Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session T06: Spectroscopy and Collisions of Ultracold MoleculesLive
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Chair: David DeMille, Yale University Room: E141-142 |
Friday, June 5, 2020 10:30AM - 10:42AM Live |
T06.00001: Single weakly-bound NaCs molecule in optical tweezers Yichao Yu, Jessie Zhang, Kenneth Wang, Lewis Picard, William Cairncross, Kang-Kuen Ni Ultracold polar molecules have long-range, anisotropic, and tunable interactions providing a versatile platform for studying quantum many-body physics, quantum information, and quantum simulation. Optical tweezers allow us to trap atoms and molecules in flexible configurations and fully control their quantum states. The formation of weakly bound molecules in optical tweezers is an important intermediate step towards strongly interacting ground state molecules. I will present results on creating single Feshbach molecules in optical tweezers and progress towards optical transfer to the vibrational ground state. [Preview Abstract] |
Friday, June 5, 2020 10:42AM - 10:54AM Live |
T06.00002: Observation of photoinduced two-body loss of ultracold RbCs molecules Simon Cornish, Phillip Gregory, Jacob Blackmore, Sarah Bromley Ultracold polar molecules offer many exciting opportunities in the fields of quantum computation, quantum simulation and fundamental studies of quantum matter. Long-lived, trapped samples of molecules are crucial to many of these applications. Yet, remarkably, the nature of the collisions between molecules is poorly understood, with fast loss being observed even for chemically stable molecules such as RbCs. Here we report measurements of collisional loss in gases of ultracold RbCs molecules, comparing our findings with the `sticky collision' hypothesis that pairs of molecules form long-lived collision complexes. We demonstrate that the loss of molecules is best described by second-order rate equations, and that the rate differs from the limit of `universal loss' for s-wave collisions. Moreover, we present direct evidence that the loss of collision complexes is driven by very fast laser excitation due to the dipole trapping light. Using square-wave modulation of the optical trap intensity, we are able to suppress the photo-induced loss as the molecules experience time in the dark. By varying the frequency of the modulation, we are able to measure a lifetime of 0.53(13) ms for the collision complex. Our method represents a novel way to perform spectroscopy of long-lived molecule-pair complexes, and offers new insight into reactive and nonreactive collisions. [Preview Abstract] |
Friday, June 5, 2020 10:54AM - 11:06AM Live |
T06.00003: Photoinduced two-body loss of ultracold molecules Tijs Karman, Arthur Christianen, Martin Zwierlein, Gerrit Groenenboom Ultracold polar molecules are a promising platform for applications such as precision measurement, quantum computing, and quantum simulation. In typical experiments, the molecules’ lifetime is limited by loss due to molecule-molecule collisions. Surprisingly, collisional loss is observed even for chemically stable molecules, and cannot be explained by “sticky collisions”, proposed previously \footnote{Mayle, Ruzic, and Bohn, \emph{Phys. Rev. A}, {\bf 85}, 062712 (2013)}. Instead, we show that excitation of collision complexes by the laser used to trap the molecules leads to the effective two-body loss observed experimentally \footnote{Christianen, Zwierlein, Groenenboom, and Karman, \emph{Phys. Rev. Lett.}, {\bf 123}, 123402 (2019)} [Preview Abstract] |
Friday, June 5, 2020 11:06AM - 11:18AM Live |
T06.00004: Steering reactions of ultracold KRb molecules via long-lived intermediates. Ming-Guang Hu, Yu Liu, Matthew Nichols, Lingbang Zhu, Kang-Kuen Ni Ensembles of trapped ultracold bi-alkali molecules have been produced in many research groups. Despite being prepared in their absolute ground states, these molecular gases have been observed to undergo two-body loss, regardless of whether chemical reactions in the gas are energetically allowed or forbidden. Theories suggest that this loss is likely ascribed to the unusual properties of the intermediate complex formed during the reaction. Such properties are currently poorly understood due to a lack of experimental detection of this intermediate, as well as of the reaction products. By combining photoionization with ion velocity map imaging in a potassium-rubidium (KRb) quantum gas apparatus, we recently demonstrated the ability to detect both the products and the intermediates of the reaction KRb $+$ KRb $\to $ K$_{\mathrm{2}}$Rb$_{\mathrm{2}}$* $\to $ K$_{\mathrm{2}} \quad +$ Rb$_{\mathrm{2}}$ [Science 366,1111 (2019)]. We found this intermediate to be long-lived (of order one microsecond), which we further took advantage of to control the product formation rate using an external light source. [Preview Abstract] |
Friday, June 5, 2020 11:18AM - 11:30AM Live |
T06.00005: Thermalization and Sub-Poissonian Density Fluctuations in a Degenerate Fermi Gas of KRb Molecules Kyle Matsuda, William Tobias, Giacomo Valtolina, Luigi De Marco, Jun-Ru Li, Jun Ye Quantum degenerate gases of polar molecules, which exhibit long-range, anisotropic, and tunable dipole-dipole interactions, open new possibilities for engineering strongly-correlated quantum matter. We study atom-molecule thermalization in the creation of a degenerate Fermi gas of potassium-rubidium molecules [1]. By measuring the atom-molecule interaction strength, we estimate that the molecules experience 6 elastic collisions during the magneto-association ramp, facilitating thermalization. We observe suppressed density fluctuations in the degenerate molecular gas, similar to atomic Fermi gases, which confirms the thermometry of the gas. We will also describe efforts to create a single 2D Fermi gas of molecules, where losses due to chemical reactions are suppressed and dipolar interactions can lead to the emergence of exotic many-body phases. In particular, we will present preliminary experimental data showing efficient evaporation of the molecules via dipolar collisions, demonstrating a clear pathway toward creating a 2D Fermi gas of molecules. [1] Tobias, et al., PRL 124, 033401 (2020). [Preview Abstract] |
Friday, June 5, 2020 11:30AM - 11:42AM Live |
T06.00006: Toward Control of Collisions between Ultracold Triplet Ground State NaLi Molecule and Na Atom Hyungmok Son, Juliana Park, Yukun Lu, Alan Jamison, Wolfgang Ketterle There have been extensive efforts in understanding molecular collisions in the quantum regime. As the colliding bodies get heavier, due to the high rovibrational density-of-states of the collision complex, theoretical simulation of collisions becomes challenging and experimental observation of resolvable scattering resonances is predicted to be difficult. 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 atom-molecule and molecule-molecule collisions, as a benchmark system for theoretical quantum scattering calculations. We report progress on magnetic control of collisions between the triplet ground state NaLi molecules and Na atoms, building from a recent result on internal state control of colliding particles. This can help improve the efficiency of sympathetic cooling of a spin-polarized NaLi-Na mixture at ultracold temperature, which has been recently demonstrated, and in understanding the short-range physics and the three-body potential energy surface. [Preview Abstract] |
Friday, June 5, 2020 11:42AM - 11:54AM Live |
T06.00007: Electronic and rotational spectroscopy of cold, chiral molecules Sandra Eibenberger-Arias, Alicia O. Hernandez-Castillo, Johannes Bischoff, Ju Hyeon Lee, Marco DePas, Gerard Meijer Chiral molecules are important in nature and exist in one of two mirror-image versions, called enantiomers. Even though most physical properties of enantiomers are identical, their handedness often determines their functionality. Recently, the enantiomer-specific state transfer method [1] was developed. This method provides the means to selectively populate or depopulate a rotational level of an enantiomer by making use of the fact that the scalar triple product of dipole moment components of the two enantiomers has opposite sign. We have designed, built, and characterized a compact spectroscopy experiment capable of performing chirped-pulse Fourier transform microwave and electronic spectroscopy. Our new setup is equipped with microwave inputs with three perpendicular polarizations, allowing for chirality-sensitive measurements. We implement more sensitive detection schemes such that even small population changes can be detected. Recent experimental results and details on the new spectrometer will be discussed. 1. Eibenberger, S., Doyle, J. {\&} Patterson, D. Enantiomer-Specific State Transfer of Chiral Molecules. Phys Rev Lett 118, 123002, doi:10.1103/PhysRevLett.118.123002 (2017). [Preview Abstract] |
Friday, June 5, 2020 11:54AM - 12:06PM On Demand |
T06.00008: Ultracold Scattering of Ar–NO in Three Dimensions Alexander Teplukhin, Brian Kendrick Until now, the scattering of Ar and NO has been treated in two dimensions, with the internuclear NO distance held fixed at the equilibrium geometry. In the present study we go beyond that limitation and describe the Ar--NO ($\tilde{X}\,^2\Pi$) complex using all three dimensions. The calculations are based on new potential energy surfaces ($A'$ and $A''$), computed using the coupled-cluster CCSD(T) method in the complete basis set limit and coupled by the spin-orbit interaction. Both $^2\Pi_{3/2} \, \rightarrow \, ^2\Pi_{1/2}$ and $^2\Pi_{3/2} \, \rightarrow \, ^2\Pi_{3/2}$ transitions are studied, with the former ``downhill'' (exoergic) transition being the main focus. The rate coefficients are computed using the coupled-channel APH3D code and are analyzed for a wide range of ultracold and cold temperatures, from 1 nK to 10 K. The calculations are carried out in Delves hyperspherical coordinates and the channels are propagated using a log-derivative method. This is the first-ever theoretical treatment of Ar--NO scattering in full dimensionality and also for the ultracold energy regime. [Preview Abstract] |
Friday, June 5, 2020 12:06PM - 12:18PM On Demand |
T06.00009: Stability of Quantum Degenerate Fermi Gases of Tilted Polar Molecules Antun Balaz, Vladimir Veljic, Axel Pelster Quantum degeneracy of a dipolar Fermi gas of KRb molecules was achieved at JILA [Science {\bf 363}, 853 (2019)], which paves a way towards enabling experimental studies of a strongly dipolar regime and, in particular, many-body phenomena and phases of matter that emerge there. Here we address this topic theoretically and derive a mean-field variational approach based on the Wigner function for the description of ground-state properties of such systems [Phys. Rev. Research {\bf 1}, 012009(R) (2019)]. We show that the stability of dipolar fermions in a general harmonic trap is universal as it only depends on the trap aspect ratios and the dipoles orientation. We calculate the species-independent stability diagram and the deformation of the Fermi surface (FS) for polarized molecules, whose electric dipoles are oriented along a preferential direction. Compared to atomic magnetic species, the stability of a molecular electric system turns out to strongly depend on its geometry and the FS deformation significantly increases. We also show that tuning the trap frequencies appropriately reduces the 3D system to a quasi-2D system of either a pancake- or a cigar-shaped gas cloud, which turn out to have smaller stability regions. [Preview Abstract] |
Friday, June 5, 2020 12:18PM - 12:30PM |
T06.00010: Controlling 3-body collisions of ultracold dipolar molecules using an electric field Lucas Lassabli{\`e}re, Goulven Qu{\'e}m{\'e}ner Ultracold dipolar molecules are excellent candidates for engineering quantum applications and cold, controlled chemistry [1]. Therefore, a lot of effort is devoted nowadays to produce ground state ultracold molecules in high densities. One of the main goals is also to produce quantum degenerate gases such as Bose-Einstein condensates or degenerate Fermi gases. Unfortunately, high losses of molecules occur. Therefore, one has to shield them against those losses. In this talk, we will focus on the control of 3-body collisions using an external static electric field, as it was proposed for a shielding of 2-body collisions [2,3]. I will describe the hyperspherical formalism used and I will present preliminary results. The goal is to create a long-range potential barrier at the same value of the electric field than for the 2-body shielding. More investigations will tell us whether the 3-body rate coefficients will be suppressed using this method. [1] J. L. Bohn et al., Science 357, 1002 (2017) [2] G. Wang, G. Qu{\'e}m{\'e}ner, New J. Phys. 17 035015 (2015) [3] M. Gonz{\'a}lez-Mart{\'i}nez et al, Phys. Rev. A 96 032718 (2017) [Preview Abstract] |
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