  We investigate the ab-initio phase diagram of ultracold 87-Rb atoms in an
one-dimensional two-color superlattice. Using single-particle band structure
calculations we map the experimental setup onto the parameters of the
Bose-Hubbard model. This ab-initio ansatz allows us to express the phase
diagrams in terms of the experimental control parameters, i.e., the intensities
of the lasers that form the optical superlattice. In order to solve the
many-body problem for experimental system sizes we adopt the density-matrix
renormalization-group algorithm. A detailed study of convergence and
finite-size effects for all observables is presented. Our results show that all
relevant quantum phases, i.e., superfluid, Mott-insulator, and quasi
Bose-glass, can be accessed through intensity variation of the lasers alone.
However, it turns out that the phase diagram is strongly affected by the
longitudinal trapping potential.
