Bose-Einstein Condensation and Spin Mixtures of Optically Trapped Metastable Helium

TL;DR

This paper reports the creation of a Bose-Einstein condensate of metastable helium-4 atoms in an optical trap, investigates spin state stability, and measures inelastic loss rates to inform future experiments with spin mixtures.

Contribution

The work demonstrates BEC formation of metastable helium-4 in an optical trap and provides new measurements of spin-dependent inelastic loss rates.

Findings

Achieved BEC of metastable helium-4 in an optical dipole trap.

Confirmed instability of certain spin state combinations due to inelastic processes.

Measured spin-resolved two-body inelastic loss rate coefficients.

Abstract

We report the realization of a BEC of metastable helium-4 atoms (4He*) in an all optical potential. Up to 10^5 spin polarized 4He* atoms are condensed in an optical dipole trap formed from a single, focused, vertically propagating far off-resonance laser beam. The vertical trap geometry is chosen to best match the resolution characteristics of a delay-line anode micro-channel plate detector capable of registering single He* atoms. We also confirm the instability of certain spin state combinations of 4He* to two-body inelastic processes, which necessarily affects the scope of future experiments using optically trapped spin mixtures. In order to better quantify this constraint, we measure spin state resolved two-body inelastic loss rate coefficients in the optical trap.