Full control of far -infrared laser harmonics

• Project/Area Number: 19K22140
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 30:Applied physics and engineering and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Ishida Yukiaki 東京大学, 大学院理学系研究科(理学部), 特任講師 (30442924)
• Project Period (FY): 2019-06-28 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥6,370,000 (Direct Cost: ¥4,900,000、Indirect Cost: ¥1,470,000); Fiscal Year 2020: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000); Fiscal Year 2019: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
• Keywords: 角度分解光電子分光 / 仕事関数 / 表面分極 / 角度分解光電子分光法 / 円二色性 / 表面電子状態 / 非線形光学効果 / 第二高調波発生 / レーザー高調波 / 偏向依存性 / 表面光電効果 / 第２高調波発生 / 遠紫外 / 光電子分光 / 表面非線形光学

Outline of Research at the Start

レーザーと光電子分光（PES）の技術融合に駆動される形で非線形光学と一電子励起の学理が融合し、表面科学に新しい視座をもたらす可能性が見えてきた。この学際領域は遠紫外域において興り得る。遠紫外光は「固体表面で反射や屈折をしながら光電子も放出できる」という特徴をもつ。ここでは表面分極と光電効果の協奏現象も予言されているが、遠紫外域のPESが未発達であること、また光と表面の多体効果がしばしば先験的に省かれることも手伝って、検証は手つかずである。近年、遠紫外PESを精緻にするポテンシャルをもつ高調波が次々と登場している中で、表面科学の新展開を見据えつつ、遠紫外光がその真価を発揮するための基盤を整える。

Outline of Final Research Achievements

(1) By utilizing a 6 eV laser harmonic light source, we demonstrated a new method to accurately measure the work function with unprecedented precision below one meV. (2) We measured the response of the work function to femtosecond pulses using time-resolved photoelectron spectroscopy. We introduced a model connecting the work function and surface polarization and proposed a novel method to estimate the nonlinear susceptibility of surface polarization. (3) We constructed a second harmonic generation measurement device, a powerful tool for observing the nonlinear optical response in surface regions. We observed the step-wise 1st-order transition in the MoTe2 surface region. (4) Using an 11 eV circularly polarized laser harmonic, we investigated the circular dichroism of the angular distribution of photoelectrons. We systematically discussed classifying circular dichroism patterns based on point groups and estimated the surface localization of wave functions.

Academic Significance and Societal Importance of the Research Achievements

固体表面で反射や屈折もしながら光電子も放出することができる遠紫外域の光は、固体表層数Åの表面媒質と長波長近似を超えた複雑は相互作用をする可能性が１９３０年代から指摘されているが、この問題は全く手つかずと言っても過言ではなかった。本研究では固体表面の仕事関数を世界最高精度で測定したり表面分極の非線形感受率を求めたりする新手法を提示した。本成果により、表面分極と遠紫外域光の複雑な相互作用を解明するための足掛かりがえられた。

Research Products

• [Int'l Joint Research] Institite for Basic Science(韓国)
• [Int'l Joint Research] Lawrence Berkeley National Laboratory(米国)
• [Int'l Joint Research] 韓国科学院/ソウル国際大学(韓国)
• [Int'l Joint Research] Russian Academy of Sciences/Novosibirsk State University/Saint Petersburg State University(ロシア連邦)
• [Journal Article] A new category of “Aha!” driven by touch: A grip sensation into the directional seam on a baseball (2023)
  • Author(s): Yukiaki Ishida
  • Journal Title: i-Perception Volume: 14 Issue: 3 Pages: 1-10
  • DOI: 10.1177/20416695231175598
  • Peer Reviewed / Open Access
• [Journal Article] Effect of the sample work function on alkali metal dosing induced electronic structure change (2021)
  • Author(s): Saegyeol Jung, Yukiaki Ishida, Minsoo Kim, Masamichi Nakajima, Shigeyuki Ishida, Hiroshi Eisaki, Woojae Choi, Yong Seung Kwon, Jonathan Denlinger, Toshio Otsu, Yohei Kobayashi, Soonsang Huh, Changyoung Kim
  • Journal Title: Journal of Electron Spectroscopy and Related Phenomena Volume: 249 Pages: 147045-147045
  • DOI: 10.1016/j.elspec.2021.147045
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] A compact and stable incidence-plane-rotating second harmonics detector (2021)
  • Author(s): Kim S. H.、Jung S.、Seok B.、Kim Y. S.、Park H.、Otsu T.、Kobayashi Y.、Kim C.、Ishida Y.
  • Journal Title: Review of Scientific Instruments Volume: 92 Issue: 4 Pages: 043905-043905
  • DOI: 10.1063/5.0047337
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Work function seen with sub-meV precision through laser photoemission (2020)
  • Author(s): Ishida Y.、Jung J. K.、Kim M. S.、Kwon J.、Kim Y. S.、Chung D.、Song I.、Kim C.、Otsu T.、Kobayashi Y.
  • Journal Title: Communications Physics Volume: 3 Issue: 1 Pages: 158-158
  • DOI: 10.1038/s42005-020-00426-x
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Bidirectional surface photovoltage on a topological insulator (2019)
  • Author(s): T. Yoshikawa, K. Sumida, Y. Ishida, J. Chen, M. Nurmamat, K. Akiba, A. Miyake, M. Tokunaga, K. A. Kokh, O. E. Tereshchenko, S. Shin, A. Kimura
  • Journal Title: Physical Review B Volume: 100 Issue: 16 Pages: 165311-165311
  • DOI: 10.1103/physrevb.100.165311
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Laser ARPES for the Precise Detection of Slowest Photoelectrons and Work functions (2019)
  • Author(s): Y. Ishida
  • Organizer: The 17th Japan-Korea symposium on molecular science
  • Int'l Joint Research / Invited
• [Presentation] Time-resolved ARPES study of Dirac and topological materials (2019)
  • Author(s): Y. Ishida
  • Organizer: The 11th International Symposium on Natural Sciences
  • Int'l Joint Research / Invited
• [Presentation] Time-resolved ARPES study of Dirac and topological materials (2019)
  • Author(s): Y. Ishida
  • Organizer: 2019 KPS Fall Meeting
  • Invited
• [Presentation] Photoelectron work function seen with 1-meV precision (2019)
  • Author(s): Y. Ishida
  • Organizer: 2019 KPS Fall Meeting
  • Invited
• [Remarks] Measuring work function precisely by using laser
  • URL: https://go.nature.com/30cyXYr