Drastic change in magnetic anisotropy of UTe2 under pressure revealed by Te-125-NMR

To investigate the normal-state magnetic properties of UTe2 under pressure, we perform Te-125 nuclear magnetic resonance (NMR) measurements up to 2 GPa. Below 1.2 GPa, the b-axis NMR Knight shift shows a broad maximum at the so-called T-chi max on cooling, which is consistent with the magnetization measurement under pressure. T-chi max decreases with increasing pressure and disappears at the critical pressure P-c = 1.7 GPa, above which superconductivity is destroyed. This tendency is also observed in the temperature dependence of the nuclear spin-lattice relaxation rate 1/T-1. At low pressures, 1/T-1 shows a conventional Fermi-liquid behavior (1/T1T = const) at low temperatures, indicating the formation of the heavy-fermion state. Above P-c, 1/T1T follows a 11T behavior without any crossover to the heavy-fermion state down to the lowest temperature (similar to 3 K). In addition, the NMR signals disappear below 3 K, due to the influence of the magnetically ordered moments. From the pressure dependence of the T-chi max and Knight shift, it was found that the Fermi surface character is abruptly changed at P-c, and that superconductivity is observed only in the heavy-fermion state.

Automated summary

In this study, the normal-state magnetic properties of UTe2 under pressure were investigated using Te-125 nuclear magnetic resonance (NMR) measurements. It was found that the Fermi surface character abruptly changes at the critical pressure, above which superconductivity is only observed in the heavy-fermion state.