Exploration of huge thermoelectric response in the quantum Hall systems

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K03817
• 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: The University of Tokyo
• Principal Investigator: Endo Akira 東京大学, 物性研究所, 助教 (20260515)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 熱電効果 / 量子ホール系 / 熱電性能指数 / コルビノ型試料 / ３オメガ法 / ２次元電子系 / １次元平面超格子 / 整合性磁気振動

Outline of Final Research Achievements

We have developed experimental methods for investigating the huge thermoelectric response of the quantum Hall systems. With the methods, we measured the thermal conductivity and confirmed the expected relation to the electrical conductivity. In a high magnetic-field regime, we experimentally identified the thermal dissipation through the edge states. We deduced analytic formulas for the thermoelectric figure of merit ZT for a Corbino sample, which revealed the possibility of having a large value exceeding 100. We also deduced analytic formulas for the thermoelectric and thermal conductivity tensors in unidirectional lateral superlattices, which required the previous interpretation of the experimentally observed commensurability oscillations (CO) to be altered owing to the tilting of the temperature gradient by the magnetic field. We have also succeeded in the first observation of the CO in the Hall resistivity, which is closely related to the thermoelectricity of the system.

Free Research Field

低次元電子物性

Academic Significance and Societal Importance of the Research Achievements

本研究で開拓した磁場中２次元電子系の熱伝導率測定手法は電気抵抗の測定に通常用いられる測定装置のみを使用するため、比較的容易に測定を行うことが可能で、今後の量子ホール系の熱電変換や熱輸送現象の発展に大きく寄与することが出来ると考えている。人工的に異方性を導入した２次元平面超格子の研究は、従来あまり考慮されてこなかった、磁場により温度勾配方位が曲げられる効果の探索の有力な研究手段となる。コルビノ型試料の量子ホール系のもつ高い熱電変換効率は、将来的には効率的な廃熱利用に応用され、エネルギー問題・環境への負荷軽減に資する可能性を秘めているものである。