Laser cooling to quantum degeneracy

TL;DR

This paper demonstrates Bose-Einstein condensation of strontium atoms solely through laser cooling, achieving quantum degeneracy in a continuously cooled sample with potential for continuous atom laser generation.

Contribution

First to realize BEC in strontium using only laser cooling, with a continuous process and high atom numbers, advancing quantum gas preparation methods.

Findings

Achieved BEC with up to 10^5 atoms.

Condensates formed repeatedly within 100ms.

Established thermal equilibrium via elastic collisions.

Abstract

We report on Bose-Einstein condensation (BEC) in a gas of strontium atoms, using laser cooling as the only cooling mechanism. The condensate is formed within a sample that is continuously Doppler cooled to below 1\muK on a narrow-linewidth transition. The critical phase-space density for BEC is reached in a central region of the sample, in which atoms are rendered transparent for laser cooling photons. The density in this region is enhanced by an additional dipole trap potential. Thermal equilibrium between the gas in this central region and the surrounding laser cooled part of the cloud is established by elastic collisions. Condensates of up to 10^5 atoms can be repeatedly formed on a timescale of 100ms, with prospects for the generation of a continuous atom laser.