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Université de Fribourg

Signatures of bosonic excitations in high-harmonic spectra of Mott insulators

Lysne, Markus ; Murakami, Yuta ; Werner, Philipp

In: Physical Review B, 2020, vol. 101, no. 19, p. 195139

The high-harmonic spectrum of the Mott insulating Hubbard model has recently been shown to exhibit plateau structures with cutoff energies determined by nth-nearest- neighbor doublon-holon recombination processes. The spectrum thus allows one to extract the on-site repulsion U. Here, we consider generalizations of the single-band Hubbard model and discuss the signatures of bosonic excitations...

Université de Fribourg

Superconductivity-induced transverse plasma mode and phonon anomaly in the $c$-axis response of the bilayer compound ${\mathrm{RbCa}}_{2}{\mathrm{Fe}}_{4}{\mathrm{As}}_{4}{\mathrm{F}}_{2}$

Xu, Bing ; Munzar, Dominik ; Dubroka, Adam ; Sheveleva, Evgeniia ; Lyzwa, Fryderyk ; Maršík, Premysl ; Wang, C. N. ; Wang, Z. C. ; Cao, G. H. ; Bernhard, Christian

In: Physical Review B, 2020, vol. 101, no. 21, p. 214512

We studied the infrared response of polycrystalline samples of the iron arsenide superconductor (Rb,Cs)Ca2Fe4As4F2 (Rb,Cs-12442), which has a bilayer structure similar to the high-Tc cuprates YBa2Cu3O7 (YBCO) and Bi2Sr2CaCu2O8. The c-axis reflectivity spectra Rc have been derived from the reflectivity spectra of the polycrystalline samples Rpoly and the in-plane spectrum of a corresponding...

Université de Fribourg

Electronic structure and photoluminescence properties of Eu(η9-C9H9)2

Ramanantoanina, Harry ; Merzoud, Lynda ; Muya, Jules Tshishimbi ; Chermette, Henry ; Daul, Claude

In: The Journal of Physical Chemistry A, 2020, vol. 124, no. 1, p. 152–164

The electronic structure of Eu2+ compounds results from a complex combination of strongly correlated electrons and relativistic effects as well as weak ligand–field interaction. There is tremendous interest in calculating the electronic structure as nowadays the Eu2+ ion is becoming more and more crucial, for instance, in lighting technologies. Recently, interest in semiempirical methods to...

Université de Fribourg

Coupling of electronic and nuclear motion in a negative ion resonance: Experimental and theoretical study of benzene

Allan, Michael ; Čurík, Roman ; Čársky, Petr

In: The Journal of Chemical Physics, 2019, vol. 151, no. 6, p. 064119

We present calculated and measured elastic and vibrational excitation cross sections in benzene with the objective to assess the reliability of the theoretical method and to shed more light on how the electronic motion of the incoming electron is coupled with the nuclear motion of the vibrations. The calculation employed the discrete momentum representation method which involves solving 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.

Cette thèse de doctorat contient trois différents projets qui appartiennent aux domaines de la physique atomique des couches profondes et de la spectroscopie de rayons X en haute résolution. Le premier projet concerne l’étude des spectres d’absorption (XAS) K et L de quelques éléments de transition 3d, 4d et 5d. Les mesures ont été réalisées à Fribourg avec le spectromètre à...

Université de Fribourg

Dissociative electron attachment and electronic excitation in Fe(CO)5

Allan, Michael ; Lacko, M. ; Papp, P. ; Matejčík, Š. ; Zlatar, Matija ; Fabrikant, Ilya I. ; Kočišek, J. ; Fedor, Juraj

In: Physical Chemistry Chemical Physics, 2018, vol. 20, no. 17, p. 11692–11701

In a combined experimental and theoretical study we characterize dissociative electron attachment (DEA) to, and electronically excited states of, Fe(CO)5. Both are relevant for electron-induced degradation of Fe(CO)5. The strongest DEA channel is cleavage of one metal–ligand bond that leads to production of Fe(CO)4−. High- resolution spectra of Fe(CO)4− reveal fine structures at the...