2022 Fiscal Year Final Research Report
Anomalous optical properties by circularly polarized light in low-dimensional materials
| Project/Area Number |
18H01810
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 28020:Nanostructural physics-related
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| Research Institution | Tohoku University |
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Principal Investigator |
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| Project Period (FY) |
2018-04-01 – 2023-03-31
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| Keywords | 円偏光 / 共鳴ラマン分光 / ヘリシティ / 2次元物質 / 第一原理計算 |
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| Outline of Final Research Achievements |
A circularly polarized photon has angular momentum, and pseudoangular momentum (angular momentum defined by motion of only discrete angles) is conserved in the interaction with two-dimensional materials with rotational symmetry. In resonance Raman spectroscopy, when the incident and scattered light are circularly polarized, there is Raman scattering in which the helicity (±hbar) of the circularly polarized light does not change and Raman scattering in which the sign reverses. In this study, we theoretically analyzed this phenomenon and clarified (1) the relation between the sign of helicity in Raman scattering from the law of conservation of angular momentum. (2) From the equation of the Raman tensor, we showed that the phenomenon can be explained by a system even without rotational symmetry. (3) Furthermore, we developed a program to calculate the circularly polarized, resonant Raman intensity from first-principles calculations.
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| Free Research Field |
物性物理学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究の学術的意義は、固体の共鳴ラマン分光強度を第一原理計算でできるようになった点である。また、円偏光を用いたラマン分光が従来のラマン分光よりも、格子振動の対称性などを直接観測できるようになったことを示したことに意義がある。これらの計算を拡張することによって、回転対称性を持たない、カイラルな物質を円偏光で測定すると、右巻きと左巻きのカイラルな物質をラマン分光で区別することができるなど新奇な学理を生み出した。今日、新物質の評価として、ラマン分光が非常に多く使われているので、一般の材料科学、物理学、化学など幅広い学問や産業に貢献すると期待している。
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