Quantum transport through a graphene nanoribbon-superconductor junction

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Transport

Background:

• Graphene nanoribbons (GNRs) exhibit unique electronic properties due to quantum confinement.
• Superconductor-graphene junctions are promising for novel electronic devices.
• Understanding electron transport in these systems is crucial for device applications.

Purpose of the Study:

• Investigate electron transport through graphene nanoribbon-superconductor junctions.
• Analyze the impact of magnetic fields and disorder on transport properties.
• Examine both zigzag and armchair edge GNRs.

Main Methods:

• Utilized the tight-binding model for electronic structure calculations.
• Employed the non-equilibrium Green's function method for transport analysis.
• Derived expressions for current, conductance, and tunneling coefficients.

Main Results:

• Linear conductance increases with on-site energy in clean systems.
• Plateau structures in linear conductance emerge with magnetic fields and moderate disorder for both edge types.
• Plateau values scale with ribbon width, saturating at |ν|e²/h, with Andreev reflection coefficient stabilizing at 0.5.

Conclusions:

• Graphene nanoribbon-superconductor junctions exhibit tunable transport properties.
• Magnetic fields and disorder induce robust conductance plateaus.
• The Andreev reflection coefficient shows remarkable stability under specific conditions.