スピントロニクスデバイス・デザインに関する研究連絡調整

• Project/Area Number: 14076105
• Research Category: Grant-in-Aid for Scientific Research on Priority Areas
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: Tohoku University
• Principal Investigator: 白井 正文 東北大学, 電気通信研究所, 教授 (70221306)
• Co-Investigator(Kenkyū-buntansha): 今村 裕志 東北大学, 大学院・工学研究科, 助教授 (30323091) ; 江藤 幹雄 慶應義塾大学, 理工学部, 助教授 (00221812)
• Project Period (FY): 2002 – 2005
• Project Status: Completed (Fiscal Year 2005)
• Budget Amount: ¥15,600,000 (Direct Cost: ¥15,600,000); Fiscal Year 2005: ¥4,600,000 (Direct Cost: ¥4,600,000); Fiscal Year 2004: ¥4,600,000 (Direct Cost: ¥4,600,000); Fiscal Year 2003: ¥4,400,000 (Direct Cost: ¥4,400,000); Fiscal Year 2002: ¥2,000,000 (Direct Cost: ¥2,000,000)
• Keywords: スピントロニクス / 第一原理計算 / 希薄磁性半導体 / スピン注入 / 量子ポイントコンタクト / 量子ドット / 量子情報 / 量子メディア変換 / ハーフメタル / スピントランジスタ / 半導体人工分子 / 位相緩和 / デバイスデザイン / 高スピン偏極強磁性体 / ヘテロ接合界面 / エンタングルメント / 透明強磁性半導体

Research Abstract

光スピントロニクス材料として期待されるワイドバンドギャップ磁性半導体において、磁性不純物の空間分布や格子欠陥が強磁性転移温度に及ぼす影響を第一原理計算に基づいて検証した。磁性不純物間には引力的な相互作用がはたらくため、希薄磁性半導体においては互いに磁気的に結合していない高不純物濃度クラスタが形成され、強磁性転移温度は低くなる。また、窒化ガリウムにドープされた磁性スピン間の強磁性相互作用は窒素空孔が存在すると弱められるので、高い強磁性転移温度を得るためには、窒素空孔の生成を抑制する必要がある。(白井)
光子-電子スピン量子メディア変換を量子力学的モデルで記述し、一光子の偏光状態から電子のスピン状態へ量子情報が転写される過程のダイナミクスを解析した。詳細な解析の結果、高い転写確率を得るためには、光子-量子ドット結合強度と量子ドットからのホールのトンネルレートの両方を入射光子のスペクトル幅よりも大きくとり、かつ、マッチング条件を満たす必要があることを明らかにした。(今村)
半導体微細加工で作製される微小なくびれ構造や量子ポイントコンタクトを利用した新しいスピン注入のアイディアを提案した。スピン軌道相互作用が存在する場合の量子ポイントコンタクトの輸送特性を数値計算によって調べ、電気伝導度の量子化が見られること、透過した電子は電流に垂直な方向にスピン分極すること、InGaAsヘテロ構造において50%以上のスピン分極が得られることを示した。他に、量子ドットにおける電子格子相互作用による位相緩和の解明、2重量子ドット系でのスピン結合の評価および量子演算のシミュレーションを行った。(江藤)

Research Products

• [Journal Article] Ab initio study on stability of half-metallic Co-based full-Heusler alloys (2006)
  • Author(s): Y.Miura, M.Shirai, K.Nagao
  • Journal Title: Journal of Applied Physics (発表予定)
  • NAID: 120001182174
• [Journal Article] Half-metallicity at the (110) interface between a full Heusler alloy and GaAs (2006)
  • Author(s): K.Nagao, Y.Miura, M.Shirai
  • Journal Title: Physical Review B (発表予定)
  • NAID: 120001182177
• [Journal Article] Nonequilibrium Kondo effect in a quantum dot coupled to ferromagnetic leads (2005)
  • Author(s): Y.Utsumi, et al.
  • Journal Title: Physical Review B 71・24
• [Journal Article] Decoherence of localized spins interacting via RKKY interaction (2005)
  • Author(s): Y.Rikitake, H.Imamura
  • Journal Title: Physical Review B 72・3
• [Journal Article] Dephasing by electron-phonon interaction in an AB ring with an embedded quantum dot (2005)
  • Author(s): A.Ueda, M.Eto
  • Journal Title: Physica Status Solidi (b) 242・6 Pages: 1219-1223
• [Journal Article] Electronic States in Silicon Quantum Dot Devices (2005)
  • Author(s): Y.Hada, M.Eto
  • Journal Title: Physica Status Solidi (c) 2・8 Pages: 3035-3038
• [Journal Article] Spin polarization at semiconductor point contacts in absence of magnetic field (2005)
  • Author(s): M.Eto, T.Hayashi, Y.Kurotani
  • Journal Title: Journal of the Physical Society of Japan 74・7 Pages: 1934-1937
  • NAID: 110001979644
• [Journal Article] Numerical renormalization group studies of SU(4) Kondo effect in quantum dots (2005)
  • Author(s): T.Sato, M.Eto
  • Journal Title: Physica E 29・3-4 Pages: 652-655
• [Journal Article] 量子ポイントコンタクトを用いたスピン注入の方法 (2005)
  • Author(s): 江藤幹雄
  • Journal Title: 固体物理 40・12 Pages: 955-961
  • NAID: 40007070738
• [Journal Article] Enhanced spin accumulation and novel magnetotransport in nanoparticles (2005)
  • Author(s): K.Yakushiji, et al.
  • Journal Title: Nature Materials 4・1 Pages: 57-61
• [Journal Article] Enhancement of Kondo effect in multilevel quantum dots (2005)
  • Author(s): M.Eto
  • Journal Title: Journal of the Physical Society of Japan 74・1 Pages: 95-102
  • NAID: 110001979343
• [Journal Article] Atomic disorder effects on half-metallicity of the full-Heusler alloys Co_2(Cr_<1-x>Fe_x)Al : A first-principles study (2004)
  • Author(s): Y.Miura, et al.
  • Journal Title: Physical Review B 69・14
• [Journal Article] A first-principles study on half-metallicity of disordered Co_2(Cr_<1-x>Fe_x)Al (2004)
  • Author(s): Y.Miura, et al.
  • Journal Title: Journal of Applied Physics 95・11 Pages: 7225-7227
• [Journal Article] Ab initio calculations of zinc-blende CrAs/GaAs superlattices (2004)
  • Author(s): K.Nagao, et al.
  • Journal Title: Journal of Applied Physics 95・11 Pages: 6518-6520
• [Journal Article] Theoretical study on anti-site defects in half-metallic zinc-blende ferromagnets (2004)
  • Author(s): M.Shirai, et al.
  • Journal Title: Journal of Magnetism and Magnetic Materials 272-276 Pages: 344-345
• [Journal Article] The computational design of zinc-blende half-metals and their nanostructures (2004)
  • Author(s): M.Shirai
  • Journal Title: Journal of Physics : Condensed Matter 16・48
• [Journal Article] Ab initio calculations of spin-polarization at Co_2CrAl/GaAs interface (2004)
  • Author(s): K.Nagao, et al.
  • Journal Title: Journal of Physics : Condensed Matter 16・48
• [Journal Article] First-principles design of ferromagnetic nanostructures based on group-IV semiconductors (2004)
  • Author(s): Y.Miura, et al.
  • Journal Title: Journal of Physics : Condensed Matter 16・48
• [Journal Article] ハーフメタル強磁性体のマテリアルデザイン (2004)
  • Author(s): 白井 正文
  • Journal Title: 固体物理 39・11 Pages: 861-866
• [Journal Article] Twisted exchange interaction between localized spins embedded in a one- and two-dimensional electron gas with Rashba spin-orbit coupling (2004)
  • Author(s): H.Imamura, et al.
  • Journal Title: Physical Review B 69・12
• [Journal Article] Indirect exchange interaction between two quantum dots in an Aharonov-Bohm ring (2004)
  • Author(s): Y.Utsumi, et al.
  • Journal Title: Physical Review B 69・15
• [Journal Article] Control of spin configuration in semiconductor artificial molecules by spin field effect transistors (2004)
  • Author(s): H.Imamura, et al.
  • Journal Title: Journal of Magnetism and Magnetic Materials 272-276 Pages: 1909-1910
• [Journal Article] Exchange coupling in silicon double quantum dots (2004)
  • Author(s): Y.Hada, et al.
  • Journal Title: Japanese Journal of Applied Physics 43・10 Pages: 7329-7336
• [Journal Article] Numerical studies of transport properties through point contacts of magnetic metals (2004)
  • Author(s): K.Ueno, et al.
  • Journal Title: Physica E 22 Pages: 276-279
• [Journal Article] Entanglement of nuclear spins in spin-blocked quantum dots (2004)
  • Author(s): M.Eto, et al.
  • Journal Title: Physica E 22 Pages: 426-429
• [Journal Article] Enhanced Kondo effect via tuned orbital degeneracy in a spin 1/2 artificial atom (2004)
  • Author(s): S.Sasaki, et al.
  • Journal Title: Physical Review Letters 93・1
• [Journal Article] Kondo Effect in quantum dots near orbital degeneracy (2004)
  • Author(s): M.Eto
  • Journal Title: Proceedings of the Second Quantum-Transport Nano-Hana International Workshop (IPAP Conference Series 5) Pages: 25-29
• [Book] Half-metallic Alloys : Fundamentals and Applications, Materials Design and Molecular-Beam Epitaxy of Half-Metallic Zin-Blende CrAs and the Heterostructures (2005)
  • Author(s): H.Akinaga, et al.
  • Total Pages: 19
  • Publisher: Springer-Verlag
• [Publications] M.Shirai, et al.: "Materials design of Cr-based half-metallic ferromagnets"Journal of Superconductivity. 16・1. 27-29 (2003)
• [Publications] M.Shirai: "Possible half-metallic ferromagnetism in zinc blende CrSb and CrAs"Journal of Applied Physics. 93・10. 6844-6846 (2003)
• [Publications] 白井 正文: "新しい高スピン偏極強磁性材料の理論設計"日本応用磁気学会誌. 27・6. 730-733 (2003)
• [Publications] K.Sato, et al.: "Curie temperatures of III-V diluted magnetic semiconductors calculated from first-principles in mean field approximation"Journal of Superconductivity. 16・1. 31-35 (2003)
• [Publications] K.Sato, et al.: "Curie temperature of III-V diluted magnetic semiconductors calculated from first-principles"Europhysics Letters. 61・3. 403-408 (2003)
• [Publications] H.Katayama-Yoshida, et al.: "Spin and charge control method of ternary II-VI and III-V magnetic semiconductors for spintronics : theory vs.experiment"Journal of Physics and Chemistry of Solids. 64・9-10. 1447-1452 (2003)
• [Publications] H.Katayama-Yoshida, et al.: "Materials design for semiconductor spintronics by ab initio electronic-structure calculation"Physica B. 327・2-4. 337-343 (2003)
• [Publications] V.A.Dinh, et al.: "T_c-enhancement codoping method for GaAs-based diluted magnetic semiconductors"Japanese Journal of Applied Physics. 42・8A. L888-L891 (2003)
• [Publications] M.Seike, et al.: "Materials design of 4d-transition-metal-doped transparent and half-metallic ferromagnets with K_2S-based diluted magnetic semiconductors"Japanese Journal of Applied Physics. 42・9A/B. L1061-L1063 (2003)
• [Publications] S.Takahashi, et al.: "Spin injection and detection in magnetic nanostructures"Physical Review B. 67・5. 052409/1-052409/4 (2003)
• [Publications] T.Yamashita, et al.: "Andreev reflection in ferromagnet / superconductor / ferromagnet double junction systems"Physical Review B. 67・9. 094515/1-094515/8 (2003)
• [Publications] S.Takahashi, et al.: "Spin-current induced Hall effect in superconductors"Physica B. 329-333. 1263-1264 (2003)
• [Publications] H.Imamura, et al.: "Spin relaxation and tunnel magnetoresistance of a ferromagnet / superconductor / ferromagnet single-electron tunneling transistor"Physica E. 18・1-3. 43-44 (2003)
• [Publications] T.Yamashita, et al.: "Andreev reflection in ferromagnet / superconductor / ferromagnet structures"Physica E. 18・1-3. 52-53 (2003)
• [Publications] J.Martinek, et al.: "Kondo effect in quantum dots coupled to ferromagnetic electrodes"Physica E. 18・1-3. 75-76 (2003)
• [Publications] Y.Utsumi, et al.: "The effect of large quantum fluctuation on the noise of a single-electron transistor"Physica E. 18・1-3. 93-94 (2003)
• [Publications] J.Martinek, et al.: "Kondo effect in quantum dots coupled to ferromagnetic leads"Physical Review Letters. 91・12. 127203/1-127203/4 (2003)
• [Publications] Y.Rikitake, et al.: "Time evolution of an exciton and a photon qubit coupled with each other"Journal of the Physical Society of Japan. 72・12. 3020-3023 (2003)
• [Publications] T.Yamashita, et al.: "Crossed Andreev reflection in structures consisting of a superconductor with ferromagnetic leads"Physical Review B. 68・17. 174504/1-174504/8 (2003)
• [Publications] Y.Hada, et al.: "Multivalley effect on electronic states in Si quantum dots"Physica E. 17. 24-25 (2003)
• [Publications] T.Tasai, et al.: "Transport properties of quantum dots with strong electron-phonon interaction"Physica E. 17. 139-142 (2003)
• [Publications] M.Murata, et al.: "Modulation of electronic states in semiconducting carbon-nanotubes with external electrodes"Physica E. 17. 384-385 (2003)
• [Publications] Y.Hada, et al.: "Size and shape dependence of electronic states in silicon quantum dots"Physica Status Solidi (c). 0・4. 1153-1156 (2003)
• [Publications] A.Ueda, et al.: "Numerical studies of Fano resonance in quantum dots embedded in AB rings"Journal of the Physical Society of Japan. 72・suppl.A. 157-158 (2003)
• [Publications] T.Tasai, et al.: "Effects of polaron formation in semiconductor quantum dots on transport properties"Journal of the Physical Society of Japan. 72・6. 1495-1500 (2003)
• [Publications] K.Ueno, et al.: "Mean-field calculations of transport properties through magnetic point contacts"Journal of the Physical Society of Japan. 72・6. 1501-1509 (2003)
• [Publications] Y.Hada, et al.: "Electronic states in silicon quantum dots : Multivalley artificial atoms"Physical Review B. 68・15. 155322/1-155322/7 (2003)
• [Publications] 江藤 幹雄: "量子ドットにおける核スピンのエンタングルメント機構"固体物理. 38・11. 725-732 (2003)
• [Publications] M.Eto, et al.: "Current induced entanglement of nuclear spins in quantum dots"Journal of the Physical Society of Japan. 73・2. 307-310 (2004)
• [Publications] M.Shirai, et al.: "Theoretical study on anti-site defects in half-metallic zinc-blende ferromagnets"Journal of Magnetism and Magnetic Materials. 発表予定. (2004)
• [Publications] Y.Miura, et al.: "Atomic disorder effects on half-metallicity of the full-Heusler alloys Co_2(Cr,Fe)Al : a first-principles study"Physical Review B. 発表予定. (2004)
• [Publications] Y.Miura, et al.: "A first-principles study on half-metallicity of disordered Co_2(Cr_<1-x>Fe_x)Al"Journal of Applied Physics. 発表予定. (2004)
• [Publications] K.Nagao, et al.: "Ab initio calculations of zinc-blende CrAs/GaAs superlattices"Journal of Applied Physics. 発表予定. (2004)
• [Publications] H.Imamura, et al.: "Twisted singlet in semiconductor artificial molecules"Journal of Magnetism and Magnetic Materials. 発表予定. (2004)
• [Publications] H.Imamura, et al.: "Twisted exchange interaction between localized spins embedded in a one- or two-dimensional electron gas with Rashba spin-orbit coupling"Physical Review B. 発表予定. (2004)
• [Publications] Y.Utsumi, et al.: "Indirect exchange interaction between two quantum dots in an Aharonov-Bohm ring"Physical Review B. 発表予定. (2004)
• [Publications] M.Eto, et al.: "Entanglement of nuclear spins in spin-blocked quantum dots"Physica E. 発表予定. (2004)
• [Publications] K.Ueno, et al.: "Numerical studies of transport propterties through point contacts of magnetic metals"Physica E. 発表予定. (2004)
• [Publications] M.Shirai: "Materials design of Cr-based half-metallic ferromagnets"Journal of Superconductivity. (発表予定). (2003)
• [Publications] M.Shirai: "Possible half-metallic ferromagnetism in zincblende CrSb and CrAs"Journal of Applied Physics. (発表予定). (2003)
• [Publications] T.Yamashita, et al.: "Andreev reflection in ferromagnet/superconductor/ferromagnet double junction systems"Physical Review B. (発表予定). (2003)
• [Publications] Y.Utsumi, et al.: "Noise of a single-electron transistor in the regime of large quantum fluctuations of island charge out of equilibrium"Physical Review B. 67・3. 035317/1-035317/16 (2003)
• [Publications] Y.Hada, et al.: "Multivalley effect on electronic states in Si quantum dots"Physica E. (発表予定). (2003)
• [Publications] A.Ueda, et al.: "Numerical studies of Fano resonance in quantum dots embedded in AB rings"Journal of the Physical Society of Japan. (発表予定). (2003)