High-field superconducting halo in UTe<sub>2</sub>.

Lewin, Sylvia K; Czajka, Peter; Frank, Corey E; Saucedo Salas, Gicela; Noe Ii, G Timothy; Yoon, Hyeok; Eo, Yun Suk; Paglione, Johnpierre et al. · Science · 2025

basic_science · Level V

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Abstract

The heavy fermion material UTe<sub>2</sub> is a candidate topological superconductor that exhibits multiple magnetic field-induced superconducting phases. One such phase exists only at fields greater than 40 tesla, a considerable scale given its critical temperature of only 2 K. Here, we extend measurements of this state with fields outside of the <i>bc</i> crystallographic plane and reveal its core structure: The superconducting phase wraps around the <i>b</i> axis in a halo-like fashion and appears to be stabilized by a field component perpendicular to the magnetic easy axis. This angle dependence points to a multicomponent spin-triplet order parameter with a finite angular momentum of the Cooper pairs. The pairing mechanism remains enigmatic, and UTe<sub>2</sub>'s specific magnetophilic superconducting tendencies seem incompatible with existing models for field-enhanced superconductivity.