Evidence for finite gap minima in the superconducting state of UTe₂ from thermal transport

 UTe₂ provides an ideal platform for studying the spin-triplet superconductivity, owing to the absence of competing magnetic order at ambient conditions and its relatively simple Fermi surface topology. However, the superconducting gap structure—central to understanding both the pairing mechanism and possible topological properties—remains highly controversial, particularly regarding the presence or absence of point nodes along the b axis. To address this issue, we performed directional, bulk-sensitive thermal conductivity measurements on high-quality single crystals grown by the molten-salt flux method, with magnetic fields applied along all crystallographic directions. To maximize the contribution from the putative nodal quasiparticle, the thermal current was applied along the b axis. The field dependence of the residual thermal conductivity exhibits a clear kink at the threshold field, and Doppler-shifted quasiparticle excitations become active in thermal transport across vortex lattice only above that field. These results strongly suggest that UTe₂ hosts a highly anisotropic but nodeless superconducting state with finite gap minima along the b-axis.