Revealing momentum-dependent electron-phonon and phonon-phonon coupling in complex materials with ultrafast electron...

Area of Science:

• Condensed matter physics
• Materials science
• Ultrafast spectroscopy

Background:

• Understanding electron-phonon and phonon-phonon coupling is crucial for material properties.
• Detailed momentum-dependent information on these interactions has been limited.
• Ultrafast electron diffuse scattering (UEDS) is an emerging technique to address this gap.

Purpose of the Study:

• To describe the UEDS methodology and its information content.
• To demonstrate UEDS's capability in unraveling carrier-phonon and phonon-phonon interactions.
• To investigate nonequilibrium phonon dynamics in single-crystal materials.

Main Methods:

• Ultrafast electron diffuse scattering (UEDS) on photoexcited single crystals.
• Analysis of ultrafast, photoinduced changes in phonon-diffuse scattering.
• Complementary *ab initio* calculations.

Main Results:

• UEDS successfully provided momentum-dependent information on electron-phonon and phonon-phonon coupling.
• Carrier-phonon and phonon-phonon interactions were unraveled in both momentum and time.
• Nonequilibrium phonon dynamics were followed in detail on ultrafast timescales.
• Insights into electronic and magnetic dynamics influencing UEDS were obtained.

Conclusions:

• UEDS is a powerful technique for detailed investigation of coupled electronic and lattice dynamics.
• The study provides new insights into fundamental interactions governing material properties.
• UEDS, combined with theory, offers a comprehensive approach to studying complex material behaviors.