Probing and manipulating the spatiotemporal dynamics of hot carriers in nanoscale metals is crucial to a plethora of applications ranging from nonlinear nanophotonics to single molecule photochemistry. The direct investigation of these highly non-equilibrium carriers requires the experimental capability of high energy resolution (~ meV) broadband femtosecond spectroscopy. When considering the ultimate limits of atomic scale structures, this capability has remained out of reach until date. Using a two color femtosecond pump-probe spectroscopy, we present here the real-time tracking of hot carrier dynamics in a well-defined plasmonic picocavity, formed in the tunnel junction of a scanning tunneling microscope (STM). The excitation of hot carriers in the picocavity enables ultrafast all optical control over the broadband (~ eV) anti Stokes electronic resonance Raman scattering (ERRS) and the four-wave mixing (FWM) signals generated at the atomic length scale. By mapping the ERRS and FWM signals from a single graphene nanoribbon (GNR), we demonstrate that both signals are more efficiently generated along the edges of the GNR: a manifestation of atomic-scale nonlinear optical microscopy. This demonstration paves the way to the development of novel ultrafast nonlinear picophotonic platforms, affording unique opportunities in a variety of contexts, from the direct investigation of non equilibrium light matter interactions in complex quantum materials, to the development of robust strategies for hot carriers harvesting in single molecules and the next generation of active metasurfaces with deep-sub-wavelength meta-atoms.
Spatiotemporal Electron Microscopy of Phonon Polaritons in MoO3
Technion – Israel Institute of Technology（以色列理工学院）；Bar Ilan University（巴伊兰大学）；ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology（巴塞罗那科学和技术研究所光子科学研究所）；ICREA-Institució Catalana de Recerca i Estudis Avanats（加泰罗尼亚高级研究学院）
Measurement of Photocarrier Mean Free Path via Speckled Laser Pump -- Transient Fourier Microscopy Probe
Center for Neutron Science and Technology, Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-sen University（中山大学物理学院中子科学与技术中心、广东省铁电物理与器件重点实验室）；State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University（中山大学物理学院光电材料与技术国家重点实验室）
