发表机构
Shanghai Jiao Tong University; Renmin University of China; Institute of Physics, Chinese Academy of Sciences（上海交通大学; 中国人民大学; 中国科学院物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究以1T-TaS2为对象，通过太赫兹泵浦-光学探测等实验，揭示了非共振脉冲受激拉曼散射机制，为太赫兹场调控凝聚态集体模式提供了依据。
AI 中文摘要
时域超快非线性太赫兹光谱技术近来被应用于诸多凝聚态体系，以研究其集体激发。在中心对称体系中，这类集体模式通常具有拉曼活性，因此无法直接与太赫兹电场耦合；这类研究中光与物质相互作用的机制尚未被详细明确讨论。本研究对1T-TaS2（一种具有丰富电荷密度波（CDW）相图的材料，包含公度、近公度和非公度CDW相）开展太赫兹泵浦-光学探测及太赫兹三次谐波产生研究。这些不同状态间的转变在动态拉曼响应上留下了清晰特征。我们探究拉曼活性声子如何耦合宽带单周期太赫兹场及窄带多周期太赫兹场。结果表明，涉及双光子吸收的改进型脉冲受激拉曼散射机制（又称非共振拉曼散射）是晶格模式相干激发与观测的基础。这些结果对未来利用低能太赫兹场开展集体模式的光谱研究与相干调控，以及固体的腔电动力学修饰具有重要意义。
英文摘要
Time-domain ultrafast and nonlinear terahertz spectroscopy techniques are recently applied to many condensed matter systems for investigating their collective excitations. In centrosymmetric systems, these collective modes are typically Raman-active and therefore do not couple directly to the terahertz electric field. The mechanism by which light-matter interaction realizes in these studies has not been explicitly discussed in detail. In this work, we perform terahertz pump - optical probe and terahertz third harmonic generation investigations on 1T-TaS2, a material exhibiting a rich charge-density-wave (CDW) phase diagram including the commensurate, nearly-commensurate and incommensurate CDW phases. The transition between these distinct states leaves a clear signature on the dynamical Raman response. We investigate how the Raman-active phonons couple to a broadband monocycle terahertz field as well as a narrowband multicycle terahertz field. Our results indicate that a modified impulsively stimulated Raman scattering mechanism involving two-photon absorption, also known as non-resonant Raman scattering, underlies the coherent excitation and observation of the lattice modes. These results are relevant for future spectroscopy investigation and coherent control of collective modes using low-energy terahertz field as well as cavity electrodynamical dressing of solids.
