Spin susceptibility of triplet superconductors and application to UTe2

The heavy fermion superconductor UTe2 has attracted a lot of attention recently as a candidate for chiral triplet superconductivity. Characterizing the triplet pairing symmetry of UTe2 has been a central issue in the study of the material. Because of the ephemeral possibility of time reversal symmetry breaking in the low-field phase, there has been a good deal of interest in nonunitary pairing states. We study NMR properties of triplet states allowed for UTe2 by symmetry, first deriving the spin susceptibility, obtaining some results different from those currently in the literature, and showing how they can be used to distinguish different superconducting states. We further discuss the NMR spin-lattice relaxation time, accounting also for the influence of disorder, and compare to existing experiments.