2020, Poelchen, Georg, Schulz, Susanne, Mende, Max, Güttler, Monika, Generalov, Alexander, Fedorov, Alexander V., Caroca-Canales, Nubia, Geibel, Christoph, Kliemt, Kristin, Krellner, Cornelius, Danzenbächer, Steffen, Usachov, Dmitry Y., Dudin, Pavel, Antonov, Victor N., Allen, James W., Laubschat, Clemens, Kummer, Kurt, Kucherenko, Yuri, Vyalikh, Denis V.

Ultra-violet angle-resolved photoemission spectroscopy (UV-ARPES) was used to explore the temperature dependence of the Ce-4f spectral responses for surface and bulk in the antiferromagnetic Kondo lattice CeRh2Si2. Spectra were taken from Ce- and Si-terminated surfaces in a wide temperature range, and reveal characteristic 4f patterns for weakly (surface) and strongly (bulk) hybridized Ce, respectively. The temperature dependence of the Fermi level peak differs strongly for both cases implying that the effective Kondo temperature at the surface and bulk can be rather distinct. The greatly reduced crystal–electric-field (CEF) splitting at the surface gives reason to believe that the surface may exhibit a larger effective Kondo temperature because of a higher local-moment effective degeneracy. Further, the hybridization processes could strongly affect the 4f peak intensity at the Fermi level. We derived the k-resolved dispersion of the Kondo peak which is also found to be distinct due to different sets of itinerant bands to which the 4f states of surface and bulk Ce are coupled. Overall our study brings into reach the ultimate goal of quantitatively testing many-body theories that link spectroscopy and transport properties, for both the bulk and the surface, separately. It also allows for a direct insight into the broader problem of Kondo lattices with two different local-moment sublattices, providing some understanding of why the cross-talking between the two Kondo effects is weak.

2016, Makarova, Anna A., Grachova, Elena V., Niedzialek, Dorota, Solomatina, Anastasia I., Sonntag, Simon, Fedorov, Alexander V., Vilkov, Oleg Yu., Neudachina, Vera S., Laubschat, Clemens, Tunik, Sergey P., Vyalikh, Denis V.

The recently synthesized series of Pt II complexes containing cyclometallating (phenylpyridine or benzoquinoline) and N-heterocyclic carbene ligands possess intriguing structures, topologies, and light emitting properties. Here, we report curious physicochemical interactions between in situ PVD-grown films of a typical representative of the aforementioned Pt II complex compounds and Li, Na, K and Cs atoms. Based on a combination of detailed core-level photoelectron spectroscopy and quantum-chemical calculations at the density functional theory level, we found that the deposition of alkali atoms onto the molecular film leads to unusual redistribution of electron density: essential modification of nitrogen sites, reduction of the coordination Pt II centre to Pt 0 and decrease of electron density on the bromine atoms. A possible explanation for this is formation of a supramolecular system "Pt complex-alkali metal ion" the latter is supported by restoration of the system to the initial state upon subsequent oxygen treatment. The discovered properties highlight a considerable potential of the Pt II complexes for a variety of biomedical, sensing, chemical, and electronic applications.