Energy losses and transition radiation in multi-layer graphene traversed by a fast charged particle

K. AKBARI; Z. L. MISKOVIC; S. SEGUI; J. L. GERVASONI; N. R. ARISTA

Paris

Conferencia; NANOSMAT 2017 12th International Conference on Surfaces, Coatings and Nanostructured Materials; 2017

We present a fully relativistic formulation of the energy loss of a charged particletraversing a number of graphene layers and apply it to the case of two spatially separatedlayers probed by an energetic electron. We focus on the THz frequency range, using aDrude model to describe the conductivity of graphene and allowing for different dopingdensity in each layer. We distinguish two types of contributions to the electron energyloss: the energy deposited in graphene layers in the form of electronic excitations (Ohmlosses), which include the excitation of Dirac plasmon polaritons (DPP), and the energythat is emitted in the form of transition radiation. Using some results of our rpevioueswork [1], we study in detail the contribution of each layer to the ohmic losses and analyzethe directional decomposition of the radiation emitted in the half-spaces defined by thegraphene planes. By increasing the inter-layer distance and changing the relative dopingdensities in graphene layers, we find surprisingly strong asymmetries in both thedirectional and layerwise decompositions with respect to the direction of motion of theexternal electron. A modal decomposition is also performed in the limit of vanishingdamping in graphene, exposing quite intricate roles of bonding and antibondinghybridization between DPPs in ohmic losses.