Layer-selective half-metallicity in bilayer graphene nanoribbons

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Half-metallicity in zigzag-edge graphene nanoribbons (ZGNRs) and hydrogenated carbon nanotubes (CNTs) enables fully spin-polarized currents for carbon-based spintronics.
• Edge-localized electron states under an electric field are responsible for half-metallicity in these systems.
• A critical electric field (Dc) is required, which has been a challenge in previous ZGNR studies.

Purpose of the Study:

• To investigate the effect of electric fields on the half-metallicity of bilayer zigzag-edge graphene nanoribbons (biZGNRs).
• To explore the potential of biZGNRs for spintronic applications by controlling spin-polarized current paths.

Main Methods:

• Development of a simple model based on electrostatic potential difference between the edges of biZGNRs.
• Density Functional Theory (DFT) calculations to confirm theoretical predictions.

Main Results:

• A specific electric field direction significantly reduces Dc in narrow biZGNRs.
• For wide biZGNRs (> ~2.0 nm), only one layer exhibits half-metallicity, while the other becomes insulating.
• The electric field can induce switching of the spin-polarized current path.

Conclusions:

• Wide biZGNRs offer a controllable platform for spintronics by selectively activating half-metallicity in one layer.
• Electric field-induced switching of spin-polarized currents in biZGNRs presents a novel pathway for graphene-based spintronics.