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 G7: Interaction Effects in Spin-Orbit Coupled Gases |
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Chair: Blair Blakie, University of Otago Room: 553AB |
Wednesday, May 25, 2016 8:00AM - 8:12AM |
G7.00001: Detecting stripe phase in spin-orbit coupled condensates via optical Bragg scattering Andika Putra, Francisco Salces Carcoba, Yuchen Yue, Seiji Sugawa, Ian Spielman The stripe phase in spin-orbit coupled condensates has been predicted theoretically [1] but not yet been observed. This peculiar feature, analogue to supersolidity, originates from the interaction effects and spin-momentum locking between different spin states. Motivated by recent observation of antiferromagnetic correlations in cold atoms [2], we explore the feasibility of Bragg diffraction to observe the stripe phase. Here, we create spin-orbit coupled condensates in f$=$1 ground state manifold of Rb87 using a pair of cross-polarized 790.02 nm counter-propagating laser beams. Using similar setup, we make a spin-dependent one dimensional lattice and demonstrate Bragg scattering of light to calibrate the atomic density distribution. This enables us to do a direct measure of the stripe phase. [1] Martone et al., Phys Rev A 90, 041604 (2014) [2] Hart et al., Nature 519, 211 (2015) [Preview Abstract] |
Wednesday, May 25, 2016 8:12AM - 8:24AM |
G7.00002: Synthetic gauge fields in synthetic dimensions: the effect of interactions Leonardo Mazza, Simone Barbarino, Luca Taddia, Davide Rossini, Rosario Fazio Synthetic ladders realized with one-dimensional alkaline-earth(-like) fermionic gases and subject to a gauge field represent a promising environment for the investigation of quantum Hall physics with ultracold atoms. We unveil the existence of a hierarchy of fractional insulating and conducting states with intriguing properties by means of both analytical techniques and numerical methods. In particular, we show that the gapless phases can support helical modes, whereas the gapped states, which appear under certain conditions, are characterised both by density and magnetic order. The properties of this hierarchy of states can be experimentally studied in state-of-the-art cold-atom laboratories. [Preview Abstract] |
Wednesday, May 25, 2016 8:24AM - 8:36AM |
G7.00003: Reservoir induced topological order and quantized charge pumps in open lattice models with interactions Dominik Linzner, Malte Koster, Fabian Grusdt, Michael Fleischhauer Since the discovery of the quantum Hall effect, topological states of matter have attracted the attention of scientists in many fields of physics. By now there is a rather good understanding of topological order in closed, non-interacting systems. In contrast the extension to open systems in particular with interactions is entirely in its infancy. Recently there have been advances in characterizing topology in reservoir driven systems without interactions, but the topological invariants introduced lack a clear physical interpretation and are restricted to non-interacting systems. We consider a one-dimensional interacting topological system whose dynamics is entirely driven by reservoir couplings. By slowly tuning these couplings periodically in time we realize an open-system analogue of the Thouless charge pump that proves to be robust against unitary and non-unitary perturbations. Making use of this Thouless pump we introduce a topological invariant, which is applicable to interacting systems. Finally we propose a conceptual detection scheme that translates the open-system topological invariant into the context of a well understood closed system. [Preview Abstract] |
Wednesday, May 25, 2016 8:36AM - 8:48AM |
G7.00004: Detecting Topological Phases in Ultracold Atomic Gases with Strong Interactions Dong-Ling Deng, Sheng-Tao Wang, Kai Sun, L.-M. Duan We propose a generic scheme to unambiguously probe topological invariants in ultracold-atomic systems using momentum-resolved Raman or radio-frequency spectroscopy. The method is based on Green's function formulations and is applicable to a wide range of topological states in arbitrary spatial dimensions with or without strong interactions. Using an interacting one-dimensional topological insulator as an example, we further demonstrate that the scheme is robust against realistic experimental imperfections, such as the inhomogeneous trapping potential and limited experimental resolution. [Preview Abstract] |
Wednesday, May 25, 2016 8:48AM - 9:00AM |
G7.00005: Probing the holographic principle using dynamical gauge effects from open spin-orbit coupling Jianshi Zhao, Craig Price, Qi Liu, Nathan Gemelke Dynamical gauge fields result from locally defined symmetries and an effective over-labeling of quantum states. Coupling atoms weakly to a reservoir of laser modes can create an effective dynamical gauge field purely due to the disregard of information in the optical states. Here we report measurements revealing effects of open spin-orbit coupling in a system where an effective model can be formed from a non-abelian $SU(2)\times U(1)$ field theory following the Yang-Mills construct. Forming a close analogy to dynamical gauge effects in quantum chromodynamics, we extract a measure of atomic motion which reveals the analog of a closing mass gap for the relevant gauge boson, shedding insight on long standing open problems in gauge-fixing scale anomalies. Using arguments following the holographic principle, we measure scaling relations which can be understood by quantifying information present in the local potential. New prospects using these techniques for developing fractionalization of multi-particle and macroscopic systems using dissipative and non-abelian gauge fields will also be discussed. [Preview Abstract] |
Wednesday, May 25, 2016 9:00AM - 9:12AM |
G7.00006: Bose-Einstein condensate in an optical lattice with Raman-assisted two-dimensional spin-orbit coupling Jian-Song Pan, Wei Zhang, Wei Yi, Guang-Can Guo In a recent experiment by Wu {\textit et al.}, a Raman-induced two-dimensional spin-orbit coupling has been realized for a Bose-Einstein condensate in an optical lattice potential. In light of this exciting progress, we investigate key properties of the system including single-particle spectrum, many-body phase diagram, and quasi-particle excitations. As the lasers generating the spin-orbit coupling inevitably couple atoms to high-lying bands, all of these properties can be greatly affected. In particular, we show that high-band induced ``roton'' gaps emerge in the quasi-particle excitation spectrum, which become softened as the system approaches the stripe phase. We also calculate the topological invariants of the lowest bands in both the single-particle and the quasi-particle spectra, from which high-band induced topological boundaries are identified. These non-trivial band topologies can give rise to topological transitions in Fermi systems or to chiral edge excitations in Bose gases. Our results can be readily observed in current experiments and provide valuable insights that are helpful for future exploration of this novel two-dimensional lattice spin-orbit coupling. [Preview Abstract] |
Wednesday, May 25, 2016 9:12AM - 9:24AM |
G7.00007: Interaction driven quantum phases in spin-orbit-coupled spin-1 bosons Jedediah Pixley, Stefan Natu, William Cole, Matteo Rizzi, Ian Spielman We study the interplay of spin orbit coupling and strong correlations present for ultra cold spin-1 bosons on a square optical lattice. In addition to the conventional spinful Mott and superfluid phases contained in the spin-1 Bose-Hubbard model, we find new lattice symmetry breaking phases [1]. For weak interactions, the interplay between the lattice momentum and the spin-orbit wave-vector induces a phase transition from a uniform superfluid to a phase where bosons simultaneously condense at the center and edge of the Brillouin zone. This state is characterized by spin density wave order, which arises from the spin-1 nature of the system. Interactions suppress this spin density wave order, and for sufficiently strong interactions the system becomes a Mott insulator. Inside the Mott lobes with an odd-integer filling we derive the effective low energy magnetic Hamiltonian. Focusing on the quasi-one-dimensional limit we solve the strongly coupled magnetic model in three ways: in its classical limit, with a spin-wave analysis, and using the density matrix renormalization group. [1] J. H. Pixley, et. al. arXiv:1509.00005. (Accepted in PRB (R)) [Preview Abstract] |
Wednesday, May 25, 2016 9:24AM - 9:36AM |
G7.00008: Vortex lattice phases in bosonic ladders in the presence of gauge field Marie Piraud, Sebastian Greschner, Fabian Kolley, Ian P. McCulloch, Ulrich Schollwoeck, Fabian Heidrich-Meisner, Temo Vekua We study vortex lattices in the interacting Bose-Hubbard model defined on two- and three-leg ladder geometries in the presence of a homogeneous flux. Our work is motivated by recent experiments using laser assisted-tunneling in optical lattices [1] and lattices in synthetic dimensions [2], which studied the regime of weak interactions. We focus on the effects arising from stronger interactions, in both the real space optical lattice and the synthetic dimension schemes.\\ Based on extensive density matrix renormalization group simulations and a bosonization analysis, we show that vortex lattices form at certain commensurate vortex densities [3,4]. We identify the parameter space in which they emerge, and study their properties.\\ Very interestingly, an enlarged unit cell forms in the vortex lattice phases, which can lead to the reversal of the current circulation-direction in both geometries [3,4]. We demonstrate this effect in weak coupling and at sufficiently low temperature, and show that it is significant for intermediate interactions [4]. \medskip \\ {[1]} Atala et al., Nature Phys. 10, 588 (2014)\\ {[2]} Stuhl et al., Science 349, 1514 (2015)\\ {[3]} Kolley et al., New J. Phys. 17, 092001 (2015)\\ {[4]} Greschner et al., Phys. Rev. Lett. 115, 190402 (2015) [Preview Abstract] |
Wednesday, May 25, 2016 9:36AM - 9:48AM |
G7.00009: Quantum Critical Dynamics of Bose-Einstein Condensates in a Shaken Optical Lattice Logan W. Clark, Lei Feng, Li-Chung Ha, Cheng Chin From condensed matter to cosmology, systems which cross a continuous, symmetry-breaking phase transition are expected to generate topological defects whose density scales universally with the rate at which the phase transition is crossed. We experimentally test the application of this universal Kibble-Zurek scaling prediction to quantum phase transitions by studying ultracold bosons in a shaken optical lattice. When the lattice shaking amplitude crosses a critical threshold, an ordinary Bose condensate transitions to an effectively ferromagnetic pseudo-spinor condensate with discrete, magnetized regions separated by domain walls. We appraise the dynamic scaling laws for both the time at which the domain structure forms and the typical size of the domains by varying the quench rate across the transition. We explore the regime in which the universal prediction applies, as well as potential deviations at extreme quench rates. [Preview Abstract] |
Wednesday, May 25, 2016 9:48AM - 10:00AM |
G7.00010: Shaken lattice interferometry Carrie Weidner, Hoon Yu, Dana Anderson In this work, we report on progress towards performing interferometry using atoms trapped in an optical lattice. That is, we start with atoms in the ground state of an optical lattice potential $V(x) = V_0\cos[2kx + \phi(t)]$, and by a prescribed phase function $\phi(t)$, transform from one atomic wavefunction to another. In this way, we implement the standard interferometric sequence of beam splitting, propagation, reflection, reverse propagation, and recombination. Through the use of optimal control techniques [1], we have computationally demonstrated a scalable accelerometer that provides information on the sign of the applied acceleration. Extension of this idea to a two-dimensional shaken-lattice-based gyroscope is discussed. In addition, we report on the experimental implementation of the shaken lattice system. [1] Palao, J.P, \textit{et.al}. PRA 77, 063412, (2008). [Preview Abstract] |
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