  The transition from a superfluid to a Mott insulator (MI) phase has been
observed in a Bose-Einstein condensate (BEC) of ytterbium (Yb) atoms in an
optical lattice. An all-optically produced BEC of 174Yb atoms was loaded into
three-dimensional optical lattices produced by a 532 nm laser beam. The
interference pattern was measured after releasing the quantum gas from the
trapping potential. As increasing the optical lattice depth, we observed the
disappearance of the interference patterns, which is a signature of entering
the MI regime. This result is an important step into studies by using a
combination of the MI state and the ultranarrow optical transition of ultracold
alkaline-earth-like atoms.
