A5088703107- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Superconductivity in MgB2 and Alloys
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- X-ray Spectroscopy and Fluorescence Analysis
- Rare-earth and actinide compounds
- Advanced Chemical Physics Studies
- High-pressure geophysics and materials
- Electron and X-Ray Spectroscopy Techniques
- Magnetic properties of thin films
- Hemoglobin structure and function
- Electronic and Structural Properties of Oxides
- Superconducting Materials and Applications
- Boron and Carbon Nanomaterials Research
- X-ray Diffraction in Crystallography
- Protein Structure and Dynamics
- Surface and Thin Film Phenomena
- Quantum, superfluid, helium dynamics
- Quantum and electron transport phenomena
- Transition Metal Oxide Nanomaterials
- Inorganic Fluorides and Related Compounds
- Enzyme Structure and Function
- Theoretical and Computational Physics
- Mass Spectrometry Techniques and Applications
Rome International Center for Materials Science
2016-2025
Institute of Crystallography
2015-2024
National Research Council
2017-2024
Institute for Microelectronics and Microsystems
2024
Università di Camerino
1976-2024
Max Planck Institute for Solid State Research
2024
University of Verona
2002-2023
Moscow Engineering Physics Institute
2016-2022
Latvian Academy of Sciences
2017-2018
National Interuniversity Consortium of Materials Science and Technology
2015-2016
The measurement of the Cu-O distances by a local and fast probe, polarized Cu K-edge extended x-ray absorption fine structure (EXAFS) in L${\mathrm{a}}_{1.85}$S${\mathrm{r}}_{0.15}$Cu${\mathrm{O}}_{4}$ crystal shows two different conformations Cu${\mathrm{O}}_{6}$ octahedra below 100 K assigned to types stripes with lattice. This experiment supports model ``two components'' spatially separated superlattice quantum for anomalous properties cuprate superconductors.
Advanced synchrotron radiation focusing down to a size of 300 nm has been used visualize nanoscale phase separation in the K${}_{0.8}$Fe${}_{1.6}$Se${}_{2}$ superconducting system using scanning nanofocus single-crystal x-ray diffraction. The results show an intrinsic single crystals at $T$ 520 K, revealing coexistence (i) magnetic characterized by expanded lattice with superstructures due Fe vacancy ordering and (ii) nonmagnetic in-plane compressed lattice. spatial distribution two phases K...
The intermediate valence of formally tetravalent compounds has been detected by ${L}_{3}$ x-ray-absorption near-edge structure (XANES) in ${\mathrm{CeO}}_{2}$ and ${\mathrm{PrO}}_{2}$ but not ${\mathrm{UO}}_{2}$, which have the same ${\mathrm{CaF}}_{2}$ large f ligand mixing. found both Ce(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O, similar local different crystal structure. We show that XANES final states are a direct probe configuration interaction between...
Here we report the interpretation of all spectral features Ce ${\mathit{L}}_{3}$ x-ray-absorption near-edge structure (XANES) ${\mathrm{CeO}}_{2}$ over a 40 eV range. The local partial unoccupied density states in initial state and fully relaxed final have been calculated by full multiple-scattering approach. wave function excited electron ${\mathit{L}}_{3}$-edge XANES spectrum is found to be determined processes large size cluster formed at least 45 atoms. We predict, good agreement with...
The x-ray-absorption near-edge structure (XANES) at the Fe$K$ edge of ${\mathrm{K}}_{3}$Fe${(\mathrm{CN})}_{6}$ and ${\mathrm{K}}_{4}$Fe${(\mathrm{CN})}_{6}$ has been measured interpreted by means multiple-scattering calculations. theory is able to account for XANES over a 40-eV energy range. We demonstrate that quasidiatomic "shape resonances" arising from multiple scattering within CN groups play an important role in suggest this may be common feature metal atoms bound molecular (e.g., CO,...
By making a comparison between the Mn K-edge absorption of (${\mathrm{MnO}}_{4}$${)}^{\mathrm{\ensuremath{-}}}$ and [Mn(${\mathrm{H}}_{2}$O${)}_{6}$${]}^{2+}$ complexes in aqueous solution we obtain an experimental determination energy extent type-II multiple-scattering (MS) regime that is substantially wider than expected. Theoretical calculations based on MS formalism support this conclusion. We also recognize three regions spectra these complexes: full region, where numerous or infinite...
We report Mn $K$-edge extended x-ray absorption fine structure spectra on ${\mathrm{La}}_{0.75}{\mathrm{Ca}}_{0.25}{\mathrm{MnO}}_{3}$ up to high momentum transfer across the metal-insulator $(M\ensuremath{-}I)$ transition. The data show compelling evidence for (i) large or intermediate Jahn-Teller polarons (IJTP), characterized by an anomalous longer Mn-O bond $(\ensuremath{\Delta}R\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.09\AA{})$ in metallic phase $(T<170\mathrm{K})$, and (ii)...
Polarized Cu ${L}_{3}$-edge x-ray absorption spectra of a single crystal Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.8}$ have been measured to determine the symmetry orbital electronic holes induced by doping. The states doping in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ ($0<\ensuremath{\delta}<\ensuremath{\sim}0.5$) found be ligand ${\mathit{L}}^{*}$, giving ${3d}^{9}{\mathit{L}}^{*}$ configuration, and their weight is...
Photoemission spectra of the valence band single-crystal graphite were measured using synchrotron radiation in energy range 33-200 eV. For $\ensuremath{\hbar}\ensuremath{\omega}=122$ eV, good agreement was found with calculated density states since matrix elements for $p$-like and $s$-like are nearly same. Using constant-initial-state spectroscopy, we have that, $\ensuremath{\hbar}\ensuremath{\omega}<90$ cross section transitions from $\ensuremath{\pi}$ $\ensuremath{\sigma}$ initial to...
The x-ray-absorption near-edge structure (XANES) of transition elements in tetrahedral coordination crystals and glasses has been studied. We have identified the XANES features continuum that can be assigned to multiple scattering within first shell. energy positions ${E}_{r}$ peaks follow rule (${E}_{r}$-${E}_{b}$)${d}^{2}$= const, where ${E}_{b}$ is prepeak, defined as core excitation bound antibonding state ${T}_{2}$ symmetry, d interatomic distance. This plot allows us determine a...
Resonances in the superconducting properties, a regime of crossover from BCS to mixed Bose-Fermi superconductivity, are investigated two-band superconductor where chemical potential is tuned near band edge second mini-band generated by quantum confinement effects. The shape resonances at T=0 gaps (belonging class Feshbach-like resonances) manifested interference effects gap first large Fermi surface when proximity mini-band. case superlattice wells considered and amplification...
Temperature dependent single-crystal x-ray diffraction (XRD) in transmission mode probing the bulk of newly discovered K0.8Fe1.6Se2 superconductor (Tc = 31.8 K) using synchrotron radiation is reported. A clear evidence intrinsic phase separation at 520 K between two competing phases, (i) a first majority magnetic with ThCr2Si2-type tetragonal lattice modulated by iron vacancy ordering and (ii) minority non-magnetic having an in-plane compressed volume weak superstructure, The XRD peaks due...
Electronic functionalities in materials from silicon to transition metal oxides are a large extent controlled by defects and their relative arrangement. Outstanding examples the of copper, where defect order is correlated with high superconducting temperatures. The oxygen can be highly inhomogeneous, even "optimal" samples, which raises question nature sample regions does not exist but nonetheless form "glue" binding ordered together. Here we use scanning X-ray microdiffraction (with beam...
Abstract While 203 K high temperature superconductivity in H 3 S has been interpreted by BCS theory the dirty limit here we focus on effects of hydrogen zero-point-motion and multiband electronic structure relevant for multigap near Lifshitz transitions. We describe how topology Fermi surfaces evolves with pressure giving different Lifshitz-transitions. A neck-disrupting Lifshitz-transition (type 2) occurs where van Hove singularity, vHs, crosses chemical potential at 210 GPa new small 2D...
We report topology of the Fermi surface ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ superconducting system at optimum doping determined by sequential angle-scanning photoemission combined with high intensity synchrotron radiation. The has a pseudogap around $(\ensuremath{\pi},0)$ as in underdoped samples, showing missing segments near $M$ points, and shadow bands $(0.5\ensuremath{\pi},0.5\ensuremath{\pi})$ equivalent locations. $k$ dependence...