Shear-induced vortex decoupling in Bi2Sr2CaCu2O8 crystals

Simultaneous transport and magnetization studies in Bi(2)Sr(2)CalCu(2)O(8) crystals at elevated currents reveal large discrepancies, including finite resistivity at temperatures of 40 K below the magnetic irreversibility line . This resistivity, measured at the top surface, is nonmonotonic in tempera ture and extremely nonlinear. The vortex velocity derived from magnetizatio n is sire orders of magnitude lower than the velocity derived from simultan eous transport measurements. The findings are ascribed to a shear-induced d ecoupling, in which the pancake vortices flow only in the top few CuO2 plan es, and are decoupled from the pinned vortices in the rest of the crystal.