Berlin 2008 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 29: Poster II
DY 29.12: Poster
Thursday, February 28, 2008, 16:00–18:00, Poster C
Coulomb Gap Revisited — •Arnulf Möbius1, Peter Karmann2, and Michael Schreiber2 — 1Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden — 2Institut für Physik, Technische Universität Chemnitz
One of the most prominent features of the Coulomb glass is the Coulomb gap, a soft gap in the single-particle density of states around the chemical potential [1,2]. Previous numerical studies of the gap yielded densities considerably deviating from the analytical results.
Because of the long-range interaction, the energy region which could be considered in previous simulations was limited by severe difficulties arising from finite-size effects. To overcome this problem, we use a renormalization like iteration procedure: A cutoff length of the interaction is introduced which increases step by step during relaxation. In this way, simulations of samples of up to 2 · 109 sites were performed.
For one- to three-dimensional samples, we studied the influence of the disorder strength. The consideration of extremely large samples opens new insight: There is a tendency to universal behaviour in all three cases as predicted analytically in [1]. Asymptotic power laws with the predicted exponents seem to hold in the two- and three-dimensional cases, but the prefactors are smaller than predicted in [2] by factors of 2 to 3. However, this behaviour is observed only for very low energies so that the experimental relevance of the asymptotics has to be judged with reservation.
[1] A.L. Efros and B.I. Shklovskii, J. Phys. C 8, L49 (1975).
[2] A.L. Efros, J. Phys. C 9, 2021 (1976).