Feshbach resonances of large-mass-imbalance Er-Li mixtures

Abstract

We report on the experimental observation of Feshbach resonances in large-mass-imbalance mixtures of erbium (Er) and lithium (Li). All combinations of 168 Er, 166 Er, and 7 Li, 6 Li are cooled to temperatures of a few microkelvin, partially by means of sympathetic cooling together with ytterbium (Yb) as a third mixture component. The Er-Li inelastic interspecies collisional properties are studied for magnetic fields up to 680 G. In all cases, resonant interspecies loss features, indicative of Feshbach resonances, have been observed. While most resonances have sub-Gauss widths, a few of them are broad and feature widths of several Gauss. Those broad resonances are a key to the realization of ultracold Er-Li quantum gas mixtures with tunable interactions.

Realization of a quantum degenerate mixture of highly-magnetic and nonmagnetic atoms

“…That is by no means an a priori certainty as the expected dense inter-species Feshbach resonance structure might easily have interdicted such a state by strong inelastic collisional losses at the low magnetic fields that are typically used during standard evaporation stages. Along the way our experiment once again underlines the quite amazing versatility of the heavy Yb not only from a physics standpoint but also in its capability to efficiently cool a variety of other species sympathetically [4,11].…”

“…The setup of the experiment and the experimental sequence is largely as in our previous works [11] and we will here only highlight the key aspects and changes relevant to the present work. After first loading the 174 Yb magneto-optical trap (MOT) to saturation in 45 s a rather small amount of 168 Er is added with just 2 s of loading.…”

“…After first loading the 174 Yb magneto-optical trap (MOT) to saturation in 45 s a rather small amount of 168 Er is added with just 2 s of loading. Due to the narrow-linewidth nature of the Er MOT the obtained Er sample is automatically spinpolarized into the lowest energy m J = −6 state [7,11]. Both species are then transferred into an optical faroff resonant trap in horizontal direction (H-FORT) at 1064 nm where we typically obtain about 3×10 5 Er atoms and 4 × 10 6 Yb atoms, both at an estimated temperature of 80 µK.…”

Heavy polarons in ultracold atomic Fermi superfluids at the BEC-BCS crossover: formalism and applications

“…Indeed, several quantum mixtures consisting of a Fermi superfluid and a Bose condensate have already been demonstrated, including 6 Li-7 Li [59], 6 Li-41 K [60], and 6 Li-174 Yb [61] mixtures. Quantum mixtures such as 6 Li-133 Cs [62], 6 Li-168 Er [63], and 6 Li-168 Er [63] should also be available soon, since the interspecies Feshbach resonances have been characterized recently. In these mixtures, polaron physics can be explored by reducing the concentration of the bosonic component.…”

“…Recent experiments have already demonstrated the coexistence of Bose and Fermi superfluids in several realizable systems, 6 Li- 7 Li [59], 6 Li-41 K [60], and 6 Li-174 Yb [61] mixtures, where the heavy species can serve as the impurity at will. The combinations 6 Li-133 Cs [62], 6 Li-168 Er [63], and 6 Li-168 Er [63] are also promising candidates, where the interspecies Feshbach resonances have been characterized.…”