TRANSPORT-PROPERTIES OF HIGH-TEMPERATURE SUPERCONDUCTORS - SURFACE VSBULK EFFECT

We investigate surface-related transport properties of high-temperatur e superconductors. We find the mean vortex velocity under applied tran sport current determined by the activation energies for vortex penetra tion and exit through the Bean-Livingston barrier. We determine the cu rrent distribution between the surfaces of superconductor and the fiel d and current dependencies of the transport activation energies. For a three-dimensional superconductor the transport activation energy, U-s (3D), is found to decrease with the external field, H, and transport c urrent, J, as U(s)(3D)proportional to H--1/2 and U(s)(3D)proportional to J(-1/2), respectively. In the quasi-two-dimensional compounds, U-s( 2D) decays logarithmically with field and current. The interplay betwe en the surface and the bulk contributions to the transport properties, such as current-voltage characteristics, is discussed.