Ab initio phase diagram of ultracold 87Rb in a one-dimensional two-colour superlattice

Abstract

We investigate the ab initio phase diagram of ultracold 87Rb atoms in a one-dimensional two-colour 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.