Strongly interacting bosons in 1D disordered lattice: phase coherence of distorted Mott phases

Abstract

We explore the consequences of disorder on phase coherence in the Mott insulator phases in an optical lattice. Few bosons with contact interaction in small optical lattice can feature varieties of insulating phases: weakly interacting Mott in deep lattice, maximally fragmented and strongly interacting Mott in intermediate lattice, weak Mott with double filling and intra-well coherence, fermionized Mott with strong intra-well coherence. Utilization of the multiconfigurational time dependent Hartree method for bosons (MCTDHB) to solve the many-boson Schroedinger equation, facilitates to understand the microscopic effect of disorder on the different kinds of Mott phases in the primary lattice. The many-body properties are analyzed by distinct measures of the reduced one-body density in real and momentum space, fragmentation, order parameter, variance of spatial single-shot measurements, compressibility and the Glauber normalized correlation functions. We find very complex competition of localization due to disorder and Mott correlation. We observe distinct response of four different Mott phases in the disordered lattice. When the weakly interacting Mott exhibits the Bose Glass phase, the strongly correlated and fully fragmented Mott exhibits leakage, melting and central localization. In contrast, weak Mott with double filling which is a spatially separated dimer in each site, exhibits only some dissociation of intra-well coherence and assist in the development of inter-well coherence in the presence of strong disorder. For the fermionized Mott, when the density in each well is fragmented, strong disorder interfere with the intra-well correlation and the characteristic dip in each site starts to disappear leading to simple Mott localization with a pair of bosons.