Antiferromagnetic skyrmion crystal in Janus monolayer CrSi2N2As2

TL;DR

This paper predicts and characterizes antiferromagnetic skyrmion crystal phases in a two-dimensional Janus monolayer CrSi2N2As2 using first-principles calculations and simulations, revealing novel phases and control mechanisms.

Contribution

It is the first to identify AF-SkX in a 2D material, demonstrating the role of broken inversion symmetry and spin-orbit coupling in stabilizing these phases.

Findings

Discovery of two distinct AF-SkX phases in the monolayer.

Large Dzyaloshinskii-Moriya interaction due to broken inversion symmetry.

Control of AF-SkX creation and annihilation via ferroelectricity.

Abstract

Antiferromagnetic skyrmion crystal (AF-SkX), a regular array of antiferromagnetic skyrmions, is a fundamental phenomenon in the field of condensed-matter physics. So far, only very few proposals have been made to realize the AF-SkX, and most based on three-dimensional (3D) materials. Herein, using first-principles calculations and Monte-Carlo simulations, we report the identification of AF-SkX in two-dimensional lattice of Janus monolayer CrSi2N2As2. Arising from the broken inversion symmetry and strong spin-orbit coupling, large Dzyaloshinskii-Moriya interaction is obtained in Janus monolayer CrSi2N2As2. This, combined with the geometric frustration of its triangular lattice, gives rise to the skyrmion physics and long-sought AF-SkX in the presence of external magnetic field. More intriguingly, this system presents two different antiferromagnetic skyrmion phases, and such phenomenon is distinct from those reported in 3D systems. Furthermore, by contacting with Sc2CO2, the creation and annihilation of AF-SkX in Janus monolayer CrSi2N2As2 can be achieved through ferroelectricity. These findings greatly enrich the research on antiferromagnetic skyrmions.