QUANTUM COLLECTIVE CREEP

We study the phenomenon of quantum creep in bulk superconductors within the framework of weak-collective-pinning theory. Single-vortex pinning at moderate magnetic fields as well as creep of vortex bundles at high fields are discussed for the case of current densities near critical. In the limit of strong dissipation and for moderate magnetic fields the basic parameter determining the tunneling rate is the ratio rho-n/xi (rho-n = normal-state resistivity, xi = coherence length), with strong tunneling realized for rho-n/xi greater-than-or-similar-to 1 k-OMEGA.