Flux flow was studied over an entire temperature range down to $T\sim 2\%$ of $T_c$ by using intense pulsed current densities to overcome flux-vortex pinning. The resistivity at high vortex velocities is proportional to $B$ and roughly follows $\rho \sim {\rho }_{n}B/H_{c2\mathrm{}}$, with a prefactor of order unity. Contrary to some speculation, ${\rho }_n$ saturates to a finite residual value as $T\to 0$, indicating a metallic $(\rho \to \mathrm{finite})$ rather than insulating $(\rho \to \infty )$ normal state, and the vortex dissipation continues to be conventional as $T\to 0$.

• Received 30 November 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.5204