Tuning electric charge scattering in YBCO single crystals via irradiation with MeV electrons.

Irradiation with electrons is an efficient approach to inducing a large number of defects with a minimal impact on the material itself. Analysis of the energy transfer from an accelerated particle smashing into the crystal lattice shows that only electrons with MeV energies produce point defects in the form of interstitial ions and vacancies that form perfect scattering centers. Here, we investigate the changes in the resistive characteristics of YBCO single crystals from the 1-2-3 system after several steps of low-temperature irradiation with 0.5-2.5 MeV electrons and irradiation doses of up to 8.8×1018 cm-2. The penetration depth of such electrons is much larger than the crystal thickness. We reveal that defects appearing in consequence of such electron irradiation not only increase the residual resistance, but they affect the phonon spectrum of the system and lower the superconducting transition temperature linearly with increase of the irradiation dose. Furthermore, the irradiation-induced defects are distributed non-uniformly, that manifests itself via a broadening of the superconducting transition. Interestingly, the excess conductivity remains almost unaffected after such electron irradiation. [ABSTRACT FROM AUTHOR]