Title :
High-frequency surface impedance and penetration depth of YBa/sub 2/Cu/sub 3/O/sub 7/ films: coherent time-domain spectroscopy method
Author :
Gao, F. ; Whitaker, J.F. ; Uher, C. ; Hou, S.Y. ; Phillips, J.M.
Author_Institution :
Center for Ultrafast Optical Sci., Michigan Univ., Ann Arbor, MI, USA
fDate :
6/1/1995 12:00:00 AM
Abstract :
The transmission (/spl Jscr/) and phase shift (/spl thetav/) of 0.2-1.5 THz radiation have been measured simultaneously on unpatterned, high-quality YBa/sub 2/Cu/sub 3/O/sub 7/ films (T/sub c/=90 K) in the normal and superconducting states using a coherent, pulsed, time-domain technique. The complex surface impedance has been extracted without contacting or patterning the superconducting films using /spl Jscr/ and /spl thetav/. Above T/sub c/, both the real (R/sub s/) and imaginary (X/sub s/) parts show a metallic /spl radic//spl omega/T dependence with almost equal magnitude as predicted by the normal skin effect. Below T/sub c/, R/sub s/ scales with /spl omega//sup 2/, but only for /spl omega//2/spl pi/ <400GHz; it increases more slowly with frequency above 400 GHz. The reactance X/sub s/ is linear in /spl omega/ for T<>
Keywords :
barium compounds; high field effects; high-temperature superconductors; microwave reflectometry; penetration depth (superconductivity); quasiparticles; skin effect; superconducting thin films; superconducting transition temperature; surface conductivity; time-domain reflectometry; yttrium compounds; 0.2 to 1.5 THz; 400 GHz; 90 K; YBa/sub 2/Cu/sub 3/O/sub 7/; YBa/sub 2/Cu/sub 3/O/sub 7/ films; coherent time-domain spectroscopy; complex surface impedance; high temperature superconductors; high-frequency surface impedance; metallic dependence; microwave responses; normal state; penetration depth; power dependence; quasiparticle relaxation rate; radiation phase shift; radiation transmission; reactance; skin effect; submillimeter-wave responses; superconducting films; superconducting transition temperature; unpatterned high-quality films; Frequency measurement; High temperature superconductors; Optical films; Optical resonators; Superconducting films; Superconducting microwave devices; Superconductivity; Surface impedance; Temperature dependence; Time domain analysis;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
