In: Physical Review B, 2015, vol. 91, no. 21, p. 214502
The effects of electron-electron correlations on the low-energy electronic structure and their relationship with unconventional superconductivity are central aspects in the research on iron-based pnictide superconductors. Here we use soft x-ray angle-resolved photoemission spectroscopy to study how electronic correlations evolve in different chemically substituted iron pnictides. We find that...
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In: Physical Review B, 2015, vol. 92, no. 8, p. 081101
We present a detailed low-temperature scanning tunneling microscopy (STM) study of the commensurate charge density wave (CDW) in $1T-{\mathrm{TiSe}}_{2}$ in the presence of single atom defects. We find no significant modification of the CDW lattice in single crystals with native defect concentrations where some bulk probes already measure substantial reductions in the CDW phase transition...
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In: Physical Review B, 2014, vol. 90, no. 12, p. 125433
The properties of MgO/Ag(001) ultrathin films with substitutional Mg atoms in the interface metal layer have been investigated by means of Auger electron diffraction experiments, ultraviolet photoemission spectroscopy, and density functional theory (DFT) calculations. Exploiting the layer-by-layer resolution of the MgKL23L23 Auger spectra and using multiple scattering calculations, we first...
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In: Physical Review Letters, 2014, vol. 112, no. 19, p. 197001
The transition-metal dichalcogenide 1T−TiSe₂is a quasi-two-dimensional layered material with a charge density wave (CDW) transition temperature of TCDW≈200 K. Self-doping effects for crystals grown at different temperatures introduce structural defects, modify the temperature-dependent resistivity, and strongly perturbate the CDW phase. Here, we study the structural and doping nature...
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In: Physical Review B - Condensed matter and materials physics, 2012, vol. 85, no. 19, p. 195111
We present both theoretical ab-initio results within the Hedin's GW approximation and experimental angle-resolved photoemission and scanning tunneling spectroscopy measurements on TiSe₂. With respect to the density-functional Kohn-Sham metallic picture, the many-body GW self-energy leads to a ≈0.2-eV band-gap insulator consistent with our STS spectra at 5 K. The highest valence and the lowest...
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In: Journal of Physics: Condensed Matter, 2011, vol. 23, no. 13, p. 135003
Using angle-resolved photoelectron spectroscopy we investigate the electronic valence band structure of the Si(331)-(12 × 1) surface reconstruction for which we recently proposed a structural model containing silicon pentamers as elementary structural building blocks. We find that this surface, reported to be metallic in a previous study, shows a clear band gap at the Fermi energy, indicating...
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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...
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In: Physical Review B: condensed matter and materials physics, 2009, vol. 80, no. 21, p. 214102
We recently proposed a structural model for the Si(331)-(12×1) surface reconstruction containing silicon pentamers and adatoms as elementary structural building blocks. Using first-principles density functional theory we here investigate the stability of a variety of adatom configurations and determine the lowest-energy configuration. We also present a detailed comparison of the energetics...
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In: Physica B: Condensed Matter, 2009, vol. 404, no. 19, p. 3172-3175
Recently, detailed calculations of the excitonic insulator phase model adapted to the case of 1T-TiSe2 have been presented. Through the spectral function theoretical photoemission intensity maps can be generated which are in very good agreement with experiment [H. Cercellier, et al., Phys. Rev. Lett. 99 (2007) 146403]. In this model, excitons condensate in a BCS-like manner and give rise to a...
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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,...
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