High frequency transport properties of YBCO: Extrinsic versus intrinsic d-wave properties

In good superconducting YBCO films, the surface impedance Z (T, omega, B) = Z(int) (T, omega, B) + Z(res) (T, omega, B) is dominated for T > T-c/2 and B similar to 0 by intrinsic properties, which are difficult to improve. Below T-c/2, Z(res) usually dominates over Z, and below 0.9 T-c, Z(T, omega, B) increases with field, both are, up till now, explained by extrinsic properties related to extrinsic and intrinsic surfaces. The latter are named weak or strong links (WSL), into which around B-c1J for omega(J)(0) >> omega(A)(0) Josephson fluxons (JF) enter, where B-c1J << B-c1 holds with B-c1 the lower critical lfield of Abrikosov fluxon (AF) with omega(A)(0) similar to MHz their nucleation or pinning frequency. Below fields less than or similar to B-C1 and below the pinning or nucleation frequency omega(J)(0) similar to THz hysteresis losses increase Z = R + iX nonlinearly with r(T, w) = delta X/delta R similar to 2 with the surface resistance R and the surface reactance X. The nonlinearities decrease toward Bc1J to (small) oscillation of JF yielding r(T, omega) alpha omega(J)(0)(T)/omega. Those Z nonlinearities yield harmonics or intermodulation products IMD(T). Below B-c1J new types of nonlinearities relate to d-wave properties of HTS. Either nonlinear Meissner effect (NME) and anomalous Meissner effect (AME) at internal or external surfaces are proposed with r >> 1, observed by harmonic generation and by specific IMD(T, B) dependencies being identified recently. New developments in theory and experiment and procedures to separate extrinsic from intrinsic properties will be analyzed.