Crossover from thermal to quantum-liquid regime in a thick amorphous film

To study the change in vortex dynamics associated with the change in equilibrium vortex states from the thermal to quantum-vortex-liquid (QVL) upon cooling, we have performed measurements of the fluctuating [time (t)-dependent] component of flux-flow voltage V(t), δV(t)≡V(t)-V0, about the average voltage V0 using a thick amorphous MoxSi1-x film. Only in the QVL phase, large δV(t) is observed. The distribution of δV(t) is asymmetric having a tail along the direction of flux motion [δV(t)>0], suggesting the presence of anomalous flux-flow motion in the QVL phase