A5070789663- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Electronic and Structural Properties of Oxides
- Rare-earth and actinide compounds
- Theoretical and Computational Physics
- Quantum and electron transport phenomena
- Inorganic Chemistry and Materials
- Luminescence Properties of Advanced Materials
- Inorganic Fluorides and Related Compounds
- Iron-based superconductors research
- Multiferroics and related materials
- Magnetic properties of thin films
- Crystal Structures and Properties
- Transition Metal Oxide Nanomaterials
- High-pressure geophysics and materials
- Atomic and Subatomic Physics Research
- Advancements in Battery Materials
- Geological and Geochemical Analysis
- Radiation Detection and Scintillator Technologies
- Superconducting Materials and Applications
- Plant and Fungal Species Descriptions
- Quantum many-body systems
- Optical and Acousto-Optic Technologies
Max Planck Institute for Solid State Research
2020-2025
University of Stuttgart
2025
Max Planck Institutes for Intelligent Systems & Solid State Research Library
2024
Paul Scherrer Institute
2019-2023
Goethe University Frankfurt
2016-2023
University of Geneva
2021
The discovery of high-temperature superconductivity in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msub><a:mrow><a:mi>La</a:mi></a:mrow><a:mrow><a:mn>3</a:mn></a:mrow></a:msub><a:msub><a:mrow><a:mi>Ni</a:mi></a:mrow><a:mrow><a:mn>2</a:mn></a:mrow></a:msub><a:msub><a:mrow><a:mi mathvariant="normal">O</a:mi></a:mrow><a:mrow><a:mn>7</a:mn></a:mrow></a:msub></a:mrow></a:math> at pressures above 14 GPa has spurred extensive research efforts. Yet, fundamental...
We report the discovery of topological magnetism in candidate magnetic Weyl semimetal CeAlGe. Using neutron scattering we find this system to host several incommensurate, square-coordinated multi-k[over →] phases below T_{N}. The properties a phase stable at intermediate fields parallel c axis are suggested by observation Hall effect. Our findings highlight CeAlGe as an exceptional for exploiting interplay between nontrivial topologies magnetization real space and nodes momentum space.
Perovskite nickelate single crystals are topotactically reduced to the infinite-layer phase and show metallic properties.
We report a comprehensive study of magnetic correlations in ${\mathrm{LaNiO}}_{2}$, parent compound the recently discovered family infinite-layer (IL) nickelate superconductors, using multiple experimental and theoretical methods. Our specific heat, muon-spin rotation ($\ensuremath{\mu}\mathrm{SR}$), susceptibility measurements on polycrystalline ${\mathrm{LaNiO}}_{2}$ show that long-range order remains absent down to 2 K. Nevertheless, we detect residual entropy low-temperature which is...
The recent claim of superconductivity above room temperature in Pb10−xCux(PO4)6O with 0.9 &lt; x 1 (referred to as LK-99) has sparked considerable interest. To minimize the influence structural defects and impurity phases on physical properties, we have synthesized phase-pure single crystals a copper doping level ∼ 1. We find that are highly insulating optically transparent. X-ray analysis reveals an uneven distribution substituted Cu throughout sample. Temperature (T) dependent magnetic...
Infinite-layer (IL) nickelates are an emerging family of superconductors whose similarities and differences to cuprate under intense debate. To date, the IL phase can only be reached via topotactic oxygen reduction perovskite phase, using H$_2$ gas or reducing agents such as CaH$_2$. While method has been widely employed on thin film polycrystalline powder samples, La$_{1-x}$Ca$_x$NiO$_3$ single-crystals with lateral dimensions up 150 $\mu$m was achieved recently, indirect contact Here we...
The first multi-transition metal cathode was examined for fluoride ion batteries, showing different redox behaviour of cobalt and nickel on charging discharging.
We use resonant inelastic x-ray scattering (RIXS) at the O $K$- and Cu $K$-edges to investigate doping- temperature dependence of low-energy plasmon excitations in La$_{2-x}$Sr$_{x}$CuO$_4$. observe a monotonic increase energy scale plasmons with increasing doping $x$ underdoped regime, whereas saturation occurs above optimal $x \gtrsim 0.16$ persists least up = 0.4$. Furthermore, we find that show only marginal dependence, possible effects due superconducting transition onset strange metal...
We present the crystal structure and magnetic properties of Y$_{3}$Cu$_{9}$(OH)$_{19}$Cl$_{8}$, a stoichiometric frustrated quantum spin system with slightly distorted kagome layers. Single crystals Y$_{3}$Cu$_{9}$(OH)$_{19}$Cl$_{8}$ were grown under hydrothermal conditions. The was determined from single X-ray diffraction confirmed by neutron powder diffraction. observed reveals two different Cu-positions leading to distored layer in contrast closely related YCu$_{3}$(OH)$_{6}$Cl$_{3}$....
We explore two methods for single-crystal growth of the theoretically proposed magnetic Weyl semimetals $R\mathrm{AlGe}$ ($R$ = Pr, Ce), which prove that a floating-zone technique, being both crucible- and flux-free, is crucial to obtain perfectly stoichiometric crystals. In contrast, crystals grown by flux-growth technique tend be Al-rich. further present structural elemental analyses, along with bulk magnetization electrical resistivity data on prepared technique. Both systems intended...
Infinite-layer (IL) nickelates are an emerging class of superconductors, where the Ni$^{1+}$ valence state in a square planar NiO$_2$ coordination can only be reached via topotactic reduction perovskite phase. However, this soft chemistry with hydrogenous reagents is still at stage rapid development, and there number open issues, especially considering possibility hydrogen incorporation. Here we study time dependence transformation LaNiO$_3$ to LaNiO$_2$ for powder samples x-ray diffraction...
The recent claim of superconductivity above room temperature in Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O with 0.9 < $x$ 1 (referred to as LK-99) has sparked considerable interest. To minimize the influence structural defects and impurity phases on physical properties, we have synthesized phase-pure single crystals $x \sim 1$. We find that are highly insulating optically transparent. X-ray analysis reveals an uneven distribution substituted Cu throughout sample. Temperature ($T$) dependent...
Y${}_{3}$Cu${}_{9}$(OH)${}_{19}$Cl${}_{8}$, also known as Y-kapellasite, realizes an original anisotropic frustrated kagome model. Here, the authors study large phase-pure single crystals, obtained via external gradient method, by susceptibility, specific heat, thermal expansion, neutron scattering, and local $\ensuremath{\mu}$SR NMR techniques. These find subtle structural changes along with long-range magnetic ordering (1/3,1/3). Large quantum fluctuations reduce Cu${}^{2+}$ moments,...
The anomalous Hall {\color{black} e}ffect (AHE) has emerged as a key indicator of time-reversal symmetry breaking (TRSB) and topological features in electronic band structures. Absent magnetic field, the AHE requires spontaneous TRSB but proven hard to probe due averaging over domains. component effect is thus frequently derived from extrapolating field dependence response. We show that discerning whether an intrinsic property free system becomes intricate presence strong fluctuations....
The kapellasite family $A$Cu$_3$(OH)$_{6+x}$(Cl,Br)$_{3-x}$ forms a series of compounds, wherein the chemical pressure realized by $A-$site cation tunes spin exchange in frustrated distorted kagome lattice. Via hydrothermal synthesis we have grown single crystals whole for $A=$ rare-earths and found clear structural transition to superstructure variant at specific level exerted $A$~=~Dy. Phases with crystal structures vicinity this realize lattice Cu$^{2+}$ cations characteristic features...
We investigate the magnetic ground state of single crystals ruthenium-dimer-based hexagonal perovskite <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>Ba</a:mi><a:mn>3</a:mn></a:msub><a:msub><a:mi>ZnRu</a:mi><a:mn>2</a:mn></a:msub><a:msub><a:mi mathvariant="normal">O</a:mi><a:mn>9</a:mn></a:msub></a:mrow></a:math> using susceptibility and resonant inelastic x-ray scattering (RIXS) measurements. While a previous study on powder samples exhibited intriguing behavior,...
The continuous development of innovative optical materials with lanthanoid ions as activators has emerged a modern sector chemistry. Our experience the fabrication single crystals float zone motivated us to investigate luminescence Nd3+ and Ho3+ in garnets (Gd3-xREx)In2Ga3O12 (RE = Nd Ho, x 0; 0.15 0.30). Upon usage an Ar/O2 (80:20 ratio) atmosphere application auxiliary pressure (6 bar) suppress In2O3 evaporation, crystalline domain sizes order ~ 6 1 mm³ obtained. Structural analysis...
The continuous development of innovative optical materials with lanthanoid ions as activators has emerged a modern sector chemistry. Our experience the fabrication single crystals float zone motivated us to investigate luminescence Nd3+ and Ho3+ in garnets (Gd3-xREx)In2Ga3O12 (RE = Nd Ho, x 0; 0.15 0.30). Upon usage an Ar/O2 (80:20 ratio) atmosphere application auxiliary pressure (6 bar) suppress In2O3 evaporation, crystalline domain sizes order ~ 6 1 mm³ obtained. Structural analysis...
The anomalous Hall effect (AHE) has emerged as a key indicator of time-reversal symmetry breaking (TRSB) and topological features in electronic band structures. Absent magnetic field, the AHE requires spontaneous TRSB but proven hard to probe due averaging over domains. component is thus frequently derived from extrapolating field dependence response. We show that discerning whether an intrinsic property field-free system becomes intricate presence strong fluctuations. As study case, we use...
Recent studies of La_{3}Ni_{2}O_{7} have identified a bilayer (2222) structure and an unexpected alternating monolayer-trilayer (1313) structure, both which feature signatures superconductivity near 80 K under high pressures. Using angle-resolved photoemission spectroscopy, we measure the electronic 1313 samples. In contrast to previously studied 2222 find that hosts flat band with markedly different binding energy, as well additional electron pocket splittings. By comparison local-density...
The quantum kagome antiferromagnets YCu3(OH)6OxCl3-x (x=0,1/3) are produced using a unified solid state synthesis route for polycrystalline samples. From structural refinements based on neutron diffraction data, we clarify the structure of Y3Cu9(OH)18OCl8 (x=1/3) compound and provide revised chemical formula. We use muon spin relaxation, as local probe magnetism, to investigate exotic low temperature properties in two compounds. In agreement with find no evidence long range ordering both...
Abstract In magnetic Weyl semimetals, where magnetism breaks time-reversal symmetry, large magnetically sensitive anomalous transport responses are anticipated that could be useful for topological spintronics. The identification of new semimetals is therefore in high demand, particularly since these systems node configurations may easily modified using fields. Here we explore experimentally the semimetal PrAlGe, and unveil a direct correspondence between easy-axis Pr ferromagnetism Hall...
We report the synthesis of powder and single-crystal samples cerium pyrohafnate their characterization using neutron diffraction, thermogravimetry X-ray absorption spectroscopy. evaluate amount non-magnetic Ce$^{4+}$ defects use this result to interpret spectrum crystal-electric field transitions observed inelastic scattering. The analysis these single-ion indicates dipole-octupole nature ground state doublet a significant degree spin-lattice coupling. properties calculated from parameters...
The strong structure-property coupling in rare-earth nickelates has spurred the realization of new quantum phases rapid succession. Recently, topotactic transformations have provided a platform for controlled creation oxygen vacancies and, therewith, exploitation such nickelates. Here, we report emergence vacancy ordering Pr$_{0.92}$Ca$_{0.08}$NiO$_{2.75}$ single crystals obtained via reduction perovskite phase Pr$_{0.92}$Ca$_{0.08}$NiO$_{3}$, using CaH$_2$ as reducing agent. We unveil...