Plasmon properties of 4-bilayer graphene structures: Inhomogeneous background dielectric effects

Abstract

In this paper, we investigate the plasmon properties of a 4-BLG structure on an inhomogeneous background dielectric within the random-phase approximation. Firstly, we determine collective excitations from the zeros of the dynamical dielectric function and then calculate respective broadening functions. Computations demonstrate that there are four solutions to the zero point equation of the dynamical dielectric function, corresponding to four phases of collective excitations in the system. Three of them, acoustical modes, are lower than that in BLG at the same parameters while the optical mode has a higher frequency at a given wave vector. Secondly, we present that both the inhomogeneity of background dielectric and the inter-layer separation strongly decrease the plasmonic frequency and respective broadening functions. Moreover, the inhomogeneity of the environment strengthens the effects of separation on plasmon properties. Lastly, the increase in doping density in BLG layers decreases strongly both plasmon frequency and its broadening functions. We observe that due to the pronounced contributions to plasmon properties of 4-BLG systems of the inhomogeneity, this factor should not be neglected in calculations.