This study investigates the spin susceptibility in U-based superconductor UTe2 in the superconducting (SC) state by using Knight shift measurements for a magnetic field H along the a axis, which is the magnetic easy axis of UTe2. Although a tiny anomaly ascribed to the SC diamagnetic effect was observed just below the SC transition temperature Tc, the a-axis Knight shift in the SC state shows no significant decrease, following the extrapolation from the normal-state temperature dependence. This indicates that the spin susceptibility is nearly unchanged below Tc. Considering the previous Knight shift results for H∥b and H∥c, the dominant SC state is determined to be B3u in the spin-triplet pairing, which is consistent with the spin anisotropy in the normal state. The present result shows that UTe2 is a spin-triplet superconductor with spin degrees of freedom.
@article{arxiv.2203.08598,
title = {Superconducting order parameter in UTe$_2$ determined by Knight shift measurement},
author = {Hiroki Fujibayashi and Genki Nakamine and Katsuki Kinjo and Shunsaku Kitagawa and Kenji Ishida and Yo Tokunaga and Hironori Sakai and Shinsaku Kambe and Ai Nakamura and Yusei Shimizu and Yoshiya Homma and Dexin Li and Fuminori Honda and Dai Aoki},
journal= {arXiv preprint arXiv:2203.08598},
year = {2022}
}