Université de Fribourg

Three-dimensional momentum-resolved electronic structure of $1T\text{-}{\mathrm{TiSe}}_{2}:$ A combined soft-x-ray photoemission and density functional theory study

Vydrova, Z. ; Schwier, Eike Fabian ; Monney, Gaël ; Jaouen, Thomas ; Razzoli, Elia ; Monney, Claude ; Hildebrand, Baptiste ; Didiot, Clément ; Berger, Helmuth ; Schmitt, T. ; Strocov, V. N. ; Vanini, Fabiano ; Aebi, Philipp

In: Physical Review B, 2015, vol. 91, no. 23, p. 235129

1T−TiSe2 is a quasi-two-dimensional transition metal dichalcogenide, which exhibits a charge density wave transition at a critical temperature of ∼200 K as well as low- temperature superconductivity induced by pressure or intercalation. The electronic energy dispersion measured by soft x-ray angle-resolved photoemission is not only momentum resolved parallel to the surface but also...

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

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

Valence band electronic structure characterization of the rutile TiO₂ (110)-(1 × 2) reconstructed surface

Sánchez-Sánchez, C. ; Garnier, M.G. ; Aebi, Philipp ; Blanco-Rey, M. ; Andres, P.L. de ; Martín-Gago, J.A. ; López, M.F.

In: Surface Science, 2012, p. -

The electronic structure of the TiO₂ (110)-(1 × 2) surface has been studied by means of angular resolved ultraviolet photoemission spectroscopy (ARUPS). The valence band dispersion along the high symmetry surface directions, [001] and [1–10], has been recorded. The experimental data show no dispersion of the band-gap Ti 3d states. However, the existence of dispersive bands along the [001]...

Université de Fribourg

A Ga-doped SnO2 mesoporous contact for UV stable highly efficient perovskite solar cells

Roose, Bart ; Johansen, Christian M. ; Dupraz, Kevin ; Jaouen, Thomas ; Aebi, Philipp ; Steiner, Ullrich ; Abate, Antonio

In: Journal of Materials Chemistry A, 2018, vol. 6, no. 4, p. 1850–1857

Increasing the stability of perovskite solar cells is a major challenge for commercialization. The highest efficiencies so far have been achieved in perovskite solar cells employing mesoporous TiO2 (m-TiO2). One of the major causes of performance loss in these m-TiO2-based perovskite solar cells is induced by UV- radiation. This UV instability can be solved by replacing TiO2 with SnO2; thus ...

Université de Fribourg

Tuning electronic correlations in transition metal pnictides: Chemistry beyond the valence count

Razzoli, Elia ; Matt, Christian E. ; Kobayashi, M. ; Wang, X.-P. ; Strocov, V. N. ; Roekeghem, A. van ; Biermann, Silke ; Plumb, N. C. ; Radovic, M. ; Schmitt, T. ; Capan, C. ; Fisk, Z. ; Richard, P. ; Ding, H. ; Aebi, Philipp ; Mesot, J. ; Shi, Ming

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...

Université de Fribourg

Selective probing of hidden spin-polarized states in inversion-symmetric bulk ${\mathrm{MoS}}_{2}$

Razzoli, Elia ; Jaouen, Thomas ; Mottas, Marie-Laure ; Hildebrand, Baptiste ; Monney, Gaël ; Pisoni, A. ; Muff, S. ; Fanciulli, M. ; Plumb, N. C. ; Rogalev, V. A. ; Strocov, V. N. ; Mesot, Joël ; Shi, Ming ; Dil, J. H. ; Beck, Hans ; Aebi, Philipp

In: Physical Review Letters, 2017, vol. 118, no. 8, p. 086402

Spin- and angle-resolved photoemission spectroscopy is used to reveal that a large spin polarization is observable in the bulk centrosymmetric transition metal dichalcogenide MoS2. It is found that the measured spin polarization can be reversed by changing the handedness of incident circularly polarized light. Calculations based on a three-step model of photoemission show that the valley and...

Université de Fribourg

Scanning tunneling microscopy of the charge density wave in $1T-{\mathrm{TiSe}}_{2}$ in the presence of single atom defects

Novello, Anna M. ; Hildebrand, Baptiste ; Scarfato, A. ; Didiot, Clément ; Monney, Gaël ; Ubaldini, A. ; Berger, Helmuth ; Bowler, D. R. ; Aebi, Philipp ; Renner, Christoph

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...

Université de Fribourg

Surface science at the PEARL beamline of the Swiss Light Source

Muntwiler, Matthias ; Zhang, Jun ; Stania, Roland ; Matsui, Fumihiko ; Oberta, Peter ; Flechsig, d Uwe ; Patthey, Luc ; Quitmann, Christoph ; Glatzel, Thilo ; Widmer, Roland ; Meyer, Ernst ; Jung, Thomas A. ; Aebi, Philipp ; Fasel, Roman ; Greber, Thomas

In: Journal of Synchrotron Radiation, 2017, vol. 24, no. 1, p. 354–366

The Photo-Emission and Atomic Resolution Laboratory (PEARL) is a new soft X-ray beamline and surface science laboratory at the Swiss Light Source. PEARL is dedicated to the structural characterization of local bonding geometry at surfaces and interfaces of novel materials, in particular of molecular adsorbates, nanostructured surfaces, and surfaces of complex materials. The main experimental...