Generating Two-dimensional Ferromagnetic Charge Density Waves via External Fields

TL;DR

This paper proposes a method to generate two-dimensional ferromagnetic charge density waves in monolayer VSe2 using external strain, revealing new magnetic phases and electronic properties driven by spin-dependent forces.

Contribution

The study demonstrates a feasible approach to induce 2D ferromagnetic CDWs via external fields, supported by first-principles calculations, and explores their unique magnetic and electronic characteristics.

Findings

Two novel ferromagnetic CDWs can be generated under tensile strain.

Distinct magnetic phases exhibit flat bands or Dirac cones.

The approach enables manipulation of charge-spin correlation effects.

Abstract

Two-dimensional (2D) ferromagnetic charge density wave (CDW), an exotic quantum state for exploring the intertwining effect between correlated charge and spin orders in 2D limit, has not been discovered in the experiments yet. Here, we propose a feasible strategy to realize 2D ferromagnetic CDWs under external fields, which is demonstrated in monolayer VSe$_2$ using first-principles calculations. Under external tensile strain, two novel ferromagnetic CDWs ($\sqrt{3}$$\times$$\sqrt{3}$ and 2$\times2\sqrt{3}$ CDWs) can be generated, accompanied by distinguishable lattice reconstructions of magnetic V atoms. Remarkably, because the driving forces for generating these two ferromagnetic CDWs are strongly spin-dependent, fundamentally different from that in conventional CDWs, the $\sqrt{3}$$\times$$\sqrt{3}$ and 2$\times2\sqrt{3}$ CDWs can exhibit two dramatically different half-metallic phases under a large strain range, along with either a flat band or a Dirac cone around Fermi level. Our proposed strategy and material demonstration may open a door to generate and manipulate correlation effect between collective charge and spin orders via external fields.