Electron transitions in rippled and twisted graphenes


L.G. Bulusheva1,2, O.V. Sedelnikova1,2, V.O. Koroteev1, A.L. Chuvilin3, A.V. Okotrub1,2


11Nikolaev Institute of Inorganic Chemistry, SB RAS, 3 Academician Lavrentiev ave., Novosibirsk 630090, Russian Federation 2Tomsk State University 36 Lenina Ave., Tomsk, 634050, Russian Federation 3CIC NanoGUNE, Donostia-San Sebastian 20018, Basque Country, Spain



Abstract:

Rippling of graphene monolayer or rotation of a layer relative to another one may substantially change the electron density distribution as compared to the perfect graphene. Here, we study such effects using density functional theory (DFT) calculations of periodic models and experimental optical and electron energy loss (EEL) spectra of corresponding objects. Electronic ground-state band structure of graphene models was obtained using plane-wave self-consistent field formalism in the local density approximation as implemented in the Quantum-ESPRESSO code. Dielectric function of a model was calculated within the random phase approximation. The rippled graphene models had armchair or zigzag edge and different height of the out-of-plane bending. Calculations showed that periodic graphene deformation results in a localization of the electronic density on the top and bottom parts of the wave-like structure and creates conducting channels along the wave crest [1]. Positions of the absorption peak and plasmons calculated for the flat graphene agreed well with the experimental values showing validity of the single-particle picture for investigation of the dielectric response in graphene-based systems [2]. Analysis of interband transitions demonstrated a contribution of electron transitions being forbidden for the flat graphene in the in-plane and out-of-plane components of dielectric function of rippled graphene. We showed that positions and shape of plasmons are very sensitive to the geometry of rippled models [3]. Stressing the graphene mechanically or placing the layer on an artificial substrate one could control the graphene rippling constructing a material with optical properties adjusted for a certain application. Using the EEL spectra and calculations of twisted bilayer graphene (BLG) models, we showed that plasmonic properties of BLG are governed by a stacking pattern. As compared to graphene monolayer, the spectra of rotationally faulted BLG samples exhibit additional low-energy features, and the peak energies systematically shift with changing the rotation angle.. The interaction between twisted layers is strongly nonhomogeneous resulting in spatial localization of plasmon excitations that opens new possibilities for engineering of graphene plasmonics. [1] O.V. Sedelnikova, L.G. Bulusheva, A.V. Okotrub «Modulation of electronic density in waved graphite layers” Synth. Metals 160 (2010) 1848-1855. [2] O.V. Sedelnikova, L.G. Bulusheva, I.P. Asanov, I.V. Yushina, A.V. Okotrub «Energy shift of collective electron excitations in highly corrugated graphitic nanostructures: Experimental and theoretical investigation” Apl. Phys. Lett. 104 (2014) 161905. [3] O.V. Sedelnikova, L.G. Bulusheva, A.V. Okotrub “Ab initio study of dielectric response of rippled graphene” J. Chem. Phys. 134 (2011) 244707.