Correlation length of flux lines in the vicinity of the vortex glass-liquid transition in high-temperature superconductors

The correlation length of flux lines responsible for the scaling of current-voltage curves in the transition region between the glass and liquid states in high temperature superconductors is argued based on experimental results on various specimens of Bi-based superconductors. From the correspondence between the temperature dependence of the pinning correlation length and the static critical index upsilon, it is concluded that the responsible correlation length is the pinning correlation length. This insists that the pinning interaction governs the flux lines in the glass state. This hypothesis is supported by the fact that the transition line depends on the flux pinning strength and the dynamic critical index, z, is appreciably influenced by the width of the distribution of flux pinning strength, it is concluded that the so-called vortex glass-liquid transition is a kind of transition of flux lines between the glass state governed bq the pinning and the depinned melt state due to the thermal activation. (C) 1997 Elsevier Science B.V.