Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session M09: Spinor Gases and Magnetic PhenomenaLive
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Chair: Donald P. Fahey, US Army Research Lab |
Wednesday, June 2, 2021 2:00PM - 2:12PM Live |
M09.00001: Quantum-torque-induced breaking of magnetic interfaces in ultracold gases Arturo Farolfi Bose-Einstein Condensates (BECs) with multiple internal states allow the study of spin dynamics and magnetic phenomena on a flexible platform. Thanks to a novel experimental apparatus [1,2], we studied the spin dynamics of an elongated coherently-coupled two-component BEC in a previously inaccessible regime where the spin dynamics is both non-homogenous and non-dissipative. |
Wednesday, June 2, 2021 2:12PM - 2:24PM Live |
M09.00002: Bosonic continuum theory of one-dimensional lattice anyons Martin Bonkhoff Anyons with arbitrary exchange phases exist on 1D lattices in ultracold gases. Yet, known continuum theories in 1D do not match. We derive the continuum limit of 1D lattice anyons via interacting bosons. The theory maintains the exchange phase periodicity fully analogous to 2D anyons. This provides a mapping between experiments, lattice anyons, and continuum theories, including Kundu anyons with a natural regularization as a special case. We numerically estimate the Luttinger parameter as a function of the exchange angle to characterize long-range signatures of the theory and predict different velocities for left- and right-moving collective excitations. |
Wednesday, June 2, 2021 2:24PM - 2:36PM Live |
M09.00003: Finite-temperature topological phase and phase transitions of spin-j systems in Uhlmann processes Chih-Chun Chien, Hao Guo, Xu-Yang Hou Topological properties of noninteracting systems in their ground states have been extensively studied. However, finite-temperature topological properties still await more research. The Uhlmann phase and Loschmidt amplitude have been shown to offer promising ways to characterize topological phase and phase transitions of mixed quantum states at finite-temperatures. We present general expressions of the Uhlmann phase and Loschmidt amplitude of a quantum spin-j system under a magnetic field in a Uhlmann process. Our analyses of the spin-1/2 and spin-1 systems show finite-temperature topological phase transitions (TQPTs) corresponding to the zeros of the Loschmidt amplitude. The Uhlmann phase jumps at the TQPT, and the number of TQPTs is determined by the winding number in the parameter space of the Uhlmann process. The Uhlmann processes of spin-j systems may be realized and studied in cold-atom quantum simulators. |
Wednesday, June 2, 2021 2:36PM - 2:48PM Live |
M09.00004: Simple $N$-scaling above the superexchange energy of thermodynamic observables in the SU($N$) Fermi Hubbard Model at $1/N$ filling in the two dimensional square lattice Eduardo Ibarra Garcia Padilla, Sohail Dasgupta, Hao-Tian Wei, Kaden R Hazzard, Richard T Scalettar, Shintaro Taie, Yoshiro Takahashi The SU(2) symmetric Fermi Hubbard model (FHM) plays an essential role in the understanding of strongly correlated fermionic many-body systems. When the system is in the one particle per site and strongly interacting limit $U/t \gg 1$, it is effectively described by the Heisenberg Hamiltonian. In this limit, extending the typical SU(2) symmetry to SU(N) is predicted to give exotic phases of matter in the ground state, with complicated dependence of the ground state on $N$. The question we address in this talk is whether the situation is similarly complicated at $T$ at and above the superexchange energy. To answer this question we numerically explore the SU($N$) FHM in a two-dimensional square lattice using determinant Quantum Monte Carlo and Numerical Linked Cluster Expansion. Our main finding is that for temperatures above the superexchange energy, where the different $N$ systems are just dominated by short-range correlations, the energy, double occupancy, and kinetic energy collapse upon a simple rescaling with $1/N$. Although the physics in the regime studied is well beyond that captured by low-ordered high-temperature series, we show that an analytic description of the scaling is possible in terms of only one- and two-site correlations. |
Wednesday, June 2, 2021 2:48PM - 3:00PM Live |
M09.00005: Observation of spin correlated matter-wave emission from spinor BEC Kyungtae Kim, Junhyeok Hur, SeungJung Huh, Soonwon Choi, Jae-yoon Choi In this presentation, we introduce experimental observation of spin jet emission from F=1 spinor BEC in a quasi-2D trap. Starting from a BEC in (m=0) state of F=1 manifold, we quench the system to favor the equal composition of (+1), (-1) states. After binary collisions, the atomic spin states can be changed to m=1 and m=-1 states, where the excess internal Zeeman energy is released to the kinetic energy of the spin pair. This process can be stimulated further, forming matter-wave jets with the spin opposite spin states. The large spin-mixing rate of Lithium-7 is essential for the collisional amplification process. We study the dynamic features and the angular correlations for various spin states and reveal the spin-momentum correlation. Rotating the spin axis, the correlation peaks display a high contrast oscillation, indicating collective coherence of the atomic ensembles. We employ time-dependent BdG theory to provide a quantitative understanding of the experiment. Finally, we discuss the current experimental limitations and future improvements. |
Wednesday, June 2, 2021 3:00PM - 3:12PM On Demand |
M09.00006: Dynamics of multiple magnetic solitons with finite quadratic Zeeman energy Di Lao, XIAO CHAI, Carlos A R Sa de Melo, Kazuya Fujimoto, Chandra Raman Topological defects are intriguing objects that may exist in various classical and quantum systems and may play the role of extended particles. Like atoms, multiple topological defects can also form bound states, such as breather of multiple solitons and vortex-antivortex pairs. In this talk, we report the theoretical study of the Flemish string, a bound state of a pair of magnetic solitons with opposite magnetization, which exists in the antiferromagnetic spinor BEC. Considering the SO(3)-invariant nature of the one-dimensional Gross-Pitaevskii (GP) equations with zero quadratic Zeeman shift, we analytically construct a Flemish string by rotating the dark-bright-bright (antiferromagnetic core) soliton in the Manakov limit, that is, when spin-spin interactions are neglected. The unbraiding mechanism of the Flemish string into a pair of magnetic solitons due to spin-spin interactions is addressed using perturbation theory. By applying a spatially modulated phase imprinting beam on the BEC, multiple-soliton states can be created in experiment. Our theoretical study paves the way for the further experimental investigations of soliton interactions, collisions, and of complex solitonic matter. |
Wednesday, June 2, 2021 3:12PM - 3:24PM Live |
M09.00007: Radio frequency Ramsey interferometry with an F=1 spinor Bose-Einstein condensate Madison J Anderson, Zhifan Zhou, Donald P Fahey, Paul D Lett We report on a RF Ramsey interferometric measurement on the F = 1 ground state of our sodium Bose-Einstein condensate (BEC). Due to the spin-1 ground state level structure, the fringe pattern exhibits a more complicated beat-like structure, compared to the typical spin-½ case. We explore the theoretical origins and behavior of this more complicated spin-1 Ramsey signal, and demonstrate a measurement of our RF detuning to a precision of the order of 100 Hz or better. We further discuss its usefulness for the calibration of spin-1 BEC experiments. |
Wednesday, June 2, 2021 3:24PM - 3:36PM Live |
M09.00008: Quantum elliptic vortex in the polar phase of a spin-1 Bose-Einstein condensate Hiromitsu Takeuchi A novel topological defect in a spin-nematic superfluid is found theoretically. A quantized vortex spontaneously breaks its axisymmetry, leading to an elliptic vortex in the polar phase of spin-1 Bose-Einstein condensates of 23Na gasses with small quadrative Zeeman shift. The new vortex is considered the Joukowski transform of a conventional vortex. Its oblateness grows when the Zeeman length exceeds the spin healing length. This structure is sustained by balancing the hydrodynamic potential and the elasticity of a soliton connecting two spin spots, which are observable by in situ magnetization imaging. The theoretical analysis clearly defines the difference between half quantum vortices of the polar and anti-ferromagnetic phases in spin-1 condensates. This work is motivated by and related to the recent experiments on wall-vortex composite defects by Shin's group in Seoul National University [Phys. Rev. Lett. 122, 095301 (2019) and Phys. Rev. A, 101, 023613 (2020)]. |
Wednesday, June 2, 2021 3:36PM - 3:48PM Live |
M09.00009: Investigating thermally robust spin entanglement of an atomic 85Rb pair in an optical tweezer Lucile Sanchez, Poramaporn Ruksasakchai, Marvin Weyland, Pimonpan Sompet, Stuart Szigeti, Eyal Schwartz, Ashton Bradley, Mikkel F Andersen Spin entangled states are of a high interest for performing non-classical calculations. Recently, entanglement generated by cold collisions of atomic ensembles were validated by HOM and Bell correlation experiments.. Isolating a single atomic pair using optical tweezers allows to investigate the spin-changing collision at the particle level and the resulting entangled state. However, this procedure has so far been successful only for groundstate-cooled atoms. Being able to maintain the coherence at a higher temperature would then be a step towards an engineering implementation. |
Wednesday, June 2, 2021 3:48PM - 4:00PM On Demand |
M09.00010: Magnetic solitons in spinor Bose-Einstein condensates XIAO CHAI, Di Lao, Kazuya Fujimoto, Li You, Chandra Raman Magnetic solitons, a novel type of vector soliton in spinor Bose-Einstein condensates (BECs), have drawn considerable attention recently, as their existence depends crucially on the antiferromagnetic spin-dependent contact interaction. Here we demonstrate that the SO(3) symmetry of the underlying spinor gas allows interactions of solitons with different spin polarization [1], and intriguing collisional properties are observed in numerical simulations, including rotation and dissipation of soliton spin polarization. Moreover, we extend the study of magnetic solitons to the ferromagnetic case [2]. Characteristics of magnetic solitons with ferromagnetic interaction are identified and a proposal for experimental generation is given. [1] Chai, X., Lao, D., Fujimoto, K., & Raman, C. (2021). Magnetic soliton: from two to three components with SO (3) symmetry. Physical Review Research, 3(1), L012003. [2] Chai, X., You, L., & Raman, C. (2020). Magnetic solitons in an immiscible two-component Bose-Einstein condensate. arXiv preprint arXiv:2011.11462. |
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