Disorder-perturbed Landau levels in high electron mobility epitaxial graphene

TL;DR

This study investigates how localized defects in epitaxial graphene alter Landau levels, revealing impurity-related states through magneto-spectroscopy and theoretical modeling, with implications for understanding defect effects in graphene.

Contribution

It demonstrates the impact of short-range impurities on Landau levels in epitaxial graphene and combines experimental and theoretical approaches to characterize these effects.

Findings

Additional impurity-related transitions observed in magneto-spectroscopy.

Annealing reduces the intensity of impurity-related transitions.

Theoretical calculations match experimental absorption spectra.

Abstract

We show that the Landau levels in epitaxial graphene in presence of localized defects are significantly modified compared to those of an ideal system. We report on magneto-spectroscopy experiments performed on high quality samples. Besides typical interband magneto-optical transitions, we clearly observe additional transitions that involve perturbed states associated to short-range impurities such as vacancies. Their intensity is found to decrease with an annealing process and a partial self-healing over time is observed. Calculations of the perturbed Landau levels by using a delta-like potential show electronic states both between and at the same energies of the Laudau levels of ideal graphene. The calculated absorption spectra involving all perturbed and unperturbed states are in very good agreement with the experiments.