The Nonlinear Microwave Surface Impedance of HTS Cuprate YBA2CU3O7-δ Thin Film Patterned as a Stripline Resonator

• Published in: 2007 International Kharkov Symposium Physics and Engrg. of Millimeter and Sub-Millimeter Waves (MSMW) Vol. 1; pp. 413 - 415
• Main Authors: Kalenyuk, A.A., Kasatkin, A.L., Pan, V.M.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01-06-2007
• Subjects: Critical current; Critical current density; Electrical resistance measurement; High temperature superconductors; Microwave frequencies; Performance evaluation; Power measurement; Surface impedance; Surface resistance; Yttrium barium copper oxide
• ISBN: 9781424412372; 1424412374
• DOI: 10.1109/MSMW.2007.4294680

Our measurements performed at low input power levels (P in ≪ P pit ) have revealed the nonlinear character of the surface resistance R s (I 0 ) of the YBCO film under study. It is shown that at low enough amplitudes I 0 of the microwave current in the resonator R s (I 0 ) ˜ log(I 0 ), while at high enough I 0 amplitudes (which are less than the critical current value I c for the constriction) the R s (I 0 ) dependence is quadratic: R s (I 0 ) = α(ω,j c w,d)I 02 with a proportionality coefficient α, depending on the microwave frequency ω, critical current density j c , resonator width w and thickness of the film d: α(ω, j c , w, d) ˜ ω(j c 2 d 2 w). This type of nonlinear Rs(I 0 ) dependence (at least at high enough I 0 values) allows to assume that the origin of nonlinearity is related to the entry of microwave induced Abrikosov vortices through the film edges.