Spatially resolved dynamic correlation in the vortex state of high temperature superconductors

We report transport measurements in the mixed state of YBa2Cu3O7-delta sing le crystals using a contact geometry which enables control of the gradient of the Lorentz force acting on the vortices. The spatial dependence of the vortex velocity profile in the liquid and solid vortex phases is resolved p roviding information about the transverse dynamic correlation of vortices. While in the liquid phase the vortices respond locally to the driving force , in the solid regime they show long range velocity correlation over macros copic distances. At high driving force gradients, vortex-vortex shear stres ses exceed the elastic limit and the dynamics is characterized by plastic m otion. [S0031-9007(98)08260-X].