Commensurate-incommensurate transitions in ordered and disordered vortex flow channels

A numerical and analytical study of vortex flow behavior in weak pinning ch annels has revealed that, for a channel in a perfect lattice, incommensurab ility between channel width and the vortex lattice constant causes (point) defects in the channel with a nearly vanishing barrier J(c). The transport characteristics exhibit a crossover from low mobility (defect motion) to fu ll flux flow (coherent motion). J(c) versus commensurability parameter is a discontinuous function with sharp peaks at integer values. Disorder in the channel edges smears the sharp C-I transitions due to defect pinning at In commensurability. Also it lowers the Commensurate J(c) due to defect genera tion. These observations agree with experiments we performed on weak pinnin g vortex channels in strong pinning films.