ELECTRODYNAMICS OF YBA2CU3O7 FILMS DEDUCED FROM SUBMILLIMETER SYNCHROTRON-RADIATION TRANSMITTANCE MEASUREMENTS

Transmission measurements on YBa2Cu3O7 films in the spectral range 25 to 100 cm-1 have been performed using synchrotron radiation. In the normal state, the classical Drude conductivity function successfully explains the rise in transmission with frequency. The spectra below T(c) show a strong supercurrent screening of the infrared field. A temperature-dependent penetration depth is calculated from the transmission spectra using the local-limit-response kernel and a quasiparticle conductivity rising as (T/T(c))4. Depending on the film quality, the zero-temperature penetration depth varies from 234 to 340 nm.