Anomalous sliding friction and peak effect near the flux lattice melting transition

Recent experiments have revealed a giant "peak effect" in ultrapure high T- c superconductors. Moreover, the data show that the peak effect coincides e xactly with the melting transition of the underlying flux lattice. In this work, we show using dynamical scaling arguments that the friction due to th e pinning centers acting on the flux lattice develops a singularity near a continuous phase transition and can diverge for many systems. The magnitude of the nonlinear sliding friction of the flux lattice scales with this ato mistic friction. Thus, the nonlinear conductance should diverge for a true continuous transition in the flux lattice or peak at a weakly first-order t ransition or for systems of finite size.