| Project/Area Number |
17K14329
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Condensed matter physics II
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| Research Institution | Tohoku University |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
Fiscal Year 2019: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
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| Keywords | トポロジカル絶縁体 / 熱電材料 / 薄膜 / 電子輸送特性 / ゼーベック効果 / 量子ホール効果 / ゼーベック係数 / 異常ホール効果 / 熱電物性 |
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| Outline of Final Research Achievements |
Here, we studied the thermoelectric (TE) properties of the topological surface Dirac states (TSDSs) on the three-dimensional topological insulators (3D-TIs). By employing two high bulk insulating 3D-TI materials as Bi2-xSbxTe3-ySey and Sn-Bi1.08Sb0.9Te2S, we performed a direct observation of the TE transports of TSDSs and revealed several intrinsic properties of TSDSs: First, TSDSs shows a quite high Seebeck coefficient (S) and Power factor (PF), which is more than one magnitude higher than conventional metals and also higher than these value of other 2D materials. Second, the S and PF of TSDSs can be enhanced by introducing an energy gap between the TSDS by reducing the film thickness. Third, we revealed that the large S and PF of TSDSs are originated to the energy dependence of relaxation time of Dirac electrics.
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| Academic Significance and Societal Importance of the Research Achievements |
本研究は、理論的に提言されつつも実証されてこなかった3次元トポロジカル絶縁体の熱電性能に対し、初めて表面ディラク電子の熱電輸送特性を明瞭に観測し、そのメカニズムの一旦を明らかにした。特に、電子緩和時間のエネルギー依存性は、従来の材料研究ではほとんど考慮されなかった事象であり、それによる熱電性能の向上を示唆した本研究は、熱電材料開発に新たな指針を見出したと評価できる。更に、本研究で開発した3D-TI薄膜は大面積試料であり、今後の熱物性研究や応用利用にも大きく寄与できる。TI表面における高い熱電力（PF）を実証できたことで、今後、TI材料を用いた熱電材料研究を促進できると期待する。
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