Electron-Energy-Loss Spectra of Free-Standing Silicene*

Silicene, the silicon-based counterpart of graphene, is increasingly getting attention because it is a semi-metal material with Dirac cones and thus, in principle, has similar electronic properties [1, 2]. In this work we calculated the Electron Energy Loss Spectrum (EELS) of ideal free-standing silicene. Dielectric function is obtained by using a discretization method as suggested by Delerue, et al. [3]. Tight-binding method is applied considering 2nd Nearest Neighbors with $sp^2$ orbitals, the Slater-Koster parameterization [4] and the Harrison's rule. This has been done for plane and buckled silicon sheets, in the latter case with a structure based on DFT calculations [2]. The resulting dielectric function is compared to those of bulk silicon and graphene. Spectra of EEELS are contrasted for plane and buckled silicene, particularly the plasmon frequency as a function of the $z$ displacement of buckled silicene.\\[4pt] [1] S. Leb\`egue and O. Eriksson, Phys. Rev. B 79, 115409 (2009).\\[0pt] [2] S. Cahangirov, et al., Phys. Rev. Lett. 102, 236804 (2009).\\[0pt] [3] C. Delerue, et al., Phys. Rev. B 56, 15306 (1997).\\[0pt] [4] G. G. Guzm\'an-Verri and L. C. Lew Yan Voon, Phys. Rev. B 76, 075131 (2007).