Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session A35: Spinor Gases |
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Sponsoring Units: DAMOP Room: 702 |
Monday, March 3, 2014 8:00AM - 8:12AM |
A35.00001: Fate of Topology in Spin-1 Spinor Bose-Einstein Condensate Yun-Tak Oh, Panjin Kim, Jin-Hong Park, Jung Hoon Han One of the excitements generated by the cold atom systems is the possibility to realize varied topological phases stemming from multi-component nature of the condensate. Popular examples are the antiferromagnetic (AFM) and the ferromagnetic (FM) phases in the three-component atomic condensate with effective spin-1. It follows, from consideration of homotopy, that different sorts of topological defects will be stable in each manifold. Countering such common perceptions, here we show on the basis of a new wave function decomposition scheme that there is no physical parameter regime wherein the temporal dynamics of spin-1 condensate can be described solely within AFM or FM manifold. Initial state of definite topological number prepared entirely within one particular phase must immediately evolve into a mixed state. Accordingly, the very notion of topology and topological stability within the sub-manifold of AFM or FM become invalid. Numerical simulations of the Gross-Pitaevskii equation confirms our claim. [Preview Abstract] |
Monday, March 3, 2014 8:12AM - 8:24AM |
A35.00002: Heteronuclear coherent spinor dynamics in an ultracold spin-1 mixture Dajun Wang, Xiaoke Li, Bing Zhu, Fudong Wang, Xiaodong He, Jun Chen, Mingyang Guo Ultracold spinor gas has been a subject of great interest in quantum gas research for many years. So far, however, all the experimental studies are carried out with a single atomic species, mostly either $^{23}$Na or $^{87}$Rb atom. Only very recently, it has been proposed theoretically that spinor dynamics can also exist in heteronuclear spin-1 mixtures. To explore this, we have prepared an optically trapped ultracold mixture of spin-1 $^{23}$Na and $^{87}$Rb atoms. With well controlled initial spin populations and magnetic fields, we have observed rapid spin population and magnetization oscillations for both Na and Rb due to heteronuclear spin-spin interactions. Following this first demonstration, we believe that rich heteronuclear spinor physics can be studied in the future. We are supported by RGC Hong Kong (grant nos. CUHK 403111 and CUHK 404712). [Preview Abstract] |
Monday, March 3, 2014 8:24AM - 8:36AM |
A35.00003: Nambu-Goldstone modes in segregated Bose-Einstein condensates Hiromitsu Takeuchi, Kenichi Kasamatsu Nambu-Goldstone modes in immiscible two-component Bose-Einstein condensates are studied theoretically.$^1$ In a uniform system, a flat domain wall is stabilized and then the translational invariance normal to the wall is spontaneously broken in addition to the breaking of two U(1) symmetries in the presence of two complex order parameters. We clarify the properties of the low-energy excitations and identify that there exist only two Nambu-Goldstone modes: an in-phase phonon with a linear dispersion and a ripplon with a fractional dispersion. The ripplon in the low-energy limit is considered as a linear combination of a relative rotation of phases of order parameters and a transverse shift of the domain wall. The signature of the characteristic dispersion can be verified in segregated condensates in a harmonic potential. \\ \\ 1 Hiromitsu Takeuchi and Kenichi Kasamatsu, Phys. Rev. A {\bf 88}, 043612 (2013) [Preview Abstract] |
Monday, March 3, 2014 8:36AM - 8:48AM |
A35.00004: Magnetic resonance spectroscopy by magnetic field modulation for spinor Bose condensates Akiyuki Tokuno, Shun Uchino Spinor Bose-Einstein condensates in the presence of magnetic fields exhibit nontrivial spin orders caused by peculiar effects to atoms such as spin dependent interactions and quadratic Zeeman splitting. For such a system, one of the challenges is to develop measurement techniques to capture complicated spin orders. As an attempt for this issue we theoretically study resonance phenomena induced by magnetic fields.[1] Assuming a dynamically modulated magnetic field, we formulate the experimentally measurable energy absorption rate (EAR) for spin-F interacting bosons within linear response theory. The EAR spectrum is found to be described by a new type of spin correlation function: the autocorrelation of a quadratic Zeeman term. In addition, in order to test whether the states with different spinor order can be specified from the viewpoint of such a spectral feature, we consider spin-1 Bose condensate, and calculate the EAR spectrum of the ordered states by using Bogoliubov theory. As a result the spectrum in each phase is found to show individual characteristic behavior, and this spectroscopy is expected to have possibility to specify various magnetic states in other systems. [1] A. Tokuno and S. Uchino, Phys. Rev. A 87, 061604 (2013). [Preview Abstract] |
Monday, March 3, 2014 8:48AM - 9:00AM |
A35.00005: Rotating $SU(2)$ Bose-Einstein condensates Peder Galteland, Asle Sudbo The topological excitations inherent in Bose-Einstein condensates are important elements of both superconductors and superfluids, and are even relevant in cosmology and high energy physics. Condensates with multiple components and intercomponent couplings open up new possibilities for novel vortex physics, and which have been studied numerically and realized experimentally. We have studied a uniformly frustrated $2$-component Ginzburg-Landau theory with amplitude fluctuations and density-density interactions included, through the use of Metropolis Monte Carlo techniques. We have explored the ground states as a function of rotational frequency, and inter- and intra-component coupling strength. It was found that the model exhibits both hexagonal lattices of co-centered vortices, and square lattices of interpenetrating vortices. These lattices exhibit a first order melting transition. The special case of an $SU(2)$ symmetric potential was also explored. With this additional symmetry, dimer vortex configurations, strong staggering of the amplitude fields and massive degeneracy of the ground states appear. [Preview Abstract] |
Monday, March 3, 2014 9:00AM - 9:12AM |
A35.00006: 10 dB of Spin Squeezing via Measurement -- a Useful Entanglement Resource Kevin Cox, Justin Bohnet, Matthew Norcia, Joshua Weiner, Zilong Chen, James Thompson We report results from an experiment to generate and directly observe 10.2(6) dB of spin squeezing using a quantum non-demolition measurement (QND), the most directly observed spin squeezing in an atomic ensemble to date. The squeezing is generated by measuring state populations through an optical cavity on a closed optical transition in an ensemble of $5\ast {10}^{5} \quad^{87}$Rb atoms. Such a scheme can be applied to optical lattice clocks using Sr and Yb. [Preview Abstract] |
Monday, March 3, 2014 9:12AM - 9:24AM |
A35.00007: Realizing SU(N) magnets in thermal alkaline-earth gases Michael Beverland, Alexey Gorshkov, Ana Maria Rey, Gorjan Alagic We show that thermal fermionic alkaline-earth atoms in flat-bottom traps allow one to implement a spin model displaying two symmetries: the symmetry that swaps atoms occupying different vibrational levels of the trap and the SU(N) symmetry associated with N nuclear spin states. The high symmetry allows us to analytically calculate the full spectrum, the eigenstates, and the dynamics. Armed with such a solid understanding, we show how this system can be used to generate entangled states usable for Heisenberg limited metrology (e.g. clocks), to make measurements useful for quantum information processing, and to understand spin diffusion in SU(N) systems. The best news is that this highly symmetric spin model should be readily realizable even when the vibrational levels are occupied according to a high-temperature thermal or a non-thermal distribution. [Preview Abstract] |
Monday, March 3, 2014 9:24AM - 9:36AM |
A35.00008: Classification of Spin Ordering of Fermions with Large Spin Biao Huang, Tin-Lun Ho Cold atom research provides a unique opportunity for studying the physics of high spin particles, as most bosonic atoms have non-zero spin, and most fermionic atoms have spin larger than 1/2. While there have been many experiments of large spin bosons, there are few experimental studies of large spin fermions. Here, we present a general scheme for classifying the spin ordering of fermions with arbitrary spins by studying the symmetry of their single particle density matrices. Our scheme is based on the Majorana representation of spins, which provides a geometric representation of the ordering in spin space. It readily concludes that there are no spin orders with tetrahedron symmetry. We have also used mean field theory to illustrate the emergence of various type of spin ordering. [Preview Abstract] |
Monday, March 3, 2014 9:36AM - 9:48AM |
A35.00009: Dynamical scalability and control of totally connected spin networks across quantum phase transitions \'Oscar L. Acevedo, Luis Quiroga, Ferney J. Rodr\'Iguez, Neil F. Johnson Dynamical quantum phase crossings of spin networks have recently received increased attention thanks to their relation to adiabatic quantum computing, and their feasible realizations using ultra-cold atomic and molecular systems with a highly tunable degree of connectivity. Dynamical scaling of spatially distributed systems like Ising models have been widely studied, and successfully related to well-known theories like the Kibble-Zurek mechanism. The case of totally connected networks such as the Dicke Model and Lipkin-Meshkov-Glick Model, however, is known to exhibit a breakdown of these frameworks. Our analysis overcomes the lack of spatial correlation structure by developing a general approach which (i) is valid regardless the connectivity of the system, (ii) goes beyond critical exponents, and (iii) provides a time-resolved picture of dynamical scaling. By treating these models as a method for macroscopic quantum control of their subsystems, we have found microscopic signatures of the dynamical scaling as well as instances of dynamical enhancement of distinctive quantum properties such as entanglement and coherence. Our results yield novel prescriptions for the fields of quantum simulations and quantum control, and deepen our fundamental understanding of phase transitions. [Preview Abstract] |
Monday, March 3, 2014 9:48AM - 10:00AM |
A35.00010: Competing exotic quantum phases of spin-1/2 ultra-cold lattice bosons with extended spin interactions Chia-Chen Chang, Valery Rousseau, Richard T. Scalettar, George Batrouni Rapid progress in pure optical trapping techniques makes it possible now to create degenerate Bose gases with spin degrees of freedom. Systems such as ${}^{87}$Rb or ${}^{23}$Na in the $F=1$ hyperfine state offer a unique platform for studying the interplay of superfluidity and magnetism, phases resulting from macroscopic quantum coherence and symmetry breaking respectively. Motivated by these experimental developments, we study ground state phases of a two-component spinor Bose gas loaded on an optical lattice. The system is described effectively by the Bose-Hubbard Hamiltonian with onsite and extended spin-spin interactions. Using mean-field theory and quantum Monte Carlo simulations, we map out the phase diagram of the system. A rich variety of phases is identified, including antiferromagnetic (AF) Mott insulators, ferromagnetic or AF superfluids, and supersolids. [Preview Abstract] |
Monday, March 3, 2014 10:00AM - 10:12AM |
A35.00011: Fluctuations in a Spin Chain and the Entanglement Hamiltonian Ari Turner, Eugene Demler How are quantum fluctuations and thermal fluctuations different in many-body systems? I will compare the variance of the fluctuations of spin in a segment of a spin chain in the ground state and at a finite temperature, showing that fluctuations in the ground state are much more correlated than in the thermal state. The full distribution function of spin can also be determined, and is non-Gaussian. These effects could possibly be measured in a chain of sodium atoms in an optical lattice. The method involves mapping the system to an imaginary thermal system called the ``entanglement Hamiltonian.'' Measuring the ground state fluctuations of the spin chain gives an indirect way of measuring the entanglement Hamiltonian. [Preview Abstract] |
Monday, March 3, 2014 10:12AM - 10:24AM |
A35.00012: Enhanced Mobility in a two-species ultracold atomic system Derek Lee, Mike Gunn, Nicola Wilkin We consider the mobility of two species of interacting atoms in an optical lattice. The behaviour of the system is radically modified as a function of the relative detuning of the optical lattice to resonances of the two atomic species. We will discuss the polaronic and pairing physics in such systems. We will also present proposals for possible experimental realizations of our theoretical model using Feshbach resonances. [Preview Abstract] |
Monday, March 3, 2014 10:24AM - 10:36AM |
A35.00013: Improving the Hubbard-Lattice Gauge Theory correspondence on optical lattices Yannick Meurice, Alexei Bozavov, Yuzhi Liu, Chen-Yen Lai, Shan-Wen Tsai There exists a strong coupling equivalence between the Hubbard model with repulsive on site interactions and SU(2) lattice gauge theory with one fermion. The correspondence holds at lowest nontrivial order in degenerate perturbation theory, but fails to reproduce the plaquette interactions of the gauge theory. We discuss modifications that can be implemented experimentally on optical lattices and could improve this situation. This includes bipartite lattices with s and p orbitals (plaquette currents) and dipolar molecules in an external field (long range dipole interactions). We discuss recent numerical calculations based on determinantal Monte Carlo and aimed at testing improvement ideas obtained from mean field theory or strong coupling arguments. [Preview Abstract] |
Monday, March 3, 2014 10:36AM - 10:48AM |
A35.00014: ABSTRACT MOVED TO M35.00015 |
Monday, March 3, 2014 10:48AM - 11:00AM |
A35.00015: Magnetic properties of ultracold fermions in multilayered Lieb lattices Kazuto Noda, Kensuke Inaba, Makoto Yamashita The recent experimental development in atomic physics enables us to realize novel many-body systems using optical lattices. We study the magnetic properties of cold fermions in multilayered Lieb lattices, which are the ideal model systems for investigating the flat-band ferromagnetism. Our dynamical mean-field results of bilayer, trilayer, and several multilayers elucidate that finite magnetization at the surface layers in the odd-layered lattices emerges even in the infinitesimal small interaction region. This is a striking feature of the flat-band ferromagnetism in multilayered systems as a consequence of the Lieb theorem. We also discuss how this phenomenon appears in the infinite-layered (three dimensional) system. [Preview Abstract] |
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