Full control of far -infrared laser harmonics

2022 Fiscal Year Final Research Report

• 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
• Keywords: 角度分解光電子分光 / 仕事関数 / 表面分極

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.

Free Research Field

固体および固体表面の電子物性

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。