Anomalous Absorption Line in the Magneto-Optical Response of Graphene

TL;DR

This paper investigates the infrared absorption spectrum of graphene under magnetic fields, revealing how the anomalous Landau level influences absorption lines and how a gap causes line splitting, providing insights into graphene's electronic structure.

Contribution

It demonstrates how the absorption line pattern encodes the presence of the anomalous Landau level and how a gap affects the spectral features in graphene.

Findings

The first absorption line related to the lowest Landau level appears fully or not at all.

All other absorption lines disappear in two steps as the chemical potential varies.

A gap causes the main absorption line to split into two when the chemical potential exceeds the gap.

Abstract

The intensity as well as position in energy of the absorption lines in the infrared conductivity of graphene, both exhibit features that are directly related to the Dirac nature of its quasiparticles. We show that the evolution of the pattern of absorption lines as the chemical potential is varied encodes the information about the presence of the anomalous lowest Landau level. The first absorption line related to this level always appears with full intensity or is entirely missing, while all other lines disappear in two steps. We demonstrate that if a gap develops, the main absorption line splits into two provided that the chemical potential is greater than or equal to the gap.