论文标题
纳米级 - 前二秒介电响应的莫特绝缘子由两彩色近野超快电子显微镜捕获
Nanoscale-femtosecond dielectric response of Mott insulators captured by two-colour near-field ultrafast electron microscopy
论文作者
论文摘要
表征和控制纳米结构的Mott绝缘子的不平衡状态对新兴量子技术有着巨大的承诺，同时为研究强相关系统的基本物理学提供了一个令人兴奋的操场。在这里，我们使用两色近场超快电子显微镜在单个VO2纳米线中拍摄绝缘体到金属的过渡，并使用结合的纳米前三秒分辨率探测随之而来的电子动力学。我们利用了由红外激光脉冲介导的电子脉冲的飞秒时间门控，并利用非弹性电子光散射的灵敏度对材料介电函数的变化的敏感性。通过空间映射VO2单个纳米线的近场动力学，我们观察到，超快的光掺杂将系统驱动到金属状态，在大约150 fs的时间尺度上，却不会扰乱结晶晶格。由于电子探针的多功能性和灵敏度，我们的方法将允许捕获具有最终时空分辨率的各种纳米级材料的电子动力学。
Characterizing and controlling the out-of-equilibrium state of nanostructured Mott insulators hold great promises for emerging quantum technologies while providing an exciting playground for investigating fundamental physics of strongly-correlated systems. Here, we use two-colour near-field ultrafast electron microscopy to photo-induce the insulator-to-metal transition in a single VO2 nanowire and probe the ensuing electronic dynamics with combined nanometer-femtosecond resolution. We take advantage of a femtosecond temporal gating of the electron pulse mediated by an infrared laser pulse, and exploit the sensitivity of inelastic electron-light scattering to changes in the material dielectric function. By spatially mapping the near-field dynamics of an individual nanowire of VO2, we observe that ultrafast photo-doping drives the system into a metallic state on a time scale of about 150 fs without yet perturbing the crystalline lattice. Due to the high versatility and sensitivity of the electron probe, our method would allow capturing the electronic dynamics of a wide range of nanoscale materials with ultimate spatio-temporal resolution.
