Giant spin orbit interaction due to rotating magnetic fields in graphene nanoribbons

TL;DR

This paper demonstrates that spatially varying magnetic fields can induce a giant Rashba spin orbit interaction in graphene nanoribbons, enabling helical modes and potential Majorana fermions for spintronic and topological quantum devices.

Contribution

It introduces a method to generate large spin orbit interactions in graphene nanoribbons using non-uniform magnetic fields, facilitating new topological phases.

Findings

Giant Rashba SOI (~10 meV) induced by non-uniform magnetic fields.

Existence of helical modes with high spin polarization.

Potential realization of Majorana fermions in graphene nanoribbons.

Abstract

We theoretically study graphene nanoribbons in the presence of spatially varying magnetic fields produced e.g. by nanomagnets. We show both analytically and numerically that an exceptionally large Rashba spin orbit interaction (SOI) of the order of 10 meV can be produced by the non-uniform magnetic field. As a consequence, helical modes exist in armchair nanoribbons that exhibit nearly perfect spin polarization and are robust against boundary defects. This paves the way to realizing spin filter devices in graphene nanoribbons in the temperature regime of a few Kelvins. If a nanoribbon in the helical regime is in proximity contact to an s-wave superconductor, the nanoribbon can be tuned into a topological phase sustaining Majorana fermions.