Microwave vortex dynamics in Tl-2212 thin films

• Published in: Physica. C, Superconductivity Vol. 468; no. 7-10; pp. 852 - 855
• Main Authors: Pompeo, N., Schneidewind, H., Silva, E.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01-04-2008; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cuprates superconductors (high tc and insulating parent compounds); Decoupling; Dynamics; Exact sciences and technology; Fluid flow; Magnetic fields; Physics; Pinning; Properties of type I and type II superconductors; Softening; Superconductivity; Surface impedance; Thin films; Tl2Ba2CaCu2O8+x; Vortex lattices ,flux pinning, flux creep; Vortices; Pinning; 74.25.Qt; Surface impedance; Tl2Ba2CaCu2O8+x; 74.25.Nf; 74.72.Jt; Viscosity; Flux line; Inorganic compounds; Creep; Microwave radiation; Transition element compounds; Dielectric resonators; Magnetic field effects; Cerium oxide; Thin films; Vortices; High-Tc superconductors; High field; High frequency; Barium Copper Yttrium Oxides Mixed
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2007.11.063

We present measurements of the effective surface impedance changes due to a static magnetic field, ΔZ(H,T)=ΔR(H,T)+iΔX(H,T), in a Tl-2212 thin film with Tc>103K, grown on a CeO2 buffered sapphire substrate. Measurements were performed through a dielectric resonator operating at 47.7GHz, for temperatures 60K⩽T<Tc and magnetic fields μ0H⩽0.8T. We observe exceptionally large field induced variations and pronounced super-linear field dependencies in both ΔR(H)andΔX(H) with ΔX(H)>ΔR(H) in almost the whole (H,T) range explored. A careful analysis of the data allows for an interpretation of these results as dominated by vortex dynamics. In the intermediate-to-high field range we extract the main vortex parameters by resorting to standard high frequency model and by taking into proper account the creep contribution. The pinning constant shows a marked decrease with the field which can be interpreted in terms of flux lines softening associated to an incipient layer decoupling. Small vortex viscosity, by an order of magnitude lower than in Y-123 are found. Some speculations about these findings are provided.