Four-Dimensional Imaging of Lattice Dynamics using Inelastic Scattering

Time-resolved mapping of lattice dynamics in real and momentum-space is essential to better understand several ubiquitous phenomena. In this work, we demonstrate that inelastic scattering methods, are competent to provide similar information as one could obtain from the time-resolved diffraction and imaging measurements. To illustrate the robustness of the proposed method, our simulated result of lattice dynamics in germanium is in excellent agreement with the time-resolved x-ray diffuse scattering measurement performed using x-ray free-electron laser. For a given inelastic scattering data in energy and momentum space, the proposed method is useful to image in-situ lattice dynamics under different environmental conditions. Few tens of femtoseconds temporal and ~ 1 Å spatial resolutions can be achieved during the reconstruction of lattice dynamics by utilizing the superior energy and momentum resolutions of inelastic scattering measurements. Our proposed theoretical method allows for direct imaging of lattice dynamics and enables us to extract the lifetime of selective phonon modes. The technique will profoundly impact where time-resolved diffraction within the pump–probe setup is not feasible, for instance, in inelastic neutron scattering.