# Colossal infrared and terahertz magneto-optical activity in a two-dimensional Dirac material

## TL;DR

This study demonstrates exceptionally strong infrared and terahertz magneto-optical effects in high-mobility monolayer graphene, revealing new potential for magnetic tuning in 2D Dirac materials for optoelectronic applications.

## Contribution

The paper reports the first observation of record-high magneto-optical activity in high-quality graphene, surpassing previous measurements and highlighting its potential for long-wavelength optoelectronics.

## Key findings

- Maximum 50% light absorption in IR and THz ranges
- 100% magnetic circular dichroism observed
- Record high Faraday rotation achieved

## Abstract

When two-dimensional electron gases (2DEGs) are exposed to magnetic field, they resonantly absorb electromagnetic radiation via electronic transitions between Landau levels (LLs). In 2DEGs with a Dirac spectrum, such as graphene, theory predicts an exceptionally high infrared magneto-absorption, even at zero doping. However, the measured LL magneto-optical effects in graphene have been much weaker than expected because of imperfections in the samples available so far for such experiments. Here we measure magneto-transmission and Faraday rotation in high-mobility encapsulated monolayer graphene using a custom designed setup for magneto-infrared microspectroscopy. Our results show a strongly enhanced magneto-optical activity in the infrared and terahertz ranges characterized by a maximum allowed (50%) absorption of light, a 100% magnetic circular dichroism as well as a record high Faraday rotation. Considering that sizeable effects have been already observed at routinely achievable magnetic fields, our findings demonstrate a new potential of magnetic tuning in 2D Dirac materials for long-wavelength optoelectronics and plasmonics.