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...

Université de Fribourg

Short-range phase coherence and origin of the $1T-{\mathrm{TiSe}}_{2}$ charge density wave

Hildebrand, Baptiste ; Jaouen, Thomas ; Didiot, Clément ; Razzoli, Elia ; Monney, Gaël ; Mottas, Marie-Laure ; Ubaldini, A. ; Berger, Helmuth ; Barreteau, C. ; Beck, Hans ; Bowler, D. R. ; Aebi, Philipp

In: Physical Review B, 2016, vol. 93, no. 12, p. 125140

The impact of variable Ti self-doping on the 1T−TiSe2 charge density wave (CDW) is studied by scanning tunneling microscopy. Supported by density functional theory, we show that agglomeration of intercalated-Ti atoms acts as preferential nucleation centers for the CDW that breaks up in phase-shifted CDW domains whose size directly depends on the intercalated-Ti concentration and which are...

Université de Fribourg

Evolution of the charge density wave superstructure in ${\mathrm{ZrTe}}_{3}$ under pressure

Hoesch, Moritz ; Garbarino, Gaston ; Battaglia, Corsin ; Aebi, Philipp ; Berger, Helmuth

In: Physical Review B, 2016, vol. 93, no. 12, p. 125102

The material ZrTe3 is a well-known example of an incommensurate periodic lattice distortion (PLD) at low temperatures due to a charge density wave (CDW). Previous studies have found a sharp boundary as a function of pressure between CDW below 5 GPa and bulk superconductivity above this value. We present a study of low-temperature-high-pressure single crystal x-ray diffraction along with ab initio...

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

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

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

Quasi one-dimensional Ag nanostructures on Si(331)–(12 × 1)

Mariotti, Nicolas ; Didiot, Clément ; Schwier, Eike Fabian ; Monney, Claude ; Battaglia, Corsin ; Aebi, Philipp

In: Surface Science, 2015, vol. 639, p. 39-42

We report on the deposition of sub-monolayer Ag on the Si(331)–(12 × 1) surface. The growth of one-dimensional Ag nanostructures is observed by means of low- temperature scanning tunneling microscopy and low energy electron diffraction. We find that the deposited Ag is organized in nanostructures consistently taking “sawtooth” shapes. While the structures are not perfectly organized,...

Université de Fribourg

Excited states at interfaces of a metal-supported ultrathin oxide film

Jaouen, Thomas ; Razzoli, Elia ; Didiot, Clément ; Monney, Gaël ; Hildebrand, Baptiste ; Vanini, Fabiano ; Muntwiler, M. ; Aebi, Philipp

In: Physical Review B, 2015, vol. 91, no. 16, p. 161410

We report layer-resolved measurements of the unoccupied electronic structure of ultrathin MgO films grown on Ag(001). The metal-induced gap states at the metal/oxide interface, the oxide band gap, and a surface core exciton involving an image-potential state of the vacuum are revealed through resonant Auger spectroscopy of the MgKL23L23 Auger transition. Our results demonstrate how to obtain new...

Université de Fribourg

Impact of electron-hole correlations on the $1T\text{-}{\mathrm{TiSe}}_{2}$ electronic structure

Monney, Gaël ; Monney, Claude ; Hildebrand, Baptiste ; Aebi, Philipp ; Beck, Hans

In: Physical Review Letters, 2015, vol. 114, no. 8, p. 086402

Several experiments have been performed on 1T−TiSe2 in order to identify whether the electronic structure is semimetallic or semiconducting without reaching a consensus. In this Letter, we theoretically study the impact of electron-hole and electron-phonon correlations on the bare semimetallic and semiconducting electronic structure. The resulting electron spectral functions provide a...

Université de Fribourg

Induced work function changes at Mg-doped MgO/Ag(001) interfaces: Combined Auger electron diffraction and density functional study

Jaouen, Thomas ; Aebi, Philipp ; Tricot, S. ; Delhaye, G. ; Lépine, B. ; Sébilleau, D. ; Jézéquel, G. ; Schieffer, Philippe

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...