Dielectric resonators for the measurement of superconductor thin films surface impedance in magnetic fields at high microwave frequencies

• Published in: Journal of superconductivity and novel magnetism Vol. 20; no. 1; pp. 71 - 82
• Main Authors: POMPEO, N, MARCON, R, SILVA, E
• Format: Conference Proceeding Journal Article
• Language: English
• Published: New York, NY Springer 01-01-2007
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Physics; Properties of type I and type II superconductors; Response to electromagnetic fields (nuclear magnetic resonance, surface impedance, etc.); Superconductivity; Surface impedance; Mixed state; Superconducting transitions; superconductors; Dielectric resonators; Magnetic field effects; Microwave conductivity; Quality factor; Surface conductivity; Vortices; Dissipation; High-Tc superconductors; High field; 74.25 Nf; dielectric resonator
• ISSN: 1557-1939; 1557-1947
• DOI: 10.1007/s10948-006-0192-5

We present the design and realization of cylindrical dielectric resonators operating in the 40-60 GHz frequency range, designed for the measurement of the surface resistance and of the surface reactance shift in High-T c Superconductors (HTS) thin films in a dc magnetic field. The resonators are single tone, based on the TE 011 mode, and multiple tone, the latter allowing in principle to exploit the simultaneous determination of the surface impedance at different frequencies. As an application example, we report the temperature and field dependencies of the effective surface impedance of some cuprate superconductors thin films. The results are compared with those obtained through the use of a standard metal cavity with a similar Q-factor and operating in the same frequency range. The comparison highlights a superior stability and a higher sensitivity, resulting in an increase of about two orders of magnitude in the resolution of the surface impedance measurement. By contrast, the dissipative part of the superconducting transition (above T/T c = 0.97) is better studied with the metal cavity. We also present measurements in the vortex state in YBaCa2Cu3O7-delta and Tl2Ba2CaCu2O8+x that show significantly different physics.