A5059164090- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Magnetic Properties of Alloys
- Advanced X-ray Imaging Techniques
- Magnetic and transport properties of perovskites and related materials
- X-ray Spectroscopy and Fluorescence Analysis
- High-pressure geophysics and materials
- Advanced Chemical Physics Studies
- Advanced X-ray and CT Imaging
- Electron and X-Ray Spectroscopy Techniques
- Medical Imaging Techniques and Applications
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Advanced Materials Characterization Techniques
- Nuclear Materials and Properties
- Topological Materials and Phenomena
- Catalytic Cross-Coupling Reactions
- Catalytic C–H Functionalization Methods
- Inorganic Chemistry and Materials
- Chalcogenide Semiconductor Thin Films
- Machine Learning in Materials Science
- Nuclear Physics and Applications
- Anatomy and Medical Technology
University of Cologne
2018-2024
Max Planck Institute for Chemical Physics of Solids
2018-2024
European Synchrotron Radiation Facility
2016-2019
Politecnico di Milano
2014-2019
National Interuniversity Consortium for the Physical Sciences of Matter
2014
Sapienza University of Rome
1989
Istituto di Metodologie Chimiche
1989
Significance Charge correlations have now been identified in the low-temperature phase of essentially all families underdoped cuprates, but two apparently distinct types. The first hosts locked charge and spin stripes which material La 1.875 Ba 0.125 CuO 4 (LBCO <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>/</mml:mo> <mml:mn>8</mml:mn> </mml:mrow> </mml:math> ) is a paradigmatic example. In second type, density wave (CDW)...
Using resonant inelastic soft x-ray scattering, the authors observe charge collective modes in Pb-Bi2212 at optimal doping that compete with superconductivity. Together prior observations underdoped region, these results suggest are a universal feature pseudogap regime.
Significance The interplay of band-formation and electron-correlation effects in uranium heavy fermion compounds is the subject an ongoing debate. Here unexpected insight has been gained from advanced spectroscopies on isostructural members U <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> <mml:mi mathvariant="normal">S</mml:mi> mathvariant="normal">i</mml:mi> </mml:math> family...
Magnetic excitations in the optimally doped high-$T_\mathrm{c}$ superconductor Bi$_{1.5}$Pb$_{0.55}$Sr$_{1.6}$La$_{0.4}$CuO$_{6+\delta}$ (OP-Bi2201, $T_\mathrm{c}\simeq 34$ K) are investigated by Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS), below and above pseudogap opening temperature. At both temperatures broad spectral distribution disperses along (1,0) direction up to $\sim$350~meV at zone boundary, similarly other hole-doped cuprates. However, $\sim$0.22 reciprocal lattice...
A new high-field magnet endstation for X-ray magnetic dichroism experiments has been installed and commissioned at the ESRF soft beamline ID32. The consists of two split-pairs superconducting coils which can generate up to 9 T along beam 4 orthogonal beam. It is connected a cluster ultra-high-vacuum chambers that offer comprehensive set surface preparation characterization techniques. properties have designed provide optimum experimental conditions linear circular in range between 400 1600...
A procedure for quantifying the U <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>5</a:mn><a:mi>f</a:mi></a:mrow></a:math> electronic covalency and degree of localization in intermetallic compounds is presented. To this end, bulk sensitive hard soft x-ray photoelectron spectroscopy were utilized combination with density-functional theory (DFT) plus dynamical mean-field (DMFT) calculations. The energy dependence photoionization cross sections allows disentanglement <b:math...
Using high resolution tender x-ray resonant inelastic scattering and hard nonresonant beyond the dipole limit we were able to detect electronic excitations in intermetallic ${\mathrm{UGa}}_{2}$ that are highly atomic nature. Analysis of spectral lineshape reveals local $5{f}^{2}$ configuration characterizes correlated nature this ferromagnet. The orientation directional dependence spectra indicate ground state is made ${\mathrm{\ensuremath{\Gamma}}}_{1}$ singlet and/or...
We investigated the electronic structure of enigmatic CeRh$_3$B$_2$ using resonant inelastic scattering and x-ray absorption spectroscopy in combination with $ab$ $initio$ density functional calculations. find that Rh 4$d$ states are irrelevant for high-temperature ferromagnetism Kondo effect. also Ce 4$f$ crystal-field strength is too small to explain strong reduction magnetic moment. The data reveal instead presence two different active orbitals, each coupling selectively bands...
The magnetic properties of rare earth compounds are usually well captured by assuming a fully localized $f$ shell and only considering the Hund's rule ground state multiplet split crystal electric field (CEF). Currently, standard technique for probing CEF excitations in lanthanides is inelastic neutron scattering. Here we show that with recent leap energy resolution, resonant soft x-ray scattering (RIXS) has become an attractive alternative looking at excitations. This been used studying...
In the last years, with development of Additive Manufacturing processes, research on mechanical behaviour lattice structures has gained significant attention. Depending application, properties unit cell can be modified by varying its geometry. The geometry is generally designed through Finite Element Analyses. However, simulation response components made rather complex, due to long computation time. Therefore, efficient simplified models should employed, but, in this case, an experimental...
The potential of resonant inelastic soft x-ray scattering to measure $4f$ crystal electric-field excitation spectra in Ce Kondo lattices has been examined. Spectra have obtained for several systems and show a well-defined structure determined by crystal-field, spin-orbit, charge-transfer excitations only. spectral shapes the can be well understood framework atomic multiplet calculations. For ${\mathrm{CeCu}}_{2}{\mathrm{Si}}_{2}$ we found notable disagreement between x-ray-scattering...
The crystal-field ground state wave function of CeCu$_2$Si$_2$ has been investigated with linear polarized $M$-edge x-ray absorption spectroscopy from 250mK to 250K, thus covering the superconducting ($T_{\text{c}}$=0.6K), Kondo ($T_{\text{K}}$$\approx$20K) as well Curie-Weiss regime. comparison full-multiplet calculations shows that temperature dependence experimental dichroism is explained a $\Gamma_7^{(1)}$ ground-state and thermal population excited states at around 30meV. scheme does...
The one-dimensional cobaltate Ca3Co2O6 is an intriguing material having unconventional magnetic structure, displaying quantum tunneling phenomena in its magnetization. Using a newly developed experimental method, s-core-level non-resonant inelastic x-ray scattering (s-NIXS), we were able to image the atomic Co 3d orbital that responsible for Ising magnetism this system. We show can directly observe it complex d2 occupied by sixth electron at high-spin Co-trig{3+} (d6) sites generates...
Effective models focused on pertinent low-energy degrees of freedom have substantially contributed to our qualitative understanding quantum materials. An iconic example, the Kondo model, was key demonstrating that rich phase diagrams correlated metals originate from interplay localized and itinerant electrons. Modern electronic structure calculations suggest achieve quantitative material-specific models, accurate consideration crystal field spin-orbit interactions is imperative. This poses...
We have investigated the local low-energy excitations in CeRu$_4$Sn$_6$, a material discussed recently framework of strongly correlated Weyl semimetals, by means Ce $M_5$ resonant inelastic x-ray scattering (RIXS). The availability both $^2$F$_\frac{5}{2}$ and $^2$F$_\frac{7}{2}$ $4f^1$ configuration spectra allows for determination crystal-electric field parameters that explain quantitatively temperature dependence anisotropy magnetic susceptibility. absence an azimuthal indicates all...
The 4$f$ orbital shape correlates with the ground state of strongly correlated Ce$M$In${}_{5}$ family, $M$=Co, Rh, and Ir. remaining question as to how these orbitals are oriented has now been answered through nonresonant inelastic x-ray scattering (NIXS) measurements. Quantitative analysis reveals a hybridization-induced contribution first excited crystal-field superconducting CeCoIn${}_{5}$, an important finding that suggests degeneracy larger than two constrains realistic calculations...
The crystal-field (CF) splitting of the ${}^{6}{H}_{5/2}$ Hund's rule ground state ${\mathrm{Sm}}^{3+}$ in strongly correlated topological insulator ${\mathrm{SmB}}_{6}$ has been determined with high-resolution resonant inelastic x-ray scattering (RIXS) at Sm ${M}_{5}$ edge. valence selectivity RIXS allows isolating crystal-field-split excited multiplets ($4{f}^{5}$) configuration from those ${\mathrm{Sm}}^{2+}$ ($4{f}^{6}$) intermediate valent ${\mathrm{SmB}}_{6}$. We find that quartet...
${\mathrm{CeRh}}_{3}{\mathrm{Si}}_{2}$ has been reported to exhibit metamagnetic transitions below 5 K, a giant crystal field splitting, and anisotropic magnetic properties from single magnetization heat capacity measurements. Here we report results of neutron x-ray scattering studies the structure crystal-field excitations further understand magnetism this compound. Inelastic resonant inelastic reveal ${J}_{z}\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}1/2$ ground state for Ce...
The application of pressure as well the successive substitution Ru with Fe in hidden order (HO) compound ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$ leads to formation large-moment antiferromagnetic phase. Here, we investigate series ${\mathrm{URu}}_{2\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{Si}}_{2}$ from $x=0.0$ 2.0 by U $4f$ core-level photoelectron spectroscopy and observe nonmonotonic changes spectra. initial increase subsequent decrease spectral weight satellite increasing $x$ stands for a...
A software with a graphical user interface has been developed the aim of facilitating data analysis for users new resonant inelastic X-ray scattering (RIXS) spectrometer installed at ESRF beamline ID32. The is organized in modules covering all relevant steps reduction from stack several hundred two-dimensional CCD images to single RIXS spectrum. It utilizes both full charge integration and single-photon centroiding cope high-flux high-resolution requirements. Additional further extraction...