THE PINNING POTENTIAL AT SINGLE FLUX VORTICES INVESTIGATED USING SUBMICRON HALL PROBES

We have imaged individual flux vortices in 200 nm-thick superconductin g Pb films using sub-micron Hall probes with an excellent combination of spatial and temporal resolution. Correlation of signals at separate Hall contacts shows that flux enters the film in correlated bundles o f approximately 5 mum diameter. With an applied supercurrent, we have been able to move individual vortices distances of typically 30-40 nm between minima in the pinning potential that differ by approximately 0 .5eV. We have determined pinning forces as a function of temperature f or individual pinning sites. At higher applied fields the intervortex interaction alone is sufficient to move vortices between different pot ential minima as the temperature approaches T(c).