ABSENCE OF BIMODAL PEAK SPACING DISTRIBUTION IN THE COULOMB-BLOCKADE REGIME

Using exact diagonalization numerical methods, as well as analytical a rguments, we show that for typical electron densities in chaotic and d isordered dots the peak spacing distribution is not bimodal but Gaussi an. This is in agreement with experimental observations. We attribute this behavior to the tendency of an even number of electrons to gain o n-sire interaction energy by removing the spin degeneracy. We predict that the dot will show a nontrivial electron-number-dependent spin pol arization. Experimental tests of this hypothesis based on the spin pol arization measurements are proposed.