Thermally activated vortex diffusion in high T-c superconductors
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Due to the thermal activation, for different fields and temperatures, the voltage-current E-J characteristics, current J and temperature T dependence of the resistivity p rho of layered High-T-c superconductors (HTSC) have been calculated in the Framework of overdamped Brownian motion. A single vortex moving in a sinusoidally periodic pinning potential in the direction perpendicular to the layers has been considered and it has been shown that a vortex moving in a sinusoidally periodic pinning potential gives strictly power-law behaviour for E-J and rho -J curves by the solution of the Langevin type stochastic equation of motion of a single particle. in addition, the non-linear terms in the pinning potential, especially, at the distances greater than the coherence length (i.e. logarithmic pinning potential) have been considered and the same calculations have been carried out for the logarithmic pinning potential. It has been obtained that the results of both calculations corresponding to the power-law behaviours for E-J, rho -J and the broadening in the temperature dependence of the resistivity in the presence of an external magnetic field are qualitatively consistent with the experimental results given in the literature.