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 J8: Impurities in Quantum Gases 
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Chair: Michael FossFeig, United States Army Research Laboratory Room: 555AB 
Wednesday, May 25, 2016 2:00PM  2:12PM 
J8.00001: Dynamics and response functions of an impurity in a BEC Yulia Shchadilova, Fabian Grusdt, Richard Schmidt, Eugene Demler We discuss the nonequilibrium quantum dynamics of an impurity in an ultracold Bose gas. In our theoretical description we take into account the microscopic interactions beyond the FrÃ¶hlich approximation. We calculate the response functions of the system for weak and strong RFdriving between two hyperfine states of the impurity. We show that in the weak driving regime the population transfer of the impurity is in agreement with spectral functions obtained by the linear response calculations. This is in contrast with the strong RF regime where we observe the strong renormalization of the Rabi frequency close to the interspecies Feshbach resonance. [Preview Abstract] 
Wednesday, May 25, 2016 2:12PM  2:24PM 
J8.00002: Impurity driven diffusion and destruction of solitons in quasi1D BoseEinstein condensates Lauren Aycock, Hilary Hurst, HsinI Lu, Dina Genkina, Ian Spielman Current experimental research on solitons focuses on their collisions with each other and how dimensionality influences their stability and decay. Here, we investigate the effect of evenly distributed impurity atoms on soliton dynamics. We launch lone, longlived solitons in highly elongated $^{\mathrm{87}}$Rb BoseEinstein condensates (BECs) by phase imprinting and observe oscillations stable over many seconds. We compare these longlived solitons to those launched in BECs containing a few percent of impuritythe same atomic species in a different Zeeman sublevelcontrollably introduced just before evaporation to degeneracy. These impurities  evenly distributed throughout the condensate  dramatically decrease the soliton lifetime and enhance Brownianlike diffusion in the soliton's trajectory. [Preview Abstract] 

J8.00003: ABSTRACT WITHDRAWN 
Wednesday, May 25, 2016 2:36PM  2:48PM 
J8.00004: Dynamics of Ultracold Atoms in the Presence of an Impurity Ion Johannes M. Schurer, Antonio Negretti, Peter Schmelcher Recently, hybrid atomion systems have attracted more and more attention, both theoretically and experimentally. They open up new perspectives on the field of ultracold gases and allow for the study of intriguing phenomena as e.g. the formation of molecular ions [1] or ion induced density bubbles [2]. In our work, we simulate an ultracold ensemble of bosonic atoms in contact with a single ion. Thereby, we focus on effects induced by the atomion interaction and the impact of possible bound states onto the properties of the atomic system. Having started with the ground state properties in dependence of atom number and atomatom interaction [3], we analyzed the atomic dynamics after a sudden creation of the ion in the atomic cloud [4]. The additional length scale in the system becomes clearly apparent and we show the necessity of the description beyond a GrossPitaevskii type approach. This is only possible since our study is carried out by means of the (multilayer) multiconfiguration timedependent Hartree method for bosons [56]. \newline [1] C\^{o}t\'e et al, Lett. 89, 093001 (2002) [2] Goold et al, PRA 81, 041601 (2010) [3] Schurer et al, PRA 90, 033601 (2014) [4] Schurer et al, NJP 17 083024 (2015) [5] Alon et al, PRA 77, 033613 (2008) [6] Cao et al, JCP 139, 134103 (2013) [Preview Abstract] 
Wednesday, May 25, 2016 2:48PM  3:00PM 
J8.00005: Study of superfluid BoseFermi mixture Sebastien Laurent, Marion Delehaye, Shuwei Jin, Matthieu Pierce, Tarik Yefsah, Frederic Chevy, Christophe Salomon Using fermionic and bosonic isotopes of lithium we produce and study ultracold BoseFermi mixtures \footnote{M.~Delehaye, S.~Laurent, I.~FerrierBarbut, S.~Jin, F.~Chevy, C.~ Salomon \emph{Physical Review Letters} \textbf{115} 265303 (2015)}\footnote{I.~FerrierBarbut, M.~Delehaye, S.~Laurent, A.~Grier, M.~Pierce, B.~Rem, F.~Chevy, C.~Salomon \emph{Science} \textbf{345} 1035 (2014).}. First in a low temperature counterflow experiment, we measure the critical velocity of the system in the BECBCS crossover. Around unitarity, we observe a remarkably high superfluid critical velocity which reaches the sound velocity of the strongly interacting Fermi gas. Second, when we increase the temperature of the system slightly above the superfluid transitions we observe an unexpected phase locking of the oscillations of the clouds induced by dissipation. Finally, as suggested in \footnote{T.~Ozawa, A.~Recati, M.~Delehaye, F.~Chevy, S.~ Stringari \emph{Physical Review A} \textbf{90}, 043608 (2014)}, we explore the nature of the superfluid phase when we impose a spin polarization in the situation where the mean field potential created by the bosons on the fermions tends to cancel out the trapping potential of the latter. [Preview Abstract] 
Wednesday, May 25, 2016 3:00PM  3:12PM 
J8.00006: Probing a scattering resonance with Rydberg molecules inside a BoseEinstein condensate J. PerezRios, M. Schlagm\"{u}ller, T. C. Liebisch, H. Nguyen, G. Lochead, F. Engel, F. B\"{o}ottcher, K. M. Westphal, K. S. Kleinbach, R. L\"{o}w, S. Hofferberth, T. Pfau, C. H. Greene The spectroscopy of a single Rydberg atom within a BoseEinstein condensate is studied, and as a result a line shape dependence on the principal Rydberg quantum number n is observed, apart from the expected density shift due to the large number of neutrals inside the Rydberg orbit [1]. The observed line broadening depends on the Rydberg electronneutral interaction, in particular, it manifests the influence of the eRb(5S) pwave scattering shape resonance, which dramatically affects the potential energy landscape for the neutrals embedded within the Rydberg orbit. The observed spectroscopic line shapes are reproduced with an overall good agreement by means of a microscopic model, in which the atoms overlapped with the Rydberg orbit are treated as zerovelocity pointlike particles, with binding energies associated with the ionneutral distance [1] E. Amaldi and E. Segr\`{e}, Nature {\bf 133}, 141 (1934). [2] M. Schlagm\"{u}ller et al. arXiv:1510.07003v1 (accepted in PRL) [Preview Abstract] 
Wednesday, May 25, 2016 3:12PM  3:24PM 
J8.00007: LatticeBased Studies of Weakly Coupled AtomReservoir Systems Ludwig Krinner, Michael Stewart, Arturo Pazmino, Dominik Schneble The coupling of a small quantum system to a much larger one (serving as a reservoir) can give rise to both coherent and dissipative behavior. We report our progress on characterizing a system composed of atoms trapped in a statedependent optical lattice subject to coupling to a variable bosonic background. This system is predicted to display both polaronic energy shifts and spinbosontype dissipative dynamics, phenomena that can be studied in our system utilizing precise magnetic field control. [Preview Abstract] 
Wednesday, May 25, 2016 3:24PM  3:36PM 
J8.00008: NonEquilibrium Dynamics of an Atomic Gas Coupled to a Synthetic Thermal Body Craig Price, Qi Liu, Jianshi Zhao, Nathan Gemelke One takes for granted that thermal equilibrium can be established between two bodies by bringing them into physical contact with one another  viewed externally however, any statistical reservoir must therefore interact in ways such that the exchange of conserved quantities satisfy basic constraints which define the equilibrium it and any attached bodies reach. We describe the experimental construction of a "synthetic thermal body," engineered by controlling the spatiotemporal modulation of nominally conservative optical, radiofrequency, and microwave couplings of a $^{87}$Rb neutral atomic gas carrying hyperfinespin to a spindependent spatially and temporally disordered bath. We measure the outofequilibrium response through its resultant diffusive motion, extracting drift and diffusion parameters, and making comparison to the EinsteinSmoluchowski and generalized fluctuationdissipation relations. We discuss new limits on temperature and density for direct cooling by suitably engineered baths, by simultaneously avoiding the constraints of photonrecoil and densitydependent losses from lightassisted collisional processes in traditional laser cooling, and discuss new avenues in quantum simulation by coupling atomic gasses to statisticallygenerated and open environments. [Preview Abstract] 
Wednesday, May 25, 2016 3:36PM  3:48PM 
J8.00009: Numerical Simulation of mobile BECimpurity interaction Tobias Lausch, Fabian Grusdt, Michael Fleischhauer, Artur Widera Cooling atoms to temperatures, where quantum effects become dominant, has become a standard in cold atom experiments. Especially interactions of quantum baths such as fermi gases and the implementation of impurities, which form fermi polarons, have been studied theoretically and experimentally in detail. However, detailed experiments on the bose polaron and the interaction between impurities and a bose gas are still elusive. We consider a model, where we immerse a single impurity into a BEC, which is described by Bogoliubov approximation. From the master equation, we derived the impurity's momentum resolved scattering and cooling dynamics for numerical simulations. Such cooling processes should enable momentum resolved radiofrequency spectroscopy of the BEC polaron. [Preview Abstract] 
Wednesday, May 25, 2016 3:48PM  4:00PM 
J8.00010: Phase Separation and Dynamics of Trapped Twocomponent BoseEinstein condensates NP Proukakis, KL Lee, M Edmonds, IK Liu, NB Jorgensen, L Wacker, JJ Arlt Twocomponent BoseEinstein condensates (BECs) are an attractive system to study the nonequilibrium dynamics of interacting quantum gases. We recently formulated [1] a selfconsistent kinetic model to study such systems at finitetemperature, where both components are partiallycondensed. The BECs and the thermal atoms are coupled together through both the meanfield interactions and all possible collisional processes. We demonstrate the potential dominance of an energyconserving exchange collision involving a BEC atom and a thermal atom from different components, and discuss the control of the hydrodynamicity through variations of temperature, trap frequencies and trap geometries [1]. Numerically analysing the miscibilityimmiscibility phase diagram for the trapped 87Rb39K experimental system [2], we demonstrate deviations from the simple (homogeneous) interaction strength criterion ($g_{12}^2/g_{11}g_{22}=1$), with the transition boundary depending on the BEC atom numbers. We propose the experimental mapping of this boundary by monitoring the damping rate of the dipole oscillations, supported by detailed numerical simulations at zero and finite temperatures. [1] Edmonds et al., PRA 91,011602(R) (2015); ibid. PRA 92,063607 (2015) [2] Wacker et al., PRA 92,053602 (2015) [Preview Abstract] 
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