Nature of Intermediate States between Superfluid and Mott insulator for Interacting Bosons in One-dimension with a Harmonic Trapping Potential

Successive quantum transitions in an intermediate regime are shown to exist between the superfluid and Mott insulating states for interacting bosonic atoms in one dimension with a trapping potential. These transitions, which are caused by the interplay of the trapping potential with the competition between the kinetic energy and the interaction, reveal novel many-body effects as reflected by low-lying excitation behavior, unconventional long-range correlations and an even-odd alternating squeezing process of superfluid bosons into the Mott insulating state. These features, most likely being generic for all dimensions when a trapping potential is involved, are relevant for both experimental observations and physical interpretation of the Mott insulator transition.