Strain engineering and the hidden role of magnetism in monolayer VTe$_2$

TL;DR

This study reveals the hidden antiferromagnetic order in monolayer VTe$_2$ and demonstrates how strain can induce phase transitions, highlighting the interplay between magnetism, charge density waves, and lattice structure.

Contribution

It uncovers the role of antiferromagnetism in monolayer VTe$_2$'s charge density wave states and proposes strain engineering to control its magnetic phases.

Findings

The 4x1 charge density wave is linked to a double-stripe antiferromagnetic order.

The ground state is stabilized by the specific spin order.

Strain induces phase transitions from charge density wave to ferromagnetic order.

Abstract

Two-dimensional transition metal dichalcogenides have attracted great attention recently. Motivated by a recent study of crystalline bulk VTe$_2$, we theoretically investigated the spin-charge-lattice interplay in monolayer VTe$_2$. To understand the controversial experimental reports on several different charge density wave ground states, we paid special attention to the 'hidden' role of antiferromagnetism as its direct experimental detection may be challenging. Our first-principles calculations show that the 4$\times$1 charge density wave and the corresponding lattice deformation are accompanied by the 'double-stripe' antiferromagnetic spin order in its ground state. This phase has not only the lowest total energy but also the dynamical phonon stability, which supports a group of previous experiments. Interestingly enough, this ground state is stabilized only by assuming the underlying spin order. By noticing this intriguing and previously unknown interplay between magnetism and other degrees of freedom, we further suggest a possible strain engineering. By applying tensile strain, monolayer VTe$_2$ exhibits phase transition first to a different charge density wave phase and then eventually to a ferromagnetically ordered one.