Université de Fribourg

Unusual temperature dependence of the spectral weight near the Fermi level of NdNiO₃ thin films

Schwier, Eike Fabian ; Scherwitzl, R. ; Vydrovà, Z. ; García-Fernández, Mirian ; Gibert, M. ; Zubko, P. ; Garnier, Michael G. ; Triscone, J.-M. ; Aebi, Philipp

In: Physical Review B - Condensed Matter and Materials Physics, 2012, vol. 86, no. 19, p. 195147

We investigate the behavior of the spectral weight near the Fermi level of NdNiO3 thin films as a function of temperature across the metal-to-insulator transition (MIT) by means of ultraviolet photoelectron spectroscopy. The spectral weight was found to exhibit thermal hysteresis, similar to that of the dc conductivity. A detailed analysis of the temperature dependence reveals two distinct...

Université de Fribourg

Reversible control of the electronic density of states at the Fermi level of Ca₃Co₄O9+δ misfit-layered oxide single crystals through O⁺/H⁺ plasma exposure

Moser, D. ; Garnier, Michael G. ; Karvonen, L. ; Shkabko, A. ; Aebi, Philipp ; Weidenkaff, A.

In: Journal of Materials Science, 2012, p. -

Misfit-layered Ca₃Co₄O₉ crystals were grown and characterized via XRD, SEM, and photo-emission spectroscopy (PES). The evolution of the intensity at the Fermi level (E F) with varying oxygen content was studied by PES. Oxygen species were successfully introduced and removed through O⁺ and H⁺ microwave-plasma (2.45 GHz, 2–5 mbar) treatments, respectively. A 5 min...

Université de Fribourg

Mapping of electron-Hole excitations in the charge-density-wave system 1T-TiSe2 using resonant inelastic x-ray scattering

Monney, Claude. ; Zhou, K. J. ; Cercellier, H. ; Vydrova, Z. ; Garnier, Michael G. ; Monney, G. ; Strocov, V. N. ; Berger, Helmuth ; Beck, Hans ; Schmitt, T. ; Aebi, Philipp

In: Physical Review Letters, 2012, vol. 109, p. 047401

In high-resolution resonant inelastic x-ray scattering at the Ti L edge of the charge-density-wave system 1T-TiSe₂, we observe sharp low energy loss peaks from electron-hole pair excitations developing at low temperature. These excitations are strongly dispersing as a function of the transferred momentum of light. We show that the unoccupied bands close to the Fermi level can effectively be...

Université de Fribourg

Influence of elastic scattering on the measurement of core-level binding energy dispersion in X-ray photoemission spectroscopy

Schwier, Eike Fabian ; Monney, Claude ; Mariotti, Nicholas ; Vydrovà, Z. ; García-Fernández, Mirian ; Didiot, Clément ; Garnier, Michael G. ; Aebi, Philipp

In: The European Physical Journal B - Condensed Matter And Complex Systems, 2011, vol. 81, no. 4, p. 399-403

We explore the interplay between the elastic scattering of photoelectrons and the surface core level shifts with regard to the determination of core level binding energies in Au(111) and Cu3Au(100). We find that an artificial shift is created in the binding energies of the Au 4f core levels, that exhibits a dependence on the emission angle, as well as on the spectral intensity of the core...

Université de Fribourg

Dramatic effective mass reduction driven by a strong potential of competing periodicity

Monney, Claude ; Schwier, Eike Fabian ; Garnier, Michael G. ; Battaglia, C. ; Mariotti, N. ; Didiot, Clément ; Cercellier, H. ; Marcus, J. ; Berger, H. ; Titov, A. N. ; Beck, Hans ; Aebi, Philipp

In: Europhysics Letters, 2010, vol. 92, no. 4, p. 47003

We present angle-resolved photoemission experiments on 1T-TiSe₂ at temperatures ranging from 13 K to 288 K. The data evidence a dramatic renormalization of the conduction band below 100 K, whose origin can be related to the new potential responsible for the charge density wave phase at low temperature in this system. The renormalization translates into a substantial effective mass...

Université de Fribourg

Temperature-dependent photoemission on 1T-TiSe₂: Interpretation within the exciton condensate phase model

Monney, Claude ; Schwier, Eike Fabian ; Garnier, Michael G. ; Mariotti, Nicholas ; Didiot, Clément ; Beck, Hans ; Aebi, Philipp ; Cercellier, H. ; Marcus, J. ; Battaglia, C. ; Berger, H.

In: Physical Review B, 2010, vol. 81, no. 15, p. 1551104

The charge-density-wave phase transition of 1T-TiSe₂ is studied by angle-resolved photoemission over a wide temperature range. An important chemical-potential shift which strongly evolves with temperature is evidenced. In the framework of the exciton condensate phase, the detailed temperature dependence of the associated order parameter is extracted. Having a mean-field-like behavior at low...

Université de Fribourg

On the electronic impact of abnormal C4-bonding in N-heterocyclic carbene complexes

Heckenroth, Marion ; Neels, Antonia ; Garnier, Michael G. ; Aebi, Philipp ; Ehlers, Andreas W. ; Albrecht, Martin

In: Chemistry - A European Journal, 2009///doi: 10.1002/chem.200900249

Sterically similar palladium dicarbene complexes have been synthesized that comprise permethylated dicarbene ligands which bind the metal center either in a normal coordination mode via C2 or abnormally via C4. Due to the strong structural analogy of the complexes, differences in reactivity patterns may be attributed to the distinct electronic impact of normal versus abnormal carbene bonding,...