Time-resolved spectroscopy of photo-induced transitions and electronic excitations in quasi-1D metal wires on semiconductors

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The project E5 aims at a fundamental understanding of the non-equilibrium properties of quasi-1D metal wires on semiconductor surfaces and focuses on the ultrafast dynamics of electronic excitations, including spectroscopy and lifetimes of unoccupied electronic states as well as on transient changes of the electronic band structure during photoinduced phase transitions in such systems. These topics will be addressed using In/Si(111), Pb/Si(557), and Au/Si(553) as model systems. The activities located in Duisburg and Berlin share joint scientific goals, but use different experimental approaches: The group at the University of Duisburg-Essen focuses on the spectroscopy and dynamics of unoccupied electronic states near the center of the Brillouin zone using time- and angle-resolved photoemission (ARPES) and two-photon photoemission (2PPE) spectroscopy. The group at the Fritz Haber Institute in Berlin develops time-resolved XUV-based ARPES to study electron dynamics and electronic structure changes during photoinduced phase transitions throughout the complete Brillouin zone. The latter experiments will be complemented by time-resolved optical spectroscopy (SFG, RAS) in the regime of high laser fluence building on experiments with static optical spectroscopy (RAS) performed in E3. The ultrafast techniques employed in our project investigate the excited state electron dynamics. Within the Research Unit our activity forms together with projects T1 and T2, which theoretically treat changes in the electronic structure upon CDW formation and photo-induced phase transitions, and with project E7, which analyzes the complementary structural dynamics by femtosecond electron diffraction, a focus area on dynamics in 1D systems.