Probing Layer Localization in Twisted Graphene Bilayers via Cyclotron Resonance

Abstract

Electron wavefunctions in twisted bilayer graphene may have a strong single layer character or be intrinsically delocalized between layers, with their nature often determined by how energetically close they are to the Dirac point. In this paper, we demonstrate that in magnetic fields, optical absorption (cyclotron resonance) spectra contain signatures which may be used to distinguish the nature of these wavefunctions at low energies, as well as to locate low energy critical points in the zero-field energy spectrum. Optical absorption for two different configurations -- electric field parallel and perpendicular to the bilayer -- are calculated, which are shown to have different selection rules with respect to which states are connected by the perturbation. Interlayer bias further distinguishes transitions involving states of a single layer nature from those with support in both layers. For doped systems, a sharp increase in intra-Landau level absorption occurs with increasing field as the level passes through the zero-field saddle point energy, where the states change character from single layer to bilayer.

9 pages

References in corpus (11)

• Biased bilayer graphene: semiconductor with a gap tunable by electric field effect
• Infrared spectroscopy of Landau levels in graphene
• Topological confinement in bilayer graphene
• Cyclotron Resonance study of the electron and hole velocity in graphene monolayers
• Cyclotron resonance in bilayer graphene
• Kohn-Luttinger superconductivity in graphene
• Topologically Protected Zero Modes in Twisted Bilayer Graphene
• f-Sum Rule and Unconventional Spectral Weight Transfer in Graphene
• Gapped phase in AA stacked bilayer graphene
• Valley-kink in Bilayer Graphene at $\nu =0$: A Charge Density Signature for Quantum Hall Ferromagnetism
• Resonant Excitation of Graphene K-Phonon and Intra-Landau-Level Excitons in Magneto-Optical Spectroscopy