Electronic structure of UTe$_2$ under pressure

TL;DR

This study investigates how pressure affects the electronic structure of UTe$_2$, revealing that certain electronic properties are pressure-sensitive, especially with increased f-electron contributions and density of states at the Fermi level under compression.

Contribution

The paper provides the first detailed analysis of UTe$_2$'s electronic structure under pressure using density functional theory, highlighting the role of Coulomb interactions and stress direction.

Findings

Fermi surfaces are insensitive to pressure without f-electron involvement.

Significant pressure dependence observed in f-electron contributions at the Fermi level.

Density of states increases under compressive stress along the [010] axis.

Abstract

A heavy-fermion paramagnet UTe$_2$ has been a strong candidate for a spin-triplet superconductor. Experiments on UTe$_2$ under pressure have been vigorously conducted, and rich phase diagrams have been suggested. Multiple superconducting phases exist in the pressure region of $0 \leq P < 1.8 \mathrm{\;GPa}$, and an antiferromagnetic ordered state is observed in the high pressure region $P > 1.8 \mathrm{\;GPa}$. However, under pressure, the underlying electronic structure in the normal state has not been clarified, although knowledge of electronic structures is essential for studying magnetic and superconducting states. As an indispensable step toward understanding the phase diagram of UTe$_2$, we study the electronic structure under hydrostatic and uniaxial stresses based on the density functional theory with and without employing structural optimization. It is shown that the low-energy band structure and Fermi surfaces are not sensitive to pressure for parameters where itinerant $f$-electrons are not essential. However, we find a significant pressure dependence for a certain Coulomb interaction $U$ of the GGA+$U$ calculation, where the large weight of $f$-electrons appears at the Fermi level. An increase in the density of states at the Fermi level is observed under pressure, which is attributed to compressive stress along the [010] crystallographic axis.