Chiral Superconductivity in UTe$_2$ via Emergent $C_4$ Symmetry and Spin Orbit Coupling

Abstract

A lot of attention has been drawn to superconductivity in UTe$_2$, with suggestions of time-reversal symmetry breaking triplet chiral superconducting order parameter. The chirality of the order parameter has been attributed to an accidental near degeneracy of two superconducting components belonging to 1D irreps $B_{2u}$ and $B_{3u}$ of the relevant $D_{2h}$ point group, and it has been argued that the chiral $B_{2u}+iB_{3u}$ combination is selected by ferromagnetic fluctuations. In this work we present a possible explanation of the near-degeneracy as a result of an accidental $C_4$ symmetry of the band structure, with the superconducting order parameter belonging the 2D $E_u$ irrep of $D_{4h}$ that uniquely descends to the sought after $B_{2u}+iB_{3u}$ combination. We show that the $C_4$ symmetry is emergent at the level of the interactions using a renormalization group calculation and argue that the chiral combination of the order parameter is favored when spin-orbit coupling is added to the model.