Microwave Response of Nanostructured High-Tc Superconductor Thin Films

Abstract

A model for the microwave response of a nanostructured high-Tc superconductor (HTS) film, with implanted nanoparticles and nanorods of a dielectric material or point-like and columnar irradiation defects with a nano-sized cross-section is developed. In this case, the microwave surface resistance Rs(T,H,ω) is calculated both for the Meissner and mixed states of a superconductor film in an applied dc magnetic field. The obtained results indicate that the implantation of dielectric nanoparticles or point-like radiation defects can significantly improve superconductor characteristics at microwave frequencies. Namely, these nano-sized structural defects can decrease the surface resistance in the Meissner state and eliminate the oscillations of Abrikosov vortices and the related microwave energy losses, thus decreasing the contribution of Abrikosov vortices to the Rs value in the mixed state of a HTS film.

Improvement of microwave characteristics for high-T c superconductor (YBCO) films by ion irradiation treatment

“…about 10 11 cm −2 -similar to the S1 dose in the present work), mainly leads to the formation of additional point-like structural defects [5,6,24]. The latter manifests itself through enhanced vortex pinning and a related increase in the critical current density as well as a decrease in rf loss, caused by vortex oscillations in the applied rf field [14][15][16]. Another effect that arises due to the insertion of additional point-like structural defects concerns changes in the electron properties of moderately irradiated superconductors; namely, the enhancement of quasiparticle scattering by structural defects and a corresponding increase in the electron momentum relaxation rate.…”

“…In the framework of London electrodynamics, the microwave surface impedance, Z s (T, ω), for a rather thick superconducting film with thickness d > 2λ (λ is the London penetration depth) is described by the well-known relations [12,16,25,26]…”

“…On the other hand, as observed from a few experimental works, the incorporation of dielectric nanoparticles, as well as the formation of point-like irradiation defects in the matrix of HTS film, can significantly improve its microwave characteristics. For instance, the inserted dielectric nanoparticles and nanorods of different nature and content, as well as radiation nano-sized defects, can noticeably decrease the surface resistance in the Meissner state [12,13] and contribution to Abrikosov vortex oscillations and related microwave energy losses to the surface resistance value in the mixed state of a superconductor [14][15][16]. In addition, there are more sophisticated possibilities to use nanostructured superconducting materials in electronics [17,18].…”