Spin Dependent Novel Quantum Phenomena In Semiconductors

The research on spin-based electronics (spintronics) is one of the most importantsubjects in modern condensed matter physics. In spintronics where it is not the electroncharge but the electron spin that carries the information. The control and probe of electronspin are indispensable parts of spintronics. In this thesis, we first review the history andcurrent status on spintronics research. Then we discuss pure spin currents (PSCs) whichplay a key role in information transfer. Starting from the basic properties of PSCs and thecurrent experimental techniques for PSCs measurements, we present our theory on opticalefects of PSCs in the direct-gap semiconductors, i.e. the Faraday rotation and nonlinearoptics, which provide a direct measurement of PSCs in semiconductors. Soon after theproposal, the second-harmonics generation of PSCs has been experimental verified. Wehave also studied the electron spin decoherence in III-V semiconductor quantum dots, andproposed to explore the electromagnetic vacuum fluctuations for spin-flip control and touse nonlinear optical spectroscopy to realized the spin echo.Searching new states of matter is the key part in condensed matter physics. The spin-orbit coupling (SOC) in semiconductors and low-dimensional structures will give rise tomany novel quantum states, which brings new development to spintronics. Here we fo-cus on topological insulators (TIs), which are characterized by the fully bulk insulatinggaps and gapless surface states. Quantum spin Hall efect (QSHE) is a physical realiza-tion of two-dimensional TIs. We discuss the basic properties of TIs and its field theorydescription. Then we study the electron-electron interactions in TIs, we find that magneticfluctuations of TIs coupled to the electromagnetic fields behave like the axions. The axionfield hybridizes with photons, leading to an axion polariton. We refer such an antiferro-magnetic insulator as a 'topological magnetic insulators'(TMI). Then we study a transitionmetal oxide of corundum structure, in which both SOC and electron-electron interactionplay crucial roles, it may realize TMI phase. Many novel quantum phenomena resultedfrom the topological surface states which are protected by time-reversal symmetry, finallywe discuss the Landau quantization and quasi-particle interference of surface states.