Pseudo point nodal superconducting gap in spin-triplet UTe<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 42463704.
- Also identified by DOI 10.1038/s41467-026-75566-9.
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Abstract
UTe<sub>2</sub> is an unconventional heavy-fermion superconductor discussed as a candidate for spin-triplet pairing. However, conflicting reports on gap structure, particularly regarding point nodes, have hindered understanding of the order parameter symmetry. Here, we report b-axis thermal conductivity κ<sub>b</sub>/T measurements on high-quality UTe<sub>2</sub> single crystals down to ~ 50 mK that definitively resolve the gap anisotropy. κ<sub>b</sub>/T shows negligible residual conductivity as T → 0, while magnetic fields induce only weak enhancement of the residual term. Remarkably, a threshold-like field scale is observed at low fields for H∥a, characterized by a kink signaling a change in quasiparticle transport normal to the field. Above this threshold, strong anisotropy develops for transport along and normal to the field. These results strongly suggest that UTe<sub>2</sub> hosts a fully gapped state with pseudo point nodes, where the gap minima approach but never reach zero, placing strong constraints on the order parameter and exotic pairing mechanism.