Dielectric function of a two-dimensional electron gas under intense laser radiation

We present a theoretical study on the dielectric function of a two-dimensional electron gas (2DEG) driven by linearly polarised intense laser fields. A tractable method in dealing with time-dependent many-body problem has been developed. We derive the electron density-density correlation function in t-space using Green's function approach. With this result, the inverse dielectric function matrix for a 2DEG in t- and Omega-representation is obtained under the random-phase approximation. Furthermore, the influence of the laser radiation on plasmon spectrum in a 2DEG is investigated. Using these nonperturbative approaches. the effect of the laser field can be included exactly. These results can be used to the case where the laser radiation is provided by recently developed free-electron laser sources.