Probing the bright exciton state in twisted bilayer graphene via resonant Raman scattering
arXiv:2106.13278 · doi:10.1063/5.0049458
Abstract
The band structure of bilayer graphene is tunable by introducing a relative twist angle between the two layers, unlocking exotic phases, such as superconductor and Mott insulator, and providing a fertile ground for new physics. At intermediate twist angles around 10°, highly degenerate electronic transitions hybridize to form excitonic states, a quite unusual phenomenon in a metallic system. We probe the bright exciton mode using resonant Raman scattering measurements to track the evolution of the intensity of the graphene Raman G peak, corresponding to the E2g phonon. By cryogenically cooling the sample, we are able to resolve both the incoming and outgoing resonance in the G peak intensity evolution as a function of excitation energy, a prominent manifestation of the bright exciton serving as the intermediate state in the Raman process. For a sample with twist angle 8.6°, we report a weakly temperature dependent resonance broadening 0.07 eV. In the limit of small inhomogeneous broadening, the observed places a lower bound for the bright exciton scattering lifetime at 10 fs in the presence of charges and excitons excited by the light pulse for Raman measurement, limited by the rapid exciton-exciton and exciton-charge scattering in graphene.
arXiv comment9 pages, 3 figures, 2 supplemental figures, appearing in Applied Physics Letters
References in corpus (29)
- The Raman Fingerprint of Graphene
- Magic-angle graphene superlattices: a new platform for unconventional superconductivity
- Correlated Insulator Behaviour at Half-Filling in Magic Angle Graphene Superlattices
- Moire bands in twisted double-layer graphene
- Tuning superconductivity in twisted bilayer graphene
- Making graphene visible
- Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene
- Electrical Control of Two-Dimensional Neutral and Charged Excitons in a Monolayer Semiconductor
- Observation of Van Hove singularities in twisted graphene layers
- Electric Field Effect Tuning of Electron-Phonon Coupling in Graphene
- Origin of Magic Angles in Twisted Bilayer Graphene
- Excitonic Effects on the Optical Response of Graphene and Bilayer Graphene
- Raman spectroscopy study of rotated double-layer graphene: Misorientation-angle dependence of electronic structure
- Optical Absorption in Twisted Bilayer Graphene
- Electronic properties of graphene-based bilayer systems
- Mapping the twist angle and unconventional Landau levels in magic angle graphene
- A mechanism for anomalous Hall ferromagnetism in twisted bilayer graphene
- The Interlayer Shear Modes in Twisted Multi-layer Graphenes: Interlayer coupling, Davydov Splitting and Intensity Resonance
- Twisted Bilayer Graphene Aligned with Hexagonal Boron Nitride: Anomalous Hall Effect and a Lattice Model
- Observation of Anomalous Phonon Softening in Bilayer Graphene
- Coulomb-bound four- and five-particle valleytronic states in an atomically-thin semiconductor
- Observation of Low Energy Raman Modes in Twisted Bilayer Graphene
- Van Hove Singularities and Excitonic Effects in the Optical Conductivity of Twisted Bilayer Graphene
- Tuning many-body interactions in graphene: The effects of doping on excitons and carrier lifetimes
- θ-Tunable Photoluminescence from Interlayer Excitons in Twisted Bilayer Graphene
- Strongly bound excitons dominate electronic relaxation in resonantly excited twisted bilayer graphene
- Superior valley polarization and coherence of 2s excitons in monolayer WSe2
- Optical properties of the Hofstadter butterfly in the Moiré superlattice
- New Mechanism for Strongly Bound Excitons in Gapless Two-Dimensional Structures