Penetration depth and microwave loss measurements with a YBa2Cu3O7−δ/LaAlO3/YBa2Cu3O7−δ trilayer transmission line

Abstract

A trilayer YBa₂Cu₃O_7−δ/LaAlO₃/YBa₂Cu₃O_7−δ transmission line was fabricated to measure the penetration depth of the high‐temperature superconducting layers, to determine the microwave losses, and to demonstrate the potential for practical high‐temperature superconductor multilayer microwave circuits. All layers were deposited onto a (100) MgO substrate by pulsed laser deposition. The superconducting films are c‐axis oriented with critical temperatures of 89 K. From the phase velocity measurements, the penetration depth was found to be consistent with weak‐coupled BCS theory in the local limit with a zero‐temperature value of 135 nm. A simple phenomenological temperature dependence for the penetration depth is also presented. This successful trilayer fabrication process, besides allowing the determination of the penetration depth and microwave loss, also expands the possible applications of the high‐temperature superconductors.