Ca Doped YBCO Films in THz Frequency range

Ca doped YBaCuO thin films were investigated using frequency and time domain THz spectroscopy. A non-monotonic behavior was observed in with a maximum at about 1.8 meV and 1.2 meV depending on Ca concentration. Two batches of thin films 500–600Å thick where used; one of 5% and the other of 10% Ca concentration. The films show a clear c-axis orientation and 77K for the 5% Ca and 10% Ca respectively. Both thin film batches show a decrease in plasma frequency as temperature increases and superconducting transition is approached. The quasiparticles scattering rate decreases in the normal state and drops when Tc is approached. The imaginary part of the conductivity was found to be proportional to 1/ω, known from the delta-function response.