Induced spin-orbit coupling in twisted graphene-TMDC heterobilayers: twistronics meets spintronics

TL;DR

This paper develops an analytical model to predict how twist angles in graphene-TMDC heterobilayers influence induced spin-orbit coupling, with potential implications for twistronics and spintronics applications.

Contribution

It introduces a twist-angle independent tunneling model and provides predictions for spin-orbit coupling variations at different angles.

Findings

Induced spin-orbit coupling peaks near 18 degrees twist angle.

Analytic formula relates spin-orbit coupling to band parameters and tunneling.

Model predictions align with existing DFT calculations at zero twist angle.

Abstract

We propose an interband tunneling picture to explain and predict the interlayer twist angle dependence of the induced spin-orbit coupling in heterostructures of graphene and monolayer transition metal dichalcogenides (TMDCs). We obtain a compact analytic formula for the induced valley Zeeman and Rashba spin-orbit coupling in terms of the TMDC band structure parameters and interlayer tunneling matrix elements. We parametrize the tunneling matrix elements with few parameters, which in our formalism are independent of the twist angle between the layers. We estimate the value of the tunneling parameters from existing DFT calculations at zero twist angle and we use them to predict the induced spin-orbit coupling at non-zero angles. Provided that the energy of the Dirac point of graphene is close to the TMDC conduction band, we expect a sharp increase of the induced spin-orbit coupling around a twist angle of 18 degrees.