| Project/Area Number |
16560002
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Yamagata University |
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Principal Investigator |
TAKAHASHI Yutaka Yamagata University, Dept.of Electrical Eng., Associate Professor, 工学部, 助教授 (00260456)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | Spintronics / Quantum Computing / Two-dimensional Electron Gas / Spin Relaxation / Spin Transport / Electronic Spin Control / Spin Injection |
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| Research Abstract |
We have studied basic manipulations of spin-polarized electrons in semiconductor nanostructures in terms of real-space transport and spinor-space precession. We have concentrated our study upon (1) effects of electron-electron scattering on electron transport in spin polarized system, and (2) spin precessions (rotations) in spinor space.
In the real-space transport study, we formulated transport equations for two-dimensional degenerate electrons, and obtained low temperature transport coefficients (mobilities and diffusion coefficients) with electron-impurity (e-imp) and electron-electron (e-e) scatterings included in the first phase of our research (academic year 2004). Then we extended our calculations to include electron-phonon (e-ph) scattering in order to study temperature dependence of the transport coefficients (academic year 2005). In an unpolarized electron gas, mobilities of spin-up electrons are identical to those of spin-down electrons, and e-e scattering does not affect the
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mobilities. (Thus e-e scattering is disregarded in conventional analyses of electronic transport.) We have found in a spin-polarized electrons (density of spin-up > density of spin-down) that spin-up mobilities (majority electrons) are larger than spin-down electrons (minority electrons), and mobilities are dependent on spin-polarization. As the temperature is raised the majority spins are decelerated while the minority spins are accelerated. This signifies the presence of the effect of e-e scattering in mobilities : It is known that e-e scattering rate is proportional to the square of temperature. Then the friction between a spin-up electron and a spin-down electron increases with temperature. This leads to the deceleration of majority electrons (which are moving faster) and the acceleration of minority electrons (which are moving slower). We conclude that e-e scattering has significant consequences for electron transport in spin-polarized system, and expect that they are likely to be observed in the transport measurements.
In order to measure the spin precessions in semiconductors we have grown trial samples of InGaAs/GaAs and GaAs/AlGaAs heterostructures. However, in the available samples, the quality of crystal is not high enough, or the structure is not adequate for experiments at present. We are improving the growth technique. Less
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