Publications by authors named "Buchner B"

Controlling the layer-by-layer chemistry and structure of nanomaterials remains a crucial focus in nanoscience and nanoengineering. Specifically, the integration of atomically thin semiconductors with antiferromagnetic two-dimensional materials holds great promise for advancing research. In this work, we successfully demonstrate a new synthesis approach for high-crystallinity CrCl/MoS van der Waals heterostructures a thermodynamically optimized chemical vapor transport (CVT) process on -sapphire (0001) substrates.

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Linear conducting polymers show ballistic transport, imposed by mobile carriers moving along the polymer chains, whereas conductance in the extended dimension, that is, between polymer strands or layers, remains weak due to the lack of intermolecular ordering and electronic coupling. Here we report a multilayer-stacked two-dimensional polyaniline (2DPANI) crystal, which shows metallic out-of-plane charge transport with high electrical conductivity. The material comprises columnar π arrays with an interlayer distance of 3.

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Two-dimensional magnetic materials with tunable physical parameters are emerging as potential candidates for topological phenomena as well as applications in spintronics. The famous Mermin-Wagner theorem states that spontaneous spin symmetry cannot be broken at finite temperature in low dimensional magnetic systems which forbids the possibility of a transition to a long-range ordered state in a two-dimensional magnetic system at finite temperature. Though, there are some exceptions to Mermin-Wagner theorem in particular low dimensional magnetic systems with topologically ordered phase transitions.

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Topological superconductivity is a promising concept for generating fault-tolerant qubits. Early experimental studies looked at hybrid systems and doped intrinsic topological or superconducting materials at very low temperatures. However, higher critical temperatures are indispensable for technological exploitation.

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Kagome magnets provide a fascinating platform for the realization of correlated topological quantum phases under various magnetic ground states. However, the effect of the magnetic spin configurations on the characteristic electronic structure of the kagome-lattice layer remains elusive. Here, utilizing angle-resolved photoemission spectroscopy and density functional theory calculations, we report the spectroscopic evidence for the spin-reorientation effect of a kagome ferromagnet FeGe, which is composed solely of kagome planes.

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Article Synopsis
  • Next week, global negotiators will meet in Baku, Azerbaijan, for COP29, aimed at addressing climate change through international agreements.
  • The conference is nicknamed "The Finance COP" due to its emphasis on securing financial commitments and mechanisms needed to mobilize large investments to combat climate change.
  • While the required investment amounts may seem daunting, they are deemed achievable, and delaying action could lead to significant economic and social losses.
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Our knowledge about endohedral metallofullerenes (EMFs) is restricted to the structures with sufficient kinetic stability to be extracted from the arc-discharge soot and processed by chromatographic and structural techniques. For the most abundant rare-earth monometallofullerene M@C, experimental studies repeatedly demonstrated (9) and (6) carbon cage isomers, while computations predicted equal stability of the "missing" (8) isomer. Here we report that this isomer is indeed formed but has not been recovered from soot using standard protocols.

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Magnetic materials featuring triangular arrangements of spins are frequently investigated as platforms hosting magnetic frustration. Hexagonal perovskites with ordered vacancies serve as excellent candidates for two-dimensional triangular magnetism due to the considerable separation of the magnetic planes. In this work, the effects of chemical pressure on the ferromagnetic ground state of BaLaNiWO by substitution of Ba with Sr to produce SrLaNiWO are investigated.

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A ZnO-Graphene oxide nanocomposite (Z-G) was prepared in order to exploit the biomedical features of each component in a single anticancer material. This was achieved by means of an environmentally friendly synthesis, taking place at a low temperature and without the involvement of toxic reagents. The product was physicochemically characterized.

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Recently, MnTe was established as an altermagnetic material that hosts spin-polarized electronic bands as well as anomalous transport effects like the anomalous Hall effect. In addition to these effects arising from altermagnetism, MnTe also hosts other magnetoresistance effects. Here, we study the manipulation of the magnetic order by an applied magnetic field and its impact on the electrical resistivity.

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Heteroanionic materials show promising potential as 2D semiconductors due to their tunable band gaps, making them excellent candidates for photocatalytic water splitting applications. We conducted detailed theoretical and experimental analysis of two selected materials by synthesizing crystals through chemical vapor transport and investigating the impact of anion variation on crystal structure and properties. Using powder X-ray diffraction and convergent beam electron diffraction, we elucidated the non-centrosymmetric space groups of these compounds.

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Magnetic topological insulators (TIs) herald a wealth of applications in spin-based technologies, relying on the novel quantum phenomena provided by their topological properties. Particularly promising is the (MnBiTe)(BiTe) layered family of established intrinsic magnetic TIs that can flexibly realize various magnetic orders and topological states. High tunability of this material platform is enabled by manganese-pnictogen intermixing, whose amounts and distribution patterns are controlled by synthetic conditions.

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Here, we report the first time- and angle-resolved photoemission spectroscopy (TR-ARPES) with the new Fermiologics "FeSuMa" analyzer. The new experimental setup has been commissioned at the Artemis laboratory of the UK Central Laser Facility. We explain here some of the advantages of the FeSuMa for TR-ARPES and discuss how its capabilities relate to those of hemispherical analyzers and momentum microscopes.

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In this work we instigated the fragmentation of Au microparticles supported on a thin amorphous carbon film by irradiating them with a gradually convergent electron beam inside the Transmission Electron Microscope. This phenomenon has been generically labeled as "electron beam-induced fragmentation" or EBIF and its physical origin remains contested. On the one hand, EBIF has been primarily characterized as a consequence of beam-induced heating.

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Article Synopsis
  • Pentacene, a widely studied organic semiconductor, has its exciton motion influenced by inter-molecular exciton coupling through charge-transfer processes.
  • The study investigates how adding tetracene, which has a larger band gap, affects exciton behavior in pentacene by disrupting pentacene-pentacene interactions.
  • Results reveal that increasing tetracene concentration leads to a significant decrease in both Davydov splitting and exciton band width in pentacene, with the exciton band width reduction being notably larger.
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The noncentrosymmetric ferromagnetic Weyl semimetal CeAlSi with simultaneous space-inversion and time-reversal symmetry breaking provides a unique platform for exploring novel topological states. Here, by employing multiple experimental techniques, we demonstrate that ferromagnetism and pressure can serve as efficient parameters to tune the positions of Weyl nodes in CeAlSi. At ambient pressure, a magnetism-facilitated anomalous Hall/Nernst effect (AHE/ANE) is uncovered.

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Nd-based nitride clusterfullerenes NdMN@C with rare-earth metals of different sizes (M = Sc, Y, Lu) were synthesized to elucidate the influence of the cluster composition, shape and internal strain on the structural and magnetic properties. Single crystal X-ray diffraction revealed a very short Nd-N bond length in NdScN@C. For Lu and Y analogs, the further shortening of the Nd-N bond and pyramidalization of the NdMN cluster are predicted by DFT calculations as a result of the increased cluster size and a strain caused by the limited size of the fullerene cage.

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[Legal regulation of digital public health interventions-hindrance or stimulus?].

Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz

March 2024

The potential benefits of digital health technologies in population-based health research depend mainly on whether and to what extent these technologies can be based on the processing of personal health data. However, there needs to be more certainty in the application and interpretation of the relevant legal regulations on the processing of research data using digital health technologies. Research practice primarily uses consent as a legitimation basis for data processing, although the information model of the German and European legislator, with its ambitious requirements for voluntary and informed consent, is unrealistic and needs to be revised.

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An essential ingredient for the production of Majorana fermions for use in quantum computing is topological superconductivity. As bulk topological superconductors remain elusive, the most promising approaches exploit proximity-induced superconductivity, making systems fragile and difficult to realize. Due to their intrinsic topology, Weyl semimetals are also potential candidates, but have always been connected with bulk superconductivity, leaving the possibility of intrinsic superconductivity of their topological surface states, the Fermi arcs, practically without attention, even from the theory side.

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Quantum spin liquids (QSLs) are novel phases of matter which remain quantum disordered even at the lowest temperature. They are characterized by emergent gauge fields and fractionalized quasiparticles. Here we show that the sub-kelvin thermal transport of the three-dimensional S=1/2 hyperhyperkagome quantum magnet PbCuTe_{2}O_{6} is governed by a sizeable charge-neutral fermionic contribution which is compatible with the itinerant fractionalized excitations of a spinon Fermi surface.

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An ultrasharp photoluminescence line intimately related to antiferromagnetic order has been found in NiPS_{3}, a correlated van der Waals material, opening prospects for magneto-optical coupling schemes and spintronic applications. Here we unambiguously clarify the singlet origin of this excitation, confirming its roots in the spin structure. Based on a comprehensive investigation of the electronic structure using angle-resolved photoemission and q-dependent electron energy loss spectroscopy as experimental tools we develop, in a first step, an adequate theoretical understanding using density functional theory (DFT).

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Mitochondrial membrane protein-associated neurodegeneration (MPAN) is an ultraorphan neurogenetic disease from the group of neurodegeneration with brain iron accumulation (NBIA) disorders. Here we report cross-sectional and longitudinal data to define the phenotype, to assess disease progression and to estimate sample sizes for clinical trials. We enrolled patients with genetically confirmed MPAN from the Treat Iron-Related Childhood-Onset Neurodegeneration (TIRCON) registry and cohort study, and from additional sites.

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Zinc oxide/Curcumin (Zn(CUR)O) nanocomposites were prepared hydrothermal treatment of Zn(NO) in the presence of hexamethylenetetramine as a stabilizing agent and CUR as a bioactive element. Three ZnO : CUR ratios were investigated, namely 57 : 43 (Zn(CUR)O-A), 60 : 40 (Zn(CUR)O-B) and 81 : 19 (Zn(CUR)O-C), as assessed by thermogravimetric analyses, with an average hydrodynamic diameter of nanoaggregates in the range of 223 to 361 nm. The interaction of CUR with ZnO hydroxyl and ketoenol groups (as proved by X-ray photoelectron spectroscopy analyses) was found to significantly modify the key properties of ZnO nanoparticles with the obtainment of a bilobed shape (as shown by scanning electron microscopy), and influenced the growth process of the composite nanoparticles as indicated by the varying particle sizes determined by powder X-ray diffraction.

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Since the transmission electron microscope (TEM) has the capacity to observe the atomic structure of materials,TEM synthesis methods are uniquely suited to advance our fundamental understanding of the bottom-up dynamics that drive the formation of nanostructures. E-beam induced fragmentation (potentially identified as a manifestation of Coulomb explosion) and electron stimulated desorption are phenomena that have received attention because they trigger chemical and physical reactions that can lead to the production of various nanostructures. Here we report a simple TEM protocol implemented on WOmicroparticles supported on thin amorphous carbon substrates.

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