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Université de Fribourg

Uniaxial strain-induced phase transition in the 2D topological semimetal IrTe2

Nicholson, Christopher W. ; Rumo, Maxime ; Pulkkinen, Aki ; Kremer, Geoffroy ; Salzmann, Björn ; Mottas, Marie-Laure ; Hildebrand, Baptiste ; Jaouen, Thomas ; Kim, Timur K. ; Mukherjee, Saumya ; Ma, KeYuan ; Muntwiler, Matthias ; von Rohr, Fabian O. ; Cacho, Cephise ; Monney, Claude

In: Communications Materials, 2021, vol. 2, no. 1, p. 25

Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties is still in its infancy. In particular, strain control over the diverse phase transitions and topological states in two-dimensional transition metal dichalcogenides remains an open challenge. Here, we...

Université de Fribourg

Unveiling the complete dispersion of the giant Rashba split surface states of ferroelectric α−GeTe(111) by alkali doping

Kremer, Geoffroy ; Jaouen, Thomas ; Salzmann, Björn ; Nicolaï, L. ; Rumo, Maxime ; Nicholson, Christopher W. ; Hildebrand, Baptiste ; Dil, J. Hugo ; Springholz, G. ; Krempasky, Juraj ; Monney, Claude

In: Physical Review Research, 2020, vol. 2, no. 3, p. 033115

α−GeTe(111) is a noncentrosymmetric ferroelectric material for which a strong spin- orbit interaction gives rise to giant Rashba split states in the bulk and at the surface. The detailed dispersions of the surface states inside the bulk band gap remains an open question because they are located in the unoccupied part of the electronic structure, making them inaccessible to static...

Université de Fribourg

Unveiling the Semimetallic Nature of 1$T$-TiSe$_2$ by Doping its Charge Density Wave

Jaouen, Thomas ; Rumo, Maxime ; Hildebrand, Baptiste ; Mottas, Marie-Laure ; Nicholson, Christopher W. ; Kremer, Geoffroy ; Salzmann, Björn ; Vanini, Fabiano ; Barreteau, C. ; Giannini, E. ; Beck, Hans-Peter ; Aebi, Philipp ; Monney, Claude

The semimetallic or semiconducting nature of the transition metal dichalcogenide 1$T$-TiSe$_2$ remains under debate after many decades mainly due to the fluctuating nature of its 2 x 2 x 2 charge-density-wave (CDW) phase at room- temperature. In this letter, using angle-resolved photoemission spectroscopy, we unambiguously demonstrate that the 1$T$-TiSe$_2$ normal state is semimetallic with ...

Université de Fribourg

Quantification of Lithological Heterogeneity Within Opalinus Clay : Toward a Uniform Subfacies Classification Scheme Using a Novel Automated Core Image Recognition Tool

Lauper, Bruno ; Zimmerli, Géraldine N. ; Jaeggi, David ; Deplazes, Gaudenz ; Wohlwend, Stephan ; Rempfer, Johannes ; Foubert, Anneleen

In: Frontiers in Earth Science, 2021, vol. 9, p. 645596

The Opalinus Clay is notable in Switzerland as being the selected host rock for deep geological disposal of radioactive waste. Since the early 1990’s, this argillaceous mudstone formation of Jurassic age has been intensively studied within the framework of national and international projects to characterize its geological, hydrological, mechanical, thermal, chemical, and biological...

Université de Fribourg

Ultrafast dynamics of the surface photovoltage in potassium-doped black phosphorus

Kremer, Geoffroy ; Rumo, Maxime ; Yue, Changming ; Pulkkinen, Aki ; Nicholson, Christopher W. ; Jaouen, Thomas ; Von Rohr, Fabian ; Werner, Philipp ; Monney, Claude

In: Physical Review B, 2021, vol. 104, no. 3, p. 035125

Black phosphorus is a quasi-two-dimensional layered semiconductor with a narrow direct band gap of 0.3 eV. A giant surface Stark effect can be produced by the potassium doping of black phosphorus, leading to a semiconductor to semimetal phase transition originating from the creation of a strong surface dipole and associated band bending. By using time- and angle-resolved photoemission ...

Université de Fribourg

Insensitivity of the striped charge orders in ${\mathrm{IrTe}}_{2}$ to alkali surface doping implies their structural origin

Rumo, Maxime ; Pulkkinen, Aki ; Salzmann, Björn ; Kremer, Geoffroy ; Hildebrand, Baptiste ; Ma, Keyan ; von Rohr, Fabian ; Nicholson, Christopher W. ; Jaouen, Thomas ; Monney, Claude

In: Physical Review Materials, 2021, vol. 5, no. 7, p. 074002

We present a combined angle-resolved photoemission spectroscopy and low-energy electron diffraction (LEED) study of the prominent transition metal dichalcogenide IrTe2 upon potassium (K) deposition on its surface. Pristine IrTe2 undergoes a series of charge-ordered phase transitions below room temperature that are characterized by the formation of stripes of Ir dimers of different...

Université de Fribourg

Kinetik des Ionentransports durch supramolekulare Kanäle in Einkristallen

Assouma, Cyrille D. ; Crochet, Aurélien ; Chérémond, Yvens ; Giese, Bernd ; Fromm, Katharina M.

In: Angewandte Chemie, 2013, vol. 125, no. 17, p. 4780-4783

Einkristall-zu-Einkristall-Umwandlungen sind durch Ionenaustausch- und Transportreaktionen durch supramolekulare Kanäle möglich, die aus Kronenether- Molekülen bestehen und Trihalogenid-Ionen als Gerüst nutzen. In kinetischen Messungen des Ionentransports bei unterschiedlichen Temperaturen wurde die Aktivierungsenergie für solche Systeme bestimmt, und ein schneller Austausch zwischen K+-...

Université de Fribourg

Elektronentransfer in Peptiden : Bildung von Silbernanopartikeln

Kracht, Sonja ; Messerer, Matthias ; Lang, Matthieu ; Eckhardt, Sonja ; Lauz, Miriam ; Grobéty, Bernard ; Fromm, Katharina M. ; Giese, Bernd

In: Angewandte Chemie, 2015, vol. 127, no. 10, p. 2954-2958

Einige Mikroorganismen zeigen anaerobe mineralische Respiration, bei der sie Metallionen zu Metallnanopartikeln reduzieren. Hierbei werden Peptide als Medium für den Elektronentransfer (ET) verwendet. Diese Reaktionsklasse wird anhand eines Modellpeptids und Silber als Metall diskutiert. Erstaunlicherweise können Silberionen, die von Peptiden mit Histidin als silberbindender Aminosäure und...

Université de Fribourg

New Antimicrobial and Biocompatible Implant Coating with Synergic Silver–Vancomycin Conjugate Action

Varisco, Massimo ; Khanna, Nina ; Brunetto, Priscilla S. ; Fromm, Katharina M.

In: ChemMedChem, 2014, vol. 9, no. 6, p. 1221-1230

Materials foreign to the body are used ever more frequently, as increasing numbers of patients require implants. As a consequence, the numbers of implant-related infections have grown as well, and with increasing resistance. Treatments often fail; thus, new antibacterial coating strategies are being developed by scientists to avoid, or at least strongly reduce, bacterial adhesion to implant...

Université de Fribourg

Neue Erkenntnisse über die Nashorn-Funde von Rickenbach (SO) (Oberes Oligozän, Kanton Solothurn, Schweiz) aus der Sammlung des Naturmuseums Olten

Tissier, Jérémy ; Geiger-Schütz, Pia ; Flückiger, Peter F. ; Becker, Damien

In: Naturforschende Gesellschaft Des Kantons Solothurn, 2021, vol. 44, p. 25-51

The fossiliferous locality of Rickenbach (SO) is particularly well known as the reference locality of the mammal level MP29 (Late Oligocene, ca. 23.5 million years) of the European mammalian biochronology. The revision of the specimens of Rhinocerotidae housed in the Olten natural history Museum has permitted to describe for the first time the association of three species, Ronzotherium...