Sub-Doppler Laser Cooling of Fermionic K-40 Atoms

TL;DR

This paper demonstrates sub-Doppler laser cooling of fermionic K-40 atoms to temperatures significantly below the Doppler limit, advancing the preparation of ultracold Fermi gases.

Contribution

It introduces a laser cooling method achieving temperatures near the lowest possible in 3D molasses, without evaporative cooling, for fermionic K-40 atoms.

Findings

Achieved temperatures of 15 microK, ten times below Doppler limit.

Reached velocities within twice the lowest rms velocity in 3D molasses.

Presents a step towards creating degenerate Fermi gases.

Abstract

We report laser cooling of fermionic K-40 atoms, with temperatures down to (15 +/- 5) microK, for an enriched sample trapped in a MOT and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of two of the lowest realizable rms velocity (~3.5v rec) in 3D optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of K-40 atoms.