Exchange Scattering in Superconductors

Abstract

The theory of superconductivity is discussed in view of previous theories and experiments. It was previously suggested that the depression of the superconducting transition temperatare of lanthanum as a function of rare earth impurity content may be traced to the exchange interaction between the conduction electron spins and the f-shell spins of the rare earth ions and conduction electrons interact via the ionic spins to modify the effective V. From present and previous works, it is concluded that the important course of the depression of Tc by exchange scattering is the disparity in the free-energy depressions of the normal and superconducting states. Shift V effects, whether due to changes in wave function or due to electron iateractions via virtual states, are small by comparison. The exchange energy between conduction electrons and ionic spins necessary to account for the observed reductions in Tc is 0.15 volt. (J.H.M.)