High-Density Trapping of Cold Ytterbium Atoms by an Optical Dipole Force

We have succeeded in trapping a high density of rare-earth atom of ytterbium (Yb) in a crossed far-off resonance trap. The peak density reaches more than ${10}^{14}{\mathrm{c}\mathrm{m}}^{-3}$. With a new method of a delayed crossed far-off resonance trap, we have elucidated that the atoms became concentrated into the cross region by atom-atom collisions. We trap fermionic Yb atoms in the same way as bosonic ones.