High Temperature Superconductors in High Frequency Fields

Abstract

The potential for application of high temperature superconductors captured the imagination of the media as soon as the discovery was announced. [1] As expected by anybody familiar with the history of superconductvity, the path to marketable products has proved to be extremely arduous. However, due to an unprecedented effort in research and development some technologically viable products have already reached the market. Notable among these are high frequency devices made of YBa₂Cu₃O_{7-ð (YBCO) films. [2, 3] It was realized early on that of all HTC materials, optimally or slightly overdoped YBCO showed the lowest losses in high frequency fields. The focus on this material has led to the manufacture of extremely high quality films and a thorough investigation of their properties. While the emphasis of device oriented research is on nonlinear effects [4] which limit the power that can be transmitted without deterioration of the device performance, the high quality of the material gives some hope that in the linear regime one actually observes intrinsic properties related to the fundamental question of the symmetry of the pair state and the nature of the pairing mechanism. It is on this regime that we will focus our attention on in this paper}