Resonant Excitation of Graphene K-Phonon and Intra-Landau-Level Excitons in Magneto-Optical Spectroscopy

TL;DR

This study uses high-field magneto-optical spectroscopy on multilayer graphene to observe resonant interactions between Landau levels, phonons, and excitons, supported by a developed theoretical model.

Contribution

The paper introduces a theory explaining the resonance phenomena involving K-phonons and intra-Landau-level excitons in graphene, matching experimental observations.

Findings

Spectral feature changes at resonance conditions

Broadening of cyclotron transition peaks

Quantitative agreement between theory and experiment

Abstract

Precise infrared magnetotransmission experiments have been performed in magnetic fields up to 32 T on a series of multilayer epitaxial graphene samples. We observe changes in the spectral features and broadening of the main cyclotron transition when the incoming photon energy is in resonance with the lowest Landau level separation and the energy of a K point optical phonon. We have developed a theory that explains and quantitatively reproduces the frequency and magnetic field dependence of the phenomenon as the absorption of a photon together with the simultaneous creation of an intervalley, intra-Landau-level exciton, and a K phonon.