Magnetic-field dependent trap loss of ultracold metastable helium

TL;DR

This study investigates how magnetic fields affect trap loss in ultracold metastable helium Bose-Einstein condensates, confirming theoretical loss rates, identifying decay mechanisms, and searching for Feshbach resonances.

Contribution

It provides experimental validation of loss rate calculations, clarifies decay mechanisms for different magnetic substates, and reports on the search for a predicted Feshbach resonance.

Findings

Loss rate coefficient increases above 50 G

Decay in m=-1 atoms is due to three-body recombination

No evidence of the predicted d-wave Feshbach resonance

Abstract

We have experimentally studied the magnetic-field dependence of the decay of a Bose-Einstein condensate of metastable 4He atoms confined in an optical dipole trap, for atoms in the m=+1 and m=-1 magnetic substates, and up to 450 G. Our measurements confirm long-standing calculations of the two-body loss rate coefficient that show an increase above 50 G. We demonstrate that for m=-1 atoms, decay is due to three-body recombination only, with a three-body loss rate coefficient of 6.5(0.4)(0.6)10^(-27)cm^6s^(-1), which is interesting in the context of universal few-body theory. We have also searched for a recently-predicted d-wave Feshbach resonance, but did not observe it.