Study of nonlinear terahertz response in Weyl semimetals with broken inversion symmetry

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K13858
• 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: Matsuda Takuya 東京大学, 物性研究所, 特別研究員 (30881239)
• Project Period (FY): 2021-04-01 – 2023-03-31
• Keywords: テラヘルツ / ワイル半金属 / 非線形応答

Outline of Final Research Achievements

Weyl semimetals with broken inversion symmetry exhibit a second-order nonlinear interaction owing to its nonreciprocity. So far, the electromagnetic response has been investigated by dc or high-frequency light (0.1-1 eV), and terahertz spectroscopy, which fills the gap between dc and high-frequency light, is very important in that it explores the response near the Fermi surface.
In this study, we investigated the electromagnetic response of the Weyl semimetal Td-WTe2 in the terahertz frequency. We have successfully observed the second and third harmonic generation at room temperature for the first time. We also found that the contribution of the room-temperature nonlinear Hall effect in the terahertz frequency is sufficiently small. Furthermore, we developed on-chip terahertz spectroscopy measurement system which enables the measurement of the terahertz response of tiny or flake samples such as Td-WTe2.

Free Research Field

光物性

Academic Significance and Societal Importance of the Research Achievements

本研究では空間反転対称性の破れたワイル半金属のテラヘルツ応答を調べたが、特に室温で高効率な第２および第３高調波発生を観測したことは、基礎物理学的側面のほかテラヘルツ周波数変換素子などの高速エレクトロニクス応用においても重要であると考えられる。また、オンチップテラヘルツ分光計測技術開発を進めたことは、従来のテラヘルツ分光測定ではなしえない剥片試料にも適用できるため、今後、様々な物質の低エネルギー応答の理解が進むことが期待される。