Anisotropic response of spin susceptibility in the superconducting state of UTe2 probed with 125Te -NMR measurement

To investigate spin susceptibility in a superconducting (SC) state, we measured the Te-125-NMR Knight shifts at magnetic fields (H) up to 6.5 T along the b and c axes of single-crystal UTe2, a promising candidate for a spin-triplet superconductor. In the SC state, the Knight shifts along the b and c axes (K-b and K-c, respectively) decreased slightly, and the decrease in K-b was almost constant up to 6.5 T. The reduction in K-c decreased with increasing H, and K-c was unchanged through the SC transition temperature at 5.5 T, excluding the possibility of spin-singlet pairing. Our results indicate that spin susceptibilities along the b and c axes slightly decrease in the SC state in low H, and the H response of SC spin susceptibility is anisotropic on the bc plane. We discuss the possible d-vector state within the spin-triplet scenario and suggest that the dominant d-vector component for the case of H parallel to b changes above 13 T, where T-c increases with increasing H.

Automated summary

Investigating the spin susceptibility in a superconducting state, Te-125-NMR Knight shifts were measured along the b and c axes of single-crystal UTe2 at magnetic fields up to 6.5 T. The results show a slight decrease in spin susceptibility along the b and c axes in the superconducting state at low magnetic fields, with an anisotropic response on the bc plane. The dominant d-vector component changes above 13 T, leading to an increase in Tc with increasing magnetic field.