Gate controlled valley polarizer in bilayer graphene.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Bilayer graphene exhibits unique electronic properties, including valley-dependent transport.
• Gate-controlled valley polarizers are crucial for spintronics and valleytronics applications.
• Previous devices required magnetic fields, limiting practical applications.

Purpose of the Study:

• To enhance the performance of a gate-controlled valley polarizer in bilayer graphene.
• To achieve high-contrast valley polarization without external magnetic fields.
• To enable further research on valley-polarized electrons in zero magnetic field.

Main Methods:

• Optimized device geometry and stacking methods for bilayer graphene.
• Electrical transport measurements to characterize device performance.
• Utilized gate voltages to induce and control valley polarization.

Main Results:

• Achieved up to two orders of magnitude difference in conductance between valley-polarized and gapped states.
• Demonstrated a valley-polarized state with conductance close to 4e^2/h.
• Showcased contrast in a subsequent valley analyzer, confirming effective valley polarization.

Conclusions:

• The optimized device significantly improves gate-controlled valley polarization in bilayer graphene.
• High-performance valley polarization is achievable in zero magnetic field.
• This work facilitates future investigations into valleytronics and related quantum phenomena.