Anomalous influence of electrode width on the critical current of Nb/Au Josephson junctions

Abstract We study the effect of electrode width on superconducting current transport in Nb–Au–Nb Josephson bridges. The critical current as well as the normal bridge resistance drop with decreasing electrode width on scales of a few <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> , which are orders of magnitude larger than the estimated coherence length of the Au strip. We consider several physical reasons for such an anomalous influence of the width W of the superconducting electrode on the critical current <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>I</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> (AIWIc) and provide model fits for the resistive and superconducting properties of the bridges. The smooth dependence of the Nb–Au–Nb bridge parameters on the electrode width can be used to optimize the design of superconducting devices for specific applications.