Density-functional theory of spin-polarized disordered quantum dots

Using density-functional theory, we investigate fluctuations of the ground-state energy of spin-polarized, disordered quantum dots in the metallic regime. To compare to experiment, we evaluate the distribution of addition energies and find a convolution of the Wigner-Dyson distribution, expected for noninteracting electrons, with a narrower Gaussian distribution. The width of the Gaussian is accurately given by the fluctuations in the screened Coulomb interaction between a pair of electrons at the Fermi energy.