Proximity spin-orbit coupling in graphene on alloyed transition metal dichalcogenides

TL;DR

This study investigates how alloying transition metal dichalcogenides affects proximity-induced spin-orbit coupling in graphene, revealing that the SOC and topological states can be tuned by alloy composition.

Contribution

It introduces a comprehensive simulation of alloyed TMDC/graphene heterostructures, showing the SOC behavior depends mainly on alloy composition rather than local defect details.

Findings

SOC strength varies with alloy composition

Effective medium model describes low-energy behavior

Topological states can be tuned via alloy ratio

Abstract

The negligible intrinsic spin-orbit coupling (SOC) in graphene can be enhanced by proximity effects in stacked heterostructures of graphene and transition metal dichalcogenides (TMDCs). The composition of the TMDC layer plays a key role in determining the nature and strength of the resultant SOC induced in the graphene layer. Here, we study the evolution of the proximity-induced SOC as the TMDC layer is deliberately defected. Alloyed ${\rm G/W_{\chi}Mo_{1-\chi}Se_2}$ heterostructures with diverse compositions ($\chi$) and defect distributions are simulated using density functional theory. Comparison with continuum and tight-binding models allows both local and global signatures of the metal-atom alloying to be clarified. Our findings show that, despite some dramatic perturbation of local parameters for individual defects, the low-energy spin and electronic behaviour follow a simple effective medium model which depends only on the composition ratio of the metallic species in the TMDC layer. Furthermore, we demonstrate that the topological state of such alloyed systems can be feasibly tuned by controlling this ratio.