Monte Carlo Studies of Systems with Disorder

Carey Huscroft

J. W. Lee, Shailesh Chandrasekharan A, Harold U. Baranger

Robert L. Sugar

A. Muramatsu, Werner R. Hanke

We study the effect of diagonal disorder on a one-dimensional (1-D) Hubbard model by means of a Monte Carlo simulation. Contrary to previous analytical studies of interacting disordered systems in one dimension, the numerical simulation is not restricted to the weak coupling regime in disorder and/or interaction. Quantum fluctuations are introduced using the scheme developed by J. Hirsch [Phys. Rev. B 31, 4403 (1985)] for Grand Canonical ensembles and arbitrary dimensions. A second Monte Carlo loop creates the configurations for the disorder potential. Preliminary results for various correlation functions are presented.

Hans-O Heuer

We report extensive Monte Carlo simulations of the site-disordered 2-dimensional Ising system. For concentrations between p = 0.6 and p = 1.0 ( p c = 0.59) we have studied the magnetic and caloric properties as well as the cumulants of the magnetization distribution in the critical region. We have found that disorder induces a strong increase of γ eff (γ max = 2.16 for p = 0.7) in the usual experimental temperature range ( T - T c )/ T c = 10 -2 ÷ 10 0 . Asymptotically near T c , γ approaches the theoretical value γ = 1.75 independent of the concentration. We propose a model of weakly coupled compact clusters of spins to describe this crossover behaviour of disordered spin systems.

Kurt Binder, Erik Luijten, Marcus Müller +2 more