Commensurate-incommensurate transitions in ordered and disordered vortex flow channels

A numerical and analytical study of vortex flow behavior in weak pinning channels has revealed that, for a channel in a perfect lattice, incommensurability 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 full 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 Incommensurability. Also it lowers the Commensurate J(c) due to defect generation. These observations agree with experiments we performed on weak pinning vortex channels in strong pinning films.