Broken Symmetries, Zero-Energy Modes, and Quantum Transport in Disordered Graphene: From Supermetallic to Insulating Regimes

TL;DR

This paper investigates how defect-induced zero-energy modes affect charge transport in disordered graphene, revealing regimes from supermetallic to insulating states depending on defect configuration and measurement geometry.

Contribution

It provides a comprehensive analysis of the impact of broken symmetries and zero-energy modes on graphene's transport properties across various disorder regimes.

Findings

Dirac point conductivity can be robust or suppressed depending on defect distribution.

Zero-energy modes can lead to supermetallic or insulating behavior.

Transport regimes include tunneling, evanescent modes, and localization phenomena.

Abstract

The role of defect-induced zero-energy modes on charge transport in graphene is investigated using Kubo and Landauer transport calculations. By tuning the density of random distributions of monovacancies either equally populating the two sublattices or exclusively located on a single sublattice, all conduction regimes are covered from direct tunneling through evanescent modes to mesoscopic transport in bulk disordered graphene. Depending on the transport measurement geometry, defect density, and broken sublattice-symmetry, the Dirac point conductivity is either exceptionally robust against disorder (supermetallic state) or suppressed through a gap opening or by algebraic localization of zero-energy modes, whereas weak localization and the Anderson insulating regime are obtained for higher energies. These findings clarify the contribution of zero-energy modes to transport at the Dirac point, hitherto controversial.