Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session H09: Dynamics of Long-Range Dipolar InteractionsLive
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Chair: Mark Saffman, University of Wisconsin, Madison Room: Portland 256 |
Wednesday, June 3, 2020 10:30AM - 10:42AM Live |
H09.00001: Supersolidity in a trapped dipolar quantum gas Tim Langen, Mingyang Guo, Fabian Boettcher, Jan-Niklas Schmidt, Jens Hertkorn, Kevin Ng, Viraatt Anasuri, Matthias Schmidt, Sean Graham, Tilman Pfau A supersolid is a counter-intuitive state of matter that combines the frictionless flow of a superfluid with the crystal-like periodic density modulation of a solid. It thus simultaneously breaks both global gauge and translational symmetry. Although the existence of this counterintuitive state has been predicted more than 50 years ago, only recently it has become possible to realize and study its properties using ultracold quantum gases. In our experiment with strongly-dipolar dysprosium atoms, we realise a supersolid state based on an array of quantum droplets that is both self-organized and coherent. We observe a low-energy Goldstone mode, which manifests itself as an out-of-phase oscillation of the crystal array and the superfluid density. The corresponding dynamics directly prove the genuine superfluidity of the observed state. By theoretically studying the excitation spectrum, we further show that the Goldstone, as well as a distinct Higgs amplitude mode, emerge from softening roton modes at the phase transition point. [Preview Abstract] |
Wednesday, June 3, 2020 10:42AM - 10:54AM Live |
H09.00002: Fingering instabilities and pattern formation in a two-component dipolar Bose-Einstein condensate Kui-Tian Xi, Tim Byrnes, Hiroki Saito We study fingering instabilities and pattern formation at the interface of an oppositely polarized two-component Bose-Einstein condensate (BEC) with strong dipole-dipole interactions (DDIs) in three dimensions. It is shown that the rotational symmetry is spontaneously broken by fingering instabilities when the DDIs are strengthened. Frog-shaped and mushroom-shaped patterns have been shown with different strengths of the DDIs. A Bogoliubov analysis gives a qualitative understanding of the interfacial instabilities of the two dipolar BECs, and a dispersion relation similar to that in classical fluids is obtained. Spontaneous density modulation and dipolar domain growth in the dynamics have also been demonstrated, in which we have analyzed the characteristic sizes of the dipolar domains corresponding to different patterns at the initial and later times in the evolution. We have also investigated the parameter dependence of the ground states, and found that the droplet patterns are formed due to the population imbalance in the two components. Labyrinthine patterns grow as the trap ratio increases, and a striped phase appears as the angle of tilted polarization increases. Our findings may establish further connections between superfluids and classical fluids. [Preview Abstract] |
Wednesday, June 3, 2020 10:54AM - 11:06AM Live |
H09.00003: Creating quantum many-body scars through topological pumping of a 1D dipolar gas Kuan-Yu Li, Wil Kao, Kuan-Yu Lin, Sarang GopalaKrishnan, Benjamin Lev Quantum many-body scars, long-lived excited states of strongly correlated quantum chaotic systems that evade thermalization, are of great fundamental and technological interest. We create novel scar states by quantum-quenching the short-range interactions of a repulsively dipolar near-integrable 1D bosonic dysprosium gas from strongly repulsive to strongly attractive. Stiffness and energy measurements show that repulsive long-range interactions render the resulting dipolar super-Tonks-Girardeau gas dynamically stable against collapse and thermalization. As the short-range interactions are subsequently made weak, the system remains in a nonthermal excited state. Cycling the interactions from weakly to strongly repulsive, then strongly attractive, and finally weakly attractive implements a quantum holonomy that offers an unexplored topological pumping method for creating scars. [Preview Abstract] |
Wednesday, June 3, 2020 11:06AM - 11:18AM Live |
H09.00004: Reservoir engineering and many-body decoherence in the quantum Ising model Lincoln Carr, Daniel Jaschke, Ines de Vega We present quantitative predictions for quantum simulator experiments on Ising models from trapped ions to Rydberg chains and show how the thermalization, and thus decoherence times, can be controlled by considering common, independent, and end-cap couplings to the bath. We find (i) independent baths enable more rapid thermalization in comparison to a common one; (ii) the thermalization timescale depends strongly on the position in the Ising phase diagram; (iii) for a common bath larger system sizes show a significant slowdown in the thermalization process; and (iv) finite-size scaling indicates a subradiance effect slowing thermalization rates toward the infinite spin chain limit. We find it is necessary to treat the full multi-channel Lindblad master equation rather than the commonly used single-channel local Lindblad approximation to make accurate predictions on a classical computer. This method reduces the number of qubits one can practically classical simulate by at least a factor of 4, in turn showing a quantum advantage for such thermalization problems at a factor of 4 smaller qubit number for open quantum systems as opposed to closed ones. Thus, our results encourage open quantum system exploration in noisy intermediate-scale quantum technologies. [Preview Abstract] |
Wednesday, June 3, 2020 11:18AM - 11:30AM Live |
H09.00005: Slow spin dynamics in a 2D dipolar spin ensemble on the surface of diamond Alexander Sushkov, Kristine Rezai, Soonwon Choi, Phillip Weinberg, Timo Graesser, Gotz Uhrig, Mikhail Lukin We observe remarkably slow local spin dynamics in a two-dimensional disordered many-body dipolar spin system, formed by naturally-occurring electronic spins on the surface of a diamond crystal. Shallow NV centers are used to access individual spins, or small spin sub-ensembles. We characterize and control the strength of disorder and dipolar interactions among the surface electronic spins, and measure spin transport at the level of single-spin correlation functions. We model the observed spin relaxation dynamics with a combination of exact dynamics simulation for nearest-neighbor spins, and a dynamical mean-field treatment of the rest of the spin ensemble. [Preview Abstract] |
Wednesday, June 3, 2020 11:30AM - 11:42AM Live |
H09.00006: Relativistic studies of anisotropic properties in magnetic lanthanide erbium and thulium dimers Jacek Klos, Eite Tiesinga, Ming Li, Alexander Petrov, Svetlana Kotochigova The recent realization of quantum degenerate gases of magnetic atoms, cooled and trapped to sub-$\mu$K temperatures, is expected to stimulate studies of magnetic superfluid matter. Atom-atom interactions play a central role in the behavior of such matter. Here, we study the anisotropic interactions for two high-spin magnetic species: ${j=6}$ erbium and ${j=7/2}$ thulium. Non-relativistic coupled-cluster calculations are combined with fully-relativistic configuration-interaction calculations to determine the electronic potentials for homonuclear Er$_2$ and Tm$_2$ dissociating to ground-state atoms with their partially-filled f-electron shells. State-of-the-art non-relativistic coupled-cluster calculations determine the potential for the ``stretched'' electronic state with the largest electron spin and orbital angular-momentum projection quantum numbers, while relativistic configuration-interaction calculations give the splittings among the potentials. We find a complicated picture of 91 and 36 potentials characterizing the Er$_2$ and Tm$_2$ dimers, respectively. An analysis in terms of spin-spin Hamiltonians shows that the splittings are well described by an anisotropic dipolar coupling between the atomic angular momentum with the mechanical rotation of the atom pair. [Preview Abstract] |
Wednesday, June 3, 2020 11:42AM - 11:54AM On Demand |
H09.00007: Dipolar gas dynamics in periodically modulated traps Reuben Wang, Andrew Sykes, John Bohn We study the nonequilibrium dynamics of an ultracold dipolar gas in a cylindrically symmetric harmonic trap, subject to periodic axial-frequency modulations. These dipolar atoms have a differential scattering cross-section that is highly anisotropic, leading to interesting dynamics absent in similar systems of ordinary hard spheres. The gas is dilute and in a temperature regime above quantum degeneracy, allowing its dynamics to be well modeled by the Boltzmann equation. We thus interpret the normal modes of this gas through analytic means via the Chapman-Enskog procedure as well as numerical Monte Carlo methods. [Preview Abstract] |
Wednesday, June 3, 2020 11:54AM - 12:06PM Not Participating |
H09.00008: Faraday and Resonant Waves in Dipolar Cigar-Shaped Bose-Einstein Condensates Dusan Vudragovic, Antun Balaz Faraday and resonant density waves emerge in Bose-Einstein condensates as a result of harmonic driving of the system. They represent nonlinear excitations and are generated due to the interaction-induced coupling of collective oscillation modes and the existence of parametric resonances. Using a mean-field variational and a full numerical approach we study here density waves in dipolar condensates at zero temperature, where breaking of the symmetry due to anisotropy of the dipole-dipole interaction plays an important role. We derive variational equations of motion for the dynamics of a driven dipolar system and identify the most unstable modes that correspond to the Faraday and resonant waves. Based on this, we derive the analytical expressions for spatial periods of both types of density waves as functions of the contact and the dipole-dipole interaction strength. We compare the obtained variational results with the results of extensive numerical simulations that solve the dipolar Gross-Pitaevskii equation in 3D, and find a very good agreement. [Preview Abstract] |
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