Reassessing Graphene Absorption and Emission Spectroscopy
arXiv:1704.07500 · doi:10.1021/acs.nanolett.7b02500
Abstract
We present a new paradigm for understanding optical absorption and hot electron dynamics experiments in graphene. Our analysis pivots on assigning proper importance to phonon assisted indirect processes and bleaching of direct processes. We show indirect processes figure in the excess absorption in the UV region. Experiments which were thought to indicate ultrafast relaxation of electrons and holes, reaching a thermal distribution from an extremely non-thermal one in under 5-10 fs, instead are explained by the nascent electron and hole distributions produced by indirect transitions. These need no relaxation or ad-hoc energy removal to agree with the observed emission spectra and fast pulsed absorption spectra. The fast emission following pulsed absorption is dominated by phonon assisted processes, which vastly outnumber direct ones and are always available, connecting any electron with any hole any time. Calculations are given, including explicitly calculating the magnitude of indirect processes, supporting these views.
References in corpus (15)
- Electric Field Effect in Atomically Thin Carbon Films
- Universal Dynamic Conductivity and Quantized Visible Opacity of Suspended Graphene
- 30 inch Roll-Based Production of High-Quality Graphene Films for Flexible Transparent Electrodes
- Graphene Photonics and Optoelectronics
- Measurement of the Optical Conductivity of Graphene
- Graphene field effect transistors as room-temperature Terahertz detectors
- Switching teraherz waves with gate-controlled active graphene metamaterials
- Microcavity-integrated graphene photodetector
- Ultrafast collinear scattering and carrier multiplication in graphene
- Ultrafast Photoluminescence from Graphene
- Snapshots of non-equilibrium Dirac carrier distributions in graphene
- Seeing many-body effects in single- and few-layer graphene: Observation of two-dimensional saddle-point excitons
- Terahertz and Infrared Spectroscopy of Gated Large-Area Graphene
- Femtosecond carrier dynamics and saturable absorption in graphene suspensions
- Interacting Electrons in Graphene: Fermi Velocity Renormalization and Optical Response