Possible Unconventional s-Wave Pairing with Point-Node–Like Gap Structure in UTe2

Abstract

We explore the pairing state and gap structure of UTe₂ using a six-orbital model which we call the f–d–p model. Our model accurately reproduces the quasi-two-dimensional Fermi surfaces, agreeing with recent de Haas–van Alphen oscillation measurements and \((0, \pm \pi ,0)\) antiferromagnetic spin fluctuations observed through neutron scattering. We incorporate on-site Coulomb repulsion for f electrons and solve the linearized Eliashberg equation within the third-order perturbation theory to investigate the superconducting symmetry in UTe₂. An s-wave state featuring a highly anisotropic superconducting gap structure and a point-node–like behavior of the specific heat at low temperatures is identified as the most probable state.