Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session K05: Ultracold collisions and photoassociation processes |
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Chair: Subhadeep Gupta, University of Washington Room: Wisconsin Center 102C |
Wednesday, May 29, 2019 2:00PM - 2:12PM |
K05.00001: Interaction of single atoms in optical tweezers Yichao Yu, Lee Liu, Kenneth Wang, Lewis Picard, Jonathan Hood, Till Rosenband, Kang-Kuen Ni Ultracold polar molecules have long-range, anisotropic, tunable interactions providing a versatile platform for studying quantum many-body physics, quantum information, and quantum simulation. The full quantum state control of atoms trapped in optical tweezers could be utilized to study the interaction between single atoms and to coherently create diatomic molecules with high fidelity and low entropy. Based on spectroscopy with single Na and Cs atoms trapped in optical tweezers, I will present results on the scattering lengths between Na and Cs atoms and the observation of NaCs molecular states. These measurements improved upon previous predictions of NaCs molecular properties and refined our scheme on creating ground state NaCs molecules. [Preview Abstract] |
Wednesday, May 29, 2019 2:12PM - 2:24PM |
K05.00002: Detecting Na+Cs Feshbach resonances in optical tweezers Jessie T. Zhang, Yen-Wei Lin, Eliot F. Fenton, Till Rosenband, Kang-Kuen Ni NaCs features one of the largest electric dipole moments (4.6D) in the bi-alkali molecules and is consequently a promising candidate for studies in quantum simulation and computation. Interspecies Feshbach resonances between Na and Cs have previously been predicted and could potentially be utilized to create NaCs Feshbach molecules as an intermediate step towards creating ground-state NaCs molecules. In this talk I will present the detection of Feshbach resonances between Na and Cs with exactly two or three atoms prepared in a single optical tweezer. This experimental approach provides a clean method to study ultracold collisions and few-body physics with fine quantum control and also paves the way to coherently create single ground-state NaCs molecules in optical tweezers starting from single Na and Cs atoms. [Preview Abstract] |
Wednesday, May 29, 2019 2:24PM - 2:36PM |
K05.00003: Coherent control of a photo-chemical reaction with ultracold atoms in quantum superposition H. Esat Kondakci, David Blasing, Chuan-Hsun Li, Yong Chen Ultracold atoms with precisely controlled internal degrees of freedom offer a variety of opportunities in ultracold quantum chemistry. Here, we demonstrate coherent control of chemical processes with Rb-87 Bose-Einstein condensates (BECs) via laser-induced molecular formation--photoassociation (PA). We prepare the condensates in a Raman-dressed spin-orbit-coupled state such that the spin quantum state of the Rb atoms is a superposition of different spin components in the F$=$1 hyperfine state. In contradistinction to reactions with BEC prepared in spin statistical mixture, the PA process results in identical fractional population losses of each spin components in the quantum superposition. Surprisingly, increasing Raman coupling suppresses the rate of molecular formation. We explain this phenomenon based on quantum destructive interference of two scattering channels with different spin combinations. We also discuss further studies of controlling PA rates by engineering initial quantum superposition states of atoms in our condensate. [Preview Abstract] |
Wednesday, May 29, 2019 2:36PM - 2:48PM |
K05.00004: A case for photoassociative production of long-range tetramers in the ultracold regime Marko Gacesa, Jason Byrd, Robin C\^ot\'e We theoretically demonstrate the feasibility of the optical formation of cold long-range tetramers in the ground electronic state from ultracold pairs of polar diatomic molecules in a planar geometry. Based on the relative orientation of two interacting dimers, we find that a tetramer can be formed either as a loosely bound "dimer-dimer" complex in a very extended halo state or as a true long-range tetramer molecule. The latter is of particular interest because it constitutes a specific type of bond between two polar molecules with possible significant consequences for quantum emulation of long-range planar Hamiltonians similar to those found in high-temperature superconductivity models. Our numerical studies were conducted for ultracold molecular gases of KRb and RbCs, resulting in production of (KRb)$_2$ and (RbCs)$_2$ complexes. However, the proposed approach is based on universal properties of polar molecules and the conclusions can be generalized to formation of polyatomic molecules with five or more atoms that have favorable ratio of dipole and quadrupole polarizabilities. [Preview Abstract] |
Wednesday, May 29, 2019 2:48PM - 3:00PM |
K05.00005: Ultracold interactions and collisions in quantum mixtures of highly magnetic atoms and alkali-metal atoms Klaudia Zaremba-Kopczyk, Piotr Zuchowski, Michal Tomza We study ultracold interactions and collisions in quantum mixtures of highly magnetic $S$-state atoms, Cr ($^7S_3$) and Eu ($^8S_{7/2}$), and alkali-metal atoms. We investigate magnetically tunable Feshbach resonances between ultracold europium atoms and between europium and alkali-metal atoms using multichannel quantum scattering calculations [1]. The calculations are carried out for representative systems of $^{153}$Eu+$^7$Li and $^{153}$Eu+$^{87}$Rb, as well as for homonuclear $^{153}$Eu+$^{153}$Eu and heteronuclear $^{153}$Eu+$^{151}$Eu systems. We analyze the prospects for the control of scattering properties and magnetoassociation into ultracold polar and paramagnetic molecules. We show that favorable resonances can be expected at experimentally feasible magnetic-field strengths below 1000 G for all investigated atomic combinations. For the mixtures of chromium with alkali-metal atoms, we consider a prototype system of $^{53}$Cr+$^6$Li. We calculate the potential energy curves for the CrLi molecule both in ground and excited states, investigate magnetic Feshbach resonances, prospects for photoassociation and application of CrLi molecules to precision measurements.\\ [1] K. Zaremba-Kopczyk, P. S. \.{Z}uchowski, M. Tomza, Phys. Rev. A 98, 032704 (2018). [Preview Abstract] |
Wednesday, May 29, 2019 3:00PM - 3:12PM |
K05.00006: Cold interaction studies in K-Ca}$^{\mathrm{\mathbf{+}}}$\textbf{ mixture in an ion-atom hybrid trap Jyothi Saraladevi, kisra Egodapitiya, Kenneth Brown Laser cooled and trapped ion-atom mixtures enable the study of cold collisions including elastic collisions, charge exchange interactions and creation of molecular ions. To facilitate these studies, we have developed an apparatus incorporating a spatially overlapped atom trap (magneto optical trap, MOT) and an ion trap (a linear Paul trap). Our ion- atom hybrid apparatus is integrated with a high resolution time of flight mass spectrometer for the identification of the reaction products. We present our initial experimental results on interactions between cold potassium (K) atoms and calcium (Ca$^{\mathrm{+}})$ ions and compare with the theoretical predictions. The prospects for rotational cooling of CaH$^{\mathrm{+}}$ molecular ions by interaction with laser cooled potassium atoms will be discussed. [Preview Abstract] |
Wednesday, May 29, 2019 3:12PM - 3:24PM |
K05.00007: Energy-dependent 3-body loss in 1D Bose gases Neel Malvania, Laura A. Zundel, Joshua M. Wilson, Lin Xia, Jean-Felix Riou, David S. Weiss We study atom loss in high density quantum Newton's cradles (QNCs) with a range of energies and transverse confinements and find that it is strongly energy dependent. A center-of-mass energy (E$_{\mathrm{cm}})$ dependent 3-body loss rate, K$_{\mathrm{3}}^{\mathrm{1D}}$(E$_{\mathrm{cm}})$, has been predicted for a one-dimensional Bose gas [1], but has not previously been observed. We adapt the 1D theory to quasi-1D gases using the assumption that the loss rate never exceeds the 3D value. Using precise measurements of the QNC momentum distributions and a semiclassical approximation, we infer the E$_{\mathrm{cm\thinspace }}$of all 3-body collisions that occur in the system. We then compare the calculated losses as a function of time to the observed losses, doing a least squares fit of two free parameters using 48 decay curves. The model conforms well with our experimental results [2]. [1] Mehta, N. P., Esry, B. D. {\&} Greene, C. H. Three-body recombination in one dimension. \textit{Phys. Rev. A.} \textbf{76}, 022711 (2007). [2] Zundel, L. A. et al., Energy-dependent 3-body loss in 1D Bose gases. \textit{Phys. Rev. Lett.}~\textbf{122}, 013402 (2019). [Preview Abstract] |
Wednesday, May 29, 2019 3:24PM - 3:36PM |
K05.00008: Effects of tunneling on three-body collisions in atom waveguides Vladimir Yurovsky Atoms with zero-range interactions under a tight transverse confinement in an atom waveguide [1] realize the integrable Lieb-Liniger-McGuire (LLMG) model. Conservation of the quasi-momentum set in this model manifests in the absence of thermalization in the quantum Newton cradle experiment [2] with a two-dimensional optical lattice – a set of parallel atom waveguides. Thermalization was observed in the recent experiment [3] due to dipole-dipole interactions, distorting the LLMG model. The present work analyses integrability lifting due to tunneling between neighboring waveguides. This effect can already take place in the case of three atoms in two waveguides. The three-body scattering problem is solved in the second order Born approximation over the interactions between atoms. Unlike the LLMG model, where the atoms can only exchange their momenta, the system becomes diffractive, i.e. the set of atom momenta is changed as a result of scattering. 1. V. A. Yurovsky, M. Olshanii, and D. S. Weiss, Adv. At. Mol. Opt. Phys. 55, 61 (2008). 2. T. Kinoshita, T. Wenger, and D. S. Weiss, Nature (London) 440, 900 (2006). 3. Y. Tang, W. Kao, K.-Y. Li, S. Seo, K. Mallayya, M. Rigol, S. Gopalakrishnan, and B. L. Lev Phys. Rev. X 8, 021030 (2018). [Preview Abstract] |
Wednesday, May 29, 2019 3:36PM - 3:48PM |
K05.00009: A coherent superposition of dimers and trimers Yaakov Yudkin, Roy Elbaz, P. Giannakeas, Chris H. Greene, Lev Khaykovich Feshbach dimers and Efimov trimers, being insensitive to the short range inter-particle interactions, display a variety of universal properties. Standard experimental techniques for the study of Efimov physics have essentially been limited to the study of loss features due to inelastic collisions subject to variable initial conditions. Such an approach is best suited for the negative scattering length region, where the shallow trimer states dissociate into the free atom continuum. In contrast, for positive scattering lengths the presence of Feshbach dimers shifts the dissociation of trimers into the atom-dimer continuum and Efimov resonances remain inaccessible for direct observations. Here we develop a novel experimental approach which turns the presence of Feshbach dimers into an advantage. We use the dimers as a local reference for the Efimov trimers by creating a coherent superposition of both states. The measurement of its coherent evolution provides information on the binding energy of trimers with unprecedented precision. Even more importantly, it yields access to previously inaccessible parameters of the system such as the Efimov trimers' lifetime and the elastic processes between atoms and the constituents of the superposition state. [Preview Abstract] |
Wednesday, May 29, 2019 3:48PM - 4:00PM |
K05.00010: Can three-body recombination purify a quantum gas? Lena Dogra, Jake Glidden, Christoph Eigen, Timon Hilker, Eric Cornell, Robert Smith, Zoran Hadzibabic While three-body recombination in quantum gases is traditionally associated with heating, it was recently observed that it can also cool some specific systems. We show that three-body loss in a partially condensed 3D homogeneous Bose gas could even lead to purification of the sample, meaning the reduction of the entropy per particle and the increase of the condensed fraction. This phenomenon is a consequence of two quantum-statistical effects - the saturation of the thermal component in a partially condensed gas and the quantum statistics of three-body collisions. We discuss the theoretical origin of this effect and the feasibility of its experimental realisation. [Preview Abstract] |
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