Abstract
The temperature-dependent optical reflectivity and complex transmissivity of an epitaxially grown thin film were measured over a wide frequency range . The opening of the superconducting gap is directly observed by vanishing optical conductivity at for . While in this range the measured temperature- and frequency-dependent electrodynamic properties agree well with the BCS predictions of a nodeless order parameter, unexpectedly a strong quasiparticle absorption shows up below 1.5 meV. The spectral weight of the condensate corresponds to a penetration depth .
- Received 6 December 2009
DOI:https://doi.org/10.1103/PhysRevB.81.060509
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