Edge currents shunt the insulating bulk in gapped graphene.

Area of Science:

• Condensed matter physics
• Materials science
• Quantum electronics

Background:

• Graphene bilayers can exhibit energy gaps up to 0.2 eV.
• These gaps typically do not result in a highly insulating state at low temperatures.
• Charge inhomogeneity is the common explanation for this phenomenon.

Purpose of the Study:

• Investigate the reasons behind the lack of a highly insulating state in gapped graphene.
• Examine proximity-induced superconductivity in gapped graphene.
• Compare normal-state measurements in different geometries.

Main Methods:

• Investigated proximity-induced superconductivity in gapped graphene.
• Performed normal-state measurements using Hall bar and Corbino geometries.
• Analyzed supercurrent propagation and resistivity at the charge neutrality point.

Main Results:

• Supercurrent in gapped graphene propagates along narrow edge channels.
• Resistivity increases exponentially with gap size in the edgeless Corbino geometry.
• Resistivity saturates at a few resistance quanta in the Hall bar geometry.

Conclusions:

• Metallic-like edge conductance in gapped graphene is attributed to the nontrivial topology of gapped Dirac spectra.
• The study provides new insights into the electronic properties of gapped graphene.
• Findings challenge conventional explanations based solely on charge inhomogeneity.