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 P8: Ultracold Bi-Alkalis |
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Chair: Nate Gemelke, Pennsylvania State University Room: 555AB |
Thursday, May 26, 2016 2:00PM - 2:12PM |
P8.00001: Short Range Photoassociation of Rb$_2$ by a high power fiber laser Henry Passagem, Ricardo Rodriguez, Paulo Ventura, Nadia Bouloufa, Olivier Dulieu, Luis Marcassa 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. If the photoassociation is done at short range, deeply bound ground state molecules can be formed [1]. Optical pumping schemes can be used to populate a single state [2]. In our experiment, we have performed trap loss spectroscopy on trapped $^{85}$Rb atoms in a MOT using a high power fiber laser. Our single mode fiber laser (linewidth $<$ 1 MHz) produces about 50 W, which can be tuned in the 1060-1070 nm range. Two vibrational bound states of the $0_{u}^{+}$ potential were observed ($ \nu = 137$ and $138$). The frequency positions as well as the rotational constants of these states are in good agreement with theoretical predictions. We have also measured the lifetime of a crossed optical dipole trap using such fiber laser. The lifetime on resonance is shorter than off resonance as expected. A simple theoretical model indicates that the molecules decay to deeply bound vibrational levels in the ground state. [1] C. Menegatti et all, Phys. Rev. A 87, 053404 (2013). [2] M. Viteau et all, Science 321, 232 (2008). [Preview Abstract] |
Thursday, May 26, 2016 2:12PM - 2:24PM |
P8.00002: Direct production of ultracold rovibronic ground state LiRb molecules through photoassociation and spontaneous decay Ian Stevenson, David Blasing, Daniel Elliott, Yong Chen We report a newly observed photoassociation resonance in $^7$Li-$^{85}$Rb, a mixed $2(1) - 4(1)$ excited state, that spontaneously decays to the rovibronic ground state. This resonance between ultracold Li and Rb is the strongest ground state molecule-forming photoassociation line observed in LiRb, and forms deeply bound $X \: ^1\Sigma^+$ molecules in large numbers. The production rate of the $v=0$ vibrational state is $\sim 4 \times 10^{3}$ molecules/s. [Preview Abstract] |
Thursday, May 26, 2016 2:24PM - 2:36PM |
P8.00003: Creation of a strongly dipolar gas of ultracold ground-state $^{23}$Na$^{87}$Rb molecules Mingyang Guo, Bing Zhu, Bo Lu, Xin Ye, Fudong Wang, Dajun Wang, Romain Vexiau, Nadia Bouloufa-Maafa, Goulven Qu\'{e}m\'{e}ner, Olivier Dulieu We report on successful creation of an ultracold sample of ground-state $^{23}$Na$^{87}$Rb molecules with a large effective electric dipole moment. Through a carefully designed two-photon Raman process, we have successfully transferred the magneto-associated Feshbach molecules to the singlet ground state with high efficiency, obtaining up to 8000 $^{23}$Na$^{87}$Rb molecules with peak number density over $10^{11}$ cm$^{-3}$ in their absolute ground-state level. With an external electric field, we have induced an effective dipole moment over 1 Debye, making $^{23}$Na$^{87}$Rb the most dipolar ultracold particle ever achieved. Contrary to the expectation, we observed a rather fast population loss even for $^{23}$Na$^{87}$Rb in the absolute ground state with the bi-molecular exchange reaction energetically forbidden. The origin for the short lifetime and possible ways of mitigating it are currently under investigation. Our achievements pave the way toward investigation of ultracold bosonic molecules with strong dipolar interactions. [Preview Abstract] |
Thursday, May 26, 2016 2:36PM - 2:48PM |
P8.00004: A quantum gas of polar KRb molecules in an optical lattice Jacob Covey, Matthew Miecnikowski, Steven Moses, Zhengkun Fu, Deborah JIn, Jun Ye Ultracold polar molecules provide new opportunities for investigation of strongly correlated many-body spin systems such as many-body localization and quantum magnetism. In an effort to access such phenomena, we load polar KRb molecules into a three-dimensional optical lattice. In this system, we observed many-body spin dynamics between molecules pinned in a deep lattice, even though the filling fraction of the molecules was only 5{\%}. We have recently performed a thorough investigation of the molecule creation process in an optical lattice, and consequently improved our filling fraction to 30{\%} by preparing and overlapping Mott and band insulators of the initial atomic gases. More recently, we switched to a second generation KRb apparatus that will allow application of large, stable electric fields as well as high-resolution addressing and detection of polar molecules in optical lattices. We plan to use these capabilities to study non-equilibrium spin dynamics in an optical lattice with nearly single site resolution. I will present the status and direction of the second generation apparatus. [Preview Abstract] |
Thursday, May 26, 2016 2:48PM - 3:00PM |
P8.00005: Control of Ultracold Chemical Reactions Through Conical Intersections Constantinos Makrides, Alexander Petrov, Svetlana Kotochigova The pioneering work on obtaining a quantum degenerate sample of ground state KRb molecules is one of the great successes in ultracold physics. The early experimental and theoretical investigations to describe quantum chemical reactions of ultracold KRb molecules with residual ultracold K atoms have been based on probing their inelastic collision loss rates. A natural progression towards control of molecular reactivity would be to study the potential landscape of the collisional complex with the inherited degeneracies and intersections between two lowest electronic states. The topology of these surfaces provide us with a qualitative understanding of the reaction mechanism. Here we study how the ability to prepare unique initial states combined with the presence of conical intersections can be used to control the outcome of ultracold chemical reactions of alkali-metal atoms and molecules. We locate and determine properties of conical intersections for the KRbK molecular system and determine signatures of non-adiabatic passage through the conical intersection to distinguish between relaxation and reaction pathways. [Preview Abstract] |
Thursday, May 26, 2016 3:00PM - 3:12PM |
P8.00006: Rotational Spectroscopy on Ultracold $^{23}$Na$^{40}$K Ground State Molecules Sebastian Will, Jee Woo Park, Zoe Yan, Huanqian Loh, Martin Zwierlein Ultracold molecules with controllable dipolar long-range interactions will open up new routes for quantum simulation and the creation of novel states of matter. In particular, the molecules’ rich internal degrees of freedom allow for versatile control of intermolecular interactions by applying static electric and microwave fields. Starting from an ultracold, spin-polarized ensemble of trapped fermionic $^{23}$Na$^{40}$K molecules in the absolute ground state, we perform microwave spectroscopy on the first rotationally excited state for a range of magnetic and electric fields. Extracting the rotational and hyperfine coupling constants, we comprehensively understand the observed spectra. Following the coherent transfer of the entire ensemble of chemically stable $^{23}$Na$^{40}$K molecules to the first rotationally excited state, we observe a lifetime of more than 3 sec, comparable to the lifetime in the rovibrational ground state. The collisional stability of excited rotational states opens up intriguing prospects for the control of intermolecular van-der-Waals interactions via electric fields. [Preview Abstract] |
Thursday, May 26, 2016 3:12PM - 3:24PM |
P8.00007: Control of anisotropic interactions with microwaves in ultracold NaK molecules Zoe Yan, Huanqian Loh, Jee Woo Park, Sebastian Will, Martin Zwierlein Ultracold polar molecules offer long range anisotropic interactions, which can provide access to novel phases of condensed matter physics. The recent creation of fermionic NaK polar molecules in the ground hyperfine-rovibronic state, which is chemically stable, demonstrates an important step towards the study of new dipolar physics. To engineer dipolar interactions between molecules with large electric dipole moments, one can apply microwaves to mix the lowest and first excited rotational states. Hyperfine interaction in the first excited rotational state mixes nuclear spin and rotation, leading to states with rich character, which we map out by performing microwave spectroscopy. The admixed hyperfine character serves as a tool to engineer wide ranges of "magic" trap polarization angles, at which the lowest and first excited rotational states have matching polarizabilities. Finally, we demonstrate that we can access large dipole moments by coherently dressing the molecules with microwaves. [Preview Abstract] |
Thursday, May 26, 2016 3:24PM - 3:36PM |
P8.00008: Trapping and cooling of sodium atoms for assembly of dipolar molecules Yichao Yu, Nicholas R Hutzler, Lee R Liu, Jessie T Zhang, Kang-Kuen Ni In order to create a diatomic molecule with a large electric dipole moment, it is generally necessary to use atoms with very different electronegativities. In the context of bi-alkali molecules, this means combining a light alkali atom with a heavy one. This is the reason why we use NaCs in our molecule assembler experiment; NaCs has the largest induced dipole moment in few kV/cm lab fields. However, the use of sodium atoms also poses challenges. The higher Doppler temperature and lack of efficient D2 polarization gradient cooling increases the necessary depth of our optical dipole (tweezer) traps. The lack of a convenient magic wavelength for the dipole trap creates a large AC stark shift on the optical transition as well as additional heating mechanisms. The light mass of the sodium, and therefore larger Lamb-Dicke parameter and higher recoil temperature, makes it more difficult to perform efficient Raman sideband cooling on the atom in the trap. I will discuss the techniques we use to overcome these challenges, in particular a method to eliminate the light shifts and associated heating mechanisms in tight optical traps. [Preview Abstract] |
Thursday, May 26, 2016 3:36PM - 3:48PM |
P8.00009: Assembling Ultracold Polar Molecules From Single Atoms Lee R Liu, Nicholas R Hutzler, Yichao Yu, Jessie T Zhang, Kang-Kuen Ni Ultracold polar molecules are promising candidates for studying quantum many-body phenomena and building quantum information systems, due to their long-range, anisotropic, and tunable interactions. This calls for a technique to create low entropy samples of ultracold polar molecules with a large dipole moment. The lowest entropy molecular gas to date was created from atomic quantum gases in bulk or in optical lattices. The entropy is limited by that of the constituent atomic gases. We propose a method that addresses this limitation by assembling sodium cesium (NaCs) molecules from individually manipulated atoms. First, we load single Na and Cs atoms in separate optical tweezers from MOTs. We will cool them to their motional ground state using Raman sideband cooling and then merge them into a single tweezer. The tweezer confinement provides enhanced wavefunction overlap between the atom pair and molecule states. Using coherent two-photon techniques, we will then transfer the atom pair into a molecule. Our method offers reduced apparatus complexity and cycle time, single-site manipulation and imaging resolution, and should be readily extended to different species. [Preview Abstract] |
Thursday, May 26, 2016 3:48PM - 4:00PM |
P8.00010: Investigations of the A-b complex of NaCs molecules Marek Haruza, Nicholas P. Bigelow We report the results of photoassociation (PA) spectroscopy of the A-b complex of NaCs molecules performed from atoms in excited and ground hyperfine states. PA from excited atomic hyperfine states provides an atomic reference for calibration, reveals excited molecular states otherwise not detected and in some cases results in large molecule formation rates. [Preview Abstract] |
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