Gate-controlled topological conducting channels in bilayer graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Exploiting electronic degrees of freedom beyond charge and spin is crucial for next-generation electronics.
• Inequivalent valleys (K and K') in 2D hexagonal lattices offer a new avenue for electronic manipulation.
• Broken inversion symmetry in materials like bilayer graphene (BLG) leads to valley-dependent Berry curvature.

Purpose of the Study:

• To experimentally realize and investigate topologically protected 1D metallic states in bilayer graphene.
• To demonstrate the potential for gate-controlled valleytronic operations.
• To explore ballistic transport properties of these engineered metallic states.

Main Methods:

• Fabrication of a dual-split-gate structure in bilayer graphene.
• Electrical transport measurements to detect and characterize 1D metallic states.
• Application of perpendicular magnetic fields to study backscattering suppression.

Main Results:

• Evidence of predicted metallic states with valley-dependent properties was observed.
• These states exhibited a mean free path up to several hundred nanometers without a magnetic field.
• A 400 nm junction showed conductance near the ballistic limit (4e²/h) at 8 T due to magnetic field-induced backscattering suppression.

Conclusions:

• The study confirms the existence of gate-controlled ballistic valley transport in BLG.
• This work provides a scalable platform for realizing valleytronic devices.
• It paves the way for future applications in atomically thin valleytronics.