Interaction of graphene monolayer with ultrashort laser pulse
  We study the interaction of graphene with ultrashort few femtosecond long optical pulse. For such a short pulse, the electron dynamics is coherent and is described within the tight-binding model of graphene. The interaction of optical pulse with graphene is determined by strong wave vector dependence of the interband dipole matrix elements, which are singular at the Dirac points of graphene. The electron dynamics in optical pulse is highly irreversible with large residual population of the conduction band. The residual conduction band population as a function of the wave vector is nonuniform with a few localized spots of high conduction band population. The spots are located near the Dirac points and the number of spots depends on the pulse intensity. The optical pulse propagating through graphene layer generates finite transferred charge, which, as a function of pulse intensity, changes its sign. At small pulse intensity, the charge is transferred in the direction of the pulse maximum, while at large pulse intensity, the direction of the charge transfer is opposite to the direction of pulse maximum. This property opens unique possibility of controlling the direction of the charge transfer by variation of the pulse intensity. 
Hamed Koochaki Kelardeh, Vadym Apalkov, and Mark I. Stockman
cond-mat.mes-hall