THEORETICAL-STUDY OF IMPURITY EFFECTS ON HIGH-TEMPERATURE SUPERCONDUCTIVITY

Non-magnetic impurity effects on high-temperature superconductivity are theoretically examined. We calculate a superconducting gap induced by SDW fluctuations in the presence of non-magnetic impurity atoms. We show that the impurity atoms cause two competing effects; (i)the reduction of the SDW gap, which leads to the increase in the fluctuations of the SDW order, thus to the increase of the superconducting gap ΔSC effectively, (ii) the pair-breaking effect, which suppresses ΔSC. We find that the latter effect dominates over the former, thus the superconducting gap ΔSC being decreased by non-magnetic impurity atoms. Our result suggests that the mechanism of high-temperature superconductivity is magnetic. © 1990.