Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session C07: Spinor Gases and Magnetic Phenomena |
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Chair: Dan Stamper-Kurn, University of California, Berkeley Room: 206 B |
Tuesday, June 6, 2023 10:45AM - 10:57AM |
C07.00001: Dynamical generation of skyrmion spin texture in a ferromagnetic spinor Bose-Einstein condensate SeungJung Huh, Gabin Yun, Samgyu Hwang, Jae-yoon Choi In this talk, we present an experimental demonstration of generating skyrmions in a two-dimensional ferromagnetic spinor Bose-Einstein condensate. The process begins by preparing a single magnetic domain wall in the easy-axis ferromagnetic phase. We then imprint the spin current onto the domain wall using a magnetic field gradient. When the spin current exceeds a critical value, a flutter-finger pattern of domain wall waves is observed, which can lead to the formation of skyrmion spin textures [1, 2]. To verify the skyrmion spin texture, we employ the simultaneous readout of magnetization along x and z directions and matter-wave interference technique. An isolated spin up (down) domain is formed in the background of spin down (up) domain, and we observe a fork-shaped interference patterns at the center of the isolated spin domain. |
Tuesday, June 6, 2023 10:57AM - 11:09AM |
C07.00002: Spin-Driven Stationary Turbulence in Spinor Bose-Einstein Condensates Jongmin Kim, Deokhwa Hong, Junghoon Lee, Jongheum Jung, Kyuhwan Lee, Seji Kang, Yong-il Shin We report the observation of stationary turbulence in antiferromagnetic spin-1 Bose-Einstein condensates under radio-frequency magnetic field driving. The quadratic Zeeman shift allows magnetic driving to inject energy into the system through spin rotation. The injected energy is then dissipated via dynamic instability, resulting in the development of an irregular spin texture in the condensate. With continuous driving the spinor condensate evolves into a nonequilibrium steady state with characteristic spin turbulence. Despite of complex velocity field appeared in a sample, the lifetime is not significantly affected by magnetic driving. Also, Isotropy is observed when the driving strength is comparable to the interaction of the system and the quadratic Zeeman energy. This research sets the foundation for future studies of quantum turbulence in spinor superfluid systems. |
Tuesday, June 6, 2023 11:09AM - 11:21AM |
C07.00003: Classifying the universal dynamics of a quenched two-dimensional ferromagnetic superfluid Simeon I Mistakidis, SeungJung Huh, Koushik Mukherjee, Kiryang Kwon, Junhyeok Hur, Hossein R Sadeghpour, Jae-yoon Choi Scale invariance and self-similarity in physics provide a unified framework to classify phases of matter and dynamical properties of near- and far-from-equilibrium many-body systems. To address universality, we monitor the non equilibrium dynamics of a two-dimensional ferromagnetic spinor gas subjected to quenches of the quadratic Zeeman and thus dynamically crossing the underlying phase boundaries triggering spin-mixing. Within the short time evolution we observe the spontaneous nucleation of topological defects (gauge or spin vortices) which annihilate through their interaction giving rise to magnetic domains for longer timescales where the gas enters the universal coarsening regime. This is characterized by the spatiotemporal scaling of the spin correlation functions and structure factor allowing to measure corresponding scaling exponents which depend on the symmetry of the order parameter and belong to distinct universality classes. These experimental observations are in excellent agreement with the predictions of the truncated Wigner method accounting both for quantum and thermal fluctuations in the initial state. Our results represent a paradigmatic example of categorizing far-from-equilibrium dynamics in quantum many-body systems. |
Tuesday, June 6, 2023 11:21AM - 11:33AM |
C07.00004: Beyond mean-field physics using multi-mode quantum gases Garrett R Williams, Rishi Lohar, Brian L DeMarco, Bryce Gadway Quantum gases have been shown to be an ideal platform for exploring fundamental aspects of magnetism and symmetry breaking. Here, we engineer a multi-component quantum gas by using Bragg laser fields to controllably couple momentum orders of a rubidium Bose-Einstein condensate. Using this synthetic momentum-state spinor gas, we present evidence for mean-field magnetic phenomena as well as beyond-mean-field effects such as symmetry breaking. In extending to three-site rings of momentum states, we further explore the influence of artificial gauge fields on phase transitions in this system. These results demonstrate the versatility of synthetic spinor gases for the exploration of fundamental mean-field and many-body physics. |
Tuesday, June 6, 2023 11:33AM - 11:45AM |
C07.00005: Exploring Spinor Bose-Einstein Condensates in and beyond the Single Mode Approximation William H Wills Spinor gases are a promising system of exploring quantum entanglement, a phenomena significant in the fields of quantum sensing and computation. The large difference in energy scales in scattering between internal states and kinetic dynamics allows one to neglect fluctuations in the density profiles of spinor gases over timescales relevant for spin dynamics. This is known as the single-mode approximation, which has proven fruitful in theoretical analysis and is a starting point for many works. Here we explore effects not described by the single-mode approximation, both in the mean-field via simulation of the Gross-Pitaevskii equation and in beyond mean-field theory computation. |
Tuesday, June 6, 2023 11:45AM - 11:57AM |
C07.00006: Topological interfaces and vortex splitting instabilities in spin-2 Bose-Einstein condensates Giuseppe Baio, Matthew T Wheeler, Janne Ruostekoski, David S Hall, Magnus O Borgh Interfaces connecting topologically distinct phases of a physical system are phenomena of interest in several contexts, from condensed matter to early-universe cosmology. Optically trapped Bose-Einstein condensates with spin degrees of freedom (spinor BECs) provide an experimental testbed to observe topological defects and their dynamical stability. In this work, we study defect connections throughout topological interfaces in spin-2 BECs, where the rich variety of order-parameter symmetries allows for fractional non-Abelian vortex charges. We demonstrate the existence of fractional vortex connections in uniaxial-to-biaxial nematic (UN-BN), cyclic-to-ferromagnetic (C-FM), and cyclic-to-biaxial nematic (C-BN) interfaces. Moreover, we characterize intriguing core deformations along connections involving higher-order defects such as monopoles and coreless vortices. Finally, we develop a semi-analytical tool to predict vortex instabilitities in terms of an interplay of ground-state phases. We provide evidence of its convenience by numerically solving the Bogoliubov-deGennes (BdG) equations, leading to an easier interpretation of unstable vortex excitations occurring at the topological interface between two phases of a spin-2 BEC. |
Tuesday, June 6, 2023 11:57AM - 12:09PM |
C07.00007: Dynamic self-trapping and non-exponential tunneling in spinor gases Jared O Austin-Harris, Zachary N Hardesty-Shaw, Qingze Guan, Doerte Blume, Robert J Lewis-Swan, Yingmei Liu We utilize a quantum simulator to realize the first observations of nonexponential tunneling within a spinor system. We examine the polarization of the induced tunneling and investigate the effect of nonlinearity upon the tunneling rate for each spin component revealing the presence of near identical nonexponential tunneling for all spin populations. In contrast to prior work studying tunneling dynamics of scalar Bose Einstein condenstates, the spin degrees of freedom in spinor gases realize a nonlinear six-state Landau-Zener model. We find that, for the parameters considered, the observed nonlinear tunneling dynamics are well described by a reduced spin-independent two-state model involving a pair of states labelled only by their momenta. Combined with our demonstration that an evolution of the spatial density profile can be used to manipulate spin dynamics, our results imply an asymmetrical coupling between the spin and spatial degrees of freedom. |
Tuesday, June 6, 2023 12:09PM - 12:21PM |
C07.00008: Classification of ergodicity-breaking mechanisms in chaotic spinor condensates Bertrand Evrard, Andrea Pizzi, Simeon I Mistakidis, Ceren B Dag We find two classes of ergodicity-breaking many-body quantum eigenstates that support robust oscillatory dynamics in an otherwise chaotic spinor condensate. The first class consists of towers of low-entropy "regular" states separated from the chaotic band of states, violating Eigenstate Thermalization Hypothesis (ETH) and associated with stable periodic orbits in the limit of large atom number. The origin of these athermal states can be traced back to an integrable effective Hamiltonian. The second class consists of eigenstates that, while embedded in the chaotic band and satisfying the first criterion of ETH, are not fully ergodic, because they are scarred by unstable periodic orbits with positive Lyapunov exponents in the classical limit. Scarring affects a significant fraction of eigenstates, to an extent that we quantify with a "scarness" figure of merit. Our theory could be experimentally verified in trapped spin-1 Bose-Einstein condensates by preparing Fock and coherent states, and measuring the population of the hyperfine levels and the state fidelity. |
Tuesday, June 6, 2023 12:21PM - 12:33PM |
C07.00009: Deterministic Creation of Polar Core Vortices in Uniform Quasi-2D Ferromagnetic Spinor Bose-Einstein Condensates Guillaume Gauthier, Zachary Kerr, Halina Rubinsztein-Dunlop, Matthew J Davis, Tyler W Neely The deterministic creation of vortices in scalar Bose-Einstein Condensates (BECs) has allowed for the exploration of novel phases of vortex matter from far from equilibrium stable negative temperature vortex states to transition between non-equilibrium states. Deterministic creation of topological defects in spinor condensate is a more involved process and in particular polar-core vortices (PCVs) were first experimentally observed by Sadler et al. in 2006, but have not previously been deterministically created which has impeded in-depth study of their properties and dynamics. I will present our experimental progress towards the deterministic creation of Polar Core Vortices (PCVs). The technique uses the 790 nm tune-out wavelength combined with Digital Micromirror Device (DMD) to imprint equal but opposite 2π phase gradients to atoms in magnetized spin states |F=1, mf=±1>while being transparent to atoms in unmagnetized spin state |F=1, mf=0>. The density profile of the vortex is shaped using a 660 nm laser and the same DMD which also serves to create the trap for the planar trap for the atoms. This technique aims to allow for the creation of arbitrary spatial distribution of PCVs in a uniform spinor condensate which will allow for the probing of the properties of single PCV; as well as, few-body PCV dynamics, PCV driven spin turbulence, and help determine the thermodynamic equilibrium properties of PCV ensembles. |
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