Zigzag graphene nanoribbons without inversion symmetry

TL;DR

This paper investigates how inversion symmetry breaking and electron interactions in graphene zigzag nanoribbons lead to half-metallicity, noncollinear magnetism, and topological transitions affecting electrical conductance.

Contribution

It demonstrates the emergence of half-metallic and noncollinear magnetic phases in symmetry-broken graphene nanoribbons, revealing a topological transition between distinct half-metallic states.

Findings

Half-metallicity occurs at intermediate inversion symmetry breaking potential.

Doping influences the phase diagram, affecting magnetic and conductive states.

A topological transition between two half-metallic states changes conductance from 2e^2/h to e^2/h.

Abstract

Graphene on a substrate will suffer an inversion-symmetry-breaking (ISB) lattice potential. Taking electron-electron interaction into account, we study in this paper the possibility of half-metallicity and noncollinear (NC) magnetic phase for graphene zigzag nanoribbons without inversion symmetry. At half-filling it is found that half-metallic(HM) state can be achieved at an intermediate value of the ISB potential due to its competition with the electron-electron interaction. Away from half-filling, the phase diagrams of doping versus ISB potential for different ribbon width are given, where the regimes for the HM states and NC magnetic state are clearly indicated and discussed. For ribbons with perfect edges, we predict a topological transition between two HM states with different magnetic structures, which is accompanied by an abrupt transition of electrical conductance along the ribbon from $2e^2/h$ to $e^2/h$.