In-plane penetration depth of high-temperature superconductors with single and double CuO layers

¹ Physikalisches Institut, Lehrstuhl Experimentalphysik II, Universität Tübingen, Morgenstelle 14, D-72076 Tübingen, Germany
² II. Physikalisches Institut, Lehrstuhl Experimentalphysik II, Universität zu Köln, Zülpicherstr. 77, D-50937 Köln, Germany
³ NTT Basic Research Laboratories, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243, Japan

Received: 15 August 1996
Accepted: 10 October 1996

Abstract

A dc technique based on the measurement of the magnetic-field dependence of the critical current of bicrystal grain boundary Josephson junctions (GBJs) is used to precisely determine the temperature change of the in-plane London penetration depth of ybco (YBCO) and lsco (LSCO) thin films. The resolution of the applied measuring technique is better than 0.2 Å  and the measured dependences are not sensitive to extrinsic influences. Over a wide temperature range the data obtained for different high-temperature superconductors confirm with high accuracy the theoretical prediction for a -symmetry of the superconducting order parameter. The same temperature dependence is measured for materials with single and double CuO layers.