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

Abstract

A trilayer YBa2Cu3O7−δ/LaAlO3/YBa2Cu3O7−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.

Microwave Surface Impedance of High Temperature Superconductors

“…69 The apparent width of the critical region in all of these experiments, as much as 10 K away from T c , is larger than that corresponding to the usual Ginzberg criterion for the breakdown of mean field theory, but is consistent with estimates by Fischer et al 67 Non-mean-field behaviour in 1/A 2 (T) has not otherwise been reported for either films or crystals, but this is due in part to the lack of careful studies of this phenomenon. Many early film results gave A 2 (0)/A 2 (T) that followed 1 -(T/T C ) 2 rather well, 70,71,72 and did seem to show mean field behaviour. As will be discussed below, the often observed T 2 dependence of films at low T is certainly extrinsic.…”

Microwave propagation characteristics of a high-temperature superconducting variable spacing parallel plate transmission line

“…On the other hand, measurement of the microwave propagation characteristics, such as the phase velocity and attenuation constant of a superconducting transmission line, can also be employed to determine the penetration depth. 13 In addition, the propagation characteristics are of practical use in understanding the behavior of a superconducting microwave device. A field solution for a superconducting transmission line is a simple and direct theoretical way of investigating its propagation characteristics and was first presented by Swihart for a conventional transmission line.…”

Superconducting multiturn flux transformers for radio frequency superconducting quantum interference devices

“…24 Large leakage currents can flow through epitaxial LAO films. As reported by Pond et al, 25 the loss in a trilayer transmission line made from YBCO/LAO/YBCO trilayer structure was primarily limited by conduction currents in the LAO film and by damping by the bound charges. Figure 7 shows the simulated unloaded quality factors for different loss tangent values of the 300-nm-thick LAO film (tan ␦ film ).…”