Spontaneous antiferromagnetic order and strain effect on electronic properties of ${\alpha}$-graphyne

TL;DR

This study reveals that $ ext{ extalpha}$-graphyne naturally exhibits antiferromagnetic order with a significant band gap, and that strain can enhance this magnetic and electronic stability, highlighting the importance of electronic correlations.

Contribution

It demonstrates the spontaneous antiferromagnetic order in $ ext{ extalpha}$-graphyne and how strain influences its electronic properties, using ab initio calculations and Hubbard model analysis.

Findings

Spontaneous antiferromagnetic order with a ~0.5 eV band gap in $ ext{ extalpha}$-graphyne.

Bi-axial tensile strain enhances AF stability, spin moment, and energy gap.

Robust AF phase against moderate carrier doping up to 1.7×10^{14} electrons/cm^2.

Abstract

Using hybrid exchange-correlation functional in ab initio density functional theory calculations, we study magnetic properties and strain effect on the electronic properties of $\alpha$-graphyne monolayer. We find that a spontaneous antiferromagnetic (AF) ordering occurs with energy band gap ($\sim$ 0.5 eV) in the equilibrated $\alpha$-graphyne. Bi-axial tensile strain enhances the stability of AF state as well as the staggered spin moment and value of the energy gap. The antiferromagnetic semiconductor phase is quite robust against moderate carrier filling with threshold carrier density up to 1.7$\times$10$^{14}$ electrons/cm$^2$ to destabilize the phase. The spontaneous AF ordering and strain effect in $\alpha$-graphyne can be well described by the framework of the Hubbard model. Our study shows that it is essential to consider the electronic correlation effect properly in $\alpha$-graphyne and may pave an avenue for exploring magnetic ordering in other carbon allotropes with mixed hybridization of s and p orbitals.