Nonlinear I-V, High Flux-Flow Velocity Instability and Evidence for   Quantum Fluctuations in BSCCO Superconducting Films
  The large flux-flow velocity behavior of the high temperature superconductor BSCCO in the mixed state is studied by measurement of the current-voltage characteristic as a function of temperature and magnetic field direction. We find strong evidence for vortex-antivortex pairs that are excited by quantum fluctuations and contribute to the dissipation when dissociated by a large current. 
J. Chiaverini, J.N. Eckstein, I. Bozovic, S. Doniach, and A.   Kapitulnik