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

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

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

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

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, B. ; 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 direct...

Université de Fribourg

Doping nature of native defects in 1T−TiSe₂

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

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...

Université de Fribourg

Electron-hole fluctuation phase in 1T-TiSe₂

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

In: Physical Review B - Condensed Matter and Materials Physics, 2012, vol. 85, no. 23, p. 235150

To address the fluctuation regime above the critical temperature of the charge-density-wave phase of 1T-TiSe₂, we perform calculations using the Bethe-Salpeter equation for treating strong electron-hole correlations. Calculated photoemission intensity maps are in good agreement with the measured ones and provide a deeper understanding of the phase transition in terms of an electronic...