Non-linear IV characteristics in two-dimensional superconductors: Berezinskii-Kosterlitz-Thouless physics vs inhomogeneity.

One of the hallmarks of the Berezinskii-Kosterlitz-Thouless transition in two-dimensional superconductors is the universal jump of the superfluid density, that can be indirectly probed via the non-linear exponent of the current-voltage $IV$ characteristics. We compared the experimental measurements of $IV$ characteristics in NbN thin films and $SrTiO_{3}$-based interfaces. While the former display a paradigmatic example of BKT-like non-linear effects, the latter do not seem to justify a BKT analysis. Rather, the observed $IV$ characteristics can be well reproduced theoretically by modelling the effect of mesoscopic inhomogeneity of the superconducting state.