Study on unconventional infrared photovoltaics using quantum materials

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02605
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 29010:Applied physical properties-related
• Research Institution: Kyoto University
• Principal Investigator: Miyauchi Yuhei 京都大学, エネルギー理工学研究所, 教授 (10451791)
• Co-Investigator(Kenkyū-buntansha): 宮田 耕充 東京都立大学, 理学研究科, 准教授 (80547555)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: ワイル半金属 / 赤外光電流

Outline of Final Research Achievements

Weyl semimetal crystals TaIrTe4 and Co3Sn2S2 were synthesized for various experiments. Using TaIrTe4, devices were fabricated for polarization-resolved spatial mapping of photocurrent under infrared light (4 μm wavelength) irradiation and for measuring its dependence on the irradiation light frequency. As a result, it was found that the contributions of thermoelectric effect inside the material and nonlinear optical response near the surface could be separately captured by the frequency dependent measurements; the latter can be interpreted as originating from the topological effect. For Co3Sn2S2, the phonon modes and frequencies were identified via polarization-resolved Raman scattering measurements, and Fano effect due to the electron Raman scattering contribution was revealed. In addition, methods for synthesis of large-area atomic wires such as WTe and their conversion to ribbon-like large-area networks such as Weyl semimetal WTe2 were developed.

Free Research Field

光物性物理、物質科学、熱工学

Academic Significance and Societal Importance of the Research Achievements

TaIrTe4における赤外光電流の起源を切り分けて捉えられることを示した成果は、非従来型赤外光電変換機構の解明に向けた重要な手がかりを与えるものである。単結晶Co3Sn2S2のラマン散乱スペクトル構造とその起源を明らかにした成果は、結晶の簡易構造同定や、フェルミエネルギー近傍の低エネルギー電子状態プローブとしてのラマン分光の可能性を示したもので、今後赤外光応答を含む各種物性研究の発展に寄与すると期待される。また、本研究で開発したWTe等原子細線の大面積合成と、そのWTe2等のリボン状大面積ネットワークへの転換技術は、今後のカルコゲナイド系試料を利用した大面積素子作製の基盤となる成果である。