Penetration depth variation in high quality YBaCuO thin films

Abstract

The authors report results obtained on state-of-the-art YBCO thin films prepared by pulsed laser deposition on LaAlO{sub 3} substrates, using samples as similar as possible in two different experimental set-ups: a surface impedance measurement on 4,000 {angstrom} thick films using a parallel plate resonator (10 GHz), and a far infrared transmission (100--400 GHz) measurement which requires thinner (1,000 {angstrom}) samples. The measurements show a reduction of the penetration depth slope d{lambda}/dT with improving quality of the thin films, which exhibit a low temperature scattering rate and residual surface resistance, comparable to single crystals. A linear fitting to the {lambda}(T) experimental results yields d{lambda}/dT = 2 {angstrom}/K in both experiments in the low frequency limit.