Dresden 2006 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 23: Statistical Physics (general) II
DY 23.3: Vortrag
Dienstag, 28. März 2006, 12:15–12:30, SCH 251
The order-disorder transition in the Coulomb glass lattice model — •Arnulf Möbius and Ulrich Rößler — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
Phase transitions in the Coulomb glass have been under controversial debate for two decades, from first numerical studies to recent analytical theory [1]. Here we numerically investigate lattices half-filled with localised particles interacting via the long-range Coulomb potential. For zero static disorder and finite temperature T, order-disorder transitions are observed for dimensions d = 2 and 3. Surprisingly, the critical properites are consistent with the Ising model with short-range interaction [2].
To study the influence of static disorder at T = 0, we developed an efficient procedure for the ground state search. It combines branch-and-bound type algorithms for complex relaxation steps, thermal cycling, flooding local minima, relaxation of cluster excitations, and renormalisation. Thus ground states of samples of up to 123 sites are found with high probability. Studying 2d and 3d lattices with a random on-site potential, rectangularly distributed between −B/2 and B/2, we observed an order-disorder transition for d = 3. Using finite-size scaling, we obtained Bc = 0.375 ± 0.015 as critical disorder strength for lattice constant 1. This value exceeds the result of the nonlinear screening theory [1] by a factor of roughly 2. However, for d = 2, already arbitrarily small disorder seems to destroy the ordered phase.
[1] S. Pankov, V. Dobrosavljevic, Phys. Rev. Lett. 94, 049402 (2005).
[2] A. Möbius, U.K. Rößler, cond-mat/0309001.