Mapping momentum-dependent electron-phonon coupling and nonequilibrium phonon dynamics with ultrafast electron diffuse scattering

The nature of the coupling within and between lattice and charge degrees of freedom is central to condensed matter and materials physics. However, these interactions have so far resisted a comprehensive time-resolved experimental investigation. The authors demonstrate that ultrafast electron diffuse scattering provides direct, momentum-resolved measurements of the electron-phonon and phonon-phonon coupling strengths in graphite. Through the technique's ability to follow individual phonon population dynamics with femtosecond time resolution, this method, complimented by angle-resolved photoemission spectroscopy, can provide a complete picture of the dynamics within and between electron and phonon subsystems, and help unravel the physics of complex phases where the intertwined nature of the electron-lattice systems determine material properties.