# Insulator-metal transition and topological superconductivity in UTe2 from a first-principles calculation

## TL;DR

This paper uses first-principles calculations with electron correlation effects to reveal the insulator-metal transition and topological superconductivity in UTe$_2$, predicting its gap structure and low-energy excitations.

## Contribution

It introduces a GGA+U approach to accurately model UTe$_2$, demonstrating topological superconductivity and analyzing its gap node symmetry and topology.

## Key findings

- Insulator-metal transition driven by Coulomb interaction.
- Topological superconductivity at intermediate U values.
- Predicted gap structure and low-energy excitations.

## Abstract

We theoretically study superconductivity in UTe$_2$, which is a recently-discovered strong candidate for an odd-parity spin-triplet superconductor. Theoretical studies for this compound faced difficulty because first-principles calculations predict an insulating electronic state, incompatible with superconducting instability. To overcome this problem, we take into account electron correlation effects by a GGA$+U$ method and show the insulator-metal transition by Coulomb interaction. Using Fermi surfaces obtained as a function of $U$, we clarify topological properties of possible superconducting states. Fermi surface formulas for the three-dimensional winding number and three two-dimensional $\mathbb{Z}_2$ numbers indicate topological superconductivity at an intermediate $U$ for all the odd-parity pairing symmetry in the $Immm$ space group. Symmetry and topology of superconducting gap node are analyzed and the gap structure of UTe$_2$ is predicted. Topologically protected low-energy excitations are highlighted, and experiments by bulk and surface probes are proposed to link Fermi surfaces and pairing symmetry. Based on the results, we also discuss multiple superconducting phases under magnetic fields, which were implied by recent experiments.