Quantum degenerate mixtures of strontium and rubidium atoms
We report on the realization of quantum degenerate gas mixtures of the alkaline-earth element strontium with the alkali element rubidium. A key ingredient of our scheme is sympathetic cooling of Rb by Sr atoms that are continuously laser cooled on a narrow linewidth transition. This versatile technique allows us to produce ultracold gas mixtures with a phase-space density of up to 0.06 for both elements. By further evaporative cooling we create double Bose-Einstein condensates of 87Rb with either 88Sr or 84Sr, reaching more than 105 condensed atoms per element for the 84Sr-87Rb mixture. These quantum gas mixtures constitute an important step towards the production of a quantum gas of polar, open-shell RbSr molecules.
Momentum distribution of Rb during sympathetic narrow-line laser cooling of Rb by Sr. The Rb phase-space density ρ is increased by a factor of more than 200 in 400ms.
Time-of-flight absorption images of 84Sr and 87Rb during evaporative cooling.
Benjamin Pasquiou, Alex Bayerle, Slava Tzanova, Simon Stellmer, Jacek Szczepkowski, Mark Parigger, Rudolf Grimm, and Florian Schreck