Pseudo point nodal superconducting gap in spin-triplet UTe2

UTe2 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 κb/T measurements on high-quality UTe2 single crystals down to ~ 50 mK that definitively resolve the gap anisotropy. κb/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 UTe2 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. The authors report thermal conductivity measurements on UTe2 down to 50 mK. From the data, they argue that UTe2 exhibits a fully-gapped state with a pseudo point-nodal structure, where gap minima along the b axis approach but never reach zero.