Graphene bilayer and trilayer Moir\'e lattice with Rashba spin-orbit coupling

TL;DR

This paper investigates the effects of Rashba spin-orbit coupling on twisted bilayer and trilayer graphene, revealing sharp features in spin observables at magic angles that enhance the potential for precise spintronic applications.

Contribution

It introduces the study of Moiré spintronics in twisted graphene with Rashba coupling, highlighting sharp spin-related phenomena at magic angles and differences from untwisted graphene.

Findings

Sharp peaks in spin polarization and currents at magic angles

Sign reversals of spin observables at magic angles

Persistence of polarization patterns in the chiral limit

Abstract

We consider twisted bilayer and trilayer graphene in the presence of Rashba spin-orbit coupling and explore the physics of Moir\'e spintronics. The electronic charge density has a sharp step right at the magic angles $\theta_m$. As a result, local spin observables (polarization and equilibrium spin currents) have sharp peaks (of width about a small fraction of 1$^\circ$) as a function of the twist angle $\theta$, and abrupt sign reversals at $\theta_m$. Thereby, the magic angle can be determined in an unprecedented accuracy. In the first chiral limit, the spin currents vanish, but the peculiar pattern of the polarization at $\theta_m$ persists. Major differences result in spintronics of twisted bilayer graphene at magic angles as compared with the spintronics of single and/or {\it un-twisted} bilayer graphene. Thus, in addition to the numerous spectacular physical phenomena already reported in twisted bilayer graphene at magic angles, new phenomena also occur in twistronic spintronics.