2021 Fiscal Year Annual Research Report
Theoretical study of nonlinear optical responses of ultracold atomic systems: towards a high-resolution coherent multidimensional spectroscopy investigation of quantum many-body effects
| Project/Area Number |
19K14638
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| Research Institution | Kyoto University |
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Principal Investigator |
Nguyen Thanh 京都大学, 工学研究科, 講師 (50736337)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | coherent 2D spectroscopy / many-body interaction / nonlinear response / light-matter interaction / molecular polariton / super-reaction / collective enhancement |
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| Outline of Annual Research Achievements |
Interactions between particles play a crucial role in various physical properties of quantum many-body systems, ranging from superfluidity and superconductivity to magnetic phase transitions. On the other hand, recent advances in laser-pulse technique have enabled the manipulations and measurements of these properties on ultrafast timescales. In this project, we have developed a new method for direct and ultrafast probing of quantum many-body interactions through the coherent two-dimensional (2D) spectroscopy [Physical Review B 104, 115105 (2021)]. We found that the 2D spectrum of a noninteracting system contains only diagonal peaks and the interparticle interaction manifests itself in the emergence of off-diagonal peaks in the 2D spectrum before all the peaks coalesce into a single diagonal peak as the system approaches the strongly interacting limit. Furthermore, the evolution of the 2D spectrum as a function of the time delay between laser pulses can provide important information on the ultrafast time variation of the interaction.
In relation to the nonlinear optical responses of atoms and electrons, we have also studied the strong coupling of a molecular system to an optical cavity, by which the molecular polariton, a hybrid state of light and matter, is formed. We have investigated the effect of molecular polariton formation on the chemical reactivity and elucidated the underlying mechanism [Scientific Reports 10, 7318 (2020)], and discovered the super-reaction with a collective enhancement of reaction rate [The Journal of Chemical Physics 155, 014308 (2021)].
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