Low-temperature thermoelectric response of insulators

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05435
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Gakushuin University (2018); Tokyo Institute of Technology (2016-2017)
• Principal Investigator: Machida Yo 学習院大学, 理学部, 准教授 (40514740)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 熱電現象 / フォノン流体

Outline of Final Research Achievements

Seebeck coefficient measurements on two-dimensional layered material, black phosphorus in the wide temperature range reveal thermoelectric response in each transport regimes including the activating regime and hopping regime. Moreover, it was clarified that the Seebeck coefficient exhibits a power-law behavior at low temperature and vanishes as temperature does to zero. This result implies that two distinct contribution from hole and electron carriers to the Seebeck coefficient cancel out in extrinsic semiconductors. It was also found that the Seebeck coefficient shows a critical behavior characterized by an enhancement of the Seebeck coefficient divided by temperature in the vicinity of critical pressure of metal-insulator transition.

Free Research Field

固体物理

Academic Significance and Societal Importance of the Research Achievements

熱電効果は廃熱エネルギーを電気エネルギーに変換して有効に活用するための基盤技術である。現在、熱電材料として利用されている物質の多くは半導体である。本研究を通して得られた半導体・絶縁体のゼーベック係数に関する知見は、現状よりも更なる高効率の熱電変換材料の開発に役立てられるものと期待される。また本研究を通じて、絶縁体の低温極限におけるゼーベック係数の振る舞いや、金属絶縁体転移近傍における臨界的挙動が明らかされたことは、固体の熱電現象に関する根本的な理解を進める学術的意義をもつ。