Ballistic Transport Of Magnetic Quantum Structure

In the early 1990s, due to the development and mature of the techniques such as electron beam lithography, the magnetic modulation with the scale of nanometer on the 2DEG has been realized at laboratory. Because of the fantastic electronic transport properties in this structure, it attracts much interest of physicists. In this thesis, by utilizing the transfer matrix method we investigate the influence of spin-magnetic-field interaction and the defect on the transport properties, and the subbands and envelope wave functions in periodic magnetic structure.The thesis consists of an introduction and six chapters. In the introduction, it points out the evolution and importance of the research problem, and also reviews some important physical properties. Chapter one concerns the fundamental theories in which basic formulas used in following chapters are derived. In Chapter two and Chapter three, we study the transport properties in periodic and quasi-periodic magnetic quantum structures with the spin-magnetic-field interaction taken into account. The results show that the interaction doesn't alter the (n-l)-fold splitting of the conductance in periodic structures. But it changes the magnitude of conductance. In Fibonacci quasiperiodic sequences, the splitting of conductance has the characteristics of three-splitting and self-similarity. And in the sequences, the properties of spin filtering become in a striking way. In Chapter four, we investigate the transport properties in Fibonacci magnetic sequences including a defect. It is found that the defect plays an important role in the transport probability and ballistic conductance, especially at the low energy. The pseudo-invariant exhibits oscillating behavior. In Chapter five, we give a general formula to compute the energy-band structures and envelope wave functions. And as a typical example, we discuss them in two kinds of periodic magnetic superlattices. The results indicate that the differenceiiof the transverse wave-vector can give rise to the shift of the energy-band and the envelope wave functions are more localized at the high barriers. The chapter six presents the main points of this paper and the prospect for this investigation.