Superfluid-Mott-insulator transition in a one-dimensional optical lattice with double-well potentials

We study the superfluid-Mott-insulator transition of ultracold bosonic atoms in a one-dimensional optical lattice with a double-well confining trap using the density-matrix renormalization group method. At low density, the system behaves similarly as two separated ones inside each well. At high density, however, interesting features appear resulting from the quantum tunnelling between the two wells and the competition between the "superfluid" and Mott regions. These interesting features are characterized by a rich step-plateau structure in the visibility and the satellite peaks in the momentum distribution function, with an oscillating pattern as a function of the on-site repulsion. These properties shed light on the understanding of the quantum phase coherence between two coupled condensates.