Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X24: Vortices, Rotation, Spin-orbit Coupling and Artificial Gauge Fields |
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Sponsoring Units: DAMOP Chair: David Feder, University of Calgary Room: BCEC 159 |
Friday, March 8, 2019 8:00AM - 8:12AM |
X24.00001: Vortex Lattice in Rotating Prolate 4He Droplets Sean O'Connell, Deepak Verma, Rico Mayro P Tanyag, Weiwu Pang, Camila Bacellar, Catherine A Saladrigas, Johannes Mahl, Benjamin W Toulson, Yoshiaki Kumagai, Peter Walter, Christoph Bostedt, Oliver Gessner, Andrey F. Vilesov So far, lattices of quantum vortices have been observed in axially symmetric, rotating superfluid 4He or rotating Bose-Einstein condensates (BECs). Vortex configurations in rotating superfluids lacking axial symmetry have been discussed theoretically, but experimental observation of such systems proves to be challenging. Here, we present a study of vortices in microscopic free, prolate superfluid 4He droplets rotating around their short axis. The vortices were doped with Xe atoms and studied via coherent x-ray scattering at the LCLS free-electron laser. It was found that the vortices form a distorted lattice within the droplet. We compare the shapes of classical droplets executing rigid body rotation to rotating prolate superfluid droplets, the angular momentum of which has contributions from quantum vortices and potential flow. |
Friday, March 8, 2019 8:12AM - 8:24AM |
X24.00002: Shapes of Rotating 3He Droplets Deepak Verma, Sean O'Connell, Swetha Erukala, Alexandra Feinberg, Catherine A Saladrigas, Benjamin W Toulson, Mario Borgwardt, Niranjan Shivaram, Ming-Fu Lin, Andre Al Haddad, Christoph Bostedt, Peter Walter, Oliver Gessner, Andrey F. Vilesov Recent advent of X-ray free electron lasers (XFEL) has enabled the study of rotation in free isolated superfluid 4He droplets.[1] The work presented here extends our study of rotating quantum fluids to non-superfluid 3He droplets. Sub micrometer sized 3He droplets were obtained from free jet expansion of liquid 3He at temperatures less than 3 K and studied via X-ray scattering at the LCLS XFEL.[2] The obtained shapes and sizes of rotating 4He and 3He droplets have been compared. In contrast to superfluid 4He droplets, 3He droplets (T = 0.15 K) are devoid of quantum vortices. Tracing of quantum vortices inside 4He droplets have been previously achieved by doping with large number of Xe atoms.[3] This work presents the first experimental study of the formation dynamics of atomic clusters in a homogenous, vortex-free quantum fluid. |
Friday, March 8, 2019 8:24AM - 8:36AM |
X24.00003: Tunable spin-orbit coupling and long-period magnetic superstripe phase in Bose-Einstein condensates Xiwang Luo, Chuanwei Zhang Superstripe phases in Bose-Einstein condensates, possessing both crystalline structure and superfluidity, opens a new avenue for exploring exotic quantum matters---supersolids. However, complete detection and exploration of superstripes are still challenging in experiments because of the short period, low visibility and external factors such as magnetic field fluctuations or heating issues. Here we propose a scheme in a spin-orbit coupled BEC which overcomes these obstacles and generates a robust magnetic superstripe phase [i.e., only spin (no total) density modulation] with a long period and high visibility, ready for direct real-space observation. In the scheme, two hyperfine spin states are individually Raman coupled with a largely-detuned third state, which induce a momentum-space separation between two lower band dispersions, yielding an effective spin-1/2 system with tunable spin-orbit coupling and Zeeman fields. Without effective Zeeman fields, spin-dependent interaction dominates, yielding a magnetic superstripe phase with a long tunable period and high visibility. Our scheme provides a platform for observing and exploring exotic properties of superstripe phases as well as novel physics with tunable spin-orbit coupling. |
Friday, March 8, 2019 8:36AM - 8:48AM |
X24.00004: Anderson localization in presence of spin-orbit coupling in an atomic Bose gas Yuchen Yue, Emine Altuntas, Francisco Salces-Carcoba, Andika Putra, Chris Billington, Ian Spielman Anderson localization (AL), describing the absence of diffusion in 1D noninteracting quantum particles in disordered media, is based on multiple scattering processes. Spin-orbit coupling (SOC) is an intrinsic property in many material systems. SOC’s spin-dependent alteration of band structure affects the scattering processes leading to AL. Both disorder and SOC are difficult to tune and control in-situ. Here we describe the interplay of tunable disorder (from optical speckle) and SOC (generated by two-photon Raman coupling) in quasi-1D Bose-Einstein condensates. We show that SOC can significantly decrease the impact of disorder, thereby increasing the conductivity of 1D systems. |
Friday, March 8, 2019 8:48AM - 9:00AM |
X24.00005: Spin-Orbit Coupled Bosons in One Dimension: Entanglement Entropy and Dynamics Junhyun Lee, William Cole, Jay Sau We study the entanglement and dynamical properties of a spin-orbit coupled Bosons which describe one-dimension ultracold atoms with Raman-induced spin-orbit coupling. The two component spin-orbit coupled Bose liquid was proposed as a platform for studying quantum criticality in itinerant magnets [1]. In the presence of strong spin-independent interactions and spin-orbit coupling, this spinor Bose liquid undergoes an interaction (or density) tuned quantum phase transition similar to those in itinerant magnetic solid state systems. Although the order parameter describes a broken Z2 spin symmetry, the associated phase is qualitatively distinct from the Ising phase transition and has a dynamical critical exponent z≈2, typical of a Lifshitz transition. We discuss the unusual entanglement and dynamical features of this Lifshitz critical point stemming from its non-integrablility and absence of Lorentz symmetry. |
Friday, March 8, 2019 9:00AM - 9:12AM |
X24.00006: Ground state for trapped two-component Bose-Einstein condensates with synthetic spin-orbit interactions and magnetic fields David Feder The experimental realization of synthetic gauge fields in ultracold atomic gases has spurred great interest in the ground state and excitations of multicomponent Bose-Einstein condensates (BECs) in the presence of spin-orbit (SO) interactions and artificial magnetic fields, driven in part by the pursuit of topologically non-trivial states in these systems. While the characteristics of SO-coupled weakly interacting BECs in uniform geometries and in two-dimensional traps are well-understood, for example the existence of stripe phases, little work has been performed for fully three-dimensional harmonic potentials. In this work, the ground state is determined for interacting (effective) two-component BECs in the presence of Raman-induced synthetic SO interactions and magnetic fields, confined in three-dimensional traps. To ensure efficient calculations but also accurate results, the calculations employ a spatial mesh based on a finite element discrete variable representation. The results are compared with previous theory and simulation results and with experimental data where possible. |
Friday, March 8, 2019 9:12AM - 9:24AM |
X24.00007: Rotating sonic black hole from Spin-orbit coupled Bose-Einstein condensate Inderpreet Kaur, Sankalpa Ghosh We show that an analog of rotating black hole namely, BTZ type can be realized in a quasi-2D spin-orbit coupled Bose-Einstein condensate without using any external rotation. In hydrodynamic approximation, the equation for phase fluctuations in the total density modes, that describes the phonon field is similar to the scalar field equation in 2 + 1 dimensions whose space-time metric can be identified with the metric of BTZ black hole. By time evolving the condensate in a suitably created laser-driven potential, we show that the moving condensate forms such rotating black hole in an annular region bounded by inner and outer event horizon as well as elliptical ergo surfaces. We identify the supersonic and subsonic zones and analyze the self-amplifying Hawking radiation that strongly depends on the spin-orbit coupled anisotropy. We calculate the density-density correlation function and show the distribution of the analog Hawking temperature on the event horizon. |
Friday, March 8, 2019 9:24AM - 9:36AM |
X24.00008: Phases and phase transitions of Bose condensed light Victor Fleurov, Anatoly Kuklov Bose-Einstein condensation of light [1] is characterized by two classical complex fields corresponding to two polarizations of light as well as by the distribution of dye molecules inducing light thermalization through dipolar transition coupled to the thermal bath of molecular vibrations. We emphasize a crucial role of removing the full degeneracy of the dipolar transition in forming algebraic order of the condensate in 2D. The resulting symmetries of the condensate can be characterized by groups O(2)XZ2, O(2) and Z2 order emerging before O(2). [If the transition is triple degenerate, the symmetry becomes O(4) which excludes the algebraic condensation at any finite temperature]. The main result of this work [2] addresses orientational disorder introduced by local dipolar anisotropy. It can destroy algebraic order in one-photon density matrix while preserving it in the two-photon one. This produces a condensate of photon pairs without any attraction between photons. We call such pairing geometrical. |
Friday, March 8, 2019 9:36AM - 9:48AM |
X24.00009: Fermionic Superfluids in a Ring Trap Yanping Cai, Daniel Allman, Parth Sabharwal, Kevin Wright Multiply-connected geometries provide a natural setting for studying transport properties of quantum phases of matter. We will report on an all optical approach to create ultracold fermionic superfluids in a ring-shaped trap. The conditions for creating and observing persistent currents in fermionic superfluids are somewhat different than experiments previously conducted with bosonic superfluids. We will report on initial efforts to create and observe persistent flow in a molecular BEC of of 6Li atoms. With this new platform for studying transport in dilute fermionic superfluids, we plan to study critical velocities and dissipation mechanisms across the BEC-BCS crossover, and in rings with different dimensionality. |
Friday, March 8, 2019 9:48AM - 10:00AM |
X24.00010: Linked and knotted synthetic magnetic fields Callum Duncan, Calum Ross, Niclas Westerberg, Manuel Valiente, Bernd J Schroers, Patrik Öhberg We show that the realisation of synthetic magnetic fields via light-matter coupling in the Lambda-scheme implements a natural geometrical construction of magnetic fields, namely as the pullback of the area element of the sphere to Euclidean space via certain maps. For suitable maps, this construction generates linked and knotted magnetic fields, and the synthetic realisation amounts to the identification of the map with the ratio of two Rabi frequencies which represent the coupling of the internal energy levels of an ultracold atom. We consider examples of maps which can be physically realised in terms of Rabi frequencies and which lead to linked and knotted synthetic magnetic fields acting on the neutral atomic gas. We also show that the ground state of the Bose-Einstein condensate may inherit topological properties of the synthetic gauge field, with linked and knotted vortex lines appearing in some cases. |
Friday, March 8, 2019 10:00AM - 10:12AM |
X24.00011: Kaleidoscope vortex lasers possessing orbital angular momentum Ting-Hua Lu, Teng-De Huang, Guan-Ying Chiou We propose an efficient and robust method to generate the kaleidoscope vortex beam by employing an astigmatic laser cavity with an extra-cavity cylindrical lens. The kaleidoscope vortex beam is arising from the superposition of Laguerre-Gaussian modes with the longitudinal-transverse coupling effect in the laser cavity. The superposed Laguerre-Gaussian mode leads to the formation of complex phase singularities and implies the participation of different optical orbital angular momentum involved in a single kaleidoscope vortex beam. We experimentally demonstrate that a series of kaleidoscope vortex beams with different symmetry are systematically achieved by using a simple setup. The output power of the laser is dependent on the cavity length. This approach is expected to create high-order optical vortex beams and pave the way for optical entanglement. |
Friday, March 8, 2019 10:12AM - 10:24AM |
X24.00012: Imbalanced Fermi gas in antiparallel magnetic fields Takaaki Anzai, Yusuke Nishida We study a two-dimensional Fermi gas with the finite density imbalance between two spin components of atoms in antiparallel magnetic fields. The antiparallel magnetic fields act on two different spin components of atoms with same magnitude but opposite directions [1]. It was revealed in the absence of magnetic fields that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, where the Cooper pairing takes place with nonzero momentum, emerges in the phase diagram of an imbalanced Fermi gas. Therefore, it is an interesting problem to how the antiparallel magnetic fields compete or cooperate with the FFLO state. We investigate the ground-state phase diagram within the mean-field approximation. At the weak-coupling limit, we find that the FF state is stable with compare to the LO state when the chemical potentials of the two components lie right at Landau levels [2]. |
Friday, March 8, 2019 10:24AM - 10:36AM |
X24.00013: Unified Spin Electrodynamics of Maxwell Bosons and Dirac Fermions Farhad Khosravi, Todd Van Mechelen, Zubin Jacob Bosons and fermions show similar spin and angular momentum textures. Studies of the spin for the surface plasmon polaritons (SPPs) propagating at the interface of an insulator and a metal, as well as the solutions of the Dirac equation propagating at the interface of a positive and negative fermionic mass media (known as the Jackiw-Rebbi problem (JRP) ), show that both photons and fermions in these structures have fully transverse spin and form a momentum-decay-spin triplet. By solving Maxwell equations for bosons and Dirac equation for fermions we have derived these fundamental properties and have shown that they make consistent connection to the experimental results. We have also studied these spin properties in the cylindrical problems of an optical fiber (OF) for bosons, as well as the cylindrical problem of a Dirac wire (DW) for fermions. We have shown that the bosons in OF and fermions in DW show very similar spin and angular momentum textures with longitudinal and transverse spin components that are locked to their respective perpendicular component of the momentum. Our results present an important platform for the study of spin and angular momenta by making accurate predictions about the spin properties of bosons (fermions) by studying the spin of fermions (bosons). |
Friday, March 8, 2019 10:36AM - 10:48AM |
X24.00014: Universal properties of the Abelian Higgs model and its quantum simulator with Rydberg-dressed interactions. Jin Zhang, Judah F Unmuth-Yockey, Johannes Zeiher, Alexei Bazavov, Shan-Wen Tsai, Yannick Meurice Analog quantum simulations of lattice gauge theory are a promising direction in understanding high energy physics. We derive a Hamiltonian formulation for the (1+1)-dimensional Abelian Higgs model that is manifestly gauge-invariant. The Hamiltonian formulation of the Polyakov loop can be obtained by the same method, which makes it possible to study this order parameter for the confinement/deconfinement phase transition experimentally. The corresponding quantum simulator is an asymmetric multi-leg ladder of atoms trapped in optical lattices and interacting with Rydberg-dressed interactions, where the required quadratic attractive interactions can be realized. The finite size scaling of the energy gap created by the insertion of a Polyakov loop can be obtained accurately by choosing spin truncations (the number of legs in the ladder) properly, which are cross-checked by tensor renormalization group calculations and Monte Carlo simulations. Phase transitions and quench dynamics also can be studied with this quantum simulator. |
Friday, March 8, 2019 10:48AM - 11:00AM |
X24.00015: Dynamics of active particles in Bose superfluids Vishwanath Shukla We investigate the dynamics of active particles in two- and three-dimensional |
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