Institut für Physikalische Chemie, Universität Karlsruhe

Localization of electrons, i.e. their bonding on a spatial restricted range in a given system, can be due to different mechanisms.

In macrospoic systems, localization can appear because of disorder (Anderson localizatioin) or electronic correlations (Matt-Hubbard localization). Furthermore, metal-insulator transitions can arise from electron-phonon interactions (Peierls transition).

In microscopic or "nanoscopic" Systems like clusters consisting of only 10-10T³ atoms, one has to distinguish between localization of electrons in a speficic region in a cluster caused by electronic correlations and correlation on a cluster. The latter one can appear in cluster compounds with a periodic arrangement of clusters, where the transport between clusters is hindered by tunnel barriers and/or Coulomb blockade.

Mesoscopic systems, i.e. solids with dimensions in the nanometer regime, are excellent model systems, where tunnel barriers or the strength of the Coulomb blockade can be varied in a controlable way. Quantum phenomena in the transport, for instance interference of electrons, can be investigated in these systems.