Silicene-2DEG heterostructures: Collective excitations investigations

This paper investigates collective excitations in a heterostructure consisting of a silicene sheet and a parallel GaAs quantum well by employing the random-phase approximation within exchange-correlation effects. We find that two plasmonic modes exist in the systems, corresponding to in-phase (optical) and out-of-phase (acoustical) oscillations of charged particles in two layers. Calculations show that interactions between electrons in two layers decrease the energy of both two plasmon modes, completely differing from other double-layer structures. The increase in inter-layer separation significantly decreases both optical and acoustical modes’ frequencies. We observe that taking into account local field correction and increasing quantum well width pronouncedly decrease acoustical mode frequency. However, the increase in the bandgap, caused by an external electric field, decreases only the frequency of the optical collective mode. Finally, as carrier density in quantum well decreases, the acoustical mode energy noticeably declines while that of the optical one seems extremely stable.