A5082375333- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Magnetic properties of thin films
- Rare-earth and actinide compounds
- Electronic and Structural Properties of Oxides
- Advanced Chemical Physics Studies
- Topological Materials and Phenomena
- Multiferroics and related materials
- Magnetic Properties of Alloys
- High-pressure geophysics and materials
- Surface and Thin Film Phenomena
- Iron-based superconductors research
- Theoretical and Computational Physics
- Magnetic Properties and Synthesis of Ferrites
- ZnO doping and properties
- Electron and X-Ray Spectroscopy Techniques
- Magnetism in coordination complexes
- Graphene research and applications
- Atomic and Molecular Physics
- X-ray Diffraction in Crystallography
- Ferroelectric and Piezoelectric Materials
- Quantum and electron transport phenomena
- X-ray Spectroscopy and Fluorescence Analysis
- Magnetic Properties and Applications
Helmholtz-Zentrum Berlin für Materialien und Energie
2016-2025
University of Duisburg-Essen
2020
Karlsruhe Institute of Technology
2020
Technical University of Darmstadt
2020
Berliner Wasserbetriebe (Germany)
2017
Freie Universität Berlin
2001-2011
There are increasing indications that superconductivity competes with other orders in cuprate superconductors, but obtaining direct evidence bulk-sensitive probes is challenging. We have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations an incommensurate periodicity of $\bf \sim 3.2$ lattice units the copper-oxide planes superconductors (Y,Nd)Ba$_2$Cu$_3$O$_{6+x}$ hole concentrations $0.09 \leq p 0.13$ per planar Cu ion. The intensity and correlation length...
Besides superconductivity, copper-oxide high temperature superconductors are susceptible to other types of ordering. We use scanning tunneling microscopy and resonant elastic x-ray scattering measurements establish the formation charge ordering in high-temperature superconductor Bi2Sr2CaCu2O8+x. Depending on hole concentration, this system occurs with same period as those found Y-based or La-based cuprates, displays analogous competition superconductivity. These results indicate similarity...
The understanding of the origin superconductivity in cuprates has been hindered by apparent diversity intertwining electronic orders these materials. We combined resonant x-ray scattering (REXS), scanning-tunneling microscopy (STM), and angle-resolved photoemission spectroscopy (ARPES) to observe a charge order that appears consistently surface bulk, momentum real space within one cuprate family, Bi <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow>...
We report the results a comprehensive study of charge density wave (CDW) correlations in untwinned YBCO6+x single crystals with 0.4<x<0.99 using Cu-L3 edge resonant x-ray scattering (RXS). Evidence CDW formation is found for 0.45<x<0.93, but not samples x<0.44 that exhibit incommensurate spin-density-wave order, and slightly overdoped x=0.99. This suggests presence two proximate zero-temperature critical points at doping pc1~0.08 pc2~0.18. The reflections are observed in-plane vectors (d_a,...
We use resonant x-ray scattering to determine the momentum-dependent charge correlations in YBa(2)Cu(3) O(6.55) samples with highly ordered chain arrays of oxygen acceptors (ortho-II structure). The results reveal nearly critical, biaxial density wave (CDW) at in-plane vectors (0.315, 0) and (0, 0.325). corresponding intensity exhibits a strong uniaxial anisotropy. CDW amplitude correlation length are enhanced as superconductivity is weakened by an external magnetic field. Analogous...
Photoemission studies with varying degrees of surface sensitivity are reported for the Ce 3d core-level and 4f valence-band regions \ensuremath{\alpha}-like compounds ${\mathrm{CeIr}}_{2}$, ${\mathrm{CePd}}_{3}$, ${\mathrm{CeRh}}_{3}$. In all cases studied, strong changes electronic structure at towards a more localized \ensuremath{\gamma}-like behavior observed, requiring reanalysis previously photoemission spectra compounds. Implications an improved understanding surface-catalytic...
Spin crossover (SCO) complexes possess a bistable spin state that reacts sensitively to changes in temperature or excitation with light. These effects have been well investigated solids and solutions, while technological applications require the immobilization contacting of molecules at surfaces, which often results suppression SCO. We report on thermal light-induced SCO [Fe(bpz)2phen] direct contact highly oriented pyrolytic graphite surface. are able switch magnetic moment by illumination...
We have used resonant x-ray diffraction to develop a detailed description of antiferromagnetic ordering in epitaxial superlattices based on two-unit-cell thick layers the strongly correlated metal LaNiO3. also report reference experiments thin films PrNiO3 and NdNiO3. The resulting data indicate spiral state whose polarization plane can be controlled by adjusting Ni d-orbital occupation via two independent mechanisms: strain spatial confinement valence electrons. are discussed light recent...
Abstract Magnetic doping is expected to open a band gap at the Dirac point of topological insulators by breaking time-reversal symmetry and enable novel phases. Epitaxial (Bi 1− x Mn ) 2 Se 3 prototypical magnetic insulator with pronounced surface ∼100 meV. We show that this neither due ferromagnetic order in bulk or nor local moment Mn, making system unsuitable for realizing further does not affect inverted remains topologically nontrivial. suggest strong resonant scattering processes cause...
Ferromagnetic topological insulators exhibit the quantum anomalous Hall effect that might be used for high precision metrology and edge channel spintronics. In conjunction with superconductors, they could host chiral Majorana zero modes which are among contenders realization of qubits. Recently, it was discovered stable 2+ state Mn enables formation intrinsic magnetic A1B2C4 stoichiometry. However, first representative, MnBi2Te4, is antiferromagnetic 25 K N\'eel temperature strongly n-doped....
We have used polarized Raman scattering to probe lattice vibrations and charge ordering in 12 nm thick, epitaxially strained PrNiO$_3$ films, superlattices of with the band-insulator PrAlO$_3$. A carefully adjusted confocal geometry was eliminate substrate contribution spectra. In films under tensile strain, which undergo a metal-insulator transition upon cooling, spectra reveal phonon modes characteristic ordering. These anomalous phonons do not appear compressively remain metallic at all...
Abstract Cooperative effects determine the spin-state bistability of spin-crossover molecules (SCMs). Herein, ultimate scale limit at which cooperative spin switching becomes effective is investigated in a complex [Fe(H 2 B(pz) ) (bipy)] deposited on highly oriented pyrolytic graphite surface, using x-ray absorption spectroscopy. This system exhibits complete thermal- and light-induced transition thicknesses ranging from submonolayers to multilayers. On increasing coverage 0.35(4) 10(1)...
High-resolution resonant photoemission (PE) at the 4d\ensuremath{\rightarrow}4f and 3d\ensuremath{\rightarrow}4f thresholds is applied to study electronic structure of Ce metal. Due different surface sensitivities, resulting 4f PE spectra, which are almost free non-4f background, reflect directly a substantial change in \ensuremath{\alpha}-Ce metal towards \ensuremath{\gamma}-like behavior surface. This finding resolves longstanding discrepancy between results surface-sensitive those bulk...
Resonant soft X-ray scattering with photon energies near the O K and Cu L3 edges was used to study charge ordering in system La_{1.8-x}Eu_{0.2}Sr_xCuO_4 as a function of temperature for x = 0.125 0.15. From superstructure diffraction intensities doping dependent wave vector is derived which this well below transition low-temperature tetragonal phase but above onset spin ordering. This indicates that primary driving force formation stripe-like phases two-dimensional doped cuprates. Analysis...
Resonant soft x-ray scattering experiments with photon energies near the O K and Cu L3 edge on system La1.8-xEu0.2SrxCuO4 for 0.1 <= x 0.15 are presented. A phase diagram stripe-like charge ordering is obtained together information structural transition into low-temperature tetragonal phase. clear dome around = 1/8 detected well below transition. This result quite different from other systems in which static stripes detected. There order determined by appearing at same temperature....
Resonant x-ray scattering clarifies the link between charge order and magnetism/superconductivity in n-doped cuprates.
We present a detailed synchrotron x-ray scattering study of the charge-density-wave (CDW) order in simple tetragonal ${\mathrm{HgBa}}_{2}{\mathrm{CuO}}_{4+\ensuremath{\delta}}$ (Hg1201). Resonant soft measurements reveal that short-range appears at temperature is distinctly lower than pseudogap and excellent agreement with prior transient reflectivity result. Despite considerable structural differences between Hg1201 ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+\ensuremath{\delta}}$,...
SmB6 is predicted to be the first member of intersection topological insulators and Kondo insulators, strongly correlated materials in which Fermi level lies gap a many-body resonance that forms by hybridization between localized itinerant states. While robust, surface-only conductivity at low temperature observation surface states expected high symmetry points appear confirm this prediction, we find both (100) topologically trivial. We [Formula: see text] state Rashba split explain...
We report temperature-dependent redistribution of spectral weight in photoemission spectra ${\mathrm{La}}_{0.6}$${\mathrm{Sr}}_{0.4}$${\mathrm{MnO}}_{3}$ over a wide energy range several eV. attribute this to change the electron correlation strength induced by changing degree ferromagnetic order with temperature. discuss relationship between close Fermi level and unusual transport properties. \textcopyright{} 1996 The American Physical Society.
The electronic structure of ${\mathrm{CeRh}}_{3}$ was studied by photoemission and bremsstrahlung isochromate spectroscopy (BIS). An analysis the spectra, taken at different temperatures, on basis Anderson single-impurity model leads to considerable inconsistencies that mark limits applicability model. On other hand, BIS spectrum can be well described results a local-density-approximation band-structure calculation. These findings confirm bandlike character 4f states in strongly hybridized...