Consequences of d-wave superconductivity for high frequency applications of cuprate superconductors

A number of recent experiments suggest that the superconducting ground state wave function in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) has d-wave symmetry. However little attention has been given to the consequences of d-wave pairing symmetry on applications of the cuprates. An intrinsic finite residual loss, approximately one order of magnitude below the lowest losses measured in YBCO thin films at 10 GHz, is one important consequence. In addition, an unusual sensitivity to disorder, an intrinsic non-linear power dependence, and unique mid-gap states associated with specific film textures and possibly twin boundaries, are also expected. We present our own attempts to identify these unique properties of d-wave superconductors, and discuss how these results may dictate the ultimate limitations of the cuprates in high frequency applications.<>