In graphene, after the electric field is turned-on, the ballisticacceleration of charge carriers up to the monochromatic optic phonon energygenerates a back-and-forth motion of the whole distribution function betweenthe zero point energy and the phonon energy. This effect is predicted tomanifest in damped terahertz oscillations of the carrier drift velocity andaverage energy. The most dramatic feature of this transient phenomenon is theonset of momentum-free areas surrounded by high momentum probability in phasespace, and smooth steps or terraces in the distribution function. Thisdynamical effect that only takes place within a voltage and sample lengthwindow, is the direct consequence of the interplay between the electric forceand the randomizing nature of deformation potential optic phonons in the linearband structure of graphene.
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