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Thème : Structure, vibration, relaxations dans les systèmes désordonnés
Présentation
In the last years important progress has been made on long-standing fundamental questions such as those related to sound properties in glasses and their relation with the universal low-temperature anomalies. A comprehensive picture of the nontrivial frequency dependence of sound attenuation in oxide glasses can now be proposed. It is controlled by three processes which in increasing order of the frequency at which they dominate are : the thermal relaxation of defects, relaxation via anharmonic interactions with the thermal bath, and a remarkably rapid increase (α Ω4) towards a Ioffe-Regel crossover at THz frequencies which we have evidenced in two oxide glasses. The latter mechanism relates to the boson peak and the low temperature plateau generally observed in the thermal conductivity. The close relation between the Ioffe-Regel crossover and the boson peak implies a resonance of these rather local low-lying optic modes with acoustic modes near the Ioffe-Regel limit.
Current researches
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Dernières publications
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Hyper-Raman scattering from the LO modes of perovskite ferroelectric relaxors 
Auteur(s): Hehlen B. (Article) Publié: Physical Review B, vol. 110 p.024313 (2024) |
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From creep to flow: Granular materials under cyclic shear
Auteur(s): Yuan Ye, Zeng Zhikun, Yuan Houfei, Zhang Shuyang, Kob W. (Article) Publié: Nature Communications, vol. 15 p.3866 (2024) |
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Creating equilibrium glassy states via random particle bonding Auteur(s): Ozawa M., Barrat Jean-Louis, Kob W., Zamponi Francesco
(Article) Publié:
Journal Of Statistical Mechanics: Theory And Experiment, vol. 2024 p.013303 (2024)
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Hypersound damping in vitreous silica measured by a picosecond optical technique
Involved researchers : M. Foret, S. Ayrinhac (PhD), B. Rufflé
(Collaboration A. Devos, IEMN, Université Lille)
The attenuation of longitudinal acoustic phonons up to frequencies nearing 250 (…)
The boson peak and its relation with acoustic attenuation in glasses
Involved researchers : B. Rufflé, E. Courtens and R. Vacher
(Collaboration D.A. Parshin Université Saint Petersbourg Russie)
Experimental results on the density of states and on the acoustic (…)
Glass-specific behavior in the damping of acousticlike vibrations
Involved researchers : B. Rufflé, G. Guimbretière (PhD), E. Courtens, and R. Vacher
(Collaboration G. Monaco, ESRF, Grenoble)
High frequency sound is observed in lithium diborate glass, (…)
Anharmonic vs. relaxational sound damping in silica glasses
Involved researchers : M. Foret, R. Vacher, E. Courtens
The temperature dependence of the frequency dispersion in the sound velocity and damping of vitreous silica is reanalyzed. Thermally (…)
Hyper-Raman scattering analysis of the vibrations in borate glasses
Involved researchers : B. Hehlen, G. Simon, E. Courtens, R. Vacher
Hyper-Raman scattering has been measured on vitreous boron oxide, v-B2O3. This spectroscopy, complemented with Raman scattering (…)
Small ring density and inter-tetrahedra bond angle of permanently densified silicas : Femtosecond and Raman spectroscopy study
Involved researchers : B. Hehlen, M. Foret
(Collaboration with P. Langot, J. Burgin, and F. Vallée, CPMOH-Bordeaux)
Normal and permanently densified silica glasses (SiO2) have been (…)
Glass and environment
In the forthcoming ecological era, new European environmental regulations (horizon 2020) will impose the design of new “green” materials with lower energetic production costs. In this context, the (…)
Structure and Dynamics in Nanoconfined Self-Assembled Polymers
Involved researchers : A.C. Genix (collaboration : J. Colmenero, A. Arbe, San Sebastian –SPAIN)
We are exploiting the selectivity of neutron scattering combined with isotopic substitution to (…)
Investigation of the polymer dynamics in silica/polymer nanocomposites
Involved researchers : A.C. Genix, J. Oberdisse, C. Dupas (collaboration : F. Ganachaud, Ecole de Chimie – Montpellier / M. Tyagi, NIST – USA / J. Colmenero, A. Arbe, San Sebastian – SPAIN)
We (…)
Ferroelectric relaxors
Collaboration with J. Hlinka, Academy of Sciences of the Czech Republic Praha) (P. Papet, J. Rouquette, and J. Haines, Institut Charles Gehrardt, Montpellier)
One major interest of Hyper-Raman (…)
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