Localization-delocalization transition in quantum dots

Single-electron capacitance spectroscopy precisely measures the energies re quired to add individual electrons to a quantum dot. The spatial extent of electronic wave functions is probed by investigating the dependence of thes e energies on changes in the dot confining potential. For low electron dens ities, electrons occupy distinct spatial sites localized within the dot. At higher densities, the electrons become delocalized, and all wave functions are spread over the full dot area. Near the delocalization transition, the last remaining localized states exist at the perimeter of the dot, Unexpec tedly, these electrons appear to bind with electrons in the dot center.