We report on the production of a stable mixture of bosonic and fermionic superfluids composed of the elements 174 Yb and 6 Li which feature a strong mismatch in mass and distinct electronic properties. We demonstrate elastic coupling between the superfluids by observing the shift in dipole oscillation frequency of the bosonic component due to the presence of the fermions. The measured magnitude of the shift is consistent with a mean-field model and its direction determines the previously unknown sign of the interspecies scattering length to be positive. We also observe the exchange of angular momentum between the superfluids from the excitation of a scissors mode in the bosonic component through interspecies interactions. We explain this observation using an analytical model based on superfluid hydrodynamics.Ultracold atomic gases offer excellent opportunities to produce and investigate quantum matter, allowing fundamental studies in many-body physics and quantum simulation [1]. Beginning with the cooling of atoms to BoseEinstein condensation [2,3] and later followed by the achievement of superfluidity in atomic Fermi gases [4], such studies have found many parallels with the analogous superfluids of bosonic 4 He and fermionic 3 He as well as superconductors, familiar from condensed matter physics. While the goal of simultaneous superfluidity in mixtures of 4 He-3 He still remains elusive due to strong inter-isotope interactions [5,6], Bose-Fermi superfluidity in an atomic gas isotopic mixture of 7 Li-6 Li has recently been realized [7]. The original interest [8,9] in such dual superfluid systems is now strongly intensified [10][11][12][13][14][15][16].The extension of Bose-Fermi superfluidity to mixtures of different elements is experimentally challenging, but holds the potential to open a larger arena of scientific studies. A large mass ratio between the components is predicted to alter the interaction energy between the superfluids [12] as well as the character of excitations across the Bose-Einstein condensate to Bardeen-CooperSchreiffer (BEC-BCS) crossover for the fermion pairs [15]. Specific interaction strengths and mass ratios can aid the detection of exotic states such as the FuldeFerrell-Larkin-Ovchinnikov (FFLO) phase [10] and darkbright solitons [16]. Furthermore, species-selective potentials for relative positioning and selective addressing make two-element systems more amenable for systematic studies.In this paper, we report on the realization of a twoelement Bose-Fermi superfluid mixture of 174 Yb-6 Li. We measure their coupling by observing the interactioninduced frequency shift of the bosonic dipole mode. We also detect transfer of angular momentum between the superfluids through the excitation of a scissors mode in the bosonic component. The scattering length a F of the two-spin alkali 6 Li fermionic system is tunable across the BEC-BCS crossover through a Feshbach resonance centered at 832 G, while the scattering length a B of the alkaline-earth-like bosonic Yb remains constant throughout. The...

We report on the realization of an ultracold mixture of lithium atoms in the ground state and ytterbium atoms in an excited metastable ( 3 P2) state. Such a mixture can support broad magnetic Feshbach resonances which may be utilized for the production of ultracold molecules with an electronic spin degree of freedom, as well as novel Efimov trimers. We investigate the interaction properties of the mixture in the presence of an external magnetic field and find an upper limit for the background interspecies two-body inelastic decay coefficient of K ′ 2 < 3 × 10 −12 cm 3 /s for the 3 P2 mJ = −1 substate. We calculate the dynamic polarizabilities of the Yb( 3 P2) magnetic substates for a range of wavelengths, and find good agreement with our measurements at 1064 nm. Our calculations also allow the identification of magic frequencies where Yb ground and metastable states are identically trapped and the determination of the interspecies van der Waals coefficients.Ultracold elemental mixtures provide unique opportunities to study few-and many-body physics with mass-mismatched atomic partners [1] and diatomic polar molecules [2, 3]. While the bulk of elemental mixture experiments have been performed using ground-state bialkali systems, the recent production of ground state mixtures of alkali and alkaline-earth-like atoms [4][5][6][7] further extend the experimental possibilities. These include powerful quantum simulation and information protocols [8] and tests of fundamental symmetries [9] with paramagnetic polar molecules. While tunable two-body interactions that are important for these advances have been proposed in such mixtures [10], they have not yet been experimentally detected.In this Letter we report the realization a new class of heteronuclear mixtures in which one atomic component is in an electronically excited state, using lithium ( 6 Li) and ytterbium ( 174 Yb) atoms. This establishes a highly mass-mismatched atomic mixture where tunable anisotropic interactions are expected to play a strong role [11], laying a foundation for future studies of ultracold trapped paramagnetic polar molecules and Efimov trimers with very large mass imbalance [12]. We measure inelastic interactions in the mixture and observe the relative suppression of interspecies inelastic processes. Our experimental methods also demonstrate new techniques of production and manipulation of spin components in the metastable 3 P 2 state of Yb.The study and control of anisotropic interactions is an increasingly important topic in ultracold atomic systems. In addition to their impact on many-body physics [3,8,13], anisotropic two-body interactions are proving to be of great interest for generating magnetically tunable interactions, as has been calculated theoretically [14] and observed experimentally in a mixture of ground and excited state Yb atoms [15]. The latter result applied in the context of the Li+Yb combination points to an alternative route towards tunable interactions, where the ground

We report on a general method for the rapid production of quantum degenerate gases. Using 174 Yb, we achieve an experimental cycle time as low as (1.6 − 1.8) s for the production of BoseEinstein condensates (BECs) of (0.5−1)×10 5 atoms. While laser cooling to 30 µK proceeds in a standard way, evaporative cooling is highly optimized by performing it in an optical trap that is dynamically shaped by utilizing the time-averaged potential of a single laser beam moving rapidly in one dimension. We also produce large (> 10 6 ) atom number BECs and successfully model the evaporation dynamics over more than three orders of magnitude in phase space density. Our method provides a simple and general approach to solving the problem of long production times of quantum degenerate gases.

Spaceborne radars offer a unique three‐dimensional view of the atmospheric components of the Earth's hydrological cycle. Existing and planned spaceborne radar missions provide cloud and precipitation information over the oceans and land difficult to access in remote areas. A careful look into their measurement capabilities indicates considerable gaps that hinder our ability to detect and probe key cloud and precipitation processes. The international community is currently debating how the next generation of spaceborne radars shall enhance current capabilities and address remaining gaps. Part of the discussion is focused on how to best take advantage of recent advancements in radar and space platform technologies while addressing outstanding limitations. First, the observing capabilities and measurement highlights of existing and planned spaceborne radar missions including TRMM, CloudSat, GPM, RainCube, and EarthCARE are reviewed. Then, the limitations of current spaceborne observing systems, with respect to observations of low‐level clouds, midlatitude and high‐latitude precipitation, and convective motions, are thoroughly analyzed. Finally, the review proposes potential solutions and future research avenues to be explored. Promising paths forward include collecting observations across a gamut of frequency bands tailored to specific scientific objectives, collecting observations using mixtures of pulse lengths to overcome trade‐offs in sensitivity and resolution, and flying constellations of miniaturized radars to capture rapidly evolving weather phenomena. This work aims to increase the awareness about existing limitations and gaps in spaceborne radar measurements and to increase the level of engagement of the international community in the discussions for the next generation of spaceborne radar systems.

Quantum-degenerate mixtures of one-electron and two-electron atoms form the starting point for studying few-and many-body physics of mass-imbalanced pairs as well as the production of paramagnetic polar molecules. We recently reported the achievement of dual-species quantum degeneracy of a mixture of lithium and ytterbium atoms. Here we present details of the key experimental steps for the all-optical preparation of these mixtures. Further, we demonstrate the use of the magnetic field gradient tool to compensate for the differential gravitational sag of the two species and control their spatial overlap.