FLUX FLOW AND VORTEX TUNNELING IN TWO-DIMENSIONAL ARRAYS OF SMALL JOSEPHSON JUNCTIONS

摘要

We have measured the temperature dependence and magnetic field dependence of the zero-bias resistance (R(0)) as well as the current-voltage (I-V) characteristics for several two-dimensional arrays of small aluminum Josephson junctions. R(0)(T) decreases with decreasing temperature, which can be described in terms of two types of vortex motion: flux, flow, and vortex tunneling. At temperatures higher than the Kosterlitz-Thouless transition temperature (T>T-c) or at a bias current greater than the current corresponding to the onset of the nonlinear I-V characteristic (I>I-d), the effective damping resistance which characterizes flux-flow motion is found to be approximately equal to the junction normal-sate resistance R(N). At low temperatures and at small bias current R(0) is temperature independent and remains finite down to our minimum attainable temperature. This finite resistance is found to be dependent on the array size as well as the junction parameters. [References: 43]