Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Q08: Ultracold Atomic Gas MixturesLive
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Chair: Sebastian Will, Columbia |
Thursday, June 3, 2021 8:00AM - 8:12AM Live |
Q08.00001: Interactions Between Bosons Immersed in a Fermi Sea Krutik S Patel, Geyue Cai, Cheng Chin When a Bose-Einstein condensate is embedded in a degenerate Fermi gas, the fermionic environment induces new types of correlations between the condensed atoms. For example, bosons can interact at long range through excitations of the Fermi surface in a manner analogous to the Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism in solids. This gives rise to an effective interaction predicted to oscillate between attraction and repulsion at a length scale set by the Fermi momentum. These fermion-mediated interactions can lead to long range coupling between bosons as well as effective few-body interactions between bosons. |
Thursday, June 3, 2021 8:12AM - 8:24AM Live |
Q08.00002: Dissipationless flow in a Bose-Fermi mixture Alexander Chuang, Zoe Yan, Yiqi Ni, Eric Wolf, Carsten Robens, Martin W Zwierlein Mixtures of quantum fluids lie at the forefront of research into strongly-correlated quantum matter as they exhibit a rich many-body phase diagram. We study the dynamics of spin-polarized fermionic impurities immersed in a (superfluid) BEC via their collective excitations. We observe a dissipationless flow of the fermions, from the non-interacting to the strong-coupling regime where the impurities inherit the hydrodynamic modes of the BEC. We further probe the systems response as a function of temperature observing the fermions' transition from the collisionless to the hydrodynamic regime right at the superfluid transition temperature. Our experiments demonstrate the ability to pristinely control the fluid dynamics of a Bose-Fermi mixture in a dual-species ultracold atomic gas experiment. |
Thursday, June 3, 2021 8:24AM - 8:36AM Live |
Q08.00003: Ultracold 6Li-53Cr Fermi mixtures with tunable interactions Alessio Ciamei, Stefano Finelli, Massimo Inguscio, Andreas Trenkwalder, Matteo Zaccanti Mass-imbalanced Fermi mixtures are expected to greatly enhance the observability of elusive regimes of highly-correlated fermionic matter, primarily in the context of unconventional superfluidity and quantum magnetism. |
Thursday, June 3, 2021 8:36AM - 8:48AM Live |
Q08.00004: Double-degenerate Bose-Fermi mixture of strontium and lithium Zhu-Xiong Ye, Li-Yang Xie, Zhen Guo, Xiao-Bin Ma, Gaoren Wang, Li You, Meng Khoon Tey Quantum mixtures of alkali-metal and alkaline-earth-metal elements provide vast opportunities for studying exotic many-body states and for precision tests of fundamental physics. In this talk, we report the production of the first quantum degenerate mixture of 6Li and 84Sr in a far-off-resonant optical dipole trap. The mixture contains 1.6×105 fermionic 6Li atoms with T/TF=0.33(3) and an almost pure 84Sr BEC with 3.1×105 atoms. We also extract the absolute value of the s-wave scattering length between lithium and strontium by measuring the interspecies thermalization rates. |
Thursday, June 3, 2021 8:48AM - 9:00AM Live |
Q08.00005: Generation and dynamics of a degenerate CsYb mixture Kali E Wilson, Alexander Guttridge, Jack D Segal, Simon L Cornish We probe the collective dynamics of a quantum degenerate Bose-Bose mixture of Cs and 174Yb with attractive interspecies interactions. Specifically, we excite vertical center of mass oscillations of the Cs condensate, and observe significant damping for the Cs dipole mode, due to the rapid transfer of energy to the larger Yb component, and the ensuing acoustic dissipation. We further explore the stability of the mixture by tuning the interaction strength of Cs using a broad Feshbach resonance, and observe collapse of the Cs condensate mediated by the attractive Cs-Yb interaction. Numerical simulations based on coupled Gross-Pitaevskii equations provide good agreement with experiment. We will report on recent progress from the Durham CsYb experiment including implementation of Cs-blind optical potentials. We will discuss prospects for exploiting the unique advantages of Cs-Yb mixtures for studies of beyond-mean-field physics, including mass-imbalanced quantum liquid droplets where quantum fluctuations stabilise against mean-field collapse. |
Thursday, June 3, 2021 9:00AM - 9:12AM Live |
Q08.00006: Collective Modes of Mutually-Attractive Coupled Superfluids Nick Proukakis, I-Kang Liu Collective modes of atomic Bose-Einstein condensates have been well investigated in condensates with repulsive interactions [1], across the miscibility-immiscibility boundary [2], and in dual Bose-Fermi superfluids [3]. Here we present a detailed study of Bose-Bose mixture collective dynamics in the presence of attractive interspecies interactions: specifically, we consider a Cs-Yb(174) mixture displaced from its equilibrium position under realistic experimental conditions [4], and demonstrate the distinct excitation mechanisms (single-component excitations, counterflow instabilities) and the evolving nature of the rich dynamical mode coupling. Our findings, supported by both mean-field dynamics and detailed characterization of the mixture’s quasiparticle (Bogoliubov) excitation spectrum, reveal the emergence of beating, associated with a small splitting of the natural oscillation frequency of the dominant component due to induced coupled co-moving and counter-moving modes. Such dynamics is characterized in terms of damping rates, dependence on atom number ratio, and initial kick strength, further analyzing the co-moving and counter-moving coupled modes in terms of both attractive and repulsive interactions. |
Thursday, June 3, 2021 9:12AM - 9:24AM Live |
Q08.00007: Functional renormalization group approach to strongly-coupled Bose-Fermi mixtures in two dimensions Jonas von Milczewski, Richard Schmidt, Félix Rose We study theoretically the phase diagram of strongly-coupled two-dimensional Bose-Fermi mixtures that interact with attractive short-range potentials as a function of the boson and fermion densities. We focus on the limit where the bound state size is small compared to the average distance between bosons. To approach the problem we develop a functional renormalization group approach that accounts for the bound-state physics arising from the extended Fröhlich Hamiltonian and by including three-body correlations we are able to reproduce the polaron-to-molecule transition in two-dimensional Fermi gases in the extreme limit of vanishing boson density. We then extend our framework to describe Bose-Fermi mixtures at finite boson density. We find that when the bound state energy exceeds the Fermi energy, the fermions and bosons can form a fermionic composite with a well-defined Fermi surface constituting a Fermi sea of dressed Feshbach molecules in the case of ultracold atoms while in the case of atomically thin semiconductors a trion liquid emerges. As the boson density is further increased, the effective energy gap of the composites decreases, leading to a transition into a strongly-correlated phase where polarons are hybridized with molecular degrees of freedom. |
Thursday, June 3, 2021 9:24AM - 9:36AM Live |
Q08.00008: Atomic Boson – Fermion mixtures in box potentials Bishal Parajuli, Chih-Chun Chien We study the density profiles of binary atomic boson-fermion mixtures confined in one dimensional box potentials by modelling the system with many-body density-density interactions. The bosons can interact with themselves and with the fermions, but identical fermions do not interact with each other through two-body s-wave scattering. The effects of mass ratio and boson-boson and boson-fermion interactions were considered. Using the Gross-Pitaevskii equation for bosons and Hartree-Fock approximation for fermions, we find a variety of different density profiles in the ground state. All the final configurations are verified to be the minima of the energy functional. We found that the atomic mixtures can remain mixed or phase separate in different parameter regime. Due to the hard-wall boundary condition, the structures may differ from boson-fermion mixtures in a harmonic trap. |
Thursday, June 3, 2021 9:36AM - 9:48AM Live |
Q08.00009: Shell-shaped Bose-Einstein condensates realized with dual-species mixtures Alexander Wolf, Patrick B Boegel, Naceur Gaaloul, Matthias Meister, Maxim Efremov Recently, there has been great interest in the properties of hollow Bose-Einstein condensates (BECs) which can be generated with radio-frequency (rf) dressing. As an alternative method, we consider the realization of hollow BECs by utilizing a dual-species mixture. A proper choice of the parameters allows us to create a ground state where one species is in the center and generates a repulsive effective potential for the second species, giving rise to a shell-shaped BEC. |
Thursday, June 3, 2021 9:48AM - 10:00AM Live |
Q08.00010: Polarons and their induced interactions in highly imbalanced triple mixtures Kevin Keiler, Simeon Mistakidis, Peter Schmelcher We unravel the polaronic properties of impurities immersed in a correlated trapped one-dimensional (1D) Bose-Bose mixture. This setup allows for the impurities to couple either attractively or repulsively to a specific host, thus offering a highly flexible platform for steering the emergent polaronic properties. Specifically, the impurity residue peak and strength of induced interactions can be controlled by varying the coupling of the impurities to the individual bosonic components. In particular, it is possible to maintain the quasiparticle character for larger interaction strengths as compared to the case of impurities immersed in a single bosonic species. We explicate a hierarchy of the polaron binding energies in terms of the impurity-medium interactions, thereby elucidating the identification of the polaronic resonances in recent experimental radiofrequency schemes.For strong attractive impurity-medium couplings bipolaron formation is captured. Our findings pave the way for continuously changing the quasiparticle character, under the impact of trap effects, while exposing the role of correlations in triple mixture settings. |
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