We have realized a double-species Bose-Einstein Condensate of ⁸⁷Rb-⁴¹K both in the F=2, m_F=2 hyperfine states. The preparation of the superfluid mixtures involves different cooling stages. After a double-MOT phase we transfer the mixture in a magnetic quadrupole field where Rb is evaporated by a microwave radiation resonant on the (F=2, m_F=2) - (F=1, m_F=1) transition while K is sympathetically cooled by thermal contact with Rb. When the temperature is low enough, we transfer the mixture in a crossed optical trap through an intermediate stage of a hybrid magneto-optical trapping potential. The last stage of cooling is performed by pure optical evaporation in the crossed optical potential. At the end of our typical experimental runs we produce pure condensates of 6×10⁴ atoms for both atomic species.

We have finalized the construction of the experimental setup, and we're now able to produce the first Lithium-Chromium MOT worldwide! Fun has just begun!

Laser cooling based on dark states, i.e. states decoupled from light, has proven to be effective to increase the phasespace density of cold trapped atoms. Dark-states cooling requires open atomic transitions, in contrast to the ordinary laser cooling used for example in magneto-optical traps (MOTs), which operate on closed atomic transitions. For alkali atoms, dark-states cooling is therefore commonly operated on the D1 transition nS_1/2 → nP_1/2. We show that, for ⁸⁷Rb, thanks to the large hyperfine structure separations the use of this transition is not strictly necessary and that “quasi-dark state” cooling is efficient also on the D2 line, 5S_1/2 → 5P_1/2. We report temperatures as low as (4.0 ± 0.3) μK and an increase of almost an order of magnitude in the phase space density with respect to ordinary laser sub-Doppler cooling.

S. Rosi, et al.
Λ -enhanced grey molasses on the D₂ transition of Rubidium-87 atoms
Sci. Rep. 8, 1301 (2018)

We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the BEC–BCS crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. For small excitations, we observe dissipation and phase coherence to coexist, with a resistive current followed by well-defined Josephson oscillations. We link the junction transport properties to the phase-slippage mechanism, finding that vortex nucleation is primarily responsible for the observed trends of the conductance and critical current. For large excitations, we observe the irreversible loss of coherence between the two superfluids, and transport cannot be described only within an uncorrelated phase-slip picture. Our findings open new directions for investigating the interplay between dissipative and superfluid transport in strongly correlated Fermi systems, and general concepts in out-of-equilibrium quantum systems.

A. Burchianti, et al.,
Connecting Dissipation and Phase Slips in a Josephson Junction between Fermionic Superfluids
Phys. Rev. Lett. 120, 025302 (2018)

We observed the transition to BEC for ¹⁶²Dy atoms!
Our dipolar BECs are made up at the moment by up to 3⨯10⁴ atoms. Atoms from the MOT are transferred into an in-vacuum optical resonator where we perform a first evaporation down to a few μK. Afterwards, we load the atoms in a crossed optical trap and condensation temperature is reached by evaporation ramps. The atomic dipoles are aligned along the vertical direction by an uniform magnetic field of a few Gauss and the vertical trapping frequency is higher than the horizontal ones to prevent dipolar collapse. The transition temperature for our trapping potential is below 100 nK.