Femtosecond-Pulse Controlled Plasmon Decay in Ag-Graphene System

Plasmon decay in an Ag-graphene system induced by a femtosecond pulse is investigated using real-time time-dependent density functional theory. There exists a critical value for plasmon decay dependence on the pulse width. For pulse widths less than the critical value, plasmon remains during the time scale of ∼30 fs after the laser is withdrawn and indicates direct charge transfer from Ag to graphene. While for pulse width greater than the critical value, plasmons rapidly decay into hot electrons involving inverse charge transfer. Electron transition at the critical value of pulse width displays an obvious beat owing to mutual interference between plasmon and single-particle excitation. Femtosecond-pulse width is thus crucially important for controlling plasmon decay in a metal–semiconductor hybrid system.