Electrical spin manipulation in graphene nanostructures

TL;DR

This paper introduces a method for electrically controlling spin states in graphene nanostructures with in-gap zero modes, enabling spin resonance techniques in systems with long relaxation times.

Contribution

It demonstrates a mechanism for electrical singlet-triplet spin transitions in graphene nanostructures via Rashba spin-orbit coupling and external field modulation.

Findings

Electrical control of spin states in graphene nanostructures.

Electric field modulation enables spin resonance.

Long spin relaxation times are achievable.

Abstract

We propose a mechanism to drive singlet-triplet spin transitions electrically, in a wide class of graphene nanostructures that present pairs of in-gap zero modes, localized at opposite sublattices. Examples are rectangular nanographenes with short zigzag edges, armchair ribbon heterojunctions with topological in-gap states and graphene islands with sp$^3$ functionalization. The interplay between the hybridization of zero modes and Coulomb repulsion leads to symmetric exchange interaction that favors a singlet ground state. Application of an off-plane electric field to the graphene nanostructure generates an additional Rashba spin-orbit coupling, which results in antisymmetric exchange interaction that mixes $S=0$ and $S=1$ manifolds. We show that modulation in time of either the off-plane electric field or the applied magnetic field permits to perform electrically driven spin resonance in a system with very long spin relaxation times.