Localized excitations at the Mott insulator-superfluid interfaces for confined Bose atoms in optical lattices

In this paper, we consider a cloud of Bose atoms in an optical lattice subjected to a confinement. The equilibrium state of the system can show the coexistence of superfluid and Mott-insulating domains. We consider the surface waves at the interfaces between Mott-insulating and superfluid regions and derive their dispersion. Then, we calculate their contribution to the heat capacity of the system, showing how its low-temperature scaling is qualitatively affected by the presence/absence of the domain structure. This allows for an experimental test of the existence and properties of Mott insulator-superfluid domains, a currently open issue