Unconventional $s$-Wave Pairing with Point-Node-Like Gap Structure in UTe${}_2$

Abstract

We explore the pairing state and gap structure of UTe${}_2$ using a six-orbital model which we call the $f$-$d$-$p$ model. Our model accurately reproduces the quasi-two-dimensional Fermi surfaces consistent with recent de Haas-van Alphen oscillation measurements and the $(0,\pm \ddot{I}€,0)$ antiferromagnetic spin fluctuations observed by 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 UTe${}_2$. The most likely state is found to be an $s$-wave state with a highly anisotropic superconducting gap structure that exhibits a point-node-like behavior of the specific heat at low temperatures.

Main Text: 4 pages, 7 figures; Supplementary Material: 7 pages, 4 figures. (Published; J. Phys. Soc. Jpn. 93, 063701)