Spin polarization and spin dependent shift current in electron systems irradiated by circularly polarized light

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K03841
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Kanazawa Institute of Technology (2022); Waseda University (2020-2021)
• Principal Investigator: Tanaka Yasuhiro 金沢工業大学, 基礎教育部, 講師 (50541801)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 光誘起相転移

Outline of Final Research Achievements

We have theoretically studied spin polarization induced by circularly polarized light in semiconductors with strong spin-orbit interaction. We have used numerical simulations and the Floquet theory to investigate photoinduced dynamics of microscopic electronic models. We clarified how the magnitude and the sign of the photoinduced spin polarization depend on the light electric field, frequency, and the electronic band of the system. Our results are consistently interpreted as the inverse Faraday effect, and they enable us to understand the existing theories including phenomenological ones in a unified manner. In this research project, we have not calculated the shift current itself. However, our results show that the spin polarization mainly occurs near the Fermi surface, suggesting that the realization of spin dependent current due to circularly polarized light. This point is an important future problem.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

本研究で得られた円偏光誘起スピン偏極に関する成果は、古くから知られた逆ファラデー効果に関する過去の多くの理論を現代的かつ統一的な視点から捉え直すとともに、スピン偏極に対する電子系のバンド構造の影響といった、これまでにない知見を与えているという点で学術的な意義がある。さらに、我々が行った理論解析結果は、スピン軌道相互作用の強い半導体において観測が可能であると予測され、将来的に光で電子系のスピンや光誘起電流を制御するといった応用上の観点からも重要な結果と考えられる。