Non-equilibrium dynamics of the phonon system (B04)

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The excitation, decay, and transport of phonons in crystalline films and at their surfaces upon an optical excitation will be studied by ultrafast electron diffraction with femtosecond temporal resolution. We focus on the manipulation of electron phonon coupling through variation of electronic states, strain state, surface and interface roughness and thus control the vibrational excitation of lattice through either formation of squeezed state, e-ph coupling through surface state, or anharmonic ph-ph coupling. We force violation of equipartition in the phonon system through switching from diffusive to ballistic phonon transport.