Rash spin-orbit interaction in graphene and graphene zigzag nano-ribbons

TL;DR

This paper explores how Rashba spin-orbit interactions affect graphene's electronic structure, revealing band splitting, new Dirac points, and potential for spin-polarized currents, with implications for spintronic applications.

Contribution

It provides an exact solution to a tight-binding model showing Rashba effects on graphene and nanoribbons, including band splitting and spin separation, extending understanding beyond intrinsic spin-orbit interactions.

Findings

Rashba interactions cause band splitting and new Dirac points.

Edge band quasi-degeneracy is lifted, enabling spin separation.

Potential to generate spin-polarized currents in graphene nanoribbons.

Abstract

We investigate the effects of Rashba spin-orbit interactions on the electronic band-structure and corresponding wave-functions of graphene. By exactly solving a tight-binding model Hamiltonian we obtain the expected splitting of the bands -due to the SU(2) spin symmetry breaking- that is accompanied by the appearance of additional Dirac points. These points are originated by valence-conduction band crossings. By introducing a convenient gauge transformation we study a model for zigzag nanoribbons with RSO interactions. We show that the RSO interactions lifts the quasi-degeneracy of the edge band while introducing a state-dependent spin separation in real space. Calculation of the average magnetization perpendicular to the ribbon plane suggest that RSO could be used to produce spin-polarized currents. Comparisons with the intrinsic spin-orbit (I-SO) interaction proposed to exist in graphene are also presented.