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 Q05: Ultra Cold Molecules |
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Chair: Shimon Kolkowitz, University of Wisconsin, Madison Room: Wisconsin Center 102C |
Thursday, May 30, 2019 2:00PM - 2:12PM |
Q05.00001: Controlled Reactivity of Degenerate Polar Molecules William Tobias, Luigi De Marco, Giacomo Valtolina, Kyle Matsuda, Jun-Ru Li, Jun Ye We have recently achieved Fermi degeneracy of polar molecules via coherent association in a degenerate Bose-Fermi atomic mixture. The onset of degeneracy was accompanied by suppression of chemical reactions below the classical prediction, indicating dependence of reactivity on spatial correlations or many-body interactions in the degenerate gas and prompting further investigation into the reaction dynamics.\\\\ We present progress towards two-dimensional confinement of potassium rubidium molecules. In this geometry, electric field-induced dipole-dipole interactions are predicted to further suppress chemical reactions and assist thermalization, allowing direct evaporation to deeper degeneracy. Experimental control over dipolar interaction strength and dimensionality will provide insight into the dynamics of chemical reactions in a degenerate gas. In conditions where chemical reactions are suppressed, interactions between degenerate molecules will allow exploration of many-body correlated phases. [Preview Abstract] |
Thursday, May 30, 2019 2:12PM - 2:24PM |
Q05.00002: Toward spin physics with polar molecules in 2D Kyle Matsuda, Giacomo Valtolina, Luigi De Marco, William Tobias, Jun-Ru Li, Jun Ye Ultracold polar molecules are a promising platform for studying many-body quantum physics due to their long-range and anisotropic dipolar interactions. In particular, the interplay between the range of the interactions and spatial dimensionality leads to the emergence of exotic many-body phenomena when the molecules are confined in a 2D geometry. We will describe progress toward the preparation of a degenerate gas of KRb molecules in a single 2D plane, before we load them into a 3D optical lattice. In this setting, rotational excitations of the molecules can be mapped to a system of hard-core bosons, which are predicted to exhibit Bose condensation at a critical filling of molecules in the lattice [1]. In addition, dipolar interactions between the molecules are expected to result in an effective spin-orbit coupling [2]. [1] M. P. Kwasigroch and N. R. Cooper, PRA 96, 053610 (2017). [2] S. V. Syzranov, M. L. Wall, V. Gurarie, and A. M. Rey, Nat. Comm. 5, 5391 (2014). [Preview Abstract] |
Thursday, May 30, 2019 2:24PM - 2:36PM |
Q05.00003: Quantum-state-dependent Collision Between Ultracold Triplet Ground State NaLi Molecule and Na Atom Hyungmok Son, Juliana Park, Jiangtian Yao, Martin W. Zwierlein, Alan O. Jamison, Wolfgang Ketterle There have been extensive efforts in understanding molecular collisions in the quantum regime. As the colliding bodies get heavier, due to their rich internal structures, theoretical simulation of the collisions becomes significantly complex and experimental observation of resolvable scattering resonances is predicted to be difficult. For this reason, most of experimental progress in this field has been accomplished with light molecules like H$_{\mathrm{2}}$ and HD; however, the collision energy was in the mK-regime in these previous studies. Utracold NaLi -- the lightest bi-alkali molecule -- that lives long in the triplet manifold of the electronic spin offers a new platform for the study of molecule-atom and molecule-molecule scattering controlled at the quantum level. We report strongly hyperfine-state-dependent collisions between the triplet ground state NaLi molecules and Na atoms, which can help in understanding the short-range physics and the three-body potential energy surface. The observation of long lifetime of the NaLi molecules with the Na atoms in their stretched hyperfine states suggests a possibility of sympathetic cooling of the NaLi molecules. [Preview Abstract] |
Thursday, May 30, 2019 2:36PM - 2:48PM |
Q05.00004: Non-universal behavior in the ultracold Li + LiNa $\to$ Li$_2$ + Na reaction Brian Kendrick, James Croft, Naduvalath Balakrishnan, Ming Li, Hui Li, Svetlana Kotochigova Quantum reactive scattering calculations for the ultracold Li + LiNa $\to$ Li$_2$ + Na reaction are presented which include both the ground and first excited doublet electronic states. In the interaction region the excited electronic state exhibits a deep potential well that is energetically accessible even in the ultracold regime for Li + LiNa collisions with ground state reactants. A numerically exact full-dimensional time-independent scattering method based on hyperspherical coordinates is used to compute the total, vibrationally, and rotationally resolved non-thermal rate coefficients for collision energies between $1\,{\rm nK}$ and $0.3\,{\rm K}$. The non-adiabatic and geometric phase effects associated with the energetically accessible conical intersection between the two electronic states are shown to produce non-universal behavior in the ultracold rate coefficient. The non-adiabatic ultracold rate coefficient is approximately 1.6 times larger than the universal value computed using a single ground state electronic potential energy surface. A significant enhancement or suppression of up to two orders of magnitude is also observed in many of the rotationally resolved rate coefficients due to constructive or destructive quantum interference. [Preview Abstract] |
Thursday, May 30, 2019 2:48PM - 3:00PM |
Q05.00005: Direct observation of ultracold molecular reactions Ming-Guang Hu, Yu Liu, David Grimes, Andrei Gheorghe, Kang-Kuen Ni Ultracold atoms and molecules provide a new platform to explore chemical reactions at ultralow temperatures. In this regime, reactions could proceed surprisingly efficiently due to their quantum mechanical nature. We are investigating a likely~4-center reaction, 2KRb-\textgreater K2$+$Rb2$+$KE (1.24 meV), in the temperature regime below 1 micro-Kelvin. Towards this goal, we have built an apparatus that combines AMO techniques for ultracold reagent preparation and physical chemistry techniques for reaction product detection through velocity-map imaging (VMI) of ions. I will report our first results on direct observation of ultracold molecular reactions. [Preview Abstract] |
Thursday, May 30, 2019 3:00PM - 3:12PM |
Q05.00006: Probing reactive collisions between ultracold KRb molecules Yu Liu, Ming-Guang Hu, David Grimes, Andrei Gheorghe, Kang-Kuen Ni Ensembles of trapped ultracold bi-alkali molecules (AB) have been produced in many research groups around the world. Despite being prepared in their absolute quantum ground states, these molecular gases have been shown to undergo rapid two-body decay regardless of whether the chemical reaction AB $+$ AB $\to $ A$_{\mathrm{2}} \quad +$ B$_{\mathrm{2}}$ is endothermic or exothermic. The theory of "sticky collisions" has been put forth to explain such phenomena. Central to the theory is the formation of a long-lived collisional complex A$_{\mathrm{2}}$B$_{\mathrm{2}}$ as an intermediate state. We have constructed an apparatus that combines the production of ultracold ground state KRb molecules with the ability to directly detect the products K$_{\mathrm{2}} \quad +$ Rb$_{\mathrm{2}}$ as well as the complex K$_{\mathrm{2}}$Rb$_{\mathrm{2}}$. In this talk I will present observation of reaction products and discuss our plan to probe the lifetime and dynamics of the reaction complex. [Preview Abstract] |
Thursday, May 30, 2019 3:12PM - 3:24PM |
Q05.00007: Enlarging the tool box of ultracold molecule manipulation Roman Bause, Xingyan Chen, Ming Li, Marcel Duda, Svetlana Kototchigova, Immanuel Bloch, Xinyu Luo We present our recent progress on preparing ultracold gases of dipolar fermionic $^{23}$Na$^{40}$K molecules in 3D optical lattices and manipulating their rotational degrees of freedom. We have indentified a tune-out wavelength at which the polarizability of the first excited rotational state vanishes, while polarizability of the ground state remains finite. The tune-out wavelength is located close to the $X^1 \Sigma^+, v=0, J=0 \to b^3 \Pi, v=0, J=1, \Omega=1$ transition at 866.14 nm. The small line width of this transition makes it a good candidate for rotation-dependent dipole traps and lattices. In combination with our recent work on increasing the filling of NaK molecules in a 3D lattice, this brings us closer to simulating lattice spin models with dipolar molecules. [Preview Abstract] |
Thursday, May 30, 2019 3:24PM - 3:36PM |
Q05.00008: Progress toward ultracold quantum gases of sodium-cesium molecules Ian Stevenson, Aden Lam, Claire Warner, Niccolo Bigagli, Sebastian Will We present work towards a dipolar quantum gas of sodium-cesium (NaCs) molecules in their absolute ground state. NaCs stands out because it has the largest dipole moment, 4.6 Debye, of the non-reactive bi-alkali molecules and it is predicted to have optical transitions that can be used for ground state transfer via Stimulated-Raman-Adiabatic-Passage (STIRAP) accessible via diode lasers. We report on progress along a path to dual species condensation and eventually ground state molecules. Finally, to explore strongly dipolar physics, our work looks to combine recent advances in tailored optical potentials with NaCs molecules under large electric fields; specifically, we seek to create a homogeneous two-dimensional system using a digital micromirror device (DMD) for molecules and study dipolar crystals. [Preview Abstract] |
Thursday, May 30, 2019 3:36PM - 3:48PM |
Q05.00009: Depletion spectroscopy of ultracold $\nu_x=0$ $^{85}$Rb$_2$ molecules trapped in a crossed optical dipole trap Henry Passagem, Nadia Bouloufa-Maafa, Olivier Dulieu, Luis Marcassa In this work, we have loaded $\nu_x=0$ $^{85}$Rb$_2$ ultracold molecules into a crossed optical dipole trap from a standard magneto optical trap using a single light beam. Such beam is composed of a single frequency coherent light source, which is responsible for short range PA of cold rubidium atoms, and an incoherent broadband light source which transfers the molecules in different vibrational levels ($\nu_x$) of the singlet-ground-state X, into $\nu_x=0$, through optical pumping. The molecules were observed, by REMPI technique, through 11 transitions from the $\nu_x=0$ $X^{1}\Sigma_{g}^{+}$ ground state to the $2^{1}\Sigma_{u}^{+}$ excited state in the 20853-20985~cm$^{-1}$ energy range. Due to the bandwidth of the REMPI laser we were unable to resolve the rotational distribution of the $\nu_x=0$. Therefore, we have performed depletion spectroscopy in the $\nu_x=0$ trapped molecules using a diode laser at 682 nm to drive transitions from $v_X=0$ to $v=0$ of the $b^{1}\Pi_{u}$ potential. The pulsed dye laser frequency was set at the largest peak at 20966.9 cm$^{-1}$. The experimental depletion spectrum, which is in good agreement with theoretical predictions, allows us to determine that 75\% the $\nu_x=0$ molecules are in $J$= 0, 1 and 2 rotational states. [Preview Abstract] |
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