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Université de Fribourg

Two-dimensional conical dispersion in ${\mathrm{ZrTe}}_{5}$ evidenced by optical spectroscopy

Martino, Edoardo ; Crassee, Iris ; Eguchi, Gaku ; Santos-Cottin, David ; Zhong, R. D. ; Gu, G. D. ; Berger, H. ; Rukelj, Zoran ; Orlita, M. ; Homes, Chris C. ; Akrap, Ana

In: Physical Review Letters, 2019, vol. 122, no. 21, p. 217402

Zirconium pentatelluride was recently reported to be a 3D Dirac semimetal, with a single conical band, located at the center of the Brillouin zone. The cone’s lack of protection by the lattice symmetry immediately sparked vast discussions about the size and topological or trivial nature of a possible gap opening. Here, we report on a combined optical and transport study of ZrTe5, which...

Université de Fribourg

Anomalous anisotropic exciton temperature dependence in rutile ${\mathrm{TiO}}_{2}$

Baldini, Edoardo ; Dominguez, Adriel ; Chiodo, Letizia ; Sheveleva, Evgeniia ; Yazdi-Rizi, Meghdad ; Bernhard, Christian ; Rubio, Angel ; Chergui, and Majed

In: Physical Review B, 2017, vol. 96, no. 4, p. 041204

Elucidating the details of electron-phonon coupling in semiconductors and insulators is a topic of pivotal interest, as it governs the transport mechanisms and is responsible for various phenomena such as spectral-weight transfers to phonon sidebands and self-trapping. Here, we investigate the influence of the electron-phonon interaction on the excitonic peaks of rutile TiO2, revealing a strong...

Université de Fribourg

High-quality photonic crystals with a nearly complete band gap obtained by direct inversion of woodpile templates with titanium dioxide

Marichy, Catherine ; Muller, Nicolas ; Froufe-Pérez, Luis S. ; Scheffold, Frank

In: Scientific Reports, 2016, vol. 6, p. 21818

Photonic crystal materials are based on a periodic modulation of the dielectric constant on length scales comparable to the wavelength of light. These materials can exhibit photonic band gaps; frequency regions for which the propagation of electromagnetic radiation is forbidden due to the depletion of the density of states. In order to exhibit a full band gap, 3D PCs must present a threshold...

Université de Fribourg

Magnetic exchange interactions in Mn doped ZnSnAs₂ chalcopyrite

Bouhani-Benziane, H. ; Sahnoun, Omar ; Sahnoun, Mohammed ; Driz, Mohamed ; Daul, Claude A.

In: Journal of Magnetism and Magnetic Materials, 2015, vol. 396, p. 345–349

Accurate ab initio full-potential augmented plane wave (FP-LAPW) electronic calculations within generalized gradient approximation have been performed for Mn doped ZnSnAs₂ chalcopyrites, focusing on their electronic and magnetic properties as a function of the geometry related to low Mn-impurity concentration and the spin magnetic alignment (i.e., ferromagnetic vs antiferromagnetic). As...

Université de Fribourg

The electronic structure of TEMPO, its cation and anion

Kubala, D. ; Regeta, K. ; Janečková, R. ; Fedor, Juraj ; Grimme, S. ; Hansen, A. ; Nesvadba, P. ; Allan, Michael

In: Molecular Physics, 2013, p. -

The electronic structure of TEMPO (2,2,6,6-Tetramethylpiperidine-N-oxyl) and its cation and anion were studied experimentally using the electron spectroscopy techniques, dissociative electron attachment (DEA) spectroscopy, electron energy-loss spectroscopy, measurement of elastic and vibrational excitation (VE) cross sections and HeI photoelectron spectroscopy. The experiments were supplemented...

Université de Fribourg

Radicals and radical ions as intermediates of electron transfer processes through peptides

Giese, Bernd ; Eckhardt, Sonja ; Lauz, Miriam ; Gao, Jian ; Wang, Min

In: Chimia, 2012, vol. 66, no. 6, p. 364-367

Electron transfer (ET) through peptides and proteins is a key biochemical process, which involves radicals and radical ions as reactive intermediates. We have developed an assay that allows us to study this fundamental chemical reaction.