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Low temperature penetration depth and the effect of quasi-particle scattering measured by millimeter wave transmission in YBaCuO thin films

S. Djordjevic·L. A. de Vaulchier·N. Bontemps·J. P. Vieren·Y. Guldner·S. Moffat·J. Preston·X. Castel·M. Guilloux-Viry·A. Perrin
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Abstract

Measurement of the penetration depth as a function of temperature using millimeter wave transmission in the range 130-500GHz are reported for three YBCO thin films. The experiment provides the absolute value for the penetration depth at low temperature: the derivation from the transmission data and the experimental uncertainty are discussed. We find a zero temperature penetration depth of 199+/-20nm, 218+/-20nm and 218+/-20nm, for YBCO-50nm/LaAlO3 (pristine), YBCO-130nm/MgO and YBCO-50nm/LaAlO3 (irradiated) respectively. The penetration depth exhibits a different behavior for the three films. In the pristine sample, it shows a clear temperature and frequency dependence, namely the temperature dependence is consistent with a linear variation, whose slope decreases with frequency: this is considered as an evidence for the scattering rate being of the order of the measuring frequency. A two fluids analysis yields 1.7 10^{12} s^{-1}. In the two other samples, the penetration depth does not display any frequency dependence, suggesting a significantly larger scattering rate. The temperature dependence is different in these latter samples. It is consistent with a linear variation for the YBCO/MgO sample, not for the YBCO/LaAlO3 irradiated one, which exhibits a T^2 dependence up to 40K. We have compared our data to the predictions of the d-wave model incorporating resonant scattering and we do not find a satisfactory agreement. However, the large value of the penetration depth at zero Kelvin in the pristine sample is a puzzle and sheds some doubt on a straightforward comparison with the theory of data from thin films, considered as dirty d-wave superconductors.

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S. Djordjevic, L. A. de Vaulchier, N. Bontemps, J. P. Vieren, Y. Guldner, S. Moffat, J. Preston, X. Castel, M. Guilloux-Viry, A. Perrin. 1998-01-23. Low temperature penetration depth and the effect of quasi-particle scattering measured by millimeter wave transmission in YBaCuO thin films. https://arxiv.org/abs/cond-mat/9801244

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