8,548 research outputs found
Correlation-induced resonances and population switching in a quantum dot coulomb valley
Strong correlation effects on electron transport through a spinless quantum
dot are considered. When two single-particle levels in the quantum dot are
degenerate, a conserved pseudospin degree of freedom appears for general
tunneling matrix elements between the quantum dot and leads. Local fluctuations
of the pseudospin in the quantum dot give rise to a pair of asymmetric
conductance peaks near the center of a Coulomb valley. An exact relation to the
population switching is provided.Comment: Fig. 4 and some technical details removed. To appear in PR
Effect of ferromagnetic contacts on spin accumulation in an all-metallic lateral spin-valve system: Semiclassical spin drift-diffusion equations
We study the effect of the ferromagnetic (FM) contacts on the spin
accumulation in the lateral spin valve system for the collinear magnetization
configurations. When an additional FM electrode is introduced in the
all-metallic lateral spin-valve system, we find that the transresistance can be
fractionally suppressed or very weakly influenced depending on the position of
the additional FM electrode, and relative magnitudes of contact resistance and
the bulk resistance defined over the spin diffusion length. Nonlocal spin
signals such as nonlocal voltage drop and leakage spin currents are independent
of the magnetization orientation of the additional FM electrode. Even when the
additional contact is nonmagnetic, nonlocal spin signals can be changed by the
spin current leaking into the nonmagnetic electrode.Comment: 13 pages, 1 figure, revised versio
Spin polarization amplification within nonmagnetic semiconductors at room temperature
We demonstrate theoretically that the spin polarization of current can be
electrically amplified within nonmagnetic semiconductors by exploiting the fact
the spin current, compared to the charge current, is weakly perturbed by
electric driving forces. As a specific example, we consider a T-shaped current
branching geometry made entirely of a nonmagnetic semiconductor, where the
current is injected into one of the branches (input branch) and splits into the
other two branches (output branches). We show that when the input current has a
moderate spin polarization, the spin polarization in one of the output branches
can be higher than the spin polarization in the input branch and may reach 100%
when the relative magnitudes of current-driving electric fields in the two
output branches are properly tuned. The proposed amplification scheme does not
use ferromagnets or magnetic fields, and does not require low temperature
operation, providing an efficient way to generate a highly spin polarized
current in nonmagnetic semiconductors at room temperature.Comment: 11 pages, 2 figures, to appear in Phys. Rev.
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