  The control of transport properties is a key tool at the basis of many
technologically relevant effects in condensed matter. The clean and precisely
controlled environment of ultracold atoms in optical lattices allows one to
prepare simplified but instructive models, which can help to better understand
the underlying physical mechanisms. Here we show that by tuning a structural
deformation of the unit cell in a bipartite optical lattice, one can induce a
phase transition from a superfluid into various Mott insulating phases forming
a shell structure in the superimposed harmonic trap. The Mott shells are
identified via characteristic features in the visibility of Bragg maxima in
momentum spectra. The experimental findings are explained by Gutzwiller
mean-field and quantum Monte Carlo calculations. Our system bears similarities
with the loss of coherence in cuprate superconductors, known to be associated
with the doping induced buckling of the oxygen octahedra surrounding the copper
sites.
