Transition from two-dimensional to three-dimensional classical artificial atoms

The transition from two-dimensional (2D) to three-dimensional (3D) classical artificial atoms is studied. As a function of the confinement strength perpendicular to the plane, first- and second-order structural transitions are observed, which change the 2D ring structure into a layered structure and finally into the 3D shell structure in the case of a spherical confinement potential. A clear structural analogy exists between the infinite bilayer Wigner crystal (BLWC) and our finite system when the confinement is such that a bilayer structure exists in the central part of the atom.