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 C3: Synthetic Spin-Orbit Coupling |
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Chair: Peter Engels, Washington State University Room: 202 |
Tuesday, June 4, 2013 2:00PM - 2:12PM |
C3.00001: A direct measurement of Zitterbewegung in a BEC Lindsay LeBlanc, Matthew Beeler, Karina Jimenez-Garcia, Abigail Perry, Seiji Sugawa, Ross Williams, Ian Spielman The Dirac Hamiltonian was originally formulated to describe the dynamics of relativistic electrons within the framework of quantum mechanics. One of the phenomena to emerge from this description is ``zitterbewegung,'' a trembling motion whose frequency is related to the particles' rest energy. To study this equation through quantum simulation, we used a $^{87}$Rb Bose-Einstein condensate with two internal levels coupled by Raman lasers. The characteristic energy, frequency and length scales of this system fall within an experimentally accessible range. Using direct measurements, both insitu and time-of-flight, we measured the oscillatory motion of neutral BECs upon application of the Dirac Hamiltonian. Through this quantum simulation, we can relate zitterbewegung to a more familiar phenomenon ubiquitous in atomic physics: Rabi flopping in a two-level system. [Preview Abstract] |
Tuesday, June 4, 2013 2:12PM - 2:24PM |
C3.00002: Quantum quenches and spin dynamics in spin-orbit coupled Bose-Einstein condensates Peter Engels, Chris Hamner Spin-orbit coupled ultra-cold atoms provide an intriguing new avenue for the study of rich spin dynamics in superfluids. We investigate non-equilibrium spin dynamics in a spin-orbit coupled Bose-Einstein condensate that are induced by sudden quantum quenches of the Hamiltonian yielding dynamics analogous to Zitterbewegung as well as excited band dynamics. Current and ongoing research will be presented. [Preview Abstract] |
Tuesday, June 4, 2013 2:24PM - 2:36PM |
C3.00003: Dzyaloshinskii-Moriya Interaction and Spiral Order in Spin-orbit Coupled Optical Lattices Chuanwei Zhang, Ming Gong, Yinyin Qian, Vito Scarola We show that the recent experimental realization of spin-orbit coupling in ultracold atomic gases can be used to study different types of spiral order and resulting multiferroic effects. Spin-orbit coupling in optical lattices can give rise to the Dzyaloshinskii-Moriya (DM) spin interaction which is essential for spin spiral order. We derive an effective spin model in the deep Mott insulator region at half filling, and demonstrate that the DM interaction in optical lattices can be made extremely strong with realistic experimental parameters. The rich phase diagrams of the effective spin model for fermion and bosons are obtained via classical Monte Carlo simulations. [Preview Abstract] |
Tuesday, June 4, 2013 2:36PM - 2:48PM |
C3.00004: Adiabatic momentum space treatment of a spin-orbit coupled BEC Su-Ju Wang, Chris Greene By dressing the atomic spin states with Raman laser fields, experimentalists can create spin-orbit coupled Bose-Einstein condensates (BECs) by tuning controllable parameters in an ultracold atomic system [1]. In the presence of spin-orbit coupling, we study the spin dynamics of a harmonically-trapped spinor BEC that can be driven by non-adiabatic Landau-Zener transitions occurring at avoided crossings between the bands. \\[4pt] [1] Y. J. Lin, K. Jimenez-Garcia and I.B. Spielman, Nature, 471, 83 (2011). [Preview Abstract] |
Tuesday, June 4, 2013 2:48PM - 3:00PM |
C3.00005: Exotic Quantum Spin Models in Spin-Orbit-Coupled Mott Insulators Juraj Radic, Andrea Di Ciolo, Kai Sun, Victor Galitski We study cold atoms in an optical lattice with synthetic spin-orbit coupling in the Mott-insulator regime. We calculate the parameters of the corresponding tight-binding model using Peierls substitution and ``localized Wannier states method'' and derive the low-energy spin Hamiltonian for bosons and fermions. The spin Hamiltonian is a combination of Heisenberg model, quantum compass model and Dzyaloshinskii-Moriya interactions and it has a rich classical phase diagram with collinear, spiral and vortex phases. We discuss the state of the art of experiments to realize and detect magnetic orderings in strongly correlated optical lattices. [Preview Abstract] |
Tuesday, June 4, 2013 3:00PM - 3:12PM |
C3.00006: Bosons with Synthetic Rashba Spin-Orbit Coupling at Finite Power Brandon Anderson, Charles Clark Isotropic spin-orbit couplings, such as Rashba in two dimensions, have a continuous symmetry that produces a large degeneracy in the momentum-space dispersion. This degeneracy leads to an enhanced density-of-states, producing novel phases in systems of bosonic atoms. This model is idealistic, however, in that the symmetry of the lasers will weakly break the continuous symmetry to a discrete one in experimental manifestations. This perturbation typically scales inversely with the optical power, and only at infinite power will ideal symmetry be restored. In this talk, we consider the effects of this weak symmetry breaking in a system of bosons at finite power with synthetic Rashba coupling. We solve the mean-field equations and find new phases, such as a stripe phase with a larger symmetry group. We then consider the experimentally relevant scheme where the spin-orbit fields are turned on adiabatically from an initial spin-polarized state. At intermediate power, stripe phases are found, while at sufficiently high power it appears that the system quenches to phases similar to that of the ideal limit. Techniques for optimizing the adiabatic ramping sequence are discussed. [Preview Abstract] |
Tuesday, June 4, 2013 3:12PM - 3:24PM |
C3.00007: Spin-Orbit Coupling for a Neutral Atom inside a Ring Cavity Farokh Mivehvar, David Feder The spin-orbit (SO) interaction in solids, the coupling of an electron's center-of-mass momentum to its spin degrees of freedom, can give rise to fascinating new quantum states. These include topological insulator (TI) states, which are similar to quantum Hall states but require no external magnetic fields. Very recently, artificial SO interactions have been induced in ultracold neutral atomic gases through resonant Raman couplings. We build on these methods to show how to induce a SO interaction for a neutral atom confined inside a ring cavity. This is effected by coupling three internal states of the atom to two counter-propagating ring-cavity modes in the $\Lambda$ scheme. Unlike a linear cavity, ring cavities support traveling modes which allow momentum transfer between a photon and an atom. The scheme is able to simultaneously generate an adjustable artificial magnetic vector potential. Combined with strong cavity-mediated atom-atom interactions, this approach could readily yield strongly-correlated TI states in cavity QED. [Preview Abstract] |
Tuesday, June 4, 2013 3:24PM - 3:36PM |
C3.00008: Inter-band transitions and dynamics of Bose-Einstein condensates with modulated spin-orbit and scalar gauge field potentials Abraham Olson, Robert Niffenegger, Yong P. Chen We have experimentally studied optically-trapped Bose-Einstein condensates (BECs) of $^{87}$Rb atoms in the presence of temporally modulated synthetic spin-orbit (SO) and scalar gauge potentials. We load our BECs in spin-momentum dressed-state energy bands in either the SO or scalar gauge potential regime using a Raman coupling of the ground state atomic magnetic sublevels (following similar techniques developed by the NIST group). We then modulate the strength of the Raman coupling, and study the evolution of the BEC following the modulation for different initial conditions and modulation parameters. A number of interesting behaviors are observed, including inter-band oscillations and various complex longer-time scale dynamics. We have also developed another technique of inter-band excitation spectroscopy to probe the synthetic energy bands of the BEC. [Preview Abstract] |
Tuesday, June 4, 2013 3:36PM - 3:48PM |
C3.00009: Generating spin dependent synthetic electric and magnetic fields in BECs Robert Niffenegger, Abraham Olson, Yong Chen We report experiments aimed to generate spin dependent synthetic electromagnetic fields in $^{87}$Rb BECs subject to optical Raman fields that couple different hyperfine spin and momentum states to create dressed state energy bands with synthetic gauge fields and spin orbit interactions. In one set of experiments, we adiabatically load an optically-trapped $^{87}$Rb BEC into the single ground state minimum of the dressed state band with strong Raman coupling. This starts the BEC as a superposition between two spin states ($|F=1,m_F=-1>$ and $|F=1,m_F=0>$) with opposite momenta. We have observed that dynamically lowering the Raman coupling strength into the spin-orbit regime can actuate opposite oscillations of the two trapped spin components about their new vector potential minima, giving rise to an alternating (AC) spin current. We interpret this as due to spin dependent synthetic electric fields generated by dynamically splitting the dressed state band minimum into two. We have studied the oscillating spin current and its damping on the rate of change in vector potential, the spin populations, initial and final Raman coupling, and Raman detuning. We are also developing techniques to produce spin dependent magnetic fields in spatially varying Raman coupling. [Preview Abstract] |
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