Cooling of a Bose-Einstein Condensate by spin distillation

TL;DR

This paper introduces a novel cooling method for spinor Bose-Einstein Condensates using spin distillation, effectively increasing condensate purity by removing thermally excited spin states, demonstrated experimentally on chromium BECs.

Contribution

The authors propose and experimentally validate a new spin distillation cooling technique for spinor BECs, potentially enabling temperatures below 1 nK.

Findings

Successfully cooled a chromium BEC using spin distillation.

Demonstrated increase in BEC fraction after filtering spin-excited states.

Method is adaptable to other atomic species like Na and Rb.

Abstract

We propose and experimentally demonstrate a new cooling mechanism leading to purification of a spinor Bose-Einstein Condensate (BEC). Our scheme starts with a BEC polarized in the lowest energy spin state. Spin excited states are thermally populated by lowering the single particle energy gap set by the magnetic field. Then these spin-excited thermal components are filtered out, which leads to an increase of the BEC fraction. We experimentally demonstrate such cooling for a spin 3 52Cr dipolar BEC. Our scheme should be applicable to Na or Rb, with perspective to reach temperatures below 1 nK.