Ultrafast Diffraction Microscopy for Revealing Emerging Phases and Their Dynamics

Light-matter interaction has been an effective approach for producing emergent phases in quantum materials. However, these phases and associated dynamics often arise on nanometer scales and evolve on ultrafast time scales, making them challenging to capture. Combined with ultrafast laser excitation, x-ray and electron diffraction microscopes have become an essential tool for studying nanoscale structural evolution. In this talk, I will demonstrate the applications of laser-pumped x-ray and electron diffraction microscopy comparatively. In the first example, ultrafast x-ray diffraction imaging reveals ultrafast nanoscale phase transition in FeRh film and ferroelectric domain reconfiguration in BiFeO₃. In the second example, ultrafast electron microscopy reveals acoustic harmonic modes in FePS₃ mediated by defects. The strengths and limitations of x-ray and electron diffraction microscopy will be discussed. The exciting outlook of these techniques in the dawn of next-generation x-ray facilities will be presented.<br/><br/>These works are primarily supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under award no. DE-AC02-06CH11357 and DE-SC-0012509.