Wake effect in the interaction of an external charged particle with a graphene-sapphire-graphene structure due to excitation of plasmon-phonon hybrid modes
We study the wake effect due to excitation of a plasmon-phonon hybrid mode in a sandwich-like structure consisting of two doped graphene sheets, separated by a layer of Al2O3 (sapphire), which is induced by an external charged particle moving parallel to the structure. The response function of each graphene is obtained using two approaches within the random phase approximation: an ab initio method that includes all electronic bands in graphene and a computationally less demanding method based on the massless Dirac fermion (MDF) approximation for the low-energy excitations of electrons in the π bands. The response of the sapphire layer is described by a dielectric function consisting of several Lorentzian terms. We evaluate the total electrostatic potential in the plane of the upper graphene sheet for a particle moving at the sub-threshold speed for the wake effect in a single, free graphene. We show that, when the space between graphene sheets is air, there is only a sharp, somewhat asymmetric peak in the potential at the position of the particle. On the other hand, when the space is filled with sapphire, there is a prominent wake pattern in the potential behind the particle resulting from a low-frequency plasmon-phonon mode. It can be noted that the analytical MDF model reproduces the overall shape and the period of quasi-oscillations in the wake potential obtained from the ab initio calculations.Bucharest CA 15107 Fall Meeting : September 6-7, Bucharest, Romania, 2018
