Bose-Einstein Condensation of Europium

We report the realization of a Bose-Einstein condensate of europium atoms, which is a strongly dipolar species with unique properties, a highly symmetric $[\mathrm{X}\mathrm{e}]4f^{7}6s^2{}^8{\mathrm{S}}_{7\mathrm{/}2}$ electronic ground state and a hyperfine structure. By means of evaporative cooling in a crossed optical dipole trap, we produced a condensate of ${}^{151}$Eu containing up to $5\times {10}^4$ atoms. The scattering length of ${}^{151}$Eu was estimated to be $a_s=110(4)a_{\mathrm{B}}$ by comparing the velocities of expansion of condensates with different orientations of the atomic magnetic moments. We observed deformation of the condensate in the vicinity of the Feshbach resonance at $1.32\mathrm{G}$ with a width of $10\mathrm{m}\mathrm{G}$.