Local Spin-Polarized Density Oscillation In The Coupled Quantum Wells

In this thesis, the evolutions of local spin-polarized density in InAs/InAlAs coupled quantum wells system have been investigated by taking account of the Rashba spin-orbit coupling effect. The influence of the size of quantum well structure and structural asymmetry on the probability densities of the electrons with different spin and the local spin-polarized densities also have been discussed in detail. We have used a finite difference method to solve a time-dependent schrodinger equation and got the spin-dependent electron wave function. The time-dependent evolutions of a spin-polarized charge density in a coupling double well have been shown in our results. We have found that the energy level splits in the well due to the Rashba spin-orbit coupling. Furthermore, an oscillation of the probability densities of the electron with different spin orientation can be observed between two quantum wells. We have also discussed the oscillation amplitude and period of the probability densities of the electron with different spin. It can be seen that the amplitude would increase and reach a peak with increase of the plane wave vector. The oscillation period exponentially decrease as we increase the parallel wave vector. We can also find that the spin-splitting, which is caused by the Rashba effect, will lead to local spin-polarized density oscillate in a single quantum well. The spin-polarized densities increase as the parallel vector increasing. As time passes, the spin-polarized densities will tend to be localized. Additionally, we have also studied the effect of the size and asymmetry of our structure by changing the middle barrier thickness and the right well width. It is found the spin-polarized densities are much easily localed in a single well with increasing the barrier thickness. When the width of right quantum well is increased, a delocalizing phenomenon of spin-up probability density in left well can be seen clearly.