CHARGING SPECTRUM OF A SMALL WIGNER CRYSTAL ISLAND

Charging of a clean two-dimensional island is studied in the regime of small concentration of electrons when they form the Wigner crystal. T he number of electrons in the island is assumed to be not too large (N less than or equal to 100). It is shown that the total energy of the island as a function of N has a quasiperiodic component of a universal shape that is independent of the form of electron-electron interactio ns. These oscillations are caused by the combination of the geometric effects associated with packing of the triangular lattice into the cir cular island. These effects are the shell effect, associated with star ting a new crystalline row, and the so-called confinement polaronic ef fect. In the presence of close metallic gates, which eliminate the lon g-range part of the electron-electron interactions, the oscillations o f the energy bring about simultaneous entering of the dot by a few ele ctrons.