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arXiv · 2205.04524

Field-induced tuning of the pairing state in a superconductor

Adrien Rosuel·Christophe Marcenat·Georg Knebel·Thierry Klein·Alexandre Pourret·Nils Marquardt·Qun Niu·Simon Rousseau·Albin Demuer·Gabriel Seyfarth·Gérard Lapertot·Dai Aoki·Daniel Braithwaite·Jacques Flouquet·Jean-Pascal Brison
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Abstract

The recently discovered superconductor UTe$_2$, with a T$_c$ between 1.5~K 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 and field-induced superconducting phases. Here, we report the first complete thermodynamic determination of the phase diagram for fields applied along the three crystallographic directions. Measurements were performed up to 36~T along the hard magnetisation $b$~axis in order to follow the superconducting transition up to the metamagnetic transition at $H_{m} = 34.75$~T. They reveal the existence of a phase transition line within the superconducting phase, and drastic differences occurring between these two phases. Detailed analysis supports a different spin state between the two phases, implying a low-field spin-triplet to high-field spin-singlet transition, a unique case among superconductors, giving insight on the mechanisms leading to spin-triplet superconductivity.

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Adrien Rosuel, Christophe Marcenat, Georg Knebel, Thierry Klein, Alexandre Pourret, Nils Marquardt, Qun Niu, Simon Rousseau, Albin Demuer, Gabriel Seyfarth, Gérard Lapertot, Dai Aoki, Daniel Braithwaite, Jacques Flouquet, Jean-Pascal Brison. 2022-05-09. Field-induced tuning of the pairing state in a superconductor. https://doi.org/10.1103/physrevx.13.011022

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