Elucidation of a mechanism of high-harmonic generation in solids based on Floquet subband picture

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14624
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: The University of Tokyo
• Principal Investigator: Tomohiro Tamaya 東京大学, 物性研究所, 特任研究員 (20633697)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 半導体 / 高次高調波発生 / フロッケ理論 / GaAs / せん断応力 / ベリー位相 / 電気分極

Outline of Final Research Achievements

In this study, we propose a novel picture of high-harmonic generation (HHG) in solids by expanding our original theory published in the previous works. The picture proposed in this study is based on the Floquet subband that is derived from a concept of a temporally changing band structure. This subband picture suggests a peculiar feature of HHG intensity that becomes a non-monotonic function of the incident light amplitude. By comparing to an experiment of GaAs, we could identify this non-monotonic behavior as a function of the excitation light fields and confirm the consistency between our theory and experimental results. The picture proposed in this study not only reveals the origin of the plateau structure in HHG spectra, but also provides a connection to other high-field phenomena.

Free Research Field

光物性

Academic Significance and Societal Importance of the Research Achievements

固体における高次高調波の発生機構はこれまで主に3ステップ模型に基づいて理解されてきた。しかしながらこの理解では高次高調波と他の高強度光物理現象との関係性が不明瞭なままである。以上を踏まえ、本研究では他の高強度光物理現象と矛盾のない高次高調波の発生機構と物理的描像を提示した。本研究で得られた描像は非摂動論的な領域における非線形光学現象の基礎的かつ統一的理解を与えると共に、新たな光源開発の指針を示すものとなる。