Theory Of Electromagnetic Waves Propagation And Excitation In Novel 2D Materials

Graphene and its analogous 2D materials have caused worldwide interest,and have become a very hot research frontier in electromagnetics,thermodynamics,mechanics,material science,interdisciplinary science,etc.This is mainly because they have excellent electric,magnetic,thermal and mechanical properties.Now,2D materials are reported to be a promising platform for the development of micro/nano-devices and future highly-advanced technologies,such as the design of bendable touch screen,light aircraft,advanced electronic devices,micro/nano metamaterials or metasurface,and novel electromagnetic devices.In order to facilitate the development of high-density optical integration,it is highly desirable to flexibly control electromagnetic waves at the extreme nanoscale.This requires a profound understanding of the propagation characteristics and the excitation of electromagnetic waves in 2D materials.To address this issue,this dissertation focuses on the discussion of the propagation and excitation of electromagnetic waves in 2D materials and reveals a series of novel electromagnetic phenomena.Below are the brief summary of main contents in this dissertation:1)Research on band structures and electromagnetic properties of 2D materials.We discussed the influence of substrates on the electronic and electromagnetic properties of graphene through the first principle simulation.We found multilayer 2D silicon carbide(2D-SiC)exhibits an indirect bandgap,while monolayer 2D-SiC has a direct bandgap.We revealed that the indirect bandgap in multilayer 2D-SiC can change to the direct bandgap by the interlayer oriented misalignment.The availability of direct bandgaps can help to design 2D-SiC based light-emitting devices.2)Research on the reflectance and transmittance of electromagnetic waves in 2D materials.We introduced a new scheme to realize the TE(s-polarized)Brewster-effect in a homogeneous dielectric interface without magnetic responses,by adding ultrathin 2D-materials such as graphene.In addition,we proposed that under an external magnetic field,graphene can be used to isolate the left/right circularly polarized waves.3)Research on the propagation of ultra-confined polaritons on 2D materials.We introduced the concept of PT symmetry into the field of graphene plasmons;the loss induced plasmonic amplification or transparency,as a characteristic of exceptional point behavior,is revealed in the realm of graphene plasmonics.We found that the portion of the plasmon energy contained inside graphene can exceed 50%,despite graphene being exceptionally thin;the energy distribution can be used to intuitively analyze the parity-time symmetry breaking in graphene plasmons.We revealed that the all-angle in-plane negative refraction between graphene plasmons,BN's phonon polaritons and their hybridized polaritons can happen in graphene-BN heterostructures.This enables the flexible control of the in-plane polaritonic refraction,which is of fundamental importance for the manipulation of light at the nanoscale.4)Research on the transient electromagnetic reponse when a swift electron perpendicularly bombards a graphene monolayer.We predicted a jet-like rise of excessive charge concentration that delays the generation of graphene plasmons;exhibiting an analogue to the hydrodynamic Rayleigh jet in a splashing phenomenon prior to the launching of ripples.The transition radiation of photons,analogous to the splashing sound,accompanies the plasmon emission and can be understood as being shaken off by the Rayleigh jet-like charge concentration.Considering this newly revealed process,we argue that previous estimates on the yields of graphene plasmons in electron energy loss spectroscopy(EELS)need to be re-evaluated.