News Report
photoexcited carriers interact with lattice vibrations in thin films of the layered WSe2
Jul 2017

A team of researchers from the Structural and Electronic Surface Dynamics group of the FHI Department of Physical Chemistry, Berlin, and the MPI for Structure and Dynamics of Matter, Hamburg, have published an outstanding article in the Physical Review Letters, investigating the interactions of photoexcited carriers with lattice vibrations in thin films of the layered transition metal dichalcogenide WSe2. Employing femtosecond electron diffraction with monocrystalline samples and first-principles density functional theory calculations, a momentum-resolved picture of the energy transfer from excited electrons to phonons is obtained. The measured momentum-dependent phonon population dynamics are compared to first-principles calculations of the phonon linewidth and rationalized in terms of electronic phase-space arguments. The momentum-dependent electron-phonon coupling leads to a nonthermal phonon distribution, which relaxes to a thermal distribution via electron-phonon and phonon-phonon collisions. The results provide a basis for monitoring and predicting out of equilibrium electrical and thermal transport properties for nanoscale applications of transition metal dichalcogenides.