Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session B6: Progress in Spin-Orbit Coupling |
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Chair: Lindsay LeBlanc, University of Alberta, Canda Room: 552AB |
Tuesday, May 24, 2016 10:30AM - 10:42AM |
B6.00001: Topological invariants measured for Abelian and non-Abelian monopole fields Seiji Sugawa, Francisco Salces Carcoba, Abigail Perry, Yuchen Yue, Andika Putra, Ian Spielman Understanding the topological nature of physical systems is an important topic in contemporary physics, ranging from condensed matter to high energy. In this talk, I will present experiments measuring the 1st and 2nd Chern number in a four-level quantum system both with degenerate and non-degenerate energies. We engineered the system's Hamiltonian by coupling hyperfine ground states of rubidium-87 Bose-Einstein condensates with rf and microwave fields. We non-adiabatically drove the system and measured the linear response to obtain the local (non-Abelian) Berry curvatures. Then, the Chern numbers were evaluated on (hyper-)spherical manifolds in parameter space. We obtain Chern numbers close to unity for both the 1st and the 2nd Chern numbers. The non-zero Chern number can be interpreted as monopole residing inside the manifold. For our system, the monopoles correspond to a Dirac monopole for non-degenerate spectra and a Yang monopole for our degenerate case. We also show how the dynamical evolution under non-Abelian gauge field emerged in degenerate quantum system is different from non-degenerate case by showing path-dependent acquisition of non-Abelian geometric phase and Wilson loops. [Preview Abstract] |
Tuesday, May 24, 2016 10:42AM - 10:54AM |
B6.00002: Spin-orbit coupled lattice-band pseudospins M.A. Khamehchi, M.E. Mossman, P. Engels The experimental realization of spin-orbit coupling in quantum gases is currently met with much interest. It has opened up new possibilities to investigate condensed-matter phenomena using quantum gases as well-controlled model systems. While most experiments have exploited atomic hyperfine states as pseudospins, other properties can also serve as pseudospins and may lead to novel experimental approaches. In our experiment, we demonstrate that the s- and p-band of an optical lattice can be exploited as pseudospin orientations and show that spin-orbit coupling between these states can be generated. The current status and future directions of this experiment will be discussed. [Preview Abstract] |
Tuesday, May 24, 2016 10:54AM - 11:06AM |
B6.00003: Experimental reconstruction of the Berry curvature in a topological Bloch band Christof Weitenberg, Nick Flaeschner, Benno Rem, Matthias Tarnowski, Dominik Vogel, Dirk-Soeren Luehmann, Klaus Sengstock Topological properties lie at the heart of many fascinating phenomena in solid state systems such as quantum Hall systems or Chern insulators. The topology can be captured by the distribution of Berry curvature, which describes the geometry of the eigenstates across the Brillouin zone. Employing fermionic ultracold atoms in a hexagonal optical lattice, we engineer the Berry curvature of the Bloch bands using resonant driving and measure it with full momentum resolution. Our results pave the way to explore intriguing phases of matter with interactions in topological band structures. [Preview Abstract] |
Tuesday, May 24, 2016 11:06AM - 11:18AM |
B6.00004: Spin-orbit coupling in a strontium optical lattice clock Tobias Bothwell, Sarah Bromley, Shimon Kolkowitz, Xibo Zhang, Michael Wall, Ana Maria Rey, Jun Ye Synthetic gauge fields are a promising tool for creating complex Hamiltonians with ultracold neutral atoms that may mimic the fractional Quantum Hall effect and other topological states. A promising approach is to use spin-orbit coupling to treat an internal degree of freedom as an effective `synthetic' spatial dimension. Here, this synthetic dimension is comprised by the internal ground and excited states used for high-precision clock spectroscopy in a fermionic strontium optical lattice clock. We report on our progress towards this goal in a system where atoms tunnel through a 1D optical lattice during clock interrogation. We present measurements of the lattice band structure under varying Lamb-Dicke parameters and in a regime where s-wave collisions are expected to contribute density dependent frequency shifts. [Preview Abstract] |
Tuesday, May 24, 2016 11:18AM - 11:30AM |
B6.00005: Raman-induced Spin-Orbit Coupling in Optical Superlattices Junru Li, Wujie Huang, Boris Shteynas, Sean Burchesky, Furkan Top, Alan Jamison, Wolfgang Ketterle We demonstrate a new scheme for spin-orbit coupling (SOC) of ultracold atoms. Instead of internal (hyperfine) states, two lowest bands in an optical superlattice were used as pseudospins. ~A Raman process was implemented to provide coupling between pseudospin and momentum. With single internal state and far-detuned beams used, our new scheme will allow convenient generalisation to a wide range of atoms. Pseudospin interaction is tuneable by controlling the superlattice,~allowing us to study~many-body phenomena in SOC systems such as the stripe phase. [Preview Abstract] |
Tuesday, May 24, 2016 11:30AM - 11:42AM |
B6.00006: Direct observation of edge states in the Su-Schrieffer-Heeger model with bosonic atoms in a momentum space lattice Eric Meier, Fangzhao An, Bryce Gadway We experimentally probe topological systems within the AIII symmetry class, using ultracold atomic matter waves in a momentum-space optical lattice. By writing multiple frequency sidebands on one of our optical lattice laser beams, we couple sites in the resulting momentum-space lattice through stimulated Bragg diffraction. With time-dependent control of the frequency, amplitude, and phase of each laser sideband we are able to locally and dynamically control all system parameters and simulate fully tunable topological systems. We demonstrate this ability through the realization of the Su-Schrieffer-Heeger model in a one-dimensional optical lattice and observe evidence of the predicted dispersionless edge state in the matter wave dynamics therein. [Preview Abstract] |
Tuesday, May 24, 2016 11:42AM - 11:54AM |
B6.00007: Uniform synthetic magnetic field and effective mass for cold atoms in a shaken optical lattice. Fernando Sols, Charles E. Creffield, Gregor Pieplow, Nathan Goldman Cold atoms can be made to experience synthetic magnetic fields when placed in a suitably driven optical lattice [1]. For coherent systems the switching protocol plays an essential role in determining the long time behavior [2]. Relatively simple driving schemes may generate a uniform magnetic flux but an inhomogeneous effective mass [3,4]. A two-stage split driving scheme can recover a uniform effective mass but at the price of rendering the magnetic field space dependent [5]. We propose a four-stage split driving that generates uniform field and mass of arbitrary values for all driving amplitudes. Finally, we study a modified two-stage split driving approach that enables uniform field and mass for most of but not all values of the magnetic field. [1] N. Goldman, J. Dalibard, Phys. Rev. X 4, 031027 (2014). [2] C. E. Creffield, F. Sols, Phys. Rev. A 84, 023630 (2011). [3] A. R. Kolovsky, Europhys. Lett. 93, 20003 (2011). [4] C. E. Creffield, F. Sols, Europhys. Lett. 101, 40001 (2013). [5] C. E. Creffield, F. Sols, Phys. Rev. A 90, 023636 (2014). [Preview Abstract] |
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