Nonlinear mechanism of plasmon damping in electron gas

At plasmon resonance, the condition of applicability of the linear response theory, which is the smallness of the oscillating field, evidently breaks down. We suggest a variant of the quadratic response theory which remains valid near and at plasma frequency and demonstrate that, as could be anticipated, the nonlinearity serves itself to restrict the amplitude of plasma oscillations, thus providing a mechanism of nonlinear damping. We apply this approach to calculate the damping of plasmon in two-dimensional electron gas below the threshold wave vector, which damping has recently been observed experimentally in the S-1 surface band of Si(111)root3 x root3-Ag.