiently short pulse durations, the time-averaged Hamiltonian well approximates the Rashba Hamiltonian. Higher order corrections to the energy spectrum are calculated exactly for spin-1/2 and perturbatively for higher spins. The pulse sequence does not modify the form of rotationally symmetric atom atom interactions. Finally, we present a straightforward implementation of this pulse sequence on an atom-chip. [Preview Abstract] |
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