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Université de Fribourg

Mapping the unoccupied state dispersions in ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$ with resonant inelastic x-ray scattering

Monney, Claude ; Herzog, Marc ; Pulkkinen, Aki ; Huang, Y. ; Pelliciari, Jonathan ; Olalde-Velasco, P. ; Katayama, Naoyuk ; Nohara, Minoru ; Takagi, Hide ; Schmitt, Thorsten ; Mizokawa, Takashi

In: Physical Review B, 2020, vol. 102, no. 8, p. 085148

The transition metal chalcogenide Ta2NiSe5 undergoes a second-order phase transition at Tc=328K involving a small lattice distortion. Below Tc, a band gap at the center of its Brillouin zone increases up to about 0.35 eV. In this work, we study the electronic structure of Ta2NiSe5 in its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Ni L3 edge....

Université de Fribourg

Revealing ‘plasmaron’ feature in DySb by optical spectroscopy study

Ban, W J ; Wu, D S ; Xu, Bing ; Luo, J L ; Xiao, Hong

In: Journal of Physics: Condensed Matter, 2019, vol. 31, no. 40, p. 405701

We report magnetic susceptibility, resistivity and optical spectroscopy study on single crystal sample DySb. It exhibits extremely large magnetoresistance (XMR), and a magnetic phase transition from paramagnetic (PM) to antiferromagnetic (AFM) state at about 10 K. A 'screened' plasma edge at about 4000 cm−1 is revealed by optical measurement, which suggests that the material has a low...

Université de Fribourg

In-house setup for laboratory-based x-ray absorption fine structure spectroscopy measurements

Zeeshan, Faisal ; Hoszowska, Joanna ; Loperetti-Tornay, L. ; Dousse, Jean-Claude

In: Review of Scientific Instruments, 2019, vol. 90, no. 7, p. 073105

We report on a laboratory-based facility for in-house x-ray absorption fine structure (XAFS) measurements. The device consists of a conventional x-ray source for the production of the incident polychromatic radiation and a von Hamos bent crystal spectrometer for the analysis of the incoming and transmitted radiation. The reliability of the laboratory-based setup was evaluated by comparing the...

Université de Fribourg

Laboratory based XAS measurements, electron-induced double K-shell ionization of Sc, Cr and Cu : and, Chemical sensitivity of photoinduced Kʰβ hypersatelite transition in Cr compounds

Zeeshan, Faisal ; Dousse, Jean-Claude (Dir.)

Thèse de doctorat : Université de Fribourg, 2017 ; no. 2052.

The present PhD thesis includes three different projects which belong to the domain of inner-shell atomic physics and high energy resolution X-ray spectroscopy. The first project consists of a series of in-house measurements of the characteristic K and L X-ray absorption spectra (XAS) of several 3d, 4d and 5d transition metals. For this project the target chamber of the von Hamos curved crystal...

Université de Fribourg

Anisotropic magnetic excitations and incipient N\’eel order in $\mathrm{Ba}{({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x})}_{2}{\mathrm{As}}_{2}$

Garcia, Fernando A. ; Ivashko, Oleh ; McNally, Daniel E. ; Das, Lakshmi ; Piva, Mario M. ; Adriano, C. ; Pagliuso, Pascoal G. ; Chang, Johan ; Schmitt, Thorsten ; Monney, Claude

In: Physical Review B, 2019, vol. 99, no. 11, p. 115118

It is currently understood that high temperature superconductivity (SC) in the transition metal (M) substituted iron arsenides Ba(Fe1−xMx)2As2 is promoted by magnetic excitations with wave vectors (π,0) or (0,π). It is known that while a small amount of Co substitution lead to SC, the same does not occur for Mn for any value of x. In this work, magnetic excitations in the iron arsenides ...