Coupling Dynamics between Dirac Electrons and Phonons in Nanocarbons(Research)

Abstract

Using ultrabroadband and ultrashort laser pulses, we investigated coherent phonons in graphene, carbon nanotubes, and graphite. By resolving spectrum of probe pulses, resonant properties due to the strong electron-phonon coupling were clearly observed. In graphene and defected graphite, the double resonant Raman scattering process dominates the coherent phonon generation and detection processes, leading to the excitation of nanoscale coherent optical-phonon wave-packet. In metallic carbon nanotubes, strong resonance appears at the energy below the van-Hove singularity by an amount of the phonon energy, indicating dominant contribution of Stokes stimulated Raman scattering process. The results demonstrate that wavelength-resolved coherent phonon spectroscopy is crucial for investigating the electron-phonon coupling dynamics in materials.