Sebastian Bustingorry | PubMed Health

PubMed2006

Out-of-equilibrium dynamics of the vortex glass in superconductors.

We study the relaxational dynamics of flux lines in high-temperature superconductors with random pinning using Langevin dynamics. At high temperatures the dynamics is stationary and the fluctuation dissipation theorem (FDT) holds. At low temperatures the system does not equilibrate with its thermal bath: a simple multiplicative aging is found, the FDT is violated, and we find that an effective temperature characterizes the slow modes of the system. The generic features of the evolution--scaling laws--are dictated by those of the single elastic line in a random environment.

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PubMed2004

Diffusion and percolation in anisotropic random barrier models.

An anisotropic random barrier model is presented, in which the transition probabilities in different directions have different probability density functions. At low temperatures, the anisotropic long-time diffusion coefficients, obtained using an effective medium approximation, follow an Arrhenius temperature dependence, with the same activation energy for each direction. Such activation energy is related to the anisotropic percolation properties of the lattice, and can be analyzed in terms of the critical percolation path approximation. The anisotropic effective medium approximation is shown to predict the correct percolation threshold for an anisotropic two-dimensional square lattice. In addition, results are compared with numerical simulations using a fast kinetic Monte Carlo algorithm.

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