Quasi-two-dimensional Fermi surfaces and unitary spin-triplet pairing in the heavy fermion superconductor UTe$_2$

TL;DR

This paper combines first-principles and strongly-correlated calculations to elucidate the magnetic, electronic, and superconducting properties of UTe$_2$, revealing a unitary spin-triplet pairing state with specific Fermi surface features.

Contribution

It presents a novel theoretical scenario explaining UTe$_2$'s properties, including a unitary spin-triplet pairing and its electronic structure, supported by first-principles calculations.

Findings

Identification of quasi-two-dimensional Fermi surfaces with electron and hole cylinders.

Proposal of a unitary spin-triplet pairing state with point nodes.

Explanation of magnetic frustration and anisotropy in UTe$_2$.

Abstract

We report first-principles and strongly-correlated calculations of the newly-discovered heavy fermion superconductor UTe$_2$. Our analyses reveal three key aspects of its magnetic, electronic, and superconducting properties, that include: (1) a two-leg ladder-type structure with strong magnetic frustrations, which might explain the absence of long-range orders and the observed magnetic and transport anisotropy; (2) quasi-two-dimensional Fermi surfaces composed of two separate electron and hole cylinders with similar nesting properties as in UGe$_2$, which may potentially promote magnetic fluctuations and help to enhance the spin-triplet pairing; (3) a unitary spin-triplet pairing state of strong spin-orbit coupling at zero field, with point nodes presumably on the heavier hole Fermi surface along the $k_x$-direction, in contrast to the previous belief of non-unitary pairing. Our proposed scenario is in excellent agreement with latest thermal conductivity measurement and provides a basis for understanding the peculiar magnetic and superconducting properties of UTe$_2$.