Quantum degenerate mixtures of strontium and rubidium atoms

TL;DR

This paper demonstrates the creation of quantum degenerate mixtures of strontium and rubidium atoms using sympathetic cooling, achieving Bose-Einstein condensates and paving the way for RbSr molecule formation.

Contribution

It introduces a novel sympathetic cooling technique for combining alkaline-earth and alkali atoms to produce quantum degenerate mixtures.

Findings

Achieved phase-space density up to 0.06 for both elements.

Created double Bose-Einstein condensates with over 10^5 atoms each.

Established a method for producing ultracold RbSr mixtures for molecule research.

Abstract

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 10^5 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.