Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session D04: Synthetic Gauge Fields and Spin-orbit coupling in Cold Gases I |
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Chair: Jonathan Simon, U. Chicago Room: Grand C |
Tuesday, May 29, 2018 2:00PM - 2:12PM |
D04.00001: Exposing the quantum geometry of spin-orbit coupled Fermi superfluids Menderes Iskin The coupling between a quantum particle's intrinsic angular momentum and its center-of-mass motion gives rise to the so-called helicity states that are characterized by the projection of the spin onto the direction of momentum. In this paper, by unfolding the superfluid-density tensor into its intra-helicity and inter-helicity components, we reveal that the latter contribution is directly linked with the total quantum metric of the helicity bands. We consider both Rashba and Weyl spin-orbit couplings across the BCS-BEC crossover, and show that the geometrical inter-helicity contribution is responsible for up to a quarter of the total superfluid density. We believe this is one of those elusive effects that may be measured within the highly-tunable realm of cold Fermi gases. [Preview Abstract] |
Tuesday, May 29, 2018 2:12PM - 2:24PM |
D04.00002: Abstract Withdrawn
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Tuesday, May 29, 2018 2:24PM - 2:36PM |
D04.00003: Artificial Magnetic Field Quenches in Synthetic Dimensions Firat Yilmaz, Mehmet Oktel Recent cold atom experiments have realized models where each hyperfine state at an optical lattice site can be regarded as a separate site in a synthetic dimension. Precise control over the hopping matrix elements in the synthetic dimension makes it possible to dynamically create an artificial magnetic field much faster than atomic motion. We consider such a magnetic flux quench scenario in synthetic dimensions. We first study the difference between a time varying real magnetic field and an artificial magnetic field using a minimal six site model. We then investigate the dynamics of a wavepacket in an infinite ladder following a flux quench and find that the gauge choice has a dramatic effect on the packet dynamics.A packet splits into smaller packets moving with different velocities. Both the weights and the number of packets depend on the implemented gauge. If an initial packet, in a n--leg ladder, is quenched to Hamiltonian with a vector potential parallel to the ladder; it splits into at most $n$ smaller wavepackets. The same initial wavepacket splits into up to $n^2$ packets if the vector potential is implemented to be along the rungs. Finally, we show that edge states in a thick ribbon are robust under the quench only if there is an edge state in the gap after the quench. [Preview Abstract] |
Tuesday, May 29, 2018 2:36PM - 2:48PM |
D04.00004: Majorana Doublets, Flat Bands, and Dirac Nodes in s-Wave Superfluids Haiping Hu, Fan Zhang, Chuanwei Zhang Time-reversal-invariant topological superfluids are exotic states of matter possessing Majorana Kramers pairs (MKPs), yet their realizations have long been hindered by the requirement of unconventional pairing. We propose to realize such a topological superfluid by utilizing s-wave pairing and emergent symmetries in two coupled 1D ultracold atomic Fermi gases with spin-orbit coupling. By stacking such systems into 2D, we discover topological and Dirac-nodal superfluids hosting distinct MKP flat bands. We show that the MKPs and their flat bands are stable against pairing fluctuations that otherwise annihilate paired Majoranas. Exploiting new experimental developments, our scheme provides a unique platform for exploring MKPs and their applications in quantum computation. [Preview Abstract] |
Tuesday, May 29, 2018 2:48PM - 3:00PM |
D04.00005: Spin-1 degenerate Fermi gases with 2D spin-orbit coupling Junpeng Hou, Tian-sheng Zeng, Haiping Hu, Chuanwei Zhang Recent researches reveal many interesting phenomena on the topological properties of matters, for instance, triply-degenerate points (TPD), high-order band touching (HoBT) and multi-Weyl fermions. However, those fascinating phenomenons usually rely on extra degree of freedom and requires certain lattice symmetry, making them difficult to realize in experiments. In this work, we present an unified approach towards those fascinating topological features through a pristine generalization of Rashba spin-orbit coupling (SOC) to spin-1 degenerate Fermi gases. Remarkably, we identify exotic band touching types, including a single Dirac point, TPD and HoBT through the tuning of linear and quadratic Zeeman fields. We further consider the SU(3) Fermi-Hubbard interaction effects. We show that (i) for attractive interactions, the system hosts a topological $s$-wave superfluid with a large Chern number in 2D, and multiple-Weyl nodes in 3D, and (ii) for repulsive interactions, the system hosts an interaction-driven quantum anomalous Hall phase with a quadratic band touching. Our work shows that the spin degree of freedom itself is sufficient to induce intriguing topological properties, and provides a guideline towards the observability and understanding of 2D SO coupled large spin system. [Preview Abstract] |
Tuesday, May 29, 2018 3:00PM - 3:12PM |
D04.00006: Collective modes of vortex lattices in two-component Bose-Einstein condensates Takumi Yoshino, Sho Higashikawa, Shunsuke Furukawa, Masahito Ueda There has been an ever-growing interest in artificial gauge fields in ultracold atomic gases, which are induced by rotating gases or by optically dressing atoms. When the gas is composed of two components, the former (latter) method induces mutually parallel (antiparallel) synthetic magnetic fields in the two components. Within the mean-field theory, two-component Bose-Einstein condensates (BECs) in parallel and antiparallel fields show the same vortex-lattice phase diagram with five phases determined by the ratio of the intercomponent interaction $g_{\uparrow\downarrow}$ to the intracomponent one $g$. It is interesting to ask whether and how the difference between the cases of parallel and antiparallel fields occurs. Here we study the collective modes of the vortex lattices in two-component BECs by applying the Bogoliubov theory and an effective field theory. We find that two modes with linear and quadratic dispersion relations appear in both the cases. For negative $g_{\uparrow\downarrow}$, while the excitation spectra are significantly different between the two cases, their low-energy parts are found to coincide by a simple rescaling. This relation is violated for positive $g_{\uparrow\downarrow}$ with increasing degree of violation for larger $g_{\uparrow\downarrow}$. [Preview Abstract] |
Tuesday, May 29, 2018 3:12PM - 3:24PM |
D04.00007: ABSTRACT WITHDRAWN |
Tuesday, May 29, 2018 3:24PM - 3:36PM |
D04.00008: Microscopy of the interacting Harper-Hofstadter model on a real-space ladder Robert Schittko, Eric Tai, Alexander Lukin, Matthew Rispoli, Tim Menke, Dan Borgnia, Philipp Preiss, Fabian Grusdt, Adam Kaufman, Markus Greiner While artificial gauge fields in optical lattices have become an increasingly prominent topic in quantum gas research, the corresponding experiments have mostly been restricted to the regime of weak interactions. Here, using microscopic atomic control and detection, we investigate a strongly-interacting two-body system which is described by the interacting Harper-Hofstadter model. Specifically, we create a ladder-like real-space lattice and deterministically populate it with two atoms in a chosen quantum state. We subsequently observe chiral dynamics in the two-particle evolution, which are shown to depend on the freely-tunable flux of the artificial gauge field. Our experimental platform combines all of the necessary components for investigations of highly-entangled topological states, and our observations lay the groundwork for future experiments in the fractional quantum Hall regime. [Preview Abstract] |
Tuesday, May 29, 2018 3:36PM - 3:48PM |
D04.00009: Observation of symmetry-protected topological phases with ultracold fermions Zejian Ren, Bo Song, Long Zhang, Chengdong He, Ting Fung Jeffrey Poon, Elnur Hajiyev, Shanchao Zhang, Xiong-Jun Liu, Gyu-Boong Jo Synthetic spin-orbit coupling in cold atoms paves an intriguing new way to explore nontrivial topological orders beyond natural conditions. Here we report the observation of a novel kind of symmetry-protected topological (SPT) phase with spin-orbit coupled fermions in a Raman-dressed one-dimensional optical lattice [1]. This new SPT phase protected by a magnetic group symmetry and a nonlocal chiral symmetry is beyond traditional Altland-Zirnbauer tenfold classification. We determine topological invariant based on symmetric momenta in Bloch states. Furthermore, we investigate quench dynamics between topologically distinct phases by suddenly changing the band topology, which exhibits distinct behavior when the system is quenched to topological phase and trivial phase. Our work opens a new avenue for studying equilibrium and non-equilibrium topological physics with ultracold atoms.\\ $[1]$ B.Song {\it et al.}, {\bf Science Advances} {\it in press} (2018), \it preprint :arXiv1706.00768. [Preview Abstract] |
Tuesday, May 29, 2018 3:48PM - 4:00PM |
D04.00010: A Superconducting Harper-Hofstadter Lattice for Microwave Photons Clai Owens, Aman LaChapelle, Brendan Saxberg, Ruichao Ma, David Schuster, Jonathan Simon We present the latest progress in developing a novel architecture for exploration of topological matter. We construct photonic lattices from tunnel-coupled, time-reversal-broken microwave cavities that are both low loss and compatible with Josephson junction-mediated particle-particle interactions, allowing us access to topological phenomena such as the fractional quantum Hall effect. We employ seamless 3D microwave cavities all machined from a single block of high purity superconductor, along with Yttrium-Iron-Garnet (YIG) spheres magnetically biased below the critical field so our meta-material is scalable and directly compatible with the circuit QED toolbox. After demonstrating the essential properties of a time-reversal broken topological insulator at room temperature without interactions, we now push towards coupling Josephson junction qubits to a cryo-compatible superconducting lattice. [Preview Abstract] |
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