Interactions between the lattice and charge carriers can drive the formation of phases and ordering phenomena that give rise to conventional superconductivity, insulator-to-metal transitions, and charge-density waves. These couplings also play a determining role in properties that include electric and thermal conductivity. Ultrafast electron diffuse scattering (UEDS) has recently become a viable laboratory-scale tool to track energy flow into and within the lattice system across the entire Brillouin zone, and to deconvolve interactions in the time domain. Here, we present a detailed quantitative framework for the interpretation of UEDS signals, ultimately extracting the phonon mode occupancies across the entire Brillouin zone. These transient populations are then used to extract momentum-and mode-dependent electron-phonon and phonon-phonon coupling constants. Results of this analysis are presented for graphite, which provides complete information on the phonon-branch occupations and a determination of the A 1 phonon mode-projected electronphonon coupling strength g 2 e,A 1 = 0.035 ± 0.001 eV 2 that is in agreement with other measurement techniques and simulations.

Predictions of high thermoelectric performance in RECuZnP2 were verified by elastic, electrical, and thermal measurements. Low thermal conductivities result from strong anharmonicity, with electron transport limited by polar optical phonons.

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