Shear-induced vortex decoupling in Bi2Sr2CaCu2O8 crystals

Simultaneous transport and magnetization studies in Bi2Sr2CaCu2O8 crystals at elevated currents reveal large discrepancies, including finite resistivity at temperatures of 40K below the magnetic irreversibility line. This resistivity, measured at the top surface, is non-monotonic in temperature and extremely non-linear. The vortex velocity derived from magnetization is six orders of magnitude lower than the velocity derived from simultaneous transport measurements. The new findings are ascribed to a shear-induced decoupling, in which the pancake vortices flow only in the top few CuO2 planes, and are decoupled from the pinned vortices in the rest of the crystal.