Our simulation method which was derived for athermal motion of flexible dislocations through obstacle arrays is extended to include thermally activated glide. The deterministic differential equations which describe the dynamics of dislocation motion get an additional stochastic term corresponding to thermal motion of atoms involved. Our approach is based on publications of Langevin, Fokker‐Planck, and Klein‐Kramers. The investigation of jerky glide reveals that there is an essential influence of the kinetic energy even in case of rather simple obstacle arrangements. Primary results of the simulations are waiting times at obstacles. Thus an activation analysis of our simulated data can be performed by Arrhenius plots in strict analogy to the procedure applied to experimental results.
2014 Dans un champ magnétique intense, orthogonal au plan d'un système désordonné bi-dimensionnel, un modèle à N orbitales par site est considéré. L'Hamiltonien est projeté dans le niveau de Landau fondamental. Dans la limite de N grand, le résultat correspond à un col, invariant par translation, d'une théorie des champs. Le développement en puissances de 1/N est effectué diagrammatiquement et la conductivité est calculée jusqu'à l'ordre 1/N2. Dans ce développement on n'observe aucun seuil de mobilité. Le résultat est conforme au modèle 03C3 non linéaire unitaire; il est indépendant du champ magnétique et de l'intensité du désordre si l'on exprime l'énergie en unités de la largeur de bande. Abstract. 2014 An N-orbital model is considered for a two-dimensional disordered system in a strong perpendicular magnetic field. The Hamiltonian is projected on the lowest Landau level. In a field theoretical formulation the large N limit result corresponds to the translationally invariant saddle point for this model. A diagrammatic expansion in powers of 1/N is performed around the large N limit. The conductivity is calculated up to order 1/N2. No mobility edge is found in this expansion. The result is consistent with the non-linear unitary 03C3-model and independent of magnetic field and disorder strength if the energy is measured in units of the bandwidth.
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