Quantum Faraday and Kerr rotations in graphene.

Area of Science:

• Condensed matter physics
• Materials science
• Quantum optics

Background:

• Graphene's unique electronic properties stem from massless Dirac electrons.
• The half-integer quantum Hall effect indicates Dirac cones and a topological Berry's phase.
• Investigating the impact of these Dirac electron features on optical properties is crucial.

Purpose of the Study:

• To explore quantum magneto-optical effects in graphene within the terahertz frequency range.
• To correlate optical responses with the electronic properties of Dirac electrons.

Main Methods:

• Observation of quantum magneto-optical Faraday and Kerr effects in graphene.
• Measurement of rotations in the terahertz frequency range.
• Analysis of quantum Hall plateaus in optical measurements.

Main Results:

• Quantum plateaus were observed in Faraday and Kerr rotations.
• These plateaus precisely align with quantum Hall steps characteristic of Dirac electrons.
• The rotation angle was found to be defined by the fine-structure constant.

Conclusions:

• The study confirms robust quantum Hall plateaus in graphene's optical regime.
• These findings highlight the interplay between electronic and optical properties in graphene.
• Potential applications in graphene-based optoelectronics are suggested.