Abstract
In this work we address optical orientation, a process consisting in the excitation of spin polarized electrons across the gap of a semiconductor. We show that the combination of optical orientation with spin-dependent scattering leading to the inverse spin-Hall effect, i.e., to the conversion of a spin current into an electrical signal, represents a powerful tool to generate and detect spin currents in solids. We consider a few examples where these two phenomena together allow addressing the spin-dependent transport properties across homogeneous samples or metal/semiconductor Schottky junctions.
Highlights
IntroductionSpintronics (spin transport electronics or spin-based electronics) consists in the study and, possibly, in the active control of spin degrees of freedom in solid-state systems
Spintronics consists in the study and, possibly, in the active control of spin degrees of freedom in solid-state systems
The charge/spin conversion mechanism described in Figure 1 has been experimentally shown to be active in n-doped III-V semiconductors, where spin-dependent electron scattering can lead to a transverse spin accumulation at the sample edges when a charge current is flowing [34,35,36], or, to inverse spin Hall effect (ISHE) when a spin current is injected into the system [29,37]
Summary
Spintronics (spin transport electronics or spin-based electronics) consists in the study and, possibly, in the active control of spin degrees of freedom in solid-state systems. Where γ and σc represent the spin-Hall angle and the electrical conductivity of the material, respectively, and P is the spin polarization vector defined as P = (n↑ − n↓ )/(n↑ + n↓ )uk , uk being the unit vector parallel to the quantization axis (which is taken parallel to the light propagation axis when the spins are generated by optical orientation) Such a spin-to-charge current conversion can occur either in the same semiconductor where optical orientation is achieved [29,30] or inside a high-Z metal layer, such as Pt, Au or Bi, deposited on the semiconductor surface [31,32], in which the spin-polarized electrons produced by optical orientation are injected. One can exploit the sizable value of the spin Hall angle γ of the high-Z material, which can be exploited as a non-magnetic electrode sensitive to pure spin-currents able to provide larger EISHE signals than those that could be measured directly in the semiconductor
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