Quantized Landau level spectrum and its density dependence

TL;DR

This study uses scanning tunneling microscopy to investigate how Landau levels in graphene depend on carrier density, revealing abrupt Fermi level jumps and interaction effects on Landau level spacing.

Contribution

It provides experimental evidence of density-dependent Landau level spectra and interaction-induced renormalization in graphene.

Findings

Abrupt Fermi level jumps after Landau level filling

Increase in Landau level spacing at low doping

Observation of interaction effects on Dirac cone

Abstract

Scanning tunneling microscopy and spectroscopy in magnetic field was used to study Landau quantization in graphene and its dependence on charge carrier density. Measurements were carried out on exfoliated graphene samples deposited on a chlorinated SiO2 thermal oxide which allowed observing the Landau level sequences characteristic of single layer graphene while tuning the density through the Si backgate. Upon changing the carrier density we find abrupt jumps in the Fermi level after each Landau level is filled. Moreover, the Landau level spacing shows a marked increase at low doping levels, consistent with an interaction-induced renormalization of the Dirac cone.