Folpini Giulia, Reimann Klaus, Woerner Michael, Elsaesser Thomas, Hoja Johannes, Tkatchenko Alexandre
Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg, Luxembourg and Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
Phys Rev Lett. 2017 Sep 1;119(9):097404. doi: 10.1103/PhysRevLett.119.097404.
The nonlinear response of soft-mode excitations in polycrystalline acetylsalicylic acid (aspirin) is studied with two-dimensional terahertz spectroscopy. We demonstrate that the correlation of CH_{3} rotational modes with collective oscillations of π electrons drives the system into the nonperturbative regime of light-matter interaction, even for a moderate strength of the THz driving field on the order of 50 kV/cm. Nonlinear absorption around 1.1 THz leads to a blueshifted coherent emission at 1.7 THz, revealing the dynamic breakup of the strong electron-phonon correlations. The observed behavior is reproduced by theoretical calculations including dynamic local-field correlations.
利用二维太赫兹光谱研究了多晶乙酰水杨酸（阿司匹林）中软模激发的非线性响应。我们证明，即使对于强度适中（约50 kV/cm）的太赫兹驱动场，CH₃旋转模式与π电子集体振荡的相关性也会使系统进入光与物质相互作用的非微扰 regime。1.1太赫兹附近的非线性吸收导致1.7太赫兹处出现蓝移相干发射，揭示了强电子 - 声子相关性的动态破裂。包括动态局部场相关性的理论计算再现了观察到的行为。
