Spin-Orbit Coupling and Nuclear Magnetic Resonance in Superconducting Metals

Abstract

In this work, the effect of spin-orbit coupling (through spin-reversing scattering) on the paramagnetic spin susceptibility of conduction electrons in a superconductor has been studied. This was accomplished by investigating the nuclear magnetic resonance of two groups of (type-I) superconducting samples. In the first group of samples, consisting of different-sized samples of pure lead, the residual NMR shift in the limit of zero temperature was found to vary with particle size, as is true for pure tin. The results are consistent with the existence of a larger spin-orbit interaction in lead. The second group of samples, containing various concentrations of In, Sb, Pb, and Bi impurities, exhibited residual NMR shifts which were consistent with the spin-orbit interactions characteristic of the respective impurities. Taken together, the NMR results are consistent with the microscopic theory of superconductivity, including the effects of spin-orbit interactions.