Evidence for a bulk complex order parameter in thin filmsE. Farber1, 2, G. Deutscher1, B. Gorshunov3, 4 and M. Dressel3
1 School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Science, Tel Aviv University - Ramat Aviv 69978, Israel
2 Department of Electrical and Electronic Engineering College of Judea and Samaria - Ariel, Israel
3 1. Physikalisches Institut, Universität Stuttgart Pfaffenwaldring 57, D-70550 Stuttgart, Germany
4 General Physics Institute, Russian Academy of Sciences - Moscow, Russia
(Received 27 February 2004; accepted in final form 15 June 2004)
We have measured the penetration depth of overdoped ( - ) thin films using two different methods. The change of the penetration depth as a function of temperature has been measured using the parallel-plate resonator (PPR), while its absolute value was obtained from a quasi-optical transmission measurement. Both sets of measurements are compatible with an order parameter of the form , with and , indicating a finite gap at low temperature. Below 15 , the drop of the scattering rate of uncondensed carriers becomes steeper in contrast to a flattening observed for optimally doped films. This decrease supports our results on the penetration depth temperature dependence. The findings are in agreement with tunneling measurements on similar - thin films.
74.20.Rp - Pairing symmetries (other than s-wave).
74.72.Bk - -based cuprates.
78.66.-w - Optical properties of specific thin films.
© EDP Sciences 2004