Bardeen-Stephen flux flow law disobeyed in the high-$T_c$ superconductor Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$

Abstract

Pulsed high current experiments in single crystals of the high-$T_c$ superconductor Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ in c-axis directed magnetic field $H$ reveal that the $ab$-face resistance in the free flux flow regime is a solely logarithmic function of H, devoid of any power law component. Re-analysis of published data confirms this result and leads to empirical analytic forms for the $ab$-plane and c-axis resistivities: ${\rho }_{ab}\propto$ $H^{3/4}$, which does not obey the expected Bardeen-Stephen result for free flux flow, and ${\rho }_c\propto H^{-3/4}{\log }^{2}H$.

5 pages, 3 figures. Submitted to Phys. Rev. Lett