The Charge Transport In Bilayer Silicene Under The Modulation Of One Dimensional Periodic Potential

Bilayer silicene can be regarded as a hybrid structure consisting of two monolayer silicene vertically stacked together in some orders.It is not only an important intermediate form of silicon from monolayer silicene into bulk,but also a new two-dimensional electronic material that can be synthesised experimentally.Comparing to monolayer silicene,bilayer silicene has similar extraordinary physical properties.Moreover,bilayer silicene has stronger spin-orbit coupling and enhanced field-controllable energy gap.These properties give rise to a broader parameter window to modulate spin and valley polarized transport for fantastic electronic applications.Under this context,it is an important topic for the physical realization of related logic devices to explore the modulated strategies of spin and valley polarized transport in bilayer silicene system.In this thesis,residing on the physical properties of bilayer silicene,and applying the scattering matrix theory,we have systematically studied the spin and valley transport characteristics in an ideally electriccontrollable bilayer silicene superlattice、ferromagnetic bilayer silicene superlattice and electric-controllable bilayer silicene superlattice with defective element.The responsed characteristics of spin and valley polarized under the modulation of the external field.The specific research contents are summarized as follows:1.Spin-valley polarization in a field-controllable bilayer silicene superlattices.The results show that:(1)The near-perfect spin polarization can be observed in the bilayer silicene superlattice for a single valley transport;More importantly,its perfect spin polarization switch behavior could be observed under the modulation of perpendicular electric field.These observations are very important for the construction of quantum logic devices.(2)The calculation of superlattice subbands shows that perfect spin-polarized subbands could be efficiently modulated by electric field,namely,only one spin state in a certain energy window.These observations are completely consistent with the observed spin polarization phenomenon.2.Bilayer silicene ferromagnetic superlattice.The results show that:(1)The perfect spin and valley polarization could still be observed in the bilayer silicene ferromagnetic superlattices without single valley transport;(2)While the magnetization orientation changes of superlattice unit cell from parallel magnetization to antiparallel magnetization configuration,a colossal tunneling magnetoresistance can be observed;(3)With structural asymmetry in the bilayer silicene ferromagnetic superlattice,perfect spin and valley polarization can be observed even for the antiparallel magnetization configuration.Moreover,an enhanced of the tunneling magnetoresistance is also observed.3.Bilayer silicene superlattices with defective units.The results show that:(1)The defects caused by the size asymmetry of units suppress the particle transport in the bilayer silicene superlattice,and the oscillation amplitude is weakened;(2)The defects caused by the confinement asymmetry of barrier also suppress the particle transport in the bilayer silicene superlattice,and the emerging suppression is highly dependent on the height of the barrier of the defective unit;(3)Changing the position of the defect unit does not affect the suppression of particle transport in the system.In general,compared with the pefect periodic potential structure,the introduction of defective unit will suppress the transport of particles in the bilayer silicene superlattice system,but it does not affect the realization of the fully spin or valley polarization,which is very important for the realization of the final performance of bilayer silicene superlattice devices even with the processed-induced defects.