The discovery of superconductivity in the heavy-fermion paramagnet UTe2 has attracted a lot of attention, particularly due to the reinforcement of superconductivity near quantum phase transitions induced by magnetic field and/or pressure [Ran et al. Science 365, 684 (2019), Aoki et al., arXiv:2110.10451]. In this system, hydrostatic pressure induces an enhancement of the superconducting temperature by a factor 2, reaching about 3 K [Braithwaite et al, Commun. Phys. 2, 147 (2019)]. The effect of magnetic field on the ambient pressure superconductivity is also very unusual, with the superconducting critical field exceeding 60 T for certain directions of applied field [Ran et al. Nat. Phys. 15, 1250 (2019), Knafo et al., Commun. Phys. 4, 40 (2021)].
In collaboration with researchers at CEA in Grenoble and Charles University in Prague, scientists at LNCMI investigated the electrical resistivity of UTe2 under pressure up to 3 GPa and pulsed magnetic fields up to 58 T along the hard magnetic crystallographic directions b and c. They constructed three-dimensional phase diagrams showing a complete reshuffling of the magnetic anisotropy and strong associated effects on superconductivity. Near the critical pressure, a field-enhancement of superconductivity coincides with a boost of the effective mass near field-induced quantum magnetic instabilities. By bringing new elements about the interplay between magnetism and superconductivity, this paper appeals for microscopic theories describing the anisotropic properties of UTe2 under pressure and magnetic field.
Publication – Magnetic reshuffling and feedback on superconductivity in UTe2 under pressure
M. Valiska, W. Knafo, G. Knebel, G. Lapertot, D. Aoki, and D. Braithwaite
Phys. Rev. B 104, 214507 (2021).
Figure: Three-dimensional (p,H,T) phase diagrams and evolution of the Fermi-liquid coefficient A in the low-temperature (p,H) planes of UTe2 in magnetic fields applied along b and c.