Theory of Bernstein Modes in Graphene

TL;DR

This paper provides a theoretical framework for understanding Bernstein modes in graphene, highlighting their origin from coupling between collective excitations and inter-Landau-level transitions, with implications for experimental measurements.

Contribution

It introduces a phenomenological model accurately describing Bernstein modes in graphene under magnetic fields, linking them to Coulomb interactions and experimental observables.

Findings

Bernstein modes arise from coupling between upper-hybrid and inter-Landau-level excitations.

Avoided level crossings in spectral functions indicate these modes.

Potential for high-precision measurements of the upper-hybrid mode.

Abstract

We present a theoretical description of Bernstein modes that arise as a result of the coupling between plasmon-like collective excitations (upper-hybrid mode) and inter-Landau-level excitations, in graphene in a perpendicular magnetic field. These modes, which are apparent as avoided level crossings in the spectral function obtained in the random-phase approximation, are described to great accuracy in a phenomenological model. Bernstein modes, which may be measured in inelastic light-scattering experiments or in photo-conductivity spectroscopy, are a manifestation of the Coulomb interaction between the electrons and may be used for a high-precision measurement of the upper-hybrid mode at small non-zero wave vectors.