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Terahertz emission spectroscopy of mid-infrared active photocurrent dynamics in Weyl semimetals

Research Project

Project/Area Number 20K15198
Research Category

Grant-in-Aid for Early-Career Scientists

Allocation TypeMulti-year Fund
Review Section Basic Section 30020:Optical engineering and photon science-related
Research InstitutionThe University of Tokyo

Principal Investigator

Soutome Masato  東京大学, 先端科学技術研究センター, 特任助教 (40783999)

Project Period (FY) 2020-04-01 – 2022-03-31
Project Status Completed (Fiscal Year 2021)
Budget Amount *help
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2021: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
Fiscal Year 2020: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Keywordsシフト電流 / 光電流 / 太陽電池 / テラヘルツ / 超高速分光 / 半導体 / 中赤外 / フェムト秒 / 半金属 / ワイル半金属
Outline of Research at the Start

中赤外(波長3-15μm)の光検出器は、室温の熱放射がこの帯域であるために障害物・人感センサーなど多くの応用が期待される。近年、フェルミ面に2つのDirac点を持つWeyl半金属と呼ばれる物質群で中赤外域に敏感な光電流が発見されはじめた。Weyl半金属は直線状のバンド構造のために移動度も高く、室温動作赤外センサーに有望な物質群である。本研究では、フェムト秒レーザー励起での過渡的光電流からアンテナ放射されるテラヘルツ電場波形を測定することでサブピコ秒光電流ダイナミクスを観測し、Weyl半金属における光電流の量子力学的起源やその回路電流との関連を明らかにする。

Outline of Final Research Achievements

Photocurrent in semiconductors is widely used in photodetectors and solar cells. Recently, quantum mechanical theory of semiconductors proposed that shift-current, in which the electron cloud propagates coherently instantly, can be the basis of a new type solar cell. In this study, we experimentally evaluated the sub-picosecond dynamics of shift-current and its amplitude by observing terahertz electromagnetic waves emitted from the shift-current. We clarified ultrafast dynamics of photocurrent in a prototypical semiconductor CdS. We measured the excitation photon energy dependence (0.5-2.6 eV) of terahertz emission, and found a peak structure on its exciton resonance.

Academic Significance and Societal Importance of the Research Achievements

シフト電流のモデル物質として、化合物半導体CdSにおける励起子共鳴励起でのシフト電流ダイナミクスを観測することに成功した。シフト電流の励起光子エネルギー依存性に励起子共鳴でピークが見られ、その振幅がシフト電流の理論と定量的に一致することを見出した初めての研究である。将来の光電変換デバイス(太陽電池・光検出器など)の基本原理となる現象について電極などの影響を受けずに観測できることを示した。

Report

(3 results)
  • 2021 Annual Research Report   Final Research Report ( PDF )
  • 2020 Research-status Report
  • Research Products

    (5 results)

All 2021 Other

All Int'l Joint Research (2 results) Journal Article (3 results) (of which Int'l Joint Research: 1 results,  Peer Reviewed: 3 results,  Open Access: 1 results)

  • [Int'l Joint Research] Massachusetts Institute of Technology(米国)

    • Related Report
      2021 Annual Research Report
  • [Int'l Joint Research] National Taiwan University(その他の国・地域)

    • Related Report
      2021 Annual Research Report
  • [Journal Article] Shift current: A quantum-mechanical photovoltaic effect in noncentrosymmetric crystals2021

    • Author(s)
      中村 優男、五月女 真人、小川 直毅、川﨑 雅司
    • Journal Title

      Oyo Buturi

      Volume: 90 Issue: 2 Pages: 98-102

    • DOI

      10.11470/oubutsu.90.2_98

    • NAID

      130007981087

    • ISSN
      0369-8009, 2188-2290
    • Year and Date
      2021-02-05
    • Related Report
      2021 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Highly-efficient terahertz emission from hydrogen-bonded single molecular crystal 4-nitro-2, 5-bis (phenylethynyl) aniline2021

    • Author(s)
      M. Sotome, T. Ogaki, K. Takimiya, and N. Ogawa
    • Journal Title

      Optics Express

      Volume: 29 Issue: 7 Pages: 10048-10058

    • DOI

      10.1364/oe.418312

    • Related Report
      2021 Annual Research Report 2020 Research-status Report
    • Peer Reviewed / Open Access
  • [Journal Article] Terahertz emission spectroscopy of ultrafast exciton shift current in the noncentrosymmetric semiconductor CdS2021

    • Author(s)
      Sotome M.、Nakamura M.、Morimoto T.、Zhang Y.、Guo G.-Y.、Kawasaki M.、Nagaosa N.、Tokura Y.、Ogawa N.
    • Journal Title

      Physical Review B

      Volume: 103 Issue: 24

    • DOI

      10.1103/physrevb.103.l241111

    • Related Report
      2021 Annual Research Report
    • Peer Reviewed / Int'l Joint Research

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Published: 2020-04-28   Modified: 2023-01-30  

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