Thermoelectric transport of non-equilibrium carriers

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13504
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Tokyo University of Science
• Principal Investigator: OKAZAKI Ryuji 東京理科大学, 理工学部物理学科, 准教授 (50599602)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 熱電効果 / 輸送現象 / ゼーベック効果 / 電流効果 / 非線形伝導 / 非平衡電子状態

Outline of Final Research Achievements

When the electric voltage is applied to the sample, the electrical current, which is proportional to the applied voltage, flows to the sample. In contrast to this well-known Ohm’s law, the transport phenomenon in which the flowing current is not proportional to the applied voltage is called nonlinear conduction. As seen in various nonlinear electric components such as diodes and transistors, the nonlinear conduction becomes a fundamental technology for the present electronics. In this research, we have investigated the nonlinear Seebeck effect, in which the thermopower depends on the current as similar to the current-dependent resistivity in the nonlinear conduction, and have found that the absolute value of the thermopower is increased by applying electrical current in an organic-molecular-based conductors. We also developed a temperature evaluation method for the self-heating problem.

Free Research Field

物性物理学

Academic Significance and Societal Importance of the Research Achievements

非線形伝導は、近年、シリコンやゲルマニウムのような従来のバンド絶縁体だけでなく、モット絶縁体や電荷秩序絶縁体と呼ばれる強相関絶縁体において報告されており、それらの物質群では、数V/cmの電場で抵抗が１桁以上も変化する大きな非線形伝導が報告されています。それらは低電場で作動する新たなメモリ素子として応用上期待されるだけでなく、従来のメカニズムとは異なった、電場による電荷秩序の融解などの新しい非平衡物理現象を示すモデル物質としても注目されつつあり、本研究では通電時の抵抗の振る舞いだけでなく、ゼーベック係数も調べることで、そのような非平衡電子状態の知見を得ることに成功しました。