Realization of new electronic phase transitions based on quantum tunneling processes by a strong mid-infrared electric-field pulse

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01166
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: The University of Tokyo
• Principal Investigator: Okamoto Hiroshi 東京大学, 大学院新領域創成科学研究科, 教授 (40201991)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: フェルト秒レーザー分光 / 赤外分光 / 光誘起相転移

Outline of Final Research Achievements

In this study, we aimed to observe giant electronic responses and ultrafast phase transitions based on a new mechanism by irradiating organic molecular crystals with a mid-infrared　(MIR) pulse. First, in order to observe the response along the electric field waveform of the MIR pulse, a phase-stable MIR pulse was generated, and a high-precision sub-cycle spectroscopy system was constructed in combination with the visible ultrashort pulse. Using this system, in a neutral-ionic transition system of a molecular crystal, we observed ionic-neutral transition triggered by intermolecular charge transfers driven by molecular-vibration excitation and that caused by quantum-tunneling processes driven by non-resonant excitation. In a Mott insulator dimerized due to the spin-Peierls mechanism, we succeeded in observing a melting of spin-Peierls phase triggered by carrier generations by the electric-field-induced quantum tunneling processes.

Free Research Field

固体物性

Academic Significance and Societal Importance of the Research Achievements

光誘起相転移の研究は活発に行われているが、中赤外パルスを励起に使った研究は少ない。本研究では、分子性結晶において、中赤外パルスで分子間電子移動と強く結合する赤外活性分子内振動を励起することにより、分子間に大きな電子移動の変調を引き起こし、それをきっかけとしたイオン性－中性転移を実現した。また、中赤外パルスの強電場による量子トンネル過程を引き金とするイオン性－中性転移やスピンパイエルス相融解の実証にも成功した。これらは、中赤外パルスを使った新しい電子相制御の可能性を拓くものであり、学術的意義の高い成果である。