Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session T08: Synthetic Gauge Fields and SpinOrbit Coupling in Bose and Fermi GasesLive

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Chair: Fred Jendrzejewski, Heidelberg University Room: Portland 255 
Friday, June 5, 2020 10:30AM  10:42AM Live 
T08.00001: A Ground State of Strongly Interacting Bosons on an Optical Lattice with an Artificial Gauge Field Sooshin Kim, Julian Léonard, Robert Schittko, Joyce Kwan, Markus Greiner We study strongly interacting atoms in an artificial gauge field. We realize the ground state of a HarperHofstadter system with ultracold $^{\mathrm{87}}$Rb atoms on an optical lattice by superimposing a running lattice of two Raman beams and adding a magnetic field gradient. With the singlesite resolution provided by our quantum gas microscope, we have access to atom number distributions and highorder correlation functions. Our study presents a further step towards opticallattice experiments investigating topological phases and fractional quantum hall systems. [Preview Abstract] 
Friday, June 5, 2020 10:42AM  10:54AM Live 
T08.00002: Excitations in a spinorbit coupled stripe phase Sean Mossman, M. K. H. Ome, Junpeng Hou, Chunwei Zhang, Peter Engels Recent advances in the preparation and manipulation of supersolidlike states with ultracold atoms have opened new lines of inquiry into the dynamics of this novel state of matter. By employing synthetic spinorbit coupling (SOC) and a weak optical lattice which couples the SOC dispersion minima, we produce a ground state configuration which exhibits characteristics of a supersolid state. In this work, we explore the excitations of such a state by manipulating the phase and amplitude of the optical lattice. These investigations shed light on the degree to which this dressed system simulates a supersolid state as well as other interesting phenomena. [Preview Abstract] 
Friday, June 5, 2020 10:54AM  11:06AM Live 
T08.00003: Spinorbit coupling in the presence of strong atomic correlations Ayaka Usui, Thom\'{a}s Fogarty, Steve Campbell, Simon Gardiner, Thomas Busch The synthetic spinorbit coupling in cold atoms provides coupling between momentum and internal state degree. The ground state of the spinorbit coupled system is wellstudied in the meanfield regime [1], but not in strong interaction regime. We investigate two interacting bosons with synthetic spinorbit coupling in one dimension and explore the influence of contact interactions on the system [2]. The system is tractable since it is solvable exactly for some sets of parameters and allows to study what happens without any approximations. Even though the system we consider is bosonic, we show that a regime exists in which the competition between the contact and spinorbit interactions results in the emergence of a ground state that contains a significant contribution from the antisymmetric spin state. This ground state is unique to fewparticle systems and does not exist in the meanfield regime. The transition to this state is signalled by an inversion in the average momentum from being dominated by centreofmass momentum to relative momentum and also affects the global entanglement shared between the real and pseudospin spaces. [1] Y. Li, et al., Phys. Rev. Lett. 108, 225301 (2012). [2] A. Usui, et al., arXiv:1910.02399 (accepted in New Journal Physics). [Preview Abstract] 
Friday, June 5, 2020 11:06AM  11:18AM Live 
T08.00004: Observation of chiral edge states in a rotating BEC Richard Fletcher, Valentin Crepel, Airlia Shaffer, Cedric Wilson, Parth Patel, Zhenjie Yan, Bola Malek, Biswaroop Mukherjee, Martin Zwierlein Charged particles in a magnetic field exhibit modes which propagate along the system boundary, and possess a chirality arising from the broken timereversal symmetry. These modes are protected, showing an immunity to backscattering which would involve tunneling of particles across the sample, and play a crucial role in the quantised transverse resistivity in quantum Hall systems. Here, we engineer chiral edge states in a rotating BoseEinstein condensate, by projecting a sharp optical boundary wall. Using high resolution in situ imaging we resolve their spatial width set by the zeropoint cyclotron motion. By adding controllable optical disorder we demonstrate robustness of the edge states to boundary imperfections, and observe the crucial role of the underlying phasespace structure on their evolution and stability. [Preview Abstract] 
Friday, June 5, 2020 11:18AM  11:30AM Live 
T08.00005: Dynamics of Quantum Gas in NonAbelian Gauge Field Mehedi Hasan, Chetan Madasu, Chang Chi Kwong, Frédéric Chevy, David Wilkowski We experimentally realize SU(2)symmetric artificial gauge field with the tripod laser scheme. First, the nonAbelian nature of the artificial gauge field is revealed by performing loop operations, at different orders, in the parameter space [1]. It was found that the dynamics of internal states leads to a new thermometric scheme that exploits the interferometricdisplacement of atoms [1]. Afterwards, the coupling dynamics of internal( i.e., spin) and external(i.e., momentum)degrees of freedoms, in a twodimensional nonAbelian gauge field, is shown to exhibit an asymmetric expansion of the atomic cloud [2]. This spinorbitcoupled gas breaks the Galilean invariance and modifies the usual reflectionlaws, owing to its inherent peculiar dispersion relation. The density distribution of external dynamics markedly carries the signature of the nonAbelian nature of the underlying gauge field. \\ \\ [1] F. Leroux, K. Pandey, R. Rebhi, F. Chevy, C. Miniatura, B. Gremaud, and D. Wilkowski, NonAbelian and adiabatic geometric transformation in a cold atomic gas, Nat. Commun. \textbf{9}, 3580 (2018). \\ [2] M. Hasan, C. S. Madasu, C. C. Kwong, F. Chevy, D. Wilkowski (under preparation). [Preview Abstract] 
Friday, June 5, 2020 11:30AM  11:42AM Live 
T08.00006: Seeking BoseEinstein condensation in effective HarperHofstadter band: simulations of synthetic magnetic field by optical lattice shaking Han Fu, Setiawan Fnu, Logan Clark, Andreas Glatz, Kathryn Levin The cold atom field has been focused on generating topological and other exotic phases of quantum matter by, for example, creating strong synthetic magnetic fields. The underlying theme of the present work is to use timedependent GrossPitaevskii simulations to make ``reality checks'' of such schemes. There are several key questions we want to answer: 1. Can one implement shaking effectively so that a BEC would emerge, consistent with the effective energy minima of BlochFloquet bandstructure? 2. How realistic is it to experimentally get into the HarperHofstadter regime since it may involve extreme parameter values (such as for hopping and shaking frequency)? 3. An important attribute of applying these BlochFloquet recipes to cold atoms is that there are easily tunable manybody interactions present, which are necessary for equilibration. There is then an associated question: how much do they undermine the singleparticle Floquet band? In this talk we address these issues, and in the process provide advice for experimentalists in implementing these shaking recipes for arriving at a Hofstader BEC. Also, importantly, we try to establish what underlies ''heating'' and how it is affected by the strength of the interactions g. [Preview Abstract] 
Friday, June 5, 2020 11:42AM  11:54AM On Demand 
T08.00007: Dynamical control and detection of topological properties in 2D optical lattices Chengdong HE, Zejian Ren, Entong Zhao, Elnur Hajiyev, Gyu Boong Jo In this talk, we report our progress on the development of versatile twodimensional (2D) optical lattices with nontrivial topology induced by spinorbit coupling~\cite{soc}. Focusing on quench spin dynamics between topological trivial and nontrivial bands, we dynamically characterize band topology. In particular, topological charges can be detected from spin texture measurements by a series of sequential quench processes, which eventually classifies band topology. It is expected that this 2D lattice platform would allow us not only to engineer the topological hamiltonian in spatial domain but also to investigate different lattice structures beyond the standard square lattice structure. \begin{thebibliography}{1} \bibitem {soc} B. Song, C. He, S. Niu, L. Zhang, Z. Ren, X.J. Liu, and G.B. Jo, Nature Physics 15, 911 (2019). \end{thebibliography} [Preview Abstract] 
Friday, June 5, 2020 11:54AM  12:06PM Not Participating 
T08.00008: A Proposal for Synthetic Gauge Fields with Erbium in an Optical Lattice Lin Su, Anne Hebert, Aaron Krahn, Furkan Ozturk, Markus Greiner Synthetic gauge fields enable the ultracold atom systems to probe interesting topological physics like the Quantum Hall Effect. Ramancoupling the magnetic sublevels ($m_F$ or $m_J$) of the ground state manifold can give rise to synthetic gauge fields, as demonstrated by [1] using rubidium. Implementing this scheme using erbium in a siteresolved lattice can offer many significant improvements. The narrow transition will enable erbium to have more than an order of magnitude longer coherence comparing to alkali atoms, opening the gate to probe much longer time dynamics. Besides, since erbium's ground state can have up to $F=19/2$, there are 4 times more sites than what is demonstrated with rubidium, offering much better defined edge states in a topological system. Moreover, the magnetic dipoledipole interaction between erbium atoms offers a natural pathway towards manybody interacting physics, like the Fractional Quantum Hall Effect. Also, our experimental system features siteresolved imaging and subsecond BEC cycle time, which opens access to a new observable and empowers us to study systems that require a large number of statistics. [1] A. Celi, P. Massignan, J. Ruseckas, N. Goldman, I. B. Spielman, G. Juzeliūnas, and M. Lewenstein, Phys. Rev. Lett. 112, 043001 (2014). [Preview Abstract] 
Friday, June 5, 2020 12:06PM  12:18PM Not Participating 
T08.00009: Gram Matrices, Coherent States, and Hofstadter Butterfly with Flat Band Youjiang Xu, Han Pu We propose a new principle using which Hamiltonians supporting flat band can be systematically constructed. The principle is built upon the properties of the Gram matrices. Especially, the Gram matrices of certain subsets of coherent states can be interpreted as Hamiltonians describing a charged particle hopping on a twodimensional lattice subjected to a gauge field. The massive degeneracy of the ground states in these models is a universal property guaranteed by the (over)completeness of the coherent states, independent from the geometry of the lattice. We study the ground state wave functions and the band structure of these models. Experimental realization of the model is promising because the essential features can be seen on very small lattices. [Preview Abstract] 
Friday, June 5, 2020 12:18PM  12:30PM Not Participating 
T08.00010: Phase Transition Between a Chern Insulator and a Quantum Spin Hall Insulator in fivedimensional Quantum Systems Mingyuan He, Qi Zhou Chern insulator and Quantum spin Hall insulator are the two distinct topological states in condense matter and cold atom systems that have attracted great attentions in recent years. In this talk, I will point out a model that can realize the phase transition between a Chern insulator and a Quantum spin Hall insulator in the reduced space of a fivedimensional quantum system. Moreover, we show that the phase transition is not only characterized by the first Chern number, but also the second Chern number. Furthermore, I will show that such phase transition between different topological states that belong to specific Chern class can be generalized to $2N+1$dimensional quantum systems. Such phase transitions provide physicists a way to explore the connect between topological states of different Chern classes. [Preview Abstract] 
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