Relativistic Theory of the Interaction of Two-Dimensional Materials with Moving Charged Particles

Akbari, Kamranaffiliation1:Faculty of Mathematics ; advisor:Miskovic, Zoran ; Miskovic, Zoran ;

University of Waterloo

关键词: Doctoral Thesis;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/14856/1/Akbari_Kamran.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

Prompted by the recent surge of interest in integrating atomically thin layers of conductingmaterials into nanophotonic and nanoplasmonic devices; we propose, in this thesis, a theoretical framework to analyze the interaction of externally moving charged particles with twodimensional(2D) materials. The interactions of 2D materials with externally moving chargedparticles in the context of electron energy loss spectroscopy (EELS) has become a very popularexperimental technique for exploring the plasmon excitations in 2D layered specimens overa broad range of frequencies. On the other hand, the technological need for a stable and tunablesource of terahertz (THz) radiation has inspired researchers to explore the electromagneticradiation from a family of 2D materials, induced by their interaction with fast charged particles.We present a fully relativistic analysis of the energy loss of a charged particle traversing suchlayers. We distinguish between two contributions to this process: (i) the energy deposited inthe layers in the form of electronic excitations (Ohmic losses), which include excitation of 2Dplasmon polariton (PP) modes, and (ii) the energy emitted in the far-field region in the formof transition radiation. Owing to the proposed theoretical framework, we study various structuresconsisting of isotropic and anisotropic conducting and semiconducting sheets with differenttrajectories of the incident charged particles, including single and multiple parallel layersof graphene under normal incidence of charged particles and single-layer graphene and phosphoreneunder oblique incidence, in broad ranges of frequency, incident particle’s speed, and its angle of incidence relative to the layers.Suitable models for the 2D conductivity of each layer are chosen to represent: (a) excitationof the Dirac PP (DPP) mode in doped graphene in the THz range, (b) interband transitions ingraphene in the range from infrared to ultraviolet frequencies, and (c) hyperbolic plasmon modesin doped phosphorene at the THz to mid-infrared frequencies. Among other findings, we observethat, for multilayer graphene, strong asymmetries arise in the Ohmic losses and in the radiationspectra with respect to the direction of motion of the incident particle. These asymmetries areexplained by hybridization taking place between DPPs in different layers, which is found to bestrongly affected by the interlayer distances and the differences in the doping densities of thoselayers.In addition, we explore the possibility of exciting the so-called transverse plasmon mode ingraphene as well as the directionality of exciting anisotropic plasmons in phosphorene by anobliquely incident charged particle. Our findings may help in the ongoing studies of plasmonexcitations in 2D materials via EELS, as well as in exploring the possibility of designing a THzradiation source using an electron beam.