Measurement of the size dependence of the current-phase relation in microbridge Josephson junctions

We present the first direct measurements of the size effect on the current-phase relation of microbridge Josephson junctions. The phase difference across the bridge is obtained by subtracting the phase shift of the thin-film leads from the total phase shift. We have found that the current-phase relations are sinusoidal for both uniform and variable thickness bridges with dimensions much smaller than ξ (T). For narrow uniform thickness bridges with width ≪ξ (T), the measured length dependence of the current-phase relation is in good agreement with the calculation of Likharev and Yakobson for variable thicknes bridges.