Noncollinear exchange interaction in transition metal dichalcogenide edges

TL;DR

This paper investigates the edge-mediated exchange interactions between magnetic impurities in transition-metal dichalcogenides, highlighting the role of strong spin-orbit coupling and the potential for tuning magnetic configurations via doping or gating.

Contribution

It introduces a three-orbital tight-binding model to analyze noncollinear exchange interactions at edges, emphasizing the significance of Dzyaloshinskii-Moriya interactions in these materials.

Findings

Edge states exhibit 1/r decay of exchange interactions.

Strong spin-orbit coupling induces sizable non-collinear Dzyaloshinskii-Moriya interactions.

Fermi energy modulation can control impurity magnetic configurations.

Abstract

We study the Ruderman-Kittel-Kasuya-Yosida effective exchange interaction between magnetic impurities embedded on the edges of transition-metal dichalcogenide flakes, using a three-orbital tight-binding model. Electronic states lying midgap of the bulk structure have strong one-dimensional (1D) character, localized on the edges of the crystallite. This results in exchange interactions with $1/r$ (or slower) decay with distance $r$, similar to other 1D systems. Most interestingly, however, the strong spin-orbit interaction in these materials results in sizable non-collinear Dzyaloshinskii-Moriya interactions between impurities, comparable in size to the usual Ising and in-plane components. Varying the relevant Fermi energy by doping or gating may allow one to modulate the effective interactions, controlling the possible helical ground state configurations of multiple impurities.