Radio-frequency-induced ground-state degeneracy in a Bose-Einstein condensate of chromium atoms

Abstract

We study the effect of strong radio-frequency (rf) fields on a Bose-Einstein condensate (BEC) of chromium atoms, in a regime where the rf frequency is much larger than the Larmor frequency. We use the modification of the Land\'e factor by the rf field to bring all Zeeman states to degeneracy, despite the presence of a static magnetic field of up to $100\phantom{\rule{0.3em}{0ex}}\mathrm{mG}$. This is demonstrated by analyzing the trajectories of the atoms under the influence of dressed magnetic potentials in the strong-field regime. We investigate the problem of adiabaticity of the rf dressing process and relate it to how close the dressed states are to degeneracy. Finally, we measure the lifetime of the rf dressed BECs and identify a rf-assisted two-body loss process induced by dipole-dipole interactions.