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.