Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session C6: Ultracold Molecules II |
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Chair: Colin Connolly, Harvard University Room: 302 |
Tuesday, June 4, 2013 2:00PM - 2:12PM |
C6.00001: Suppression of anisotropic interactions between ultracold polar molecules Nadia Bouloufa-Maafa, Romain Vexiau, Mireille Aymar, Maxence Lepers, Olivier Dulieu Due to their large permanent electric dipole moment, heteronuclear bialkali molecules offer the possibility of an exceptional level of control of their quantum properties by external electric fields in the ultracold regime. To that end, a detailed modeling of the molecule-molecule long-range interactions and molecule-field interactions is requested [1]. We have computed the long-range interactions between two identical heteronuclear bialkali molecules in their ground state. In free space, their interaction is characterized by a huge van der Waals coefficient, larger by three orders of magnitude than the one for alkali atoms. In an external electric field this huge isotropic van der Waals interaction compete with the expected anisotropic dipole-dipole interaction. For critical values of the electric field magnitude and intermolecualr distances we predict the mutual orientation of the two molecules but with no preferential direction in the lab frame. The strongly correlated nature of the corresponding eigenstates opens new possibilities to study many-body quantum physics.\\[4pt] [1] M. Lepers, R. Vexiau, N. Bouloufa, O. Dulieu, and V. Kokoouline, Phys. Rev. A 83, 042707 (2011). [Preview Abstract] |
Tuesday, June 4, 2013 2:12PM - 2:24PM |
C6.00002: Theory of long-range photoassociation of ultracold atoms with ultracold molecules Olivier Dulieu, Jesus Perez-Rios, Maxence Lepers We present a dynamical model for photoassociation (PA) of ultracold alkali atoms with ultracold alkali molecules in their rovibrational ground state to create excited trimer molecules. The model involves the long-range multipolar interactions between the atom and the molecule calculated with the degenerate perturbation theory [1], connected to an arbitrary short-range potential. The rate is found significantly smaller than in the atom-atom case under typical MOT conditions, but is promising in the nanokelvin domain. We design a proposal for an experiment in the Mott insulator regime. Being a half-collision, PA could offer the possibility to probe the complex short-range dynamics along the lines developed in refs [2, 3]. \\[4pt] [1] M. Lepers and O. Dulieu, Phys. Chem. Chem. Phys. 13,19106 (2011).\\[0pt] [2] M. Mayle, B. P. Ruzic, and J. L. Bohn, Phys. Rev. A 85, 062712 (2012).\\[0pt] [3] Z. Idziaszek, G. Qu\'em\'ener, J. L. Bohn, and P. S. Julienne, Phys. Rev. A 82, 020703(R) (2010) [Preview Abstract] |
Tuesday, June 4, 2013 2:24PM - 2:36PM |
C6.00003: Short Range Photoassociation of Rb$_2$ in a Broadband Dipole Trap Carlos Renato Menegatti, Jonathan Eugene Tallant, Bruno Spolon Marangoni, Luis Gustavo Marcassa The process of photoassociation has been studied using cold trapped atomic samples for the last 20 years. Due to poor Franck-Condon overlap, a free-to-bound transition followed by spontaneous decay results in a small production of electronic ground state molecules, which are spread over several high-lying vibrational states. If the photoassociation is done at short range, deeply bound ground state molecules can be formed. In our experiment, we have performed photoassociation on trapped $^{85}$Rb atoms in a crossed broadband optical dipole trap. Our crossed beam configuration uses 40 W of power (at 1071 nm, bandwidth of 2 nm) in each beam with a 40 $\mu$m waist radius at the focus. A photoassociation laser is used and is detuned $\sim-7$ cm$^{-1}$ from the Rb D1 line. The resulting cold Rb$_2$ molecules are photoionized by a pulsed dye laser. The time evolution of the molecule population indicates that the photoassociated molecules are being optically pumped by the high flux of 1071 nm photons present in the trapping beam. Optically pumping the molecules suggests deeply bound excited molecular states may be produced by photoassociation at short range by the broadband 1071 nm photons. A simple theoretical model is discussed. [Preview Abstract] |
Tuesday, June 4, 2013 2:36PM - 2:48PM |
C6.00004: Resonant Coupling Between Near-Degenerate Levels of the $2 \, ^1 \Sigma _g^+$ and $1 \, ^1 \Pi _g$ States of Ultracold $^{85}$Rb$_2$ Ryan Carollo, Michael Bellos, David Rahmlow, Jayita Banerjee, Edward Eyler, Phillip Gould, William Stwalley We report on the anomalously high line strength of a single rotational level in the ultracold photoassociation of two $^{85}$Rb atoms to form $^{85}$Rb$_2$. The $v' = 111$, $J' = 5$ level belongs to the Hund's case~(c) $ 2 \, (0_g^+)$ state, which correlates to the Hund's case~(a) $2 \, ^1 \Sigma _g^+$ state. Its strength is caused by coupling with a very near-resonant long-range state. The long-range component is the energetically degenerate $v' = 155$, $J' = 5$ level of the case~(c) $2 \, (1_g)$ state, correlating to the case (a) $1 \, ^1 \Pi _g$ state. The line strength is enhanced by an order of magnitude through this coupling, relative to nearby vibrational levels and even to nearby rotational levels of the same vibrational level. [Preview Abstract] |
Tuesday, June 4, 2013 2:48PM - 3:00PM |
C6.00005: Deviation from Universality in Collisions of Ultracold $^6$Li$_2$ Molecules Tout T. Wang, Myoung-Sun Heo, Timur M. Rvachov, Dylan A. Cotta, Wolfgang Ketterle Collisions of $^6$Li$_2$ molecules reveal a striking deviation from universal predictions based on long-range van der Waals interactions. Li$_2$ closed-channel molecules are formed in the highest vibrational state near a narrow Feshbach resonance, and decay via two-body collisions with Li$_2$, Li, and Na. For Li$_2$+Li$_2$ and Li$_2$+Na, the decay rates agree with the universal predictions of the quantum Langevin model. In contrast, the rate for Li$_2$+Li is exceptionally small, with an upper bound ten times smaller than the universal prediction. This can be explained by the low density of available decay states in systems of light atoms [G. Qu\'em\'ener, J.-M. Launay, and P. Honvault, Phys. Rev. A \textbf{75}, 050701 (2007)], for which such collisions have not been studied before. [Preview Abstract] |
Tuesday, June 4, 2013 3:00PM - 3:12PM |
C6.00006: Increasing the filling fraction of ultracold polar KRb molecules in a 3D optical lattice Steven Moses, Bryce Gadway, Bo Yan, Jacob Covey, Deborah Jin, Jun Ye Gases of ultracold polar molecules with sufficiently low entropy are an ideal experimental scenario to look for signatures of long-range many-body interactions. Having a high filling fraction in a 3D lattice is one way to achieve a low entropy state. In earlier work, we showed that preformed pairs of K and Rb in a 3D lattice (sites that have exactly one K and one Rb) are converted to KRb Feshbach molecules with nearly 100\% efficiency. Since the STIRAP transfer from Feshbach molecules to ground-state molecules is 90-100\% efficient, loading a 3D lattice with a large fraction of preformed pairs will lead to a large filling fraction of ground-state molecules. Our scheme is to load a Mott insulator of Rb and band insulator of K. After we have loaded a lattice with a high filling fraction, we will investigate effects of dipolar interactions in a many-body system. [Preview Abstract] |
Tuesday, June 4, 2013 3:12PM - 3:24PM |
C6.00007: Creating Fermionic Ground State Molecules of $^{23}$Na$^{40}$K with Strong Dipolar Interactions Jee Woo Park, Cheng-Hsun Wu, Jennifer Schloss, Sebastian Will, Martin Zwierlein In our experiment, we work towards creating fermionic ground state molecules of $^{23}$Na$^{40}$K with strong dipolar interactions. These molecules will be chemically stable in the rovibrational ground state, and will carry a large induced dipole moment of 2.72 Debye. Building up on our previous work [1, 2], we have done photoassociation spectroscopy on the $^{23}$Na-$^{40}$K mixture in order to understand the molecular excited state potentials and identify possible intermediate states for efficient STIRAP transfer of Feshbach molecules down to the absolute rovibrational ground state. In addition, our recent effort in doing two-photon spectroscopy to locate the absolute rovibrational ground state will be presented. Our work paves the way towards creating stable dipolar quantum gases, which will open up new avenues to quantum many-body phases with intriguing properties such as supersolidity and topological phases.\\[4pt][1] J. W. Park et al., Phys. Rev. A 85, 051602(R) (2012)\\[0pt] [2] C.-H. Wu et al., Phys. Rev. Lett. 109, 085301 (2012) [Preview Abstract] |
Tuesday, June 4, 2013 3:24PM - 3:36PM |
C6.00008: Control of spin-dependent rotational decoherence of ultracold polar molecules in optical potentials Svetlana Kotochigova, Alexander Petrov, Kostas Makrides We investigate the internal rovibronic and hyperfine quantum states of ultracold fermionic ground-state KRb polar molecules, when static magnetic, static electric, and trapping laser fields are simultaneously applied. Understanding the effect of changing the relative orientation or polarization of these three fields is of crucial importance for creation of decoherence-free subspaces built from two or more rovibronic states. We also evaluate the imaginary part of the polarizability, due to spontaneous emission from excited electronic states. Here, the imaginary part is calculated assuming that excited vibrational levels have a linewidth evaluated by either using the linewidth of atomic K or Rb or using an optical-potential approach. Moreover, we evaluated the induced dipole moment of the internal rovibronic and hyperfine quantum as a function of external electric field. With this precise value of the dipole moment one can investigate of how interactions between molecules in the different optical lattice sites depend on the relative orientation of the applied fields. Our theoretical research efforts are closely linked to ongoing experiments with ultracold KRb molecules. [Preview Abstract] |
Tuesday, June 4, 2013 3:36PM - 3:48PM |
C6.00009: Observation of Feshbach resonances between ultracold Na and Rb atoms Dajun Wang, Fudong Wang, Dezhi Xiong, Xiaoke Li, Eberhard Tiemann We have successfully prepared an optically trapped ultracold mixture of $^{23}$Na and $^{87}$Rb atoms and studied their interspecies Feshbach resonances. Using different spin combinations, 9 $s$-wave and $p$-wave resonances are identified by observing the high inelastic losses and temperature increases for both species near resonant fields. The two $s$-wave resonances below 500 G between atoms in their lowest energy levels are possible candidates for Feshbach molecule association. Our results are well characterized by a coupled channel model and are used to refine the ground state interspecies collision properties between $^{23}$Na and $^{87}$Rb. This work opens up the prospect for ground-state bosonic NaRb molecules which are chemically stable and can provide strong dipolar interactions. [Preview Abstract] |
Tuesday, June 4, 2013 3:48PM - 4:00PM |
C6.00010: Observation of Feshbach resonances in the collisions of ultracold lithium-6 and cesium-133 atoms Shih-Kuang Tung, Jacob Johansen, Karina Jimenez-Garcia, Colin Parker, Cheng Chin Heteronuclear mixtures provide new degrees of freedom for ultracold atom experiments. Among them, a fermionic $^6$Li - bosonic $^{133}$Cs mixture is an excellent candidate to explore new quantum phases, perform independent optical manipulations of the two species, and study universal few-body physics. Here we report the experimental and theoretical study of two-body interaction in this mixture. We identify five $s$-wave interspecies Feshbach resonances with a magnetic field below 1000G [1]. Finally, we report experimental progress toward dual quantum degeneracy of Li and Cs atoms.\\[4pt] [1] S. Tung, C. Parker, J. Johansen, C. Chin, Y. Wang, and P. Julienne, Phys. Rev. A 87, 010702(R) (2013). [Preview Abstract] |
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