Studies On Electron Transport Properties In A Thue-morse Bilayer Graphene Superlattice

The successful preparation of graphene in 2004 has motivated further research on carbon nanomaterials in the scientific community. Natural bilayer graphene can be formed by two coupled graphene monolayers in the usual AB(or Bernal) stacking, which has attracted considerable attention due to its unusual physical properties. In this paper, we theoretically investigate electronic transport properties and shot noise through Thue-Morse(TM) AB-stacked bilayer graphene superlattices with different interlayer potential biases by using the transfer matrix method, we also study the electric field modulation of spin transport properties and tunnel magnetoresistance in a fourth-generation Thue-Morse bilayer graphene superlattice(TMBGS) and the corresponding periodic bilayer graphene superlattice(PBGS) with two ferromagnetic bilayer graphene(FBG) electrodes. The main results obtained in this paper are listed as follows:(1) We evaluate the transport properties of a TM AB-stacked bilayer graphene superlattice with different interlayer potential biases. The transmission coefficient, the conductance and the Fano factor are numerically calculated and discussed. We find that the symmetry of the transmission coefficient with respect to normal incidence depends on the structural symmetry of the system and the new transmission peak appears in the energy bandgap opening region. The conductance and the Fano factor can be greatly modulated not only by the Fermi energy and the interlayer potential bias, but also by the generation number. Interestingly, the conductance exhibits a plateau of almost zero conductance and the Fano factor plateaus with Poisson value occur in the energy bandgap opening region for large interlayer potential bias.(2) We theoretically investigate the electric field modulation of the spin transport properties and the tunnel magnetoresistance in a fourth-generation FBG/TMBGS/FBG and the corresponding FBG/PBGS/FBG tunnel junctions. One can find that the spin conductances of the two junctions are sensitive to the magnetization of the two FBG electrodes and the value of the exchange splitting energy. As the Fermi energy increases, the spin conductances in the low energy range exhibit weak oscillatory behaviors but the spin polarizations and the tunnel magnetoresistance exhibit drastic oscillations for the two junctions; while in the high energy range the spin polarizations and the tunnel magnetoresistance tend to zero. As the electric bias increases, the spin conductances of the FBG/PBGS/FBG tunnel junction exhibit a plateau of almost zero conductance, and larger tunnel magnetoresistance can be obtained more easily in the FBG/TMBGS/FBG tunnel junction.