Negative-μ vortex dynamics in high-Tc superconducting films

Abstract Using a thermally activated vortex motion model with an activation energy U(j)=(U c / μ )[j c /j) μ −1] in which U c , μ and j c are field and temperature dependent, we analyse both flux-creep data and current-voltage characteristics on the same footing. This analysis reveals the occurrence of negative-μ vortex dynamics in highly anisotropic superconductors such as Tl 2 Ba 2 CaCu 2 O 8 or Bi 2 Sr 2 CaCu 2 O 8 above a characteristic magnetic field. This is attributed to a dimensional cross-over and plastic creep.