Strain-Driven Zero-Field Near-10 nm Skyrmions in Two-Dimensional van der Waals Heterostructures

TL;DR

This paper predicts that applying compressive strain to 2D van der Waals heterostructures can stabilize near-10 nm skyrmions at low temperatures, with potential for spintronic applications.

Contribution

It demonstrates, through first-principles and atomistic simulations, that strain can induce stable, small skyrmions in 2D heterostructures, a significant advancement over previous larger skyrmions.

Findings

Strain stabilizes 10 nm skyrmions in 2D heterostructures.

Skyrmions can be stable for hours at 20 K.

Dzyaloshinskii-Moriya interaction and anisotropy are highly tunable by strain.

Abstract

Magnetic skyrmions $-$ localized chiral spin structures $-$ show great promise for spintronic applications. The recent discovery of two-dimensional (2D) magnetic materials opened new opportunities for exploring such topological spin structures in atomically thin van der Waals (vdW) materials. Despite recent progress in stabilizing metastable skyrmions in 2D magnets, their diameters are still beyond 100~nm and their lifetime, which is essential for applications, has not been explored yet. Here, using first-principles calculations and atomistic spin simulations, we predict that compressive mechanical strain leads to stabilizing zero-field skyrmions with diameters close to 10 nm in a Fe$_3$GeTe$_2$/germanene vdW heterostructure. The origin of these unique skyrmions is attributed to the high tunability of Dzyaloshinskii-Moriya interaction and magnetocrystalline anisotropy energy by strain, an effect which is shown to be general for Fe$_3$GeTe$_2$ heterostructures with buckled substrates. Based on our first-principles parameters for the magnetic interactions, we calculate the energy barriers protecting skyrmions against annihilation and their lifetimes using transition-state theory. We show that nanoscale skyrmions in strained Fe$_3$GeTe$_2$/germanene can be stable for hours at temperatures up to 20 K.