NMR Investigation of Superconductivity and Kondo-Coherency in CeCu2Si2

Abstract

In the normal dense Kondo state of CeCu ₂ Si ₂ , the nuclear magnetic relaxation rate 1/ T ₁ of ⁶³ Cu divided by T , 1/ T ₁ T is almost constant below 2.5 K with a slight increase near the superconducting transition temperature. Together with the results of other normal Kondo lattice compounds, it is concluded that the temperature dependence of 1/ T ₁ T at low temperatures does not scale to that of the specific heat divided by T , C ( T )/ T in Kondo lattice compounds in contrast with the case of dilute Kondo impurities. In the superconducting state, 1/ T ₁ T varies as T ² , suggesting the gap zeros along lines, while the reported data of C _s ( T )/ T show no simple power law dependence. It is claimed that this difference below T _c may be correlated with the difference between 1/ T ₁ T and C ( T )/ T in the normal dense Kondo state.