Theory of thermoelectricity in Dirac electron systems(Fostering Joint International Research)

2018 Fiscal Year Final Research Report

• Project/Area Number: 15KK0155
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: The University of Electro-Communications
• Principal Investigator: Fuseya Yuki 電気通信大学, 大学院情報理工学研究科, 准教授 (00377954)
• Research Collaborator: Behnia Kamran パリ高等物理化学学校, Laboratoire de Physique et d'Etude des Materiaux, CNRSディレクター
• Project Period (FY): 2016 – 2018
• Keywords: 磁気抵抗 / バレー分極 / Bi / Sb / SrTiO3 / 量子振動 / 量子極限

Outline of Final Research Achievements

By collaborating between theory (JPN) and experiment (FRA), we obtained the following results. (1) 100% valley polarization by magnetic field was achieved in Bi for the first time. (2) A new formula of magnetoresistance was derived and applied to various materials (Bi, Sb, SrTiO3). The largest magnetoresistance (10,000,000%) was achieved in Sb. The longstanding problem on magnetoresistance of Bi and SrTiO3 was solved partly.
The results were presented in the exhibition on science and art, held in Paris. During my stay, I organized an international workshop and promoted the construction of an international research network.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

電子が持つ電荷やスピンに次ぐ，新しい自由度としてバレーの自由度を制御する研究（バレートロニクス）が最近注目を集めている．本研究で達成した100%バレー分極は，バレートロニクスにおいて新しい方向性を示した．強磁性薄膜を用いた磁気抵抗は，すでにハードディスクなどで実用化されている．（発見者はノーベル賞を受賞）これとは別に，最近，半金属を用いた非常に大きな磁気抵抗が関心を集めている．本研究で得た実用的な磁気抵抗の理論は，今後磁気抵抗の実験を解析する上で，重要な役割を担いうる．
純粋に科学的研究で得られた成果の芸術性が評価されたことは，アウトリーチ活動の新たな方向性を示している．