強磁場と人工構造による低次元有機導体の電子物性制御

• Project/Area Number: 15073206
• Research Category: Grant-in-Aid for Scientific Research on Priority Areas
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: The University of Tokyo
• Principal Investigator: 長田 俊人 The University of Tokyo, 物性研究所, 准教授 (00192526)
• Co-Investigator(Kenkyū-buntansha): 大道 英二 神戸大学, 大学院・理学研究科, 准教授 (00323634)
• Project Period (FY): 2003 – 2007
• Project Status: Completed (Fiscal Year 2007)
• Budget Amount: ¥31,000,000 (Direct Cost: ¥31,000,000); Fiscal Year 2007: ¥2,500,000 (Direct Cost: ¥2,500,000); Fiscal Year 2006: ¥3,100,000 (Direct Cost: ¥3,100,000); Fiscal Year 2005: ¥3,200,000 (Direct Cost: ¥3,200,000); Fiscal Year 2004: ¥19,000,000 (Direct Cost: ¥19,000,000); Fiscal Year 2003: ¥3,200,000 (Direct Cost: ¥3,200,000)
• Keywords: 有機導体 / 低次元電子系 / 強磁場 / 半導体超格子 / 角度依存磁気抵抗振動 / Dirac電子系 / 層間コヒーレンス / 磁気貫通系 / 負性磁気抵抗 / 磁気抵抗角度効果 / 多層ディラック電子系 / ゼロギャップ伝導体 / 磁気貫通 / 電荷密度波 / 超強磁場 / 電界効果 / 微細構造 / スピン密度波 / ヘテロ接合

Research Abstract

本研究の目的は、強磁場・強電場といった極限環境や人工構造を用いて、有機導体の低次元電子系が示す新たな電子物性を探索・解明することである。本研究では、磁場中電荷密度波と層状伝導体の層間磁気伝導という2つの電子物性の問題を扱った。磁場中電荷密度波については、電荷密度波転移温度が低くエネルギー利得が軌道量子化エネルギーやZeemanエネルギーと競合する場合に発現する複雑な逐次相転移や臨界点の問題を扱った。有機導体α-(BEDT-TTF)_2KHg(SCN)_4に関する40T級パルス強磁場実験による相図決定と、磁場誘起スピン密度波転移の標準模型にZeeman効果を加えて拡張した平均場理論で現象を解明した。層状伝導体の磁場中層間伝導については、特に磁場方位依存性の問題を扱った。まず従来の半古典的Fermi面描像を超えて、磁場中層間伝導機構に関するトンネル描像を確立した。これは層間伝導を層間結合強度をパラメータとして摂動展開する方法で、dirty系(incoherent系)からclean系(coherent系)まで系統的かつ量子論的に扱うことが出来る。有機導体を模した各種のGaAs/AlGaAs系半導体多層構造を作製して層間結合を人工的に制御した実験を行うことにより、トンネル描像が予測する種々の角度依存磁気抵抗現象の層間コヒーレンス依存性を確認しその正当性を実証した。また半古典論が無効な量子系である磁気貫通系における磁気抵抗角度効果の振舞いをトンネル描像を用いて理論的に考察し、電荷密度波ギャップによる磁気貫通系である有機導体α-(BEDT-TTF)_2KHg(SCN)_4に関する2軸回転実験でそれらを実証した。さらに多層Dirac電子系における負の層間磁気抵抗をトンネル描像により予測し、負性磁気抵抗が報告されていた有機導体α-(BEDT-TTF)_2 I_3におけるDirac電子系の存在を根拠づけた。

Research Products

• [Journal Article] Negative Interlayer Magnetoresistance and Zero-Mode Landau Level in Multilayer Dirac Electron Systems (2008)
  • Author(s): T. Osada
  • Journal Title: Journal of Physical Society of Japan 77 Pages: 84711-84711
  • NAID: 110006914846
  • Peer Reviewed
• [Journal Article] Interlayer Magnetoresistance of Quasi-One-Dimensional Layered Organic Conductors. (2007)
  • Author(s): W. Kang
  • Journal Title: Physical Review Letters 99 Pages: 17002-17002
  • Peer Reviewed
• [Journal Article] Interlayer Surface Transport in Multilayer Quantum Hall Systems under Tilted Magnetic Fields (2007)
  • Author(s): S. Okui
  • Journal Title: International Journal of Modern Physics B 21 Pages: 1524-1528
  • Peer Reviewed
• [Journal Article] 層状低次元導体における磁気抵抗角度効果(II)-高電場下の層間磁気伝導- (2007)
  • Author(s): 長田俊人
  • Journal Title: 固体物理 42 Pages: 157-167
• [Journal Article] Interlayer Magnetoresistance of Quasi-One-Dimensional Layered Organic Conductors (2007)
  • Author(s): Woun Kang
  • Journal Title: Physical Review Letters 99 Pages: 170021-4
  • Peer Reviewed
• [Journal Article] Metal-Insulator Transition of Charge Transfer Salts Based on Unsym-metrical Donor DMET and Metal Halide Anions, (DMET)_4(MC1_4)(TCE)_2(M=Mn, Co, Cu, Zn; TCE=1,1,2-trichloroethane) (2007)
  • Author(s): Hiroshi Ito
  • Journal Title: Journal of American Chemical Society 129 Pages: 8510-8518
  • Peer Reviewed
• [Journal Article] Interlayer Surface Transport in Multilayer Quantum Hall Systems under Tilted Magnetic Fields (2007)
  • Author(s): Shinji Okui
  • Journal Title: International Journal of Modern Physics B 21 Pages: 1524-1528
  • Peer Reviewed
• [Journal Article] 層状低次元導体における磁気抵抗角度効果(II)-高電場下の層間磁気伝導- (2007)
  • Author(s): 長田 俊人
  • Journal Title: 固体物理 42 Pages: 157-167
• [Journal Article] Electric-Field Effect on the Angle-Dependent Magnetotransport Properties of Quasi-One-Dimensional Conductors (2006)
  • Author(s): K. Kobayashi
  • Journal Title: Physical Review Letters 96 Pages: 126601-126601
  • Peer Reviewed
• [Journal Article] Magnetotransport and Magnetic-Field-Induced Density Waves in Low-Dimensional Layered Conductors (2006)
  • Author(s): T. Osada
  • Journal Title: Journal of Physical Society of Japan 75 Pages: 51006-51006
  • NAID: 110004702296
  • Peer Reviewed
• [Journal Article] 層状低次元導体における磁気抵抗角度効果(I)-トンネル描像と層間コヒーレンス- (2006)
  • Author(s): 長田俊人
  • Journal Title: 固体物理 41 Pages: 239-249
• [Journal Article] Electric-Field Effect on the Angle-Dependent Magnetotransport Properties of Quasi-One-Dimensional Conductors (2006)
  • Author(s): K.Kobayashi
  • Journal Title: Physical Review Letters 96 Pages: 126601-126601
• [Journal Article] Magnetotransport and Magnetic-Field-Induced Density Waves in Low-Dimensional Layered Conductors (2006)
  • Author(s): T.Osada
  • Journal Title: Journal of Physical Society of Japan 75 Pages: 51006-51006
  • NAID: 110004702296
• [Journal Article] Upper Critical Field of β-Pyrochlore KOs_2O_6 Single Crystals (2006)
  • Author(s): E.Ohmichi
  • Journal Title: Journal of Physical Society of Japan 75 Pages: 45002-45002
  • NAID: 110004729285
• [Journal Article] Giant Negative Magnetoresistance Reflecting Molecular Symmetry in Dicyano(phthalocyaninato)iron Compounds (2006)
  • Author(s): N.Hanasaki
  • Journal Title: Journal of Physical Society of Japan 75 Pages: 33703-33703
• [Journal Article] Charge Disproportionation in Highly One-Dimensional Molecular Conductor TPP[Co(Pc)(CN)_2]_2 (2006)
  • Author(s): N.Hanasaki
  • Journal Title: Journal of Physical Society of Japan 75 Pages: 104713-104713
• [Journal Article] Magnetotransport Studies under Megagauss Magnetic Fields (2005)
  • Author(s): T. Osada
  • Journal Title: Proc. 10th Int. Conf. Megagauss Magnetic Field Generation and Related Topics, Berlin 2004 Pages: 227-233
  • Peer Reviewed
• [Journal Article] Electric-Field Effect on the Angle-Dependent Magnetotransport Properties of Quasi-One-Dimensional Conductors (2005)
  • Author(s): K. Kobayashi
  • Journal Title: Synthetic Metals 155 Pages: 670-673
  • Peer Reviewed
• [Journal Article] Magnetotransport Studies under Megagauss Magnetic Fields (2005)
  • Author(s): T.Osada
  • Journal Title: Proc.of 10th International Conference on Megagauss Magnetic Field Generation and Related Topics Pages: 227-233
• [Journal Article] Pulse Micromagnet for Practical High-Field Measurements (2005)
  • Author(s): E.Ohmichi
  • Journal Title: Review of Scientific Instruments 76 Pages: 76103-76103
• [Journal Article] Quantum Features of Angular Dependent Magnetoresistance Oscillations in Quasi-Two-Dimensional Conductors near High Magnetic Field Quantum Limit (2005)
  • Author(s): K.Kobayashi
  • Journal Title: Synthetic Metals 155 Pages: 670-673
• [Journal Article] Irreversibility Field and Coherence Length of Ca-substituted YBCO Single Crystals (2005)
  • Author(s): T.Masui
  • Journal Title: Physica C 426-431 Pages: 335-339
• [Journal Article] Electric Field Effect on Vertical Magnetotransport in Multilayer Systems under Tilted Magnetic Fields (2004)
  • Author(s): K. Kobayashi
  • Journal Title: Physica E 22 Pages: 385-388
  • Peer Reviewed
• [Journal Article] Electric Field Effect on Vertical Magnetotransport in Multilayer Systems under Tilted Magnetic Fields (2004)
  • Author(s): K.Kobayashi
  • Journal Title: Physica E 22 Pages: 385-388
• [Journal Article] Transport Measurement of Two-Dimensional Electron System under Ultra-High Magnetic Fields (2004)
  • Author(s): T.Inokuchi
  • Journal Title: Physica E 22 Pages: 381-384
• [Journal Article] Micro-Probe Measurement in Pulsed high Magnetic Fields (2004)
  • Author(s): E.Ohmichi
  • Journal Title: Physica B 346 Pages: 509-513
• [Journal Article] Application of a Tunnel Diode Oscillator to Noncontact Resistivity Measurement in Pulsed Magnetic Fields (2004)
  • Author(s): E.Ohmichi
  • Journal Title: Rev.Sci.Inst. 75 Pages: 2094-2097
• [Journal Article] Tunneling Picture of Interlayer Magnetotransport in Multilayer Systems (2003)
  • Author(s): T. Osada
  • Journal Title: Physica B 18 Pages: 200-201
  • Peer Reviewed
• [Journal Article] Interlayer Coherency and Angular Dependent Magnetoresistance Oscillations in Quasi-Two-Dimensional Conductors (2003)
  • Author(s): M. Kuraguchi
  • Journal Title: Synthetic Metals 133-134 Pages: 113-115
  • Peer Reviewed
• [Journal Article] General Quantum Picture for Magnetoresistance Angular Effects in Quasi-One-Dimensional Conductors (2003)
  • Author(s): T. Osada
  • Journal Title: Synthetic Metals 133-134 Pages: 75-77
  • Peer Reviewed
• [Journal Article] Influence of Interlayer and Interchain Coherence on MagnetoresistanceAngular Effects in Q1D Conductors (2003)
  • Author(s): T. Osada
  • Journal Title: Synthetic Metals 135-136 Pages: 653-654
  • Peer Reviewed
• [Presentation] Unconventional Angle-Dependent Magnetotransport and Possibility of Unconventional Charge Density Wave in α-(BEDT-TTF)_2KHg(SCN)_4 (2007)
  • Author(s): Toshihito Osada
  • Organizer: 7th International Symposium on Crystalline Organic Metals, Superconductors, and Ferro-magnets (ISCOM2007)
  • Place of Presentation: Peniscola, Spain
  • Year and Date: 2007-09-25
• [Presentation] Successive Transitions in Charge Density Wave State under High Magnetic Fields (2005)
  • Author(s): T. Osada
  • Organizer: International Symposium on Molecular Conductors (ISMC2005)
  • Place of Presentation: Hayama, Japan
• [Presentation] Successive Phase Transitions in Charge Density Wave State under High Magnetic Fields (2005)
  • Author(s): T. Osada
  • Organizer: International Symposium on Crystalline Organic Metals, Superconductors, and Ferromagnets (ISCOM2005)
  • Place of Presentation: Key West, USA.
• [Presentation] Transport Study of Low- Dimensional Conductors under Ultra-High Magnetic Fields (2004)
  • Author(s): T. Osada
  • Organizer: International Conference on Science and Technology of Synthetic Metals (ICSM2004)
  • Place of Presentation: Woolongong, Australia
• [Presentation] Ultra-High Magnetic Field Transport Measurements of Low-Dimensional Conductors (2004)
  • Author(s): T. Osada
  • Organizer: International Conference on Application of HighMagnetic Fields in Semiconductor Physics (SemiMag16)
  • Place of Presentation: Tallahassee, USA
• [Presentation] Ultra-High Magnetic Field Transport in Low-Dimensional Conductors (2003)
  • Author(s): T. Osada
  • Organizer: International Symposium on Crystalline OrganicMetals, Superconductors, and Ferromagnets (ISCOM2003)
  • Place of Presentation: Port-Bourgenay, France
• [Remarks]
  • URL: http://osada.issp.u-tokyo.ac.jp/