Quantum thermoelectric transport and nonequilibrium quantum thermodynamics at nanoscale

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03682
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: University of Tsukuba
• Principal Investigator: Taniguchi Nobuhiko 筑波大学, 数理物質系, 准教授 (70227221)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 熱電現象 / 量子ドット / 量子熱力学 / 非平衡 / ナノ量子系 / 量子輸送

Outline of Final Research Achievements

By applying both a potential difference and a temperature difference between electrodes, nanostructure quantum systems have recently gained considerable attention as thermoelectric devices converting heat into electrical energy. In this research project, we have revealed that controlling the quantum coherence of the system is highly effective in improving their thermal efficiency and output power of nanoscale quantum structures. By embedding a quantum dots in the ring and controlling quantum coherence, we could improve them by up to 5-10 times compared to a dot. We also obtained similar results in the case of nanoscale nanoribbons.
Understanding nanoscale thermoelectric phenomena requires thermodynamics based on quantum principles. By developing the "non-equilibrium quantum thermodynamics" of a single-level quantum dot, we have found that optimal driving between non-equilibrium steady states that minimizes the generalized work dissipation is characterized by thermodynamic distance.

Free Research Field

物理学

Academic Significance and Societal Importance of the Research Achievements

微細構造技術の進歩に伴い、ナノ量子系をデザインすることが可能となったものの、いかなる構造のナノ系が、エネルギー変換素子として優位性をもつかは必ずしも明らかでなかった。本研究の学術的な意義は、ナノ量子熱機関の開発において、量子コヒーレンス制御が熱電特性の向上に極めて重要である点を明らかにした点である。同時に具体的なナノ系非平衡量子熱力学の解析により、最適駆動に関する知見を得ることができた。将来的には、本課題の成果を利用したエネルギー変換技術の開発を進めることで、エネルギー効率の向上と従来の熱機関が利用できなかった状況での利用を可能とし、持続可能な社会を実現することが期待される。