| The modern computer is mainly based on semiconductors,uses the electron-charge to encode binary information "0" and "1",and completely ignores the electron-spins.If the electron-spins are used in the semiconductor,a new field of semiconductor spintronics will emerge.Compared with the traditional electronic device,the spintronic device possesses many advantages,such as the high information density,the low power consumption and the fast data-processing speed.Currently,there still exist many challenges in designing the spintronic device,because electrons are usually spin-degenerate in the semiconductor,which makes storage,precession and transfer of information by electron-spins impossible.How to realize spin-polarized electrons and effective manipulation in semiconductors,therefore,becomes a significant direction in semiconductor spintronics.So far,some effective schemes have been developed,one of which utilizes Goos-H?nchen(GH)effect for electrons in semiconductor nanostructures to separate spins and realize spin-polarized electrons in the semiconductor.This thesis chooses two typical kinds of magnetic nanostructures(magnetic-barrier nanostructure and hybrid magnetic-electrical-barrier nanostructure)as research objects,calculates GH effect induced by two intrinsic classes of spin-orbit couplings(SOC,including Rashba and Dresselhaus types)by establishing theoretical models,explores manipulation of spin-polarized GH displacements,and proposes tunable electron-spin spatial splitters for spintronics applications.It consists of five chapters.In the first chapter,we briefly introduce the research background of this thesis,including the semiconductor spin electronics,the magnetic nanostructure and the progress of electronic GH effect,as well as research contents.The second chapter introduces research methods adopted in this thesis,mainly including the improved transfer-matrix method(ITM)and the stationary-phase approach(SPM).By taking the double ?-function magnetic-barriers(MB)as an example,chapter three researches the effect of Rashba SOC and Dresselhaus SOC on the GH effect of electrons in magnetic-barrier nanostructures.Experimentally,the two ?-MBs can be formed by depositing two nanosized ferromagnetic stripes with horizontal magnetizations on top and bottom of the semiconductor heterostructure.By using ITM the Schr?dinger equation is solved exactly,then,the GH shift and its spin polarization are numerically calculated with the help of the SPM.Calculated results show that,GH shifts are related closely to Rashba or Dresselhaus SOC,and the degree of its spin polarization can be effectively manipulated by changing the SOC strength.Based on such a MB nanostructures,a SOC-controllable spin spatial splitter can be built for spintronics applications.Chapter four investigates the GH effect for electrons in a hybrid magnetic-electric-barrier(MEB)nanostructure modulated by the SOC,and explores the control of the spin-polarized GH displacement by Rashba and Dresselhaus SOCs.Such a MEB nanostructure consists of a?-MB and a square-EB,which can be realized by depositing a nanosized ferromagnetic stripe with the horizontal magnetization and a nanosized Schottky metal stripe applied a negative voltage,on the top and bottom of the semiconductor heterostructure,respectively.We find that there is a significant difference of the GH shift between electrons with the opposite spin orientations,and both magnitude and sign of its spin polarization varies strongly with the strength of the Rashba and Dresselhaus SOCs.These findings not only provide a new scheme to control the spin polarization of GH displacement,but also such a hybrid MEB nanostructure can also be employed as a SOC-controllable spatial spin splitter.Finally,in the fifth chapter,we summarize significant research results achieved in this thesis,and at the same time,point out some deficiencies existing in this thesis and the direction of further study in the future. |
PDF Full Text Request