Spin transport through a single quantum dot with ferromagnetic - PowerPoint PPT Presentation

Spin transport through a single quantum dot with ferromagnetic electrodes & coherent control of nuclear spins in quantum Hall systems IIS and INQIE, Univ. of Tokyo JST CREST Tomoki Machida JST - DFG Workshop on Nanoelectronics 2008.3.5 （ Aachen, Germany ）

Outline Spin transport in a single quantum dot spin valve device Ni / InAs quantum dot / Ni magnetic tunnel junction Spin injection and tunneling magnet resistance (TMR) Gate control of spin transport Oscillatory changes in TMR Kondo effect Coherent control of nuclear spins in a quantum Hall device QHE breakdown Rabi oscillations Coherence time

Collaborators Spin transport in a single quantum dot spin valve device K. Hamaya, M. Kitabatake (IIS) M. Jung, K. Shibata, K. Hirakawa (IIS) S. Ishida, Y. Arakawa (RCAST) Coherent control of nuclear spins in a quantum Hall device H. Takahashi, M. Kawamura (IIS) Y. Hashimoto, S. Katsumoto (ISSP)

Control of spin transport in semiconductor Spin manipulation Spin detection Spin injection S. Datta and B. Das, APL 56 , 665 (1990). J. Schliemann et al., PRL 90 , 146801 (2003). cf. Carbon nanotube channel: S. Sahoo et al ., Nature phys. 1 , 99 (2005).

Quantum dot + Ferromagnetic leads Spin manipulation Spin detection Spin injection FM FM Semiconductor quantum dot A single semiconductor QD with ferromagnetic leads Spin injection, manipulation, detection

Lateral double barrier magnetic tunnel junction InAs dot V SD Ni A GaAs AlGaAs n + -GaAs V G B Self-assembled InAs QDs 150 nm

Parallel Tunneling magnetoresistance (TMR) B Anti-parallel R P R R P R AP − P R AP R Anti-parallel = TMR Parallel

Kondo effect in a quantum dot Coulomb diamond N : odd N = 3 Kondo peak T << T K G Kondo singlet V SD

Outline Spin transport in a single quantum dot spin valve device Ni/InAs quantum dot/Ni magnetic tunnel junction Spin injection and tunneling magnet resistance (TMR) Gate control of spin transport Oscillatory changes in TMR Kondo effect Coherent control of nuclear spins in a quantum Hall device QHE breakdown Rabi oscillations

NMR quantum computation (liquid) F F F C C C C F Nuclei F Fe CO C 5 H 5 CO Electron Shor's quantum algorithm 7 qubits B ext L. M. K. Vandersypen et al . Nature 414 , 883 (2001) 1 0 NMR

NMR quantum computation (solid) 31 P ) 29 Si) Si-based QC ( All-silicon QC ( T. D. Ladd et al . ,PRL 89 , 017901 (2002) B. E. Kane, Nature 393 , 133 (1998)

Coherent control of nuclear spins in semiconductor Quantum Quantum Standard Hall dot NMR edge states K. Ono et al . T. Machida et al . PRL (2004) APL (2003) QHE Optical FQHE breakdown Sanada et al. H. Takahashi et al . G. Yusa et al . PRL (2006) APL (2007) Nature (2005)

Quantum Hall devices metal strip (local coil) B ext 5 μ m Al 0.3 Ga 0.7 As/GaAs single heterostructure Carrier density: n = 1.6 × 10 15 m -2 Mobility: μ = 220 m 2 /Vs Temperature: 50 mK

Coherent control of nuclear spins 1 RF B ext 0 t = A 0 0 + A 1 1 | A 0 | 2 | A 1 | 2 t ① Initialization ② Manipulation ③ Read out QHE breakdown Pulsed -NMR Record V xx rf-pulse τ pulse Δ V xx V xx time

Summary Spin transport in a single quantum dot spin valve device Spin injection and tunneling magnet resistance (TMR) Gate control of spin transport Oscillatory changes in TMR Kondo effect K. Hamaya, T. M et al. , APL 90 , 053108 (2007). K. Hamaya, T. M et al. , APL 91 , 022107 (2007). K. Hamaya, T. M et al. , APL 91 , 232105 (2007). K. Hamaya, T. M et al. , PRB 77 , 081302 (2008). Coherent control of nuclear spins in a quantum Hall device QHE breakdown Rabi oscillations M. Kawamura, T. M et al. , APL 90 , 022102 (2007). H. Takahashi, T. M et al. , APL 91 , 092120 (2007). M. Kawamura, T. M et al. , JPSJ 77, 023710 (2008).