Critical current suppression in high-Tc superconductors and its dependence on the defects concentration

For the first time, we have calculated the dependence of the critical current density jc on the defects concentration nd in a system simulating a HTSC layer. It was shown that jc(nd) dependence is non-monotonic and has a peak at the optimal concentration of defects nopt which is consistent with the known experimental data. We conclude that collective depinning-the reduction of effective pinning potential caused by increase of defects concentration-is the main mechanism for saturation and the subsequent decrease of jc