Effects of Spin Orbit Coupling on the NMR Response of Multiband Superconductors

Nuclear magnetic resonance (NMR) and Knight shift measurements are critical tools in the identification of spin-triplet superconductors. We discuss the effects of spin-orbit coupling on the Knight shift and susceptiblities for a variety of spin triplet multi-orbital gap functions with orbital singlet character and compare their responses to "traditional" single band spin-triplet ($p_x+ip_y$) superconductors. Surprisingly, we find no decrease in the spin susceptibility and Knight shift in any direction within the superconducting phase under weak spin-orbit coupling. We interpret this as a consequence of the dominance of inter-band pairing.