Transport measurements on ultra-thin CaBaCuO films

We investigated transport properties of ultra-thin CaBaCuO (CBCO) films, focusing on vortex dynamics. By measuring current-voltage characteristics we found evidence that at high temperatures the vortices are thermally activated at the edges of the bridge and pushed in, causing dissipation and power-law dependence of the voltage from the current. At lower temperatures, the experimental curves change shape. We compared these data with the predicted behaviour for vortex quantum tunnelling and found a very good agreement. Measurements performed at ultra-low temperatures (down to 60 mK) in a particular low noise environment provide additional evidence of the robustness of the observed effects. (c) 2007 Elsevier B.V. All rights reserved.