Delocalization due to correlations in two-dimensional disordered systems

We study the spectral statistics of interacting spin-less fermions in a two-dimensional disordered lattice. Within a full quantum treatment for small few-particle systems, we compute the low-energy many-body states numerically. While at weak disorder the interactions reduce spectral correlations and lead to localization, for the case of strong disorder we find that a moderate Coulomb interaction has a delocalizing effect. In addition, we observe a non-universal structure in the level-spacing distribution which we attribute to a mechanism reinforcing spectral correlations taking place in small systems at strong disorder.Received: 1 July 2004, Published online: 14 December 2004PACS: 71.27. + a Strongly correlated electron systems; heavy fermions - 73.20.Jc Delocalization processes - 72.15.Rn Localization effects (Anderson or weak localization)