Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Z07: Ultracold MoleculesLive
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Chair: Silke Ospelkaus, Leibniz Universität Hannover |
Friday, June 4, 2021 10:30AM - 10:42AM Live |
Z07.00001: Overlapping Bose-Einstein Condensates of Na and Cs Claire Warner, Aden Z Lam, Niccolò Bigagli, Henry Liu, Ian C Stevenson, Sebastian Will We report on the production of dual-species Bose-Einstein condensates of up to 1 x 106 sodium atoms and 5 x 104 cesium atoms, a key step towards the creation of ultracold ensembles of NaCs ground state molecules. NaCs molecules have a large dipole moment and are ideally suited to access strongly correlated states of dipolar quantum matter. We achieve dual condensation via sympathetic cooling of cesium by sodium in an optically-plugged magnetic trap and a crossed dipole trap. To associate molecules from dual condensates, the BECs must be overlapped, long-lived, and miscible. Using trapping light at 1064 nm, we find that the mass and polarizability ratios of Na and Cs almost perfectly compensate. As a result, the differential gravitational sag between the two species is negligible. With the scattering length of cesium tuned to a moderate value, we find that the condensates co-exist for several seconds. In addition, the condensates are miscible; using cross-thermalization, we determine that the interspecies scattering length between the Na |F, mF> = |1, 1> and Cs |3, 3> states is weakly repulsive. These conditions allow the association of NaCs Feshbach molecules from dual condensates. |
Friday, June 4, 2021 10:42AM - 10:54AM Live |
Z07.00002: A High-Phase Space Density Gas of NaCs Feshbach Molecules Aden Z Lam, Claire Warner, Niccolo Bigagli, Ian C Stevenson, Sebastian Will We report on the production of ultracold ensembles of sodium-cesium Feshbach molecules. We have located and characterized an s-wave Feshbach resonance at 864.12(2) G between sodium and cesium in their respective hyperfine ground states. We demonstrate that this resonance is well-suited for the creation of Feshbach molecules. By varying the atom number and temperature of the atomic clouds, we have wide-ranging control over the properties of the resulting molecular ensembles. We demonstrate the creation of large molecular ensembles with up to 4 × 104 molecules at 2 μK, as well as ensembles of about 1 × 103 molecules at temperatures below 100 nK, when associating from dual condensates. This is a key step towards the creation of sodium-cesium ground state molecules. |
Friday, June 4, 2021 10:54AM - 11:06AM Live |
Z07.00003: Atomic Bose-Einstein condensate to molecular Bose-Einstein condensate transition Zhendong Zhang, Liangchao Chen, Kai-Xuan Yao, Shu Nagata, Cheng Chin We report the formation of Bose-Einstein condensates (BECs) of spinning molecules by inducing pairing interactions in an atomic condensate near a g−wave Feshbach resonance. The trap geometry and the low temperature of the molecules help reducing inelastic loss to ensure thermal equilibrium. From the equation of state measurement, we determine the molecular scattering length to be +220(30) Bohr. We also investigate the unpairing dynamics and find that near the resonance the dynamical time scale is consistent with the unitarity limit. Our work confirms the long-sought transition between atomic and molecular condensates, the bosonic analog of the BEC-BCS (Bardeen-Cooper-Schrieffer superfluid) crossover in a Fermi gas. In addition, our experiment may shed light on condensed pairs with orbital angular momentum, where novel anisotropic superfluid with non-zero surface current is predicted for, e.g., 3He-A. |
Friday, June 4, 2021 11:06AM - 11:18AM Live |
Z07.00004: Coherent optical creation of a single molecule in an optical tweezer Kenneth Wang, Yichao Yu, Jonathan Hood, Lewis R Picard, Jessie Zhang, William B Cairncross, Jeremy Hutson, Rosario Gonzalez-Ferez, Till Rosenband, Kang-Kuen Ni Diverse species of ultracold molecules are desired for a variety of applications in precision measurement, quantum simulation, quantum information processing and ultracold chemistry. Coherent association of ultracold atoms into a molecule typically requires special properties, such as the availability of a magnetic Feshbach resonance, narrow-line excited states or weakly-bound states at the MHz level, which limits the applicability of the technique. Here, we present a more general technique, where we associate the atoms using a coherent two-photon Raman transition. In particular, we form a NaCs molecule in an optical tweezer from ground state cooled Na and Cs atoms. We systematically study the excited state landscape and the possible initial and final states for the most favorable set of parameters to perform the transfer. With these parameters and technical insights, including the use of a narrow-band optical filter, we demonstrate Rabi oscillations between the free atoms and weakly bound molecules. We achieve a transfer efficiency of 69%. Our technique should allow a wider range of molecular species to be assembled atom-by-atom. |
Friday, June 4, 2021 11:18AM - 11:30AM Live |
Z07.00005: Assembly of a single rovibrational ground-state molecule in an optical tweezer William B Cairncross, Jessie Zhang, Lewis R Picard, Yichao Yu, Kenneth Wang, Kang-Kuen Ni Gaining complete quantum state control over the external and internal degrees of freedom of single molecules has been a long-standing goal that will open the door to diverse studies in quantum information and quantum many-body physics. We have recently demonstrated the assembly of a single NaCs molecule in its rovibrational ground state in an optical tweezer from a pair of ground-state-cooled Na and Cs atoms [Cairncross, Zhang, et al., Phys. Rev. Lett. (in press)], with the resulting molecule occupying predominantly the motional ground state of the tweezer. I will discuss our determination of a suitable Raman transition from the Feshbach molecular state to the rovibrational ground state, the coherent optical transfer between these states, and our first studies of the ground-state molecules. |
Friday, June 4, 2021 11:30AM - 11:42AM Live |
Z07.00006: Optical tweezer array of rovibronic ground-state NaCs molecules Jessie Zhang, William B Cairncross, Lewis R Picard, Yichao Yu, Kenneth Wang, Kang-Kuen Ni The ability to trap and control molecules at the individual particle level is at the heart of many proposals that could utilize their rich internal states and long-range dipole-dipole interactions. In our approach to gaining full quantum state control of molecules, we assemble single molecules from single atoms trapped in optical tweezers [Zhang et al., PRL. 124, 253401 (2020); Cairncross, Zhang et al. PRL (in press)]. While we focused on building exactly one molecule from two atoms previously, in this talk, I will discuss our current progress in expanding the molecule assembly process to arrays of molecules, from which we may begin entangling such molecules for many quantum science applications. |
Friday, June 4, 2021 11:42AM - 11:54AM Live |
Z07.00007: Dipolar evaporation and resonant shielding of KRb molecules in quasi-2D Kyle Y Matsuda, Jun-Ru Li, William G Tobias, Giacomo Valtolina, Luigi de Marco, Calder Miller, Goulven Quéméner, Jun Ye Quantum degenerate gases of polar molecules open new possibilities for engineering strongly-correlated quantum matter. However, tuning molecular interactions to create a system that is both long-lived and strongly dipolar has remained an outstanding experimental challenge. We have implemented two strategies for controlling interactions in a quasi-2D geometry [1-2]. First, by polarizing the molecular dipoles perpendicular to the 2D plane, we induce repulsive dipolar interactions, which provide elastic collisions while suppressing losses. We achieve a ratio of elastic to inelastic collision rates of ~200, and demonstrate direct evaporation to below the Fermi temperature. Second, we observe resonant shielding of losses, which arises from dipolar coupling between two pairs of rotational states made degenerate by the external electric field. At the optimal shielding, we suppress the loss rate by an order of magnitude below the background value. These results provide a starting point for future explorations of collective dipolar phenomena in 2D. |
Friday, June 4, 2021 11:54AM - 12:06PM Live |
Z07.00008: Controlling anisotropic dipolar interaction with shielding resonance in a 3D molecular quantum gas Jun-Ru Li, William G Tobias, Kyle Y Matsuda, Calder Miller, Giacomo Valtolina, Luigi de Marco, Reuben R Wang, Lucas Lassablière, Goulven Quéméner, John L Bohn, Jun Ye Suppressing the detrimental two-body loss and obtaining tunability of the elastic dipolar interaction have long been an active quest in the field of ultracold polar molecules. |
Friday, June 4, 2021 12:06PM - 12:18PM Live |
Z07.00009: Realization of degenerate 23Na40K molecules Marcel Duda, Xingyan Chen, Andreas Schindewolf, Roman Bause, Xinyu Luo, Immanuel F Bloch We report on the generation of 60000 degenerate and long-lived 23Na40K Feshbach molecules at a temperature of 0.3 times the Fermi temperature. We use a species-dependent dipole trap to selectively compress a degenerate Fermi gas of K and match its density to a Bose-Einstein condensate of Na. By ramping the magnetic field across a Feshbach resonance, we are able to associate more than 60% of the bosons into weakly-bound Feshbach molecules. After the association, during which no loss is observed, the Feshbach molecules are transferred into the rovibrational ground-state by Stimulated Raman Adiabatic Passage. |
Friday, June 4, 2021 12:18PM - 12:30PM Live |
Z07.00010: Anisotropic polarizability of ultracold ground-state 23Na87Rb molecules Junyu Lin, Junyu He, Xin Ye, Dajun Wang Ultracold polar molecules with the strong, long-range, and anisotropic electric dipole-dipole interaction are attracting more and more researching interest, as a promising platform for applications in quantum simulation and quantum computation. For achieving various quantum phases, maintaining a long coherence time between the rotational levels for trapped molecules is often necessary. Here, we report measurements of the AC polarizabilities of ultracold ground-state 23Na87Rb molecules. By combining trap oscillation frequency measurement and high-resolution rotational spectroscopy driven by microwave, we obtain both the isotropic polarizability of the ground rotational state J= 0 and the anisotropic polarizability of the first excited rotational state J= 1. With the optimized light polarization angle and intensity combination, the nonuniformity of the differential AC Stark shift between the two rotational states is minimized and the rotational coherence time is observed to be the longest. |
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