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Efficient spin filter using multi-terminal quantum dot with spin-orbit interaction.

Yokoyama T, Eto M - Nanoscale Res Lett (2011)

Bottom Line: First, we formulate the spin Hall effect (SHE) in a quantum dot connected to three leads.We show that the SHE is significantly enhanced by the resonant tunneling if the level spacing in the quantum dot is smaller than the level broadening.We stress that the SHE is tunable by changing the tunnel coupling to the third lead.

View Article: PubMed Central - HTML - PubMed

Affiliation: Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan. tyokoyam@rk.phys.keio.ac.jp.

ABSTRACT
We propose a multi-terminal spin filter using a quantum dot with spin-orbit interaction. First, we formulate the spin Hall effect (SHE) in a quantum dot connected to three leads. We show that the SHE is significantly enhanced by the resonant tunneling if the level spacing in the quantum dot is smaller than the level broadening. We stress that the SHE is tunable by changing the tunnel coupling to the third lead. Next, we perform a numerical simulation for a multi-terminal spin filter using a quantum dot fabricated on semiconductor heterostructures. The spin filter shows an efficiency of more than 50% when the conditions for the enhanced SHE are satisfied.PACS numbers: 72.25.Dc,71.70.Ej,73.63.Kv,85.75.-d.

No MeSH data available.


Related in: MedlinePlus

Calculated results of the conductance G1,± to the drain 1 for spin ±1/2 in the impurity Anderson model with three leads. In the abscissa, εd = (ε1 + ε2)/2, where ε1 and ε2 are the energy levels in the quantum dot. Solid and broken lines indicate G1,+ and G1,-, respectively. The level broadening by the tunnel coupling to the source and drain 1 is ΓS = ΓD1 ≡ Γ (VS,1/VS,2 = 1/2, VD1,1/VD1,2 = -3), whereas that to drain 2 is (a) ΓD2 = 0.2Γ, (b) 0.5Γ, (c) Γ, and (d) 2Γ (VD2,1/VD2,2 = 1). Δε = ε2 - ε1 = 0.2Γ. The strength of SO interaction is ΔSO = 0.2Γ.
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Figure 2: Calculated results of the conductance G1,± to the drain 1 for spin ±1/2 in the impurity Anderson model with three leads. In the abscissa, εd = (ε1 + ε2)/2, where ε1 and ε2 are the energy levels in the quantum dot. Solid and broken lines indicate G1,+ and G1,-, respectively. The level broadening by the tunnel coupling to the source and drain 1 is ΓS = ΓD1 ≡ Γ (VS,1/VS,2 = 1/2, VD1,1/VD1,2 = -3), whereas that to drain 2 is (a) ΓD2 = 0.2Γ, (b) 0.5Γ, (c) Γ, and (d) 2Γ (VD2,1/VD2,2 = 1). Δε = ε2 - ε1 = 0.2Γ. The strength of SO interaction is ΔSO = 0.2Γ.

Mentions: Figure 2 shows the conductance of each spin, G1,+ (solid line) and G1,- (broken line), as a function of εd = (ε1 +ε2)/2, in the case of N = 3. The conductance shows a peak reflecting the resonant tunneling around the Fermi level in the leads, which is set to be zero. We set ΓS = ΓD1 ≡ Γ, whereas (a) ΓD2 = 0.2Γ, (b) 0.5Γ, (c) Γ, and (d) 2Γ. The level spacing in the QD is Δε = 0.2Γ. The strength of SO interaction is ΔSO = 0.2Γ. The calculated results clearly indicate that the SHE is enhanced by the resonant tunneling around the peak. We obtain a large spin current when ΓD2 ~ ΔSO, as pointed out previously. Therefore, the SHE is tunable by changing the tunnel coupling to the third lead, ΓD2.


Efficient spin filter using multi-terminal quantum dot with spin-orbit interaction.

Yokoyama T, Eto M - Nanoscale Res Lett (2011)

Calculated results of the conductance G1,± to the drain 1 for spin ±1/2 in the impurity Anderson model with three leads. In the abscissa, εd = (ε1 + ε2)/2, where ε1 and ε2 are the energy levels in the quantum dot. Solid and broken lines indicate G1,+ and G1,-, respectively. The level broadening by the tunnel coupling to the source and drain 1 is ΓS = ΓD1 ≡ Γ (VS,1/VS,2 = 1/2, VD1,1/VD1,2 = -3), whereas that to drain 2 is (a) ΓD2 = 0.2Γ, (b) 0.5Γ, (c) Γ, and (d) 2Γ (VD2,1/VD2,2 = 1). Δε = ε2 - ε1 = 0.2Γ. The strength of SO interaction is ΔSO = 0.2Γ.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211854&req=5

Figure 2: Calculated results of the conductance G1,± to the drain 1 for spin ±1/2 in the impurity Anderson model with three leads. In the abscissa, εd = (ε1 + ε2)/2, where ε1 and ε2 are the energy levels in the quantum dot. Solid and broken lines indicate G1,+ and G1,-, respectively. The level broadening by the tunnel coupling to the source and drain 1 is ΓS = ΓD1 ≡ Γ (VS,1/VS,2 = 1/2, VD1,1/VD1,2 = -3), whereas that to drain 2 is (a) ΓD2 = 0.2Γ, (b) 0.5Γ, (c) Γ, and (d) 2Γ (VD2,1/VD2,2 = 1). Δε = ε2 - ε1 = 0.2Γ. The strength of SO interaction is ΔSO = 0.2Γ.
Mentions: Figure 2 shows the conductance of each spin, G1,+ (solid line) and G1,- (broken line), as a function of εd = (ε1 +ε2)/2, in the case of N = 3. The conductance shows a peak reflecting the resonant tunneling around the Fermi level in the leads, which is set to be zero. We set ΓS = ΓD1 ≡ Γ, whereas (a) ΓD2 = 0.2Γ, (b) 0.5Γ, (c) Γ, and (d) 2Γ. The level spacing in the QD is Δε = 0.2Γ. The strength of SO interaction is ΔSO = 0.2Γ. The calculated results clearly indicate that the SHE is enhanced by the resonant tunneling around the peak. We obtain a large spin current when ΓD2 ~ ΔSO, as pointed out previously. Therefore, the SHE is tunable by changing the tunnel coupling to the third lead, ΓD2.

Bottom Line: First, we formulate the spin Hall effect (SHE) in a quantum dot connected to three leads.We show that the SHE is significantly enhanced by the resonant tunneling if the level spacing in the quantum dot is smaller than the level broadening.We stress that the SHE is tunable by changing the tunnel coupling to the third lead.

View Article: PubMed Central - HTML - PubMed

Affiliation: Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan. tyokoyam@rk.phys.keio.ac.jp.

ABSTRACT
We propose a multi-terminal spin filter using a quantum dot with spin-orbit interaction. First, we formulate the spin Hall effect (SHE) in a quantum dot connected to three leads. We show that the SHE is significantly enhanced by the resonant tunneling if the level spacing in the quantum dot is smaller than the level broadening. We stress that the SHE is tunable by changing the tunnel coupling to the third lead. Next, we perform a numerical simulation for a multi-terminal spin filter using a quantum dot fabricated on semiconductor heterostructures. The spin filter shows an efficiency of more than 50% when the conditions for the enhanced SHE are satisfied.PACS numbers: 72.25.Dc,71.70.Ej,73.63.Kv,85.75.-d.

No MeSH data available.


Related in: MedlinePlus