Bulletin of the American Physical Society
48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017; Sacramento, California
Session C3: Topological States and Synthetic Fields |
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Chair: Jonathan Simon, University of Chicago Room: 308 |
Tuesday, June 6, 2017 2:00PM - 2:12PM |
C3.00001: Autonomous Stabilizer for Photonic Many-Body States Brendan Saxberg, Alex Ma, Clai Owens, Aman LaChapelle, David Schuster, Jon Simon Synthetic photonic systems are a promising platform for new physics in the regime of strongly interacting and highly correlated quantum materials. However, controlled population of system Hamiltonians in the absence of particle number conservation remains challenging. Here we present an autonomous thermalizer for incompressible photonic quantum materials at non-zero chemical potential to stabilize these photonic many-body states. The thermalizer is comprised of a pumping and a lossy site, where photons can spontaneously thermalize to the ground state of the lattice when driven on the pumping site and excess energy is dissipated via the lossy site. Using the Circuit QED platform, we connect our autonomous thermalizer to a one-dimensional lattice of coupled superconducting qubits and demonstrate a Mott Insulating phase of light in a strongly interacting Bose-Hubbard chain. This work explores a new approach for preparation of quantum many-body photonic phases, and provides a potential route to topologically protected states, for example in a topological microwave cavity lattice with qubit mediated interactions. [Preview Abstract] |
Tuesday, June 6, 2017 2:12PM - 2:24PM |
C3.00002: Protocols for dynamically probing topological edge states and dimerization with fermionic atoms in optical potentials Mekena Metcalf, Chen-Yen Lai, Kevin Wright, Chih-Chun Chien Topological states and phases have been observed in ultra-cold atomic systems. However, imposing a confining harmonic potential distorts the energy spectrum and prevents the detection of topological boundary states. We propose realistic setups for generating one-dimensional topological systems with well-defined boundary and protocols to resolve the detection of edge-states arising in a dimerized lattice using ultra-cold fermions. Atoms confined in a dimerized ring lattice, whose boundary conditions are transformed from periodic to open using an off resonant laser sheet, generate topological boundary states. A particle injected onto the edge site of a dimerized structure in a topological configuration can sustain a finite density as the system evolves in time. Alternatively, depleting an initially filled lattice away from the boundary reveals prominent occupied edge states. Signatures of dimerization in the presence of onsite interactions can be found using certain correlations as the boundary condition dynamically transforms from periodic to open. These correlations reveal a memory effect of the initial state which can distinguish dimerized structures or different insulating phases. [Preview Abstract] |
Tuesday, June 6, 2017 2:24PM - 2:36PM |
C3.00003: Topological order in finite-temperature Gaussian fermionic systems Lukas Wawer, Dominik Linzner, Michael Fleischhauer Since their discovery, topological states of matter have been praised for their fascinating and potentially useful properties as protected edge states or anyonic excitations. However, these features seem to vanish at finite temperature. Exploiting the equivalence of Zak (or Berry) phase and polarization we can classify topological order in finite-temperature systems by means of the many body polarization [1]. We show that topological order defined in this way survives at any finite temperature $T$ in Gaussian fermionic systems. We first consider a 1D model for symmetry protected topological order (Su-Schrieffer-Heeger model) and find that there is a quantized winding of the polarization for closed paths in parameter space for all $T< \infty$. At $T=\infty$ a topological phase transition occurs and for $T<0$ the polarization winding reverses its sign. We then study a 2D model (Hofstadter-Hubbard model) with intrinsic topology and show a similar behavior. [1] D. Linzner, L. Wawer, F. Grusdt, and M. Fleischhauer, Phys. Rev. B \textbf{94}, 201105(R) (2016) [Preview Abstract] |
Tuesday, June 6, 2017 2:36PM - 2:48PM |
C3.00004: Observation of topological states in an optical Raman lattice with ultracold fermions Bo Song, Chengdong He, Long Zhang, Ting Fung Jeffrey Poon, Elnur Hajiyev, Zejian Ren, Bojeong Seo, Shanchao Zhang, Xiong-Jun Liu, Gyu-Boong Jo The spin-orbit coupling with cold atoms, especially in optical lattices, provides a versatile platform to investigate the intriguing topological matters. In this talk, we will present the realization of one-dimensional spin-dependent lattice dressed by the periodic Raman field. Ultracold $^{173}$Yb fermions loaded into an optical Raman lattice reveal non-trivial spin textures due to the band topology, by which we measured topological invariants and determined a topological phase transition. In addition, we explored the non-equilibrium quench dynamics between the topological and the trivial states by suddenly changing the band topology of the optical Raman lattice. The optical Raman lattice demonstrated here opens a new avenue to study the spin-orbit coupling physics and furthermore to realize novel quantum matters such as symmetry-protected topological states. [Preview Abstract] |
Tuesday, June 6, 2017 2:48PM - 3:00PM |
C3.00005: Majorana fermions in alkaline-earth-like one-dimensional gases Leonardo Mazza, Fernando Iemini, Leonardo Fallani, Peter Zoller, Rosario Fazio, Marcello Dalmonte We show how angular momentum conservation can stabilize a symmetry-protected quasi-topological phase of matter supporting Majorana quasi-particles as edge modes in a one-dimensional cold-atom gas. Differently from typical scenarios, where such quasi-particles require the presence of superconductivity, we investigate a number-conserving Hubbard model with spin and orbital degrees of freedom in the presence of spin-orbit coupling. The latter reduces the global spin symmetry to an angular momentum parity symmetry, which provides an extremely robust protection mechanism that does not rely on any coupling to additional models systems. The emergence of Majorana edge modes is elucidated using field theory techniques, and corroborated with advanced numerical simulations. Our results pave the way towards the observation of Majorana edge modes with alkaline-earth-like (Ytterbium) fermions in optical lattices, where the basic ingredients for our recipe - spin-orbit coupling and strong inter-orbital interactions - have been engineered and observed over the last two years. [Preview Abstract] |
Tuesday, June 6, 2017 3:00PM - 3:12PM |
C3.00006: Interaction-induced chiral trajectories in a ladder governed by the Harper-Hofstadter Model Matthew Rispoli, M. Eric Tai, Alexander Lukin, Robert Schittko, Tim Menke, Dan Borgnia, Philipp M. Preiss, Fabian Grusdt, Adam M. Kaufman, Markus Greiner The combination of interacting charged particles and magnetic fields can to lead to exotic physics that exhibit both spatial entanglement and topological order. Using optical fields, ultracold neutral atoms can simulate the behavior of charged particles in magnetic fields. This capability has been used to study effects such as edge states, topological band structures, and the quantum hall effect. Thus far, however, these experiments have not yet incorporated inter-particle interactions. I will describe recent experimental results in which we apply microscopy to interacting atoms exposed to a synthetic magnetic field and are confined to a 2xN real-space ladder. We observe the chiral dynamics of both single-particle and two-particle systems with strong, finite interactions. We show the interactions for the two-particle system enable chiral dynamics where they would otherwise be absent. Our observation of a novel form of interaction-induced chirality illustrates the rich physics that can emerge with these ingredients even in the few particle limit. Realizing this combination of elements is essential to advance into the regime of fractional quantum hall physics, as well as to drive explorations for new phenomena with the microscopic tools of AMO systems. [Preview Abstract] |
Tuesday, June 6, 2017 3:12PM - 3:24PM |
C3.00007: Exploring Fractional Quantum Hall Effect in Ultracold Strontium Atomic Gases Xibo Zhang, Wei Qi, Mingcheng Liang Ultracold atomic gases in the fractional quantum Hall (FQH) regime hold promise for providing new paths to exotic anyonic excitations. Realizing such atomic systems, however, has been hindered by difficulties in suppressing heating and loss problems due to spontaneous emission and in preparing and manipulating ultracold samples with very small atomic numbers. Owing to its ultra-narrow clock transition, $^{\mathrm{87}}$Sr has become a promising candidate to overcome these difficulties. We describe progress in building an apparatus that uses Raman optical lattices with novel configurations to engineer synthetic gauge fields for ultracold Sr and induce non-trivial topological flatbands. High-spatial-resolution microscopy and precision coherent spectroscopy can be combined to prepare and characterize strongly correlated states and their physical properties. [Preview Abstract] |
Tuesday, June 6, 2017 3:24PM - 3:36PM |
C3.00008: Engineering arbitrary synthetic gauge fields in multiple geometries Fangzhao An, Eric Meier, Bryce Gadway Atoms in a uniform synthetic gauge field mimic the behavior of electrons in a homogeneous magnetic field, yet realizing this simple two-dimensional topological model with tunable flux (and thus field strength) has been a challenge. By implementing multiple ``synthetic dimensions'' of atomic momentum states, we engineer easily tunable, arbitrary flux patterns to study atomic dynamics in both a two-leg ladder geometry and a zig-zag ladder geometry. Starting with a uniform flux ladder, we observe chiral edge states whose flow changes from clockwise to counterclockwise as we tune the applied flux across the entire range of values. Starting with a uniform flux ladder, we demonstrate the ability to tune the applied flux across the entire range of values, observing chiral edge states whose handedness changes from clockwise to counter-clockwise with varying flux. By introducing a step-like jump in the flux pattern, we show topological reflection from a magnetic defect. In a separate zig-zag ladder geometry, we again explore flux-dependent atom dynamics over the full range of values. Within this geometry, we further study quantum localization driven by added pseudo-disorder, and observe a flux-dependent transition between metal to insulator. [Preview Abstract] |
Tuesday, June 6, 2017 3:36PM - 3:48PM |
C3.00009: Time-reversal invariant bilayer 2D synthetic lattices Yichao Zhang, Xiwang Luo, Kuei Sun, Chuanwei Zhang Recently it has been theoretically proposed and experimentally demonstrated that a 1D spin-orbit coupled optical lattice can emulate a 2D synthetic lattice with a uniform magnetic field, where atomic spins represent the synthetic dimension. The time-reversal symmetry in this system is broken by the magnetic flux. Here we propose the time-reversal symmetry may be restored by considering a bilayer spin-orbit coupled optical lattice with opposite Raman coupling between layers. We show how such layer-spin coupling modifies chiral edge states, fractal Hofstadter butterfly, and layer-spin correlation. [Preview Abstract] |
Tuesday, June 6, 2017 3:48PM - 4:00PM |
C3.00010: Controlling vortex rings in Bose-Einstein condensates using artificial gauge fields James Schloss, Rashi Sachdeva, Lee James O'Riordan, Thomas Busch The exponentially decaying evanescent fields near the boundary of dielectric systems can be used to create artificial gauge fields for the generation of vortices in Bose-Einstein condensate (BEC) systems. Here we study the artificial gauge field created by the evanescent field outside of an optical nanofiber from the fundamental HE11 mode and its application to generating and controlling vortex rings in a toroidal BEC trapped around the nanofiber. This has been done by developing a GPU-based code that solves the Gross-Piteavskii equation for the BEC system in three dimensions and using it to study ground state vortex ring structures and their time evolution. Since these gauge fields may be controlled in a time-dependent manner, we can use this system to study the dynamics of complex vortex topologies. [Preview Abstract] |
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