Electronic glasses

Electron (or Coulomb) glass refers to Anderson insulators with Coulomb interactions between the localized electrons. The Coulomb gap is the gap in the single particle density of states which opens up in these systems as a direct consequence of interactions. The small screening capabilities of localized electrons at short distances is responsible for the importance of interactions in these systems.

We have developped several numerical algorithms to study the properties of electron glasses. In particular, we have constructed a kinetic Monte Carlo algorithm especially designed to escape efficiently from deep valleys around metastable states and we can also obtain low energy configurations. At present we are specially interested in the following properties:

We found that, during the relaxation process, the site occupancy follows a Fermi-Dirac distribution with an effective temperature much higher than the real temperature. The density of states at the Fermi level is proportional to this effective temperature and is a good thermometer to measure it. The effective temperature decreases extremely slowly, roughly as the inverse of the logarithm of time, and it should affect hopping conductance in many experimental circumstances. We are interested in aging effects, specifically in characterizing the circunstances to obtain full aging. We also want to analyze the contributions of many particle hops.

We study the nonlinear conductivity of two-dimensional Coulomb glasses. In the nonlinear regime the site occupancy in the Coulomb gap follows a Fermi-Dirac distribution with an effective temperature higher than the phonon bath temperature. We analyze possible switching mechanisms.

We are developping a numerical algorithm, based on matrix product states, to simulate quantum Coulomb glasses