Visualizing Atomic-Scale Negative Differential Resistance in Bilayer Graphene

TL;DR

This study reveals atomic-scale negative differential resistance in bilayer graphene caused by van Hove singularities, with local variations and defect influences, advancing understanding for graphene-based tunneling devices.

Contribution

It provides the first atomic-scale visualization and explanation of NDR in bilayer graphene, linking electronic structure to tunneling behavior.

Findings

NDR observed at the Dirac energy in bilayer graphene

NDR varies within the unit cell and is affected by defects

Van Hove singularities explain the origin of NDR

Abstract

We investigate the atomic-scale tunneling characteristics of bilayer graphene on silicon carbide using the scanning tunneling microscopy. The high-resolution tunneling spectroscopy reveals an unexpected negative differential resistance (NDR) at the Dirac energy, which spatially varies within the single unit cell of bilayer graphene. The origin of NDR is explained by two near-gap van Hove singularities emerging in the electronic spectrum of bilayer graphene under a transverse electric field, which are strongly localized on two sublattices in different layers. Furthermore, defects near the tunneling contact are found to strongly impact on NDR through the electron interference. Our result provides an atomic-level understanding of quantum tunneling in bilayer graphene, and constitutes a useful step towards graphene-based tunneling devices.