Controlling the spatial distribution of superfluidity in radially ordered Coulomb clusters

Abstract

When a few identical charged particles are trapped in a spherical electric field at low temperature, they form concentric shells resembling atoms. The behavior of these ``artificial atoms'' is easily controlled by varying the field strength. In particular, it is possible to transfer the system from a liquidlike to a crystal-like state. We analyze artificial atoms consisting of Bose particles and observe superfluid behavior, which even persists in the intermediate radially ordered crystal regime. Furthermore, we demonstrate that the superfluid density can be directed in a controlled way either to the core or to the boundary of the atom.