Transport Properties Of Electron In Graphene Under A Time-periodic Potential

With the development and progress of modern science and technology, the investigationon the transport properties of mesoscopic systems have attracted more and more attention.Among them, the research on shot noise has always been one of the hot research field offrontier. Shot noise is a kind of non-balanced noise, it is the result of charge quantization.Due to the discrete nature of carriers led to the current relative to its average value fluctuation.Access to system information more abundant than the conductance measurement by shotnoise experiment can be. In order to further the understanding of the transport properties ofmesoscopic system, We use the method of scattering theory research the transport propertiesof single layer graphene and double-layer graphene under a time-periodic potential. Thisarticle consists of the following parts:In the first part (i.e. Chapter Three), we obtained the expressions for the second-quantizedcurrent operator, conductivity and shot noise of charge carriers through single layer graphenein the presence of a time-periodic potential. We found that the applied external field providessidebands for charge carriers to tunnel through the graphene, and these sidebands jointly af-fect the transport properties of the system. Our results will benefit basic understanding ofphoton-assisted tunneling (PAT) and designers of electron devices based on graphene.The second part (i.e. Chapter four), by solving the Dirac equation we obtained thetransmission probability of monolayer graphene-based double-barrier structures with a time-periodic potential. We investigated transport properties of the system with the external fieldstrength α and system parameters include the barrier(well) spacing, and the incident energyin different cases, respectively. We have found that due to the presence of an time-periodicpotential, the transport properties of graphene have peculiar behavior, the conductivity, shotnoise and Fano factor is either improved or suppressed. Moreover, the shot noise, Fano factorare enhanced with the increase of the α. One could control the electron transport by tuningthe structure parameters of the system and the external field strength. We hope these work canprovide some value reference to the design of electron devices which related to the monolayergraphene material. In the third part (i.e. Chapter five), by solving the Dirac equation we obtained the trans-mission probability of monolayer graphene with a time-periodic potential. We investigatedtransport properties of the system with the external field strength α and system parameters in-clude the incident energy, and the barrier width in different cases, respectively. We have foundthat due to the presence of an time-periodic potential, the transport properties of graphenehave peculiar behavior, the conductivity, shot noise and Fano factor is improved. One couldcontrol the electron transport by modulate the external field strength and the structure param-eters of the system.In the fourth part (i.e. Chapter six), the transport property of charge carriers throughbilayer graphene in the presence of the time-periodic potential is investigated. We study thetransmission probabilities of central band and sidebands as external field strength, incidentangle, barrier width and height is changed. The results obtained in this study demonstrate thatthe applied time-periodic Potential provides sidebands for charge carriers to tunnel throughthe bilayer graphene, and transport property of bilayer graphene show various types of behav-ior with the change of external field strength and structure parameters of the system. Besides,at normal and close to normal incidence, the perfect reflection that was reported for the staticbarrier is observed to still exist for the time-periodic potential. One can control the electrontransport of the system by manipulating the external field strength and the structural parame-ters of the system. The results will benefit basic understanding of Photon-assisted tunneling(PAT) and designers of electron devices based on bilayer graphene.