On Bose–Einstein condensation in Josephson junctions star graph arrays

• We investigate the current-voltage characteristics of star-shaped Josephson junctions arrays.
• We compare the characteristics of the arrays embedded in the star with reference arrays.
• We find relevant differences in the characteristics of the two arrays.
• The differences result consistent with the prediction of a Bose–Einstein topological condensation theory.

We report on the evidence of anomalous currents in graph-shaped arrays of Josephson junctions along peculiar branches of the networks. The specific case of a star-shaped array is considered and the evidence of the anomalies is achieved by comparing the current-voltage characteristics of the arrays embedded in the star structure with those of “reference” arrays which are fabricated by-side the network structure and are dc-isolated from these. The experimental data are consistent with the results of a theoretical model predicting gradients of the populations of Cooper pairs on the islands situated in proximity of the central superconductive island as a result of a Bose–Einstein condensation process.