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Electrically tunable spin polarization in a carbon nanotube spin diode
Christopher A Merchant1, Nina Marković
1Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
Physical Review Letters
|June 4, 2008
Summary
We observed spin-dependent current rectification in a carbon-nanotube quantum dot. This effect, tunable with gate and bias voltages, arises from spin accumulation and Coulomb blockade interactions.
Area of Science:
- Condensed matter physics
- Quantum electronics
- Spintronics
Background:
- Quantum dots offer tunable electronic properties.
- Ferromagnetic and normal-metal contacts enable spin-sensitive measurements.
- Coulomb blockade and spin accumulation are key phenomena in nanoscale devices.
Purpose of the Study:
- Investigate spin-dependent transport through a carbon-nanotube quantum dot.
- Analyze the origin of observed current rectification.
- Determine the tunability of spin polarization.
Main Methods:
- Fabrication of a carbon-nanotube quantum dot device with specific leads.
- Measurement of electrical current under varying gate and bias voltages.
- Theoretical analysis of spin accumulation and Coulomb blockade effects.
Main Results:
- Observed a pronounced, bias-dependent decrease in current at resonance.
- Demonstrated that this rectification is spin-dependent.
- Showed interplay between spin accumulation and Coulomb blockade causes rectification.
- Confirmed precise tunability of spin polarization via gate and bias voltages.
Conclusions:
- Spin-dependent rectification is achievable in carbon-nanotube quantum dots.
- The interplay of spin accumulation and Coulomb blockade governs this rectification.
- Gate and bias voltages provide full control over spin polarization.
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