Determination of the perpendicular penetration depth in superconducting thin films from the observation of nonuniform supercurrent flow

By observing the nonuniform supercurrent density in wide superconducting thin films with a tunneling technique, we determine the perpendicular penetration depth ${\ensuremath{\lambda}}_{p}$ of the film. ${\ensuremath{\lambda}}_{p}$ has the predicted dependence on normalized temperature T/${T}_{c}$ and on sheet resistance ${R}_{\ensuremath{\square}}$, but is a factor of 1.5 to 2 larger than expected theoretically, even when strong electron-phonon coupling is taken into account.