Dynamic Bandstructure and Capacitance Effects in Scanning Tunneling Spectroscopy of Bilayer Graphene

TL;DR

This paper presents a self-consistent model for STS of bilayer graphene, revealing how the STS tip influences the bandstructure and Fermi level, affecting the measured density of states and revealing layer asymmetries.

Contribution

The authors develop a comprehensive model that accounts for the tip-induced effects in STS measurements of bilayer graphene, providing new insights into the interpretation of experimental data.

Findings

STS tip acts as a top gate altering bandstructure and Fermi level

Bandgap appears larger in STS than in actual LDOS

Asymmetric charge distribution effects are observable via STS

Abstract

We develop a fully self-consistent model to describe scanning tunneling spectroscopy (STS) measurements of Bernal-stacked bilayer graphene (BLG), and we compare the results of our model to experimental measurements. Our results show that the STS tip acts as a top gate that changes the BLG bandstructure and Fermi level, while simultaneously probing the voltage-dependent tunneling density of states (TDOS). These effects lead to differences between the TDOS and the local density of states (LDOS); in particular, we show that the bandgap of the BLG appears larger than expected in STS measurements, that an additional feature appears in the TDOS that is an artifact of the STS measurement, and that asymmetric charge distribution effects between the individual graphene layers are observable via STS.