Multi-Mode RF Electron Pulse Compression for Ultrafast Electron Scattering

点击翻译按钮获取中文摘要

There is currently an enormous, worldwide effort directed at the development and application of new experimental methods that make it possible to directly watch' the time evolving structure of matter. These approaches combine state-of-the-art femtosecond lasers (see Nobel Prize in Physics, 2018) and sources of either ultrashort Xray or electron pulses to acquire time-resolved diffraction/scattering patterns and images. If time-resolution approaches ~10 femtoseconds - the timescale of the highest frequency vibrations in molecules and materials - atomic motion is essentially frozen during an observation and one can completely follow the fundamental dynamics to produce a "molecular movie"; the experimental equivalent of a molecular dynamics simulation. It is possible to watch chemical bonds break/form and directly determine transition-state structures for even complex reactions, to follow phase transition dynamics uncovering the deep connections between the structure and properties of materials, and directly observe the coupling between charge, orbital and lattice degrees of freedom in time and momentum. This proposal is focused on the further development of the World's most powerful ultrafast electron scattering instrument, designed, built and operating at McGill University. We are requesting equipment that builds on our previous successes and enables ultrafast electron scattering at an unprecedented time resolution of ~50 fs. This new capability will open up an enormous new 'scientific space' to be explored. With the requested equipment, we expect to be able to shed new light on materials phenomena as diverse as superconductivity, charge density waves, thermoelectricity, photovoltaicity and carrier mobility in semiconductors and metals. We will be in a position to investigate the complex interplay between strong, multiorbital electronic correlations, structural distortions, charge and orbital order across a range of strongly correlated material where this physics determines properties (transition metal oxides, pyrochlore oxides, manganites and cuprates), and the formation dynamics of quasiparticles in these systems. Further, there is also the possibility of discovering new photoinduced phases and avenues for optical control of complex materials using the proposed tools; a topic at the forefront of materials research.