Bose-Einstein Condensation of Europium

Abstract

We report the realization of a Bose-Einstein condensate of europium atoms, which is a strongly dipolar species with unique properties, a highly symmetric $[\mathrm{Xe}]\ 4f^7 6s^2\ {}^8\mathrm{S}_{7/2}$ 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 $10\,\mathrm{mG}$.