A5004162522- Material Dynamics and Properties
- Glass properties and applications
- High-pressure geophysics and materials
- Spectroscopy and Quantum Chemical Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Condensed Matter Physics
- Electron and X-Ray Spectroscopy Techniques
- Physics of Superconductivity and Magnetism
- Advanced X-ray Imaging Techniques
- Theoretical and Computational Physics
- Magnetic and transport properties of perovskites and related materials
- X-ray Diffraction in Crystallography
- Quantum, superfluid, helium dynamics
- Geological and Geochemical Analysis
- Electronic and Structural Properties of Oxides
- Phase Equilibria and Thermodynamics
- Rare-earth and actinide compounds
- Solid-state spectroscopy and crystallography
- Crystallography and Radiation Phenomena
- Nuclear Physics and Applications
- Thermodynamic properties of mixtures
- Advanced Chemical Physics Studies
- Liquid Crystal Research Advancements
- Iron-based superconductors research
- Metallic Glasses and Amorphous Alloys
University of Padua
2021-2025
University of Trento
2013-2022
Deutsches Elektronen-Synchrotron DESY
2022
Menlo School
2020
SLAC National Accelerator Laboratory
2020
European Synchrotron Radiation Facility
2009-2019
Institute of Materials for Electronics and Magnetism
2016
European Science Foundation
2002-2013
University of Perugia
2012
Sorbonne Université
2003-2010
We measured the spin state of iron in ferropericlase (Mg0.83Fe0.17)O at high pressure and found a high-spin to low-spin transition occurring 60- 70-gigapascal range, corresponding depths 2000 kilometers Earth's lower mantle. This implies that partition coefficient between magnesium silicate perovskite, two main constituents mantle, may increase by several orders magnitude, depleting perovskite phase its iron. The mantle then be composed different layers. upper layer would consist mixture...
We measured the spin state of iron in magnesium silicate perovskite (Mg(0.9),Fe(0.1))SiO(3) at high pressure and found two electronic transitions occurring 70 gigapascals 120 gigapascals, corresponding to partial full electron pairing iron, respectively. The proportion low thus grows with depth, increasing transparency mantle infrared region, a maximum pressures consistent D" layer above core-mantle boundary. resulting increase radiative thermal conductivity suggests existence nonconvecting...
We compare the atomic dynamics of glass to that relevant crystal. In spectra inelastic scattering, boson peak appears higher than transverse acoustic (TA) singularity However, density states shows they have same number states. Increasing pressure causes transformation towards TA Once corrected for difference in elastic medium, matches energy and height. This suggests identical nature two features.
We use x-ray photon correlation spectroscopy to investigate the structural relaxation process in a metallic glass on atomic length scale. report evidence for dynamical crossover between supercooled liquid phase and metastable glassy state, suggesting different origins of across transition. Furthermore, using cooling rates, we observe complex hierarchy dynamic processes characterized by distinct aging regimes. Strong analogies with dynamics soft materials, such as gels concentrated colloidal...
The development of inelastic x-ray scattering with millielectron volt energy resolution at the European Synchrotron Radiation Facility in Grenoble, France, provides a method for studying high-frequency collective dynamics disordered systems. This has led to observation propagating acoustic phonon-like excitations glasses and glass-forming liquids down wavelengths comparable interparticle distance. Using results on glycerol as representative example, it is shown that microscopic dynamic...
When a liquid is cooled below its melting temperature, it usually crystallizes. However, if the quenching rate fast enough, system may remain in disordered state, progressively losing fluidity upon further cooling. time needed for rearrangement of local atomic structure reaches approximately 100 seconds, becomes "solid" any practical purpose, and this defines glass transition temperature Tg. Approaching from side, different systems show qualitatively dependencies viscosity, accordingly they...
High energy resolution inelastic x-ray scattering measurements in the $1--6{\mathrm{nm}}^{\ensuremath{-}1}$ momentum transfer ( $Q$) region vitreous silica $v{\ensuremath{-}\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$) at $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1050\mathrm{K}$ show existence of collective excitations propagating with a sound velocity $5800\ifmmode\pm\else\textpm\fi{}200\mathrm{m}/\mathrm{s}$ up to...
High frequency sound is observed in lithium diborate glass, Li2O-2B2O3, using Brillouin scattering of light and x rays. The attenuation exhibits a nontrivial dependence on the wave vector, with remarkably rapid increase towards Ioffe-Regel crossover as approaches boson peak from below. An analysis literature results reveals that boson-peak closely related limit for many glasses. We conjecture this relation, specific to glassy materials, might be rather common among them.
On the macroscopic scale, wavelengths of sound waves in glasses are large enough that details disordered microscopic structure usually irrelevant, and medium can be considered as a continuum. decreasing wavelength this approximation must course fail at one point. We show here takes place unexpectedly on mesoscopic scale characteristic range order glasses, where it still works well for corresponding crystalline phases. Specifically, we find acoustic excitations with nanometric clear signature...
The propagation and damping of the acoustic excitations in vitreous silica is measured at terahertz frequencies using inelastic x-ray scattering. apparent sound velocity shows a marked dispersion with frequency while attenuation undergoes crossover from fourth to second power law dependence. This finding solves recent controversy concerning location this silica, clarifying that it occurs position glass-characteristic excess vibrational modes known as boson peak, thus establishing direct...
We measured the density of vibrational states (DOS) and specific heat various glassy crystalline polymorphs ${\mathrm{SiO}}_{2}$. The typical (ambient) glass shows a well-known excess relative to crystal ($\ensuremath{\alpha}$-quartz). This, however, holds when comparing lower-density higher-density crystal. For with matched densities, DOS appears as smoothed counterpart corresponding crystal; it reveals same number Debye model, all in low-energy region, provides heat. This that glasses have...
The low-temperature thermal properties of dielectric crystals are governed by acoustic excitations with large wavelengths that well described plane waves. This is the Debye model, which rests on assumption medium an elastic continuum, holds true for microscopic scale fixed interatomic spacing, and gradually breaks down approaching it. Glasses characterized as universal are, however, anomalous respect to those corresponding crystalline phases. Related anomalies also appear in low-frequency...
It is largely accepted that liquids are characterized by a short-range order usually corresponding to of the solid phase at same density. less clear what extent dynamic properties and crystals can be compared. In particular, high-frequency collective excitations reminiscent phonons in solids exist as well liquids. They however traditionally discussed terms relaxation processes characteristic liquid phase. We report here on quantitative comparison polycrystalline sodium. show sodium exhibits...
Advances in developing ultrafast coherent sources operating at extreme ultraviolet (EUV) and x-ray wavelengths allow the extension of nonlinear optical techniques to shorter wavelengths. Here, we describe EUV transient grating spectroscopy, which two crossed femtosecond pulses produce spatially periodic nanoscale excitations sample their dynamics is probed via diffraction a third time-delayed pulse. The use radiation with down 13.3 nm allowed us gratings periods as short 28 observe thermal...
An in situ x-ray diffraction experiment has been performed on phosphorus to characterize the liquid-liquid transition which occurs at high temperature and pressure. The line measured over an extended range up 2200 \ifmmode^\circ\else\textdegree\fi{}C 0.3 GPa. From shape of this line, a thermodynamic characterization is obtained terms latent heat internal energy change. Moreover, addition high-pressure high-temperature data known phase diagram allows us conclude that first-order between dense...
High-resolution, inelastic x-ray scattering measurements of the dynamic structure factor S(q,omega) liquid water in THz frequency range have been performed as a function wave vector q (1-7 nm(-1)) and temperature T (273-473 K), using pressure (0-1.5 kbar) to keep density at rho approximately 1 g/cm(3). We show that, for q<or=2 nm(-1), spectra can be consistently explained terms hydrodynamic formalism which includes viscoelastic, q-independent contribution memory fluctuations. This allows us...
A multiple-analyser-crystal spectrometer for non-resonant inelastic X-ray scattering spectroscopy installed at beamline ID16 of the European Synchrotron Radiation Facility is presented. Nine analyser crystals with bending radii R = 1 m measure spectra five different momentum transfer values simultaneously. Using a two-dimensional detector, given by all analysers can be treated individually. The based on Rowland circle design fixed Bragg angles about 88 degrees . energy resolution chosen...
An end-station for X-ray Raman scattering spectroscopy at beamline ID20 of the European Synchrotron Radiation Facility is described. This dedicated to study shallow core electronic excitations using non-resonant inelastic scattering. The spectrometer has 72 spherically bent analyzer crystals arranged in six modular groups 12 each a combined maximum flexibility and large solid angle detection. Each modules houses one pixelated area detector allowing based imaging efficient separation desired...
An end-station for resonant inelastic X-ray scattering and (resonant) emission spectroscopy at beamline ID20 of ESRF - The European Synchrotron is presented. spectrometer hosts five crystal analysers in Rowland geometry large solid angle collection mounted on a rotatable arm both the horizontal vertical planes. optimized high-energy-resolution applications, including partial fluorescence yield or detected absorption study elementary electronic excitations solids. In addition, it can be used...
In CaIrO3, electronic correlation, spin-orbit coupling, and tetragonal crystal field splitting are predicted to be of comparable strength. However, the nature its ground state is still an object debate, with contradictory experimental theoretical results. We probe CaIrO3 assess effective coupling at play in this system by means resonant inelastic x-ray scattering. conclude that insulating not a j(eff) = 1/2 iridate discuss consequences our finding interpretation previous experiments....
The resonant X-ray scattering (magnetic elastic, RXMS, and inelastic, RIXS) of Ir$^{4+}$ at the L$_{2,3}$ edges relevant to spin-orbit Mott insulators A$_{n+1}$Ir$_{n}$O$_{3n+1}$ (A=Sr, Ba, etc.) are calculated using a single-ion model which treats tetragonal crystal-field terms on an equal footing. Both RXMS RIXS in spin-flip channel found display non-trivial dependence direction magnetic moment, $\boldsymbol\mu$. Crucially, we show that for $\boldsymbol\mu$ \emph{ab}-plane, L$_2$ edge is...
In the quest for realizations of quantum spin liquids, exploration Kitaev materials - spin-orbit entangled Mott insulators with strong bond-directional exchanges has taken center stage. However, in these local spin-orbital j=1/2 moments typically show long-range magnetic order at low temperature, thus defying formation a spin-liquid ground state. Using resonant inelastic x-ray scattering (RIXS), we here report on proximate liquid regime clear fingerprints physics excitations honeycomb...
Collective lattice dynamics determine essential aspects of condensed matter, such as elastic and thermal properties. These exhibit strong dependence on the length-scale, reflecting marked wavevector excitations. The extreme ultraviolet transient grating (EUV TG) approach has demonstrated potential accessing a range corresponding to 10s nm representing spatial scale highest relevance for fundamental physics forefront technology, previously inaccessible by optical TG other inelastic scattering...
High-resolution, inelastic x-ray scattering measurements of the dynamic structure factor $S(Q,\ensuremath{\omega})$ liquid water have been performed for wave vectors $Q$ between 4 and $30\phantom{\rule{0.3em}{0ex}}{\mathrm{nm}}^{\ensuremath{-}1}$ in distinctly different thermodynamic conditions ($T=263--420\phantom{\rule{0.3em}{0ex}}\mathrm{K}$; at, or close to, ambient pressure at $P=2\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$). In agreement with previous neutron studies, presence two...