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Phonon anomalies in Graphene induced by highly excited charge carriers.
We present Raman measurements in graphene by using a 3-ps laser excitation, generating electronic subsystem temperatures largely exceeding that of the phonon bath. We find a peculiar behaviour of the period and lifetime of both G and 2D phonons as function of the carriers temperature in the range 1700--3100 K, which is strongly suggestive of a smearing out of the Dirac cones. We rationalize such behaviour by revisiting the traditional theoretical modeling of the electron-phonon coupling in this highly excited transient scenario, which is critical in the emerging field of graphene-based nanophotonic and optoelectronic devices operating at THz rates.