发表机构
Newcastle University; Imperial College London; Max Planck Institute for the Structure and Dynamics of Matter; Flatiron Institute, Simons Foundation（纽卡斯尔大学; 帝国理工学院; 马克斯·普朗克物质结构与动力学研究所; 西蒙斯基金会平顿研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究以交替堆叠的MoSe₂和WSe₂多层结构为对象，揭示激子多极性是调控光诱导声子的设计原理，可通过面外电场切换声子状态，为超快调控晶格与电子动力学开辟新途径。
AI 中文摘要
光激发驱动的电子分布变化会使原子发生位移，在超快时间尺度上产生相干声子。二维（2D）材料及其异质结构为调控这类声子提供了强大平台。然而，尽管光激发相干声子已被广泛观测，控制其特性的设计原理仍未明确。本研究通过对交替堆叠的MoSe₂和WSe₂多层结构进行详细原子级模拟，揭示了激子多极性是调控光诱导声子从相干态转变为压缩态的设计原理。这些声子为层间呼吸模式，其中偶极激子通过线性耦合产生相干态，四极激子通过二次耦合产生压缩态。此外，面外电场可实现类开关的调控作用，将四极激子转化为偶极激子，从而将声子状态从压缩态切换为相干态。例如，在三层WSe₂/MoSe₂/WSe₂结构中，光激发产生的1.04-THz呼吸模式在零场下为压缩态，在外加垂直电场下切换为相干态。实验上，这类声子状态可通过超快X射线或电子衍射直接探测，也可通过瞬态反射率间接探测。本研究结果为皮秒时间尺度下晶格与电子动力学的超快调控开辟了新途径，对太赫兹量子声子学、纳米光子技术及量子噪声受限传感具有重要意义。
英文摘要
Photoexcitation-driven changes in the electronic distribution displace atoms, generating coherent phonons on ultrafast timescales. Two-dimensional (2D) materials and their heterostructures offer a powerful platform for engineering these phonons. Yet, despite the widespread observation of photoexcited coherent phonons, a design principle for controlling their character remains elusive. Here, using detailed atomistic simulations of multilayers of alternating MoSe$_2$ and WSe$_2$, we reveal exciton multipolarity as a design principle for tuning photoinduced phonons from coherent to squeezed. These phonons are interlayer breathing modes, with dipolar excitons coupling linearly to generate coherent states and quadrupolar excitons coupling quadratically to produce squeezed states. Moreover, an out-of-plane electric field enables switch-like control, converting quadrupolar excitons into dipolar excitons and switching the phonon state from squeezed to coherent. For example, in trilayer WSe$_2$/MoSe$_2$/WSe$_2$, the photoexcited 1.04-THz breathing mode switches from a squeezed state at zero field to a coherent state under an applied vertical field. Experimentally, these phonon states can be directly probed by ultrafast X-ray or electron diffraction and indirectly through transient reflectivity. Our results open new avenues for ultrafast control of lattice and electronic dynamics on picosecond timescales, with implications for THz quantum phononics, nanophotonic technologies, and quantum-noise-limited sensing.
