Multicomponent superconducting order parameter in UTe<sub>2</sub>.

Hayes, I M; Wei, D S; Metz, T; Zhang, J; Eo, Y S; Ran, S; Saha, S R; Collini, J et al. · Science · 2021

basic_science · Level V

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Abstract

An unconventional superconducting state was recently discovered in uranium ditelluride (UTe<sub>2</sub>), in which spin-triplet superconductivity emerges from the paramagnetic normal state of a heavy-fermion material. The coexistence of magnetic fluctuations and superconductivity, together with the crystal structure of this material, suggests that a distinctive set of symmetries, magnetic properties, and topology underlie the superconducting state. Here, we report observations of a nonzero polar Kerr effect and of two transitions in the specific heat upon entering the superconducting state, which together suggest that the superconductivity in UTe<sub>2</sub> is characterized by a two-component order parameter that breaks time-reversal symmetry. These data place constraints on the symmetries of the order parameter and inform the discussion on the presence of topological superconductivity in UTe<sub>2</sub>.