Fundamental theory for laser frequency down-conversion using time crystals

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K03811
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: The University of Tokyo
• Principal Investigator: Tsuji Naoto 東京大学, 大学院理学系研究科(理学部), 准教授 (90647752)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 非平衡 / 時間結晶 / 超伝導

Outline of Final Research Achievements

We analyzed the dynamics of electron systems driven by ac electric fields for various models based on the nonequilibrium dynamical mean-field theory and other methods. We found that there exists an electric current oscillating with frequencies different from those of the driving fields. Usually, integral multiples of the frequency of the driving fields may appear due to nonlinear response effects. However, it was found that other frequency components that are not integral multiples can also appear. In particular, a current with frequencies lower than the frequency of the driving fields may be generated. We also investigated how collective excitations such as the Higgs and Leggett modes contribute to the response to oscillating electric fields in systems with a long-range order such as superconductivity.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

本研究によって、固体電子系において様々なメカニズムで駆動電場の周波数よりも低い周波数で振動する電流成分が発生することがわかった。このことは、レーザー光の強度を高く保ちながら周波数を下方変換する技術に応用することができると期待される。また、その研究過程で固体電子系が示す様々な集団励起モードが光応答に対してどのように寄与するかが明らかになった。これらは、固体中のミクロな電子状態の性質を解明することにつながるだけでなく、レーザー光を用いて電子状態を高速に制御し、あるいは光によって超伝導をはじめとした長距離秩序を誘起・増幅することへの足掛かりになると考えられる。