Journal Article

Field-Induced Tuning of the Pairing State in a Superconductor

Marquardt, N., Marcenat, C., Knebel, G., Klein, T., Lapertot, G., Flouquet, J., Niu, Q., Rosuel, A., Pourret, A., Rousseau, S., Braithwaite, D., Demuer, A., Aoki, D., Seyfarth, G., Brison, J. P.

2023

Overview

The recently discovered superconductorUTe2, with a superconducting transition temperatureTcbetween 1.5 and 2 K, is attracting much attention due to strong suspicion of spin-triplet and topological superconductivity. Its properties under magnetic field are also remarkable, with field-reinforced (H∥b) and field-induced [Hin the(b,c)plane] superconducting phases. Here, we report the first complete thermodynamic determination of the phase diagram for fields applied along the three crystallographic directions. For field along the easyaaxis, we uncover a strong negative curvature of the upper critical field very close toTc, revealing a strong suppression of the pairing strength at low magnetic fields. By contrast, measurements performed up to 36 T along the hard magnetizationbaxis confirm a bulk field-reinforced superconducting phase. Most of all, they also reveal the existence of a phase transition line within the superconducting phase. Drastic differences occur between the low-field and high-field phases pointing to different pairing mechanisms. Detailed analysis suggests a possible transition between a low-field spin-triplet to high-field spin-singlet state, a unique case among superconductors.

• Publisher: American Physical Society
• Subject: Atomic energy levels / Condensed Matter / Condensed matter physics / Cooper pairs / Critical field (superconductivity) / Crystallography / Electron spin / Electrons / Low temperature / Magnetic fields / Magnetic properties / Phase diagrams / Phase transitions / Physics / Qubits (quantum computing) / Superconductivity / Superconductors / Thermodynamics / Uranium