Plasmons and loss function in a double-layer silicene-graphene heterostructure at zero-temperature

Abstract

We compute theoretically the plasmon frequencies and the loss function in a double layer silicene-graphene heterostructure within random phase approximation (RPA) at zero temperature. In the long wavelength approximation we obtain analytical expressions for the acoustic and optical plasmons as well as for the loss function restricted to the acoustic and optical plamon branches. In the q→0 limit the loss function restricted to the acoustic plasmon behaves as −ImTr[ΠR(q,ωac(q→0))]∼q while its restriction to the optical plasmon displays a behavior −ImTr[ΠR(q,ωop(q→0))]∼q32. Numerical simulations show that the acoustic plasmon crosses the ω=vFgq line tending towards the ω=12vFgq. To the best of our knowledge, this behavior is not exhibited in other double layer systems. Another novel feature of this system is that as the acoustic plasmon passes the ω=vFgq, the loss function restricted to the acoustic plasmon curve displays a highly concentrated peak with almost no broadening on a small interval until it disperses and shows the usual broadened peak for damped plasmons.