Study On The Plasmon Optical Properties Of Graphene And The Phonon Emission In Molybdenum Disulfide

Two-dimensional layered nanomaterials,represented by graphene and molybdenum disulfide(ML-MoS₂),have shown broad application prospects in the fields of photoelectric devices and sensors due to their excellent physical and chemical properties.Compared with other materials such as metals,two-dimensional materials have more excellent optical properties of plasmon.For example,the plasmon in graphene have longer propagation path,stronger localization and easy regulation,etc.This has led to a lot of research on the optoelectronic properties and applications of graphene plasmons.Such as graphene plasmon mode,graphene plasmon waveguide and graphene terahertz plasmon device,etc.The light absorption of graphene can be enhanced by the coupling of incident light and plasmon in graphene.However,the metal grating structure can compensate the momentum of the incident light,so that the incident light and the momentum of the graphene medium exciton can match and be coupled.In addition,the incident light can be greatly enhanced near the metal grating strip,which further enhances the coupling between the two.Therefore,we investigated the optical properties of graphene with grating structure.By placing the grating graphene structure in an optical resonator and using the finite-difference time-domain method,the light absorption spectra of graphene were obtained,and it was found that the light absorption of graphene would be greatly enhanced.The distribution of the component of the incident photoelectric field is also obtained.It is found that the component of the electric field is greatly strengthened near the metal grating strip.Moreover,we obtained the plasmon polariton mode of graphene based on the self-consistent field theory,and found that the application of grating can enhance the coupling between the two,resulting in an increase in the rabi-splitting of the two equi-ionized polariton.At the same time,it also explains the reason why the light absorption of graphene is enhanced at the resonance frequency,that is,the coupling of plasmons and cavity mode photons at the resonance frequency enhances the light absorption of graphene.This is helpful for researchers to understand the photoelectric properties of graphene and lay a good theoretical foundation for terahertz photoelectric devices based on graphene.In addition,ML-MoS₂is one of the most interesting two-dimensional materials,with a current switching ratio of up to 10⁸,which is considered to have great application prospects in field effect transistors,and molybdenum disulfide also has important applications in the field of grain electronics.However,there are relatively few studies on the acoustic properties of molybdenum disulfide.The study of acoustic phonon emission in ML-MoS₂can provide some theoretical basis for special ultrasonic device based on molybdenum disulfide.Therefore,we used the semi-classical Boltzmann equilibrium equation to study the emission of acoustic phonons from drifting electrons in a single layer of molybdenum disulfide under the action of a driving electric field.We obtained the distribution of phonon emission intensity with frequency and emission angle,and the relationship between phonon emission intensity and driving electric field intensity and electron concentration.It is found that ML-MoS₂can realize terahertz acoustic phonon emission under the action of driving electric field,and the emission intensity increases with the increase of electric field.The electron concentration mainly affects the emission frequency of the phonon but has little effect on the intensity of the emitted phonon.Phonon emission intensity of ML-MoS₂can be controlled by driving electric field and by changing electron concentration by gate voltage.These results provide a theoretical basis for us to understand the acoustic properties of ML-MoS₂and to apply ML-MoS₂in ultrasonic equipment.