Investigation of structure and ultra-fast dynamic processes of topological materials with inversion symmetry breaking using transmission momentum microscopy

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Time-resolved transmission time-of-flight momentum microscopy (TR-TToFMM) combines two innovative research approaches: investigation of dynamic processes by ultrafast electron diffraction and high-resolution time-of-flight momentum microscopy using parallel recording. The aim of this project is studying of ultra-fast dynamic processes with a novel contrast mechanism, namely transmission electron diffraction combined with energy loss spectroscopy. Full field imaging of inelastic electron scattering (IES) offers knowledge on dynamic electronic degrees of freedom in topological materials, which is not accessible by any other experimental approach. Friedel’s rule excludes detection of inversion asymmetry in a crystal structure via kinematic (single-scattering) diffraction in the absence of additional absorption processes of scattered radiation. Emitter-specific electron diffraction allows the investigation of low-dimensional structures due to both: strong multiple scattering of electrons (larger elastic interaction cross-section) and local element specificity of the pronounced inelastic absorption processes. TR-TToFMM gives access to hitherto unexplored inelastic scattering processes such as dynamic Auger transitions and spin-dependent losses. The novel approach will be exemplified by studying a thermally-induced inversion symmetry breaking in doped 1T- and 2H-(Mo1-xWx)Te2.