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Université de Fribourg

Local resilience of the $1T\text{\ensuremath{-}}{\mathrm{TiSe}}_{2}$ charge density wave to Ti self-doping

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

In: Physical Review B, 2017, vol. 95, no. 8, p. 081104

In Ti-intercalated self-doped 1T−TiSe2 crystals, the charge density wave (CDW) superstructure induces two nonequivalent sites for Ti dopants. Recently, it has been shown that increasing Ti doping dramatically influences the CDW by breaking it into phase-shifted domains. Here, we report scanning tunneling microscopy and spectroscopy experiments that reveal a dopant-site dependence of the CDW...

Université de Fribourg

Band bending in Mg-colored and O₂-activated ultrathin MgO(001) films

Jaouen, Thomas ; Hildebrand, Baptiste ; Aebi, Philipp ; Delhaye, G. ; Tricot, S. ; Lépine, B. ; Jézéquel, G. ; Schieffer, P.

In: The Journal of Physical Chemistry C, 2017, vol. 121, no. 8, p. 4363–4367

Ultrathin MgO films grown on Ag(001) have been investigated using X-ray and ultraviolet photoemission spectroscopies for oxide films successively exposed to Mg and O₂ flux. Studying work functions and layer-resolved Auger shifts allows us to keep track of band profiles from the oxide surface to the interface and reveal the charge- transfer mechanisms underlying the controlled creation of...

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

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, F. ; 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, E. F. ; 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, their...