Thermodynamics of a Bose-Einstein condensate with free magnetization

We study thermodynamic properties of a gas of spin 3 ⁢52Cr atoms across Bose-Einstein condensation. Magnetization is free, due to dipole-dipole interactions.
arXiv:1110.0786 (2011) / Phys. Rev. Lett. 108, 045307 (2012)

We show that the critical temperature for condensation is lowered at extremely low magnetic fields, when the spin degree of freedom is thermally activated.

The depolarized gas condenses in only one spin component, unless the magnetic field is set below a critical value, below which a nonferromagnetic phase is favored.

Finally, we present a spin thermometry efficient even below the degeneracy temperature.

Phase diagram of a spin 3 BEC. The solid lines delimitate the 3 phases predicted for a non interacting gas of bosons. A phase: thermal gas in each Zeeman component; B phase: BEC only in mS = −3; C phase: BEC in all Zeeman components.