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The dynamics of quasi-particles in non-equilibrium states of matter reveal the
underlying microscopic coupling between electronic, spin and vibrational degrees of
freedom. We aim for a quantum-state-resolved picture of coupling on the level of quasiparticle
self-energies, which goes beyond established ensemble-average descriptions,
and which requires ultrafast momentum-resolving techniques. The dynamics of
electrons and excitons is measured with four-dimensional time- and angle-resolved
photoelectron spectroscopy (trARPES), featuring a high-repetition-rate XUV laser source
and momentum microscope detector. I will exemplify this experimental approach by
discussing electron and exciton dynamics in the semiconducting transition metal
dichalcogenide WSe2. Our approach provides access to the transient distribution of hot
carriers in the entire Brillouin zone of photo-excited semiconductors and allows the
quantification of energy relaxation dynamics. I will sketch the capability of
multidimensional photoemission spectroscopy of providing orbital information. The
complementary view of ultrafast phonon dynamics is obtained through femtosecond
electron diffraction. The elastic and inelastic scattering signal reveals the temporal
evolution of vibrational excitation of the lattice and momentum-resolved information
of transient phonon populations.

Online-Meeting: Zugangsdaten sind auf der Webseite des Physikalischen Kolloquiums
zu finden. (https://tud.link/6og1)