Many fundamental processes of structural changes at surfaces occur on a pico- or femtosecond time scale. In order to study such ultra-fast processes, we have combined modern surface science techniques with fs-laser pulses in a pump-probe scheme. Reflection high energy electron diffraction (RHEED) with grazing incident electrons ensures surface sensitivity for the probing electron pulses. Utilizing the Debye-Waller effect, we studied the nanoscale heat transport from an ultrathin film through a hetero-interface or the damping of vibrational excitations in monolayer adsorbate systems on the lower ps-time scale. By means of spot profile analysis the different cooling rates of epitaxial Ge nanostructures of different size and strain state were determined. The excitation and relaxation dynamics of a driven phase transition far away from thermal equilibrium is demonstrated using the In-induced (8x2) reconstruction on Si(111). This Peierls-distorted surface charge density wave system exhibits a discontinuous phase transition at 130 K from a (8x2) insulating ground state to (4x1) metallic excited state. Upon excitation by a fs-laser pulse, this structural phase transition is non-thermally driven in only 700 fs into the excited state. A small barrier of 40 meV hinders the immediate recovery of the groundstate and the system is found in a metastable supercooled state for up to few nanoseconds.
Acoustic response of a laser-excited polycrystalline Au-film studied by ultrafast Debye-Scherrer diffraction at a table-top short-pulse X-ray source
利用时间分辨Debye-Scherrer X射线衍射技术，研究了激光驱动等离子体X射线源发出的超短Cu K $_α$ X射线脉冲对自支撑多晶Au薄膜在飞秒光激发下的瞬态声响应.从多个布拉格衍射峰的瞬态位移确定了应变随时间的演化。实验数据与基于双温模型和假设应变在激光激励薄膜中单轴传播的声学模型的计算结果吻合得很好。
Picosecond localization dynamics following ultrafast nanoscale magnetic switching
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH（亥姆霍兹柏林材料能源有限公司）；University of Augsburg（奥格斯堡大学）；Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy（马克斯·玻恩非线性光学和短脉冲光谱研究所）；European XFEL（欧洲X射线自由电子激光装置）；Radboud Universiteit（拉德堡德大学）；Max-Planck-Institut für Multidisziplinäre Naturwissenschaften（马克斯·普朗克多学科自然科学研究所）
Revealing domain wall stability during ultrafast demagnetization
Max Planck Institute for Multidisciplinary Sciences（马克斯·普朗克多学科研究所）；Institute of Physics, University of Augsburg（奥格斯堡大学物理研究所）；School of Electrical Engineering, Tel Aviv University（特拉维夫大学电气工程学院）；th Physical Institute, University of Göttingen（哥廷根大学第四物理研究所）；Radboud University, Institute for Molecules and Materials（拉德堡德大学分子与材料研究所）
Ultrafast Electron Microscopy of Nanoscale Charge Dynamics in Semiconductors
Technion - Israel Institute of Technology（以色列理工学院）；École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院）；University of Geneva（日内瓦大学）；ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology（ICFO-光子科学研究所，巴塞罗那科学技术研究院）；University of Milano-Bicocca（米兰比可卡大学）；Massachusetts Institute of Technology（麻省理工学院）
Low-temperature nanoscale heat transport in a gadolinium iron garnet heterostructure probed by ultrafast x-ray diffraction
利用时间分辨X射线衍射技术研究了Pt/Gd 3Fe 5 O 12//Gd 3Ga 5 O 12金属/氧化物异质结的低温热输运性质。脉冲飞秒光信号在Pt层中产生快速的温度上升，随后热传输到Gd 3Fe 5 O 12（GdIG）薄膜和Gd 3Ga 5 O 12（GGG）衬底中。使用基于加速器的飞秒X射线源跟踪来自GdIG层的X射线衍射的时间依赖性。超快衍射测量探测GdIG（1 - 1 2）X射线反射在掠入射X射线衍射几何结构中的强度。的衍射X射线强度的变化与模型，包括热传输和GdIG晶格参数的温度依赖性的比较允许的Pt/GdIG和GdIG//GGG接口的热导率被确定。GdIG层的低温热膨胀性质的互补同步加速器X射线衍射研究提供了GdIG晶格参数的温度依赖性的精确校准。从时间分辨衍射研究确定的Pt/GdIG和GdIG//GGG接口的界面热导是相同的数量级的金属/氧化物和外延介电界面的先前报告。Pt/GdIG//GGG异质结构的热参数将有助于热传输器件和纳米结构的设计和实现。
Mapping Temperature Using Transmission Kikuchi Diffraction
University of California, Los Angeles（加州大学洛杉矶分校）；California NanoSystems Institute (CNSI), University of California, Los Angeles（加州大学洛杉矶分校加州纳米系统研究所）；University of Southern California（南加州大学）
Ultrafast Nano-Imaging and Optical Control of Hyperbolic Phonon Polaritons at hBN/WS$_2$ Heterojunctions
Institute for Molecular Science, National Institutes of Natural Sciences（国立自然科学研究所分子科学研究所）；Department of Physics and Electronics, Graduate School of Engineering, Osaka Metropolitan University（大阪公立大学工学研究科物理电子学专业）；The Graduate University for Advanced Studies, SOKENDAI（日本高级研究院）；Research Center for Materials Nanoarchitectonics, National Institute for Materials Science（国立材料研究所物质结构纳米构造研究中心）；Research Center for Electronic and Optical Materials, National Institute for Materials Science（国立材料研究所电子光学材料研究中心）；Fritz-Haber-Institut der Max-Planck-Gesellschaft（马克斯·普朗克学会弗里茨·哈伯研究所）
Technische Universität Berlin（柏林工业大学）；Fritz Haber Institute of the Max Planck Society（马克斯·普朗克 Fritz Haber 研究所）；Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen（杜伊斯堡-埃森大学物理学院与杜伊斯堡-埃森纳米集成中心）；Department of Physics, University of Konstanz（康斯坦茨大学物理系）；Technical University of Applied Sciences Wildau（维尔道应用技术大学）；Helmholtz-Zentrum Berlin für Materialien und Energie GmbH（柏林亥姆霍兹材料与能源中心）；SLAC National Accelerator Laboratory（斯坦福直线加速器中心）；Department of Physics, TU Dortmund University（多特蒙德工业大学物理系）；Institute for Solid State Physics, The University of Tokyo（东京大学固体物理研究所）
Accurate quantification of lattice temperature dynamics from ultrafast electron diffraction of single-crystal films using dynamical scattering simulations
Ultrafast Dissipative Localization of Electronic Energy in AuPt Superlattices
Universität Potsdam（波茨坦大学）；Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy（马克斯·玻恩非线性光学和短脉冲光谱研究所）；European X-ray Free-Electron Laser Facility（欧洲X射线自由电子激光设施）；Helmholtz-Zentrum Berlin（赫尔姆霍兹柏林中心）；MAX IV Laboratory, Lund University（隆德大学MAX IV实验室）；University of Regensburg（雷根斯堡大学）
