Electronic transport in normal-conductor/graphene/normal-conductor junctions and conditions for insulating behavior at a finite charge-carrier density

TL;DR

This paper studies how NGN junctions can exhibit insulating behavior at finite charge-carrier densities due to mode mismatches, with implications for probing graphene's band structure.

Contribution

It demonstrates that ballistic NGN junctions can be insulating despite finite charge density, highlighting the role of mode support differences and disorder resilience.

Findings

Insulating behavior occurs even at finite charge density due to mode mismatch.

Conductance thresholds can map graphene's band structure in k space.

Moderate disorder does not eliminate the insulating effect.

Abstract

We investigate the conductance of normal-conductor/graphene/normal-conductor (NGN) junctions for arbitrary on-site potentials in the normal and graphitic parts of the system. We find that a ballistic NGN junction can display insulating behavior even when the charge-carrier density in the graphene part is finite. This effect originates in the different k intervals supporting propagating modes in graphene and a normal conductor, and persists for moderate levels of bulk, edge, or interface disorder. The ensuing conductance thresholds could be used as an electronic tool to map out details of the graphene band structure in absolute k space.