Bose-Einstein condensation of an ytterbium isotope

We report the observation of a Bose-Einstein condensate in a bosonic isotope of ytterbium $\left({}^{170}\mathrm{Yb}\right)$. More than ${10}^6$ atoms are trapped in a crossed optical dipole trap and cooled by evaporation. Condensates of approximately ${10}^4$ atoms have been obtained. From an expansion of the condensate, we have extracted the scattering length $a_{170}=3.6\pm 0.9\mathrm{nm}$.

Figure 1

Top view of the experimental setup for laser cooling, optical trapping, and probing of ${}^{170}\mathrm{Yb}$ atoms. Two MOT beams along the vertical $z$ direction are not shown for clarity. We note that the probe beam used for detection is not perpendicular to the horizontal far-off-resonance trap (FORT) beam.

Figure 2

(Color online). Absorption images (a)–(c) and density distributions integrated over the vertical $z$ direction (d)–(f) of ${}^{170}\mathrm{Yb}$ atoms after $10\mathrm{ms}$ of the free expansion: (a), (d) thermal cloud, $T=360\mathrm{nK}$; (b), (d) bimodal distribution, $T=200\mathrm{nK}$; (c), (f) almost pure condensate with $7\times {10}^3$ atoms. The solid lines show the Gaussian fits to the thermal components.

Figure 3

Measured condensate radius along the vertical $z$ direction after the free expansion of $10\mathrm{ms}$, as a function of the number of condensate atoms, $N^{1∕5}$. The solid line is a linear fit through the origin. The slope of the line extracts the scattering length $a_{170}=3.6\pm 0.9\mathrm{nm}$.