Far-Infrared Reflectance and Transmittance Studies of YBa2Cu3O7-x Single-Crystal Thin Films

概要

論文の詳細を見る
A new method of estimating the optical constants of thin films has been developed and applied to YBa2Cu3O7-x epitaxial single-crystal thin films ($T_{\text{c}}=90$ K) grown on MgO substrates to determine the far-infrared optical conductivity $\sigma_{\textit{ab}}(\omega)$, which is the response when an unpolarized excitation is applied parallel to the ab-plane in multidomain (twinned) single crystals of YBa2Cu3O7-x. In this method, both the transmittance spectra $T(\omega)$ and reflectance spectra $R(\omega)$ are measured as a function of the wave number $\omega$, and the results are substituted into a set of coupled equations which exactly describe $R(\omega)$ and $T(\omega)$ of thin films on substrates, where the complex refractive index $N=n+ik$ of the thin films is an unknown parameter. The coupled equations are numerically solved using the Newton method, and the values of $n$ and $k$ are determined as a function of $\omega$. We have determined $\sigma_{\textit{ab}}(\omega)$ of YBa2Cu3O7-x thin films for $\omega=50\text{--}250$ cm-1 at $T=34\text{--}97$ K@. Analysis of the temperature dependence of $\sigma_{\textit{ab}}(\omega)$ based on the two-fluid model suggests that the symmetry of the superconducting pairing state of the specimen is $d$-wave.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2001-05-15