Electronic structure of quasi-one-dimensional superconductor K$_2$Cr$_3$As$_3$ from first-principles calculations

TL;DR

This study uses first-principles calculations to analyze the electronic structure of the quasi-one-dimensional superconductor K$_2$Cr$_3$As$_3$, revealing its magnetic tendencies, Fermi surface characteristics, and significant spin-orbit coupling effects.

Contribution

First-principles calculations provide detailed insights into the electronic and magnetic properties of K$_2$Cr$_3$As$_3$, highlighting its proximity to ferromagnetic instability and notable spin-orbit effects.

Findings

K$_2$Cr$_3$As$_3$ is close to ferromagnetic instability.

Three bands cross the Fermi level forming 3D and quasi-1D Fermi surfaces.

Significant spin-orbit coupling splitting (~60 meV) observed.

Abstract

The electronic structure of quasi-one-dimensional superconductor K$_2$Cr$_3$As$_3$ is studied through systematic first-principles calculations. The ground state of K$_2$Cr$_3$As$_3$ is paramagnetic but very close to a ferromagnetic instability. Close to the Fermi level, the Cr-3d$_{z^2}$, d$_{xy}$, and d$_{x^2-y^2}$ orbitals dominate the electronic states, and three bands cross $E_F$ to form one 3D Fermi surface sheet and two quasi-1D sheets. The electron DOS at $E_F$ is less than 1/3 of the experimental value, indicating an intermediate electron renormalization factor around $E_F$. Despite of the relatively small atomic numbers, the antisymmetric spin-orbit coupling splitting is sizable ($\approx$ 60 meV) on the 3D Fermi surface sheet as well as on one of the quasi-1D sheets. Finally, the imaginary part of bare electron susceptibility shows large peaks at $\Gamma$, suggesting the existence of large ferromagnetic spin fluctuation in the compound.