Effect Of Polarization Field On Spin-orbit Coupling Properties In Low-dimensional Piezoelectric Semiconductors

Spin-orbit coupling involves spin qubit,quantum spin Hall effect,Majorana Fermions and other physical basis and application research fields.Rashba spin-orbit coupling provides an effective method to manipulate spin by controlling electron motion in the external potential field by breaking the inversion symmetry of the structure.Experimentally,the continuous manipulation of spin qubits in Ga As quantum dots and In As nanowires was successfully achieved by manipulating Rashba spin orbit coupling,which may have a huge impact on quantum information processing and quantum computing in the future.As a wide band gap semiconductor material,the third-generation semiconductor is widely used in high-performance,low power consumption and high extreme performance devices.Due to the influence of the wide band gap,the Rashba spin orbit coupling is weak,which restricts the application of the third-generation semiconductor in spin qubit.In this thesis,electric field is used to enhance the Rashba spin orbit coupling,a stress-induced polarization field is proposed to enhance Rashba spin-orbit coupling.The peak value of Rashba spin-orbit coupling coefficient of Zn O/Cd O quantum well structure can reach 83 me V·nm under the control of stressinduced polarization field,which is nearly 3 orders of magnitude higher than that of traditional Ga As quantum well.Meanwhile,the Rabi frequency of this quantum well can be increased from 0.19 MHz to 4.05 MHz,which correspond to Rabi frequencies of Ga As quantum dots in the same order of magnitude.This research is helpful to use piezoelectric effect to generate polarization electric field to enhance spin-orbit coupling and realize spin qubit manipulation,which is of great significance to the theory and application research of the third-generation semiconductor spin qubit.The main contents of this thesis are as follows:1.The effects of different structures and stresses on Rashba spin orbital coupling coefficient of Zn O/Cd O quantum well were studied by comparing the regulation effect of polarization field of Zn O/Cd O quantum well in normal and topological insulated systems.The maximum Rashba spin-orbit coupling coefficient and coefficient nonlinear variation of the quantum well in the topological state of insulation state are focused.2.The feasibility of the third-generation semiconductor materials as spin qubit materials is studied,and the performance parameters of Zn O/Cd O quantum Wells used as spin qubit materials are theoretically calculated.The parameters are in the same order of magnitude as those of Ga As quantum dots currently reported.At the same time,the difficulties in preparing Zn O/Cd O quantum well were investigated and the experimental feasibility was demonstrated.3.The polarization field regulation in the quantum well system composed of other third-generation semiconductor materials is analyzed to explore the physical mechanism of the spin orbit coupling coefficient regulated by the polarization field.The calculated results can be divided into two categories according to whether the level inversion can occur to topological insulating state under stress regulation.The coefficients of Zn O/Cd O and Ga N/In N quantum well have peak value and nonlinear change.In Zn O/Mg O,Al N/Ga N quantum well systems without level inversion,the coefficients change linearly.Taking Ga In N/Ga N quantum well as an example,the modulation of the polarization field on the spin-orbit coupling in different alloy ratios is studied.