Universal Dependence of the Critical Temperature in HTS on the Fractional Volume of Nanosize Defects

We report on the effect of randomly-distributed amorphous defects, ~ at the length scale of the superconducting coherence length, on T_c in YBCO. These damages were created by ions irradiation with a wide range of energy and fluence. Typically, in previous experiments, T_c was found to vary with ion fluence, species, energy, and ionization charge, and also on the chemical composition and density of the HTS. Neither a phenomenological nor a theoretical relationship between T_c and these ion properties is however known of. We now show that the decrease in T_c is a universal function of the fractional defect volume embedded in the HTS. We also re-analysed several experiments by others, and find that the same universality applies. This finding provides, for the first time, a means to calculate the effect on T_c of disorder as created by randomly-distributed amorphous nanosize defects.