Abstract:

Recent advances in nanotechnology have made it possible to transport electron spin coherently over hundreds of micrometers at low temperature. It may enable the realization of quantum spintronics by manipulating the spin degree of freedom of electrons without destroying their phase coherence. The definitions of spin orientation and polarization vectors are introduced within the particle density matrix of scattering states in leads. It is shown that spin-density vector can be defined by the product of the spin orientation vector, being a unit direction vector, and the charge density, corresponding to the amplitude of the spin-density vector, experimentally observable by a spatial charge modulation measurement. When an electron transports through a ballistic semiconductor nanostructure, due to quantum interference of two spin eigenmodes, the electron spin generally undergoes nutation on its precession around the effective magnetic field resulting from spin-orbit interactions. The nutation of electron spin is found to be crucial for spin polarization in the quantum transport. When one of two spin-dependent channels in leads is evanescent, electron spin is shown to be fully polarized for distance from the interface larger than the spin precession length.
 
 
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