Interaction effects in the mesoscopic regime: A quantum Monte Carlo study of irregular quantum dots

We address the issue of accurately treating interaction effects in the mesoscopic regime by investigating the ground-state properties of isolated irregular quantum dots. Quantum Monte Carlo techniques are used to calculate the distributions of ground-state spin and addition energy. We find a reduced probability of high spin and a somewhat larger even/odd alternation in the addition energy from quantum Monte Carlo than in local spin-density-functional theory. In both approaches, the even/odd effect gets smaller with increasing number of electrons, contrary to the theoretical understanding of large dots. We argue that the local spin-density approximation overpredicts the effects of interactions in quantum dots.