A simple model of disorder in fractional quantum Hall systems is combined with the standard exact diagonalisation technique. Electron-density-dependent gaps at filling factors 1/3,2/3,2/5, and 3/5 measured by activated transport can then be fitted with a single reasonable value of d which has the meaning of the separation of ionized donors from the quasi-2D electron gas.
We present results of Monte Carlo and stochastic spin dynamics simulations of a magnetic nanoparticle model system based on experimentally produced samples. Thermodynamic investigations as well as spin dynamics studies show characteristic features, both resembling magnetic dipole glass behaviour. While spin dynamics studies at T=0 yield a multitude of low energy configurations, thermodynamic simulations show a clear transition between a paramagnetic and a frozen magnetic state. Moreover, we demonstrate the application of experimentally inspired demagnetization protocols to compute low energy configurations of the systems under consideration efficiently.
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