Anomalous vortex flow and noise in the quantum liquid phase of amorphous films

Abstract

We measure the fluctuating component of the flux-flow voltage, δV(t), about the average voltage in the low-temperature (T) liquid phase of amorphous MoxSi1−x films. For the 100-nm-thick film δV(t) originating from the vortex motion is clearly visible in the quantum-vortex-liquid (QVL) phase, where the distribution of δV(t) is asymmetric, suggestive of the unusual vortex motion. For the thin (6 and 4nm) films, in which the QVL phase is not determined from the T dependence of the resistance, the similar unusual (avalanche-like) vortex motion is observed in nearly the same reduced-T regime. These results support the view that vortex dynamics in the low-T liquid phase of thick and thin films is dominated by common physical mechanisms related to quantum-fluctuation effects.