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The European Physical Journal B
ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)
Abstract Volume 5 Issue 4 (1998) pp 847-858
Low temperature penetration depth and the effect of quasi-particle scattering measured by millimeter wave transmission in YBa$_{\mathsf 2}$Cu$_\mathsf{3}$O$_{\mathsf 7-\delta}$ thin films
S. Djordjevic (1), L.A. de Vaulchier (1) (a), N. Bontemps (1), J.P. Vieren (1), Y. Guldner (1), S. Moffat (2), J. Preston (2), X. Castel (3), M. Guilloux-Viry (3), A. Perrin (3)
(1) Laboratoire de Physique de la Matière Condensée, École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
(2) Brockhouse Institute for Materials Research, McMaster University, Hamilton On. L8S 4M1, Canada
(3) Laboratoire de Chimie du Solide et Inorganique Moléculaire, Université de Rennes I, avenue du Général Leclerc, 35042 Rennes Cedex, France
Received: 22 January 1998 / Revised: 18 May 1998 / Accepted: 9 June 1998
Abstract: Measurement of the penetration depth $\lambda(T)$ as a function of temperature using millimeter wave transmission in the range 130-500GHz are reported for three $\rm YBa_2Cu_3O_{7-\delta}$ (YBCO) laser ablated thin films. Two films, deposited on a $\rm LaAlO_3$ substrate ($T_c = 90.2 \rm K$), exhibit a narrow resistive transition ($0.3 \rm K$). One has been subsequently irradiated with $\rm He^+$ ions in order to increase the scattering rate of the quasi-particles ($T_c = 87.8 \rm K$). The third film, grown on MgO ($T_c = 88.5 \rm K$), exhibits also a fairly narrow transition ($0.8 \rm K$) and a high crystalline quality. The experiment provides the absolute value $\lambda(T \leq 30 \rm K)$ 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 $\tilde{\lambda_0} = 1990 \pm 200$ Å, $2180 \pm 200$ Å and $2180 \pm 200$ Å, for YBCO-500 Å/$\rm LaAlO_3$(pristine), YBCO-1300 Å/MgO and YBCO-500 Å/$\rm LaAlO_3$ (irradiated) respectively. $\lambda(T \leq 30 \rm K)$ exhibits a different behavior for the three films. In the pristine sample, $\lambda(T \leq 30 \rm K)$ 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 $1/\tau(T \leq 30 \rm K) \sim 1.7 \times 10^{12} s^{-1}$.In the two other samples, $\lambda(T \leq 30 \rm K)$ 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/$\rm LaAlO_3$irradiated one, which exhibits a T2 dependence up to $40 \rm K$. 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 $\tilde{\lambda_0}$ in the pristine sample is a puzzle and sheds some doubt on a straightforward comparison with the theory of data from thin films, if considered as dirty d-wave superconductors.
PACS. 07.57.c Infrared, submillimeter wave, microwave and radiowave instruments, equipment and techniques - 74.72.h High-Tc compounds - 74.76.w Superconducting films
(a) email: Louis-Anne.deVaulchier@physique.ens.fr
Article in PDF format (453 KB)
Online publication: October 29, 1998
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