# Spin-Orbit Coupling Induced Degeneracy in the Anisotropic Unconventional Superconductor UTe$_2$

## TL;DR

This study uses DFT+U calculations to explore the electronic structure and magnetic correlations in UTe$_2$, revealing degeneracies induced by spin-orbit coupling that are relevant for its unconventional superconductivity.

## Contribution

The paper provides the first detailed DFT+U analysis of UTe$_2$, highlighting the role of spin-orbit coupling and ferromagnetic correlations in its electronic structure.

## Key findings

- States near the Fermi level are dominated by the $j=5/2$ configuration.
- Degeneracy occurs in the $j_z= \, ext{±} \, 1/2$ sectors.
- Fermi surfaces are large, metallic, and low-dimensional.

## Abstract

The orthorhombic uranium dichalcogenide UTe$_2$ displays superconductivity below 1.7 K, with the anomalous feature of retaining 50$\%$ of normal state (ungapped) carriers, according to heat capacity data from two groups. Incoherent transport that crosses over from above 50 K toward a low temperature, Kondo lattice Fermi liquid regime indicates strong magnetic fluctuations and the need to include correlation effects in theoretical modeling. We report density functional theory plus Hubbard U (DFT+U) results for UTe$_2$ to provide a platform for modeling its unusual behavior, focusing on ferromagnetic (FM, time reversal breaking) long range correlations along the ${\hat a}$ axis as established by magnetization measurements and confirmed by our calculations. States near the Fermi level are dominated by the $j=\frac{5}{2}$ configuration, with the $j_z=\pm\frac{1}{2}$ sectors being effectively degenerate and half-filled. Unlike the small-gap insulating nonmagnetic electronic spectrum, the FM Fermi surfaces are large (strongly metallic) and display low dimensional features, reminiscent of the FM superconductor UGe$_2$.