A5052679635- Physics of Superconductivity and Magnetism
- Organic and Molecular Conductors Research
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Magnetism in coordination complexes
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Advanced Polymer Synthesis and Characterization
- Magnetic Properties of Alloys
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Inorganic Chemistry and Materials
- Theoretical and Computational Physics
- Molecular Junctions and Nanostructures
- Inorganic Fluorides and Related Compounds
- High-pressure geophysics and materials
- Force Microscopy Techniques and Applications
- Hydrogels: synthesis, properties, applications
- Material Dynamics and Properties
- Solid-state spectroscopy and crystallography
- Quantum and electron transport phenomena
- Polymer Surface Interaction Studies
- Perovskite Materials and Applications
- Multiferroics and related materials
- Rheology and Fluid Dynamics Studies
Leibniz Institute of Polymer Research
2016-2025
Goethe University Frankfurt
2015-2024
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
2023
Atlantic Technological University
2022
Philadelphia University
2021
University of Pittsburgh
2021
Carrier (United States)
2020
FH Aachen
2018
DWI – Leibniz Institute for Interactive Materials
2018
Goethe Institute
2012-2017
We report the first observation of non-Fermi-liquid (NFL) effects in a clean Yb compound at ambient pressure and zero magnetic field. The electrical resistivity specific-heat coefficient high-quality single crystals ${\mathrm{YbRh}}_{2}{\mathrm{Si}}_{2}$ present linear logarithmic temperature dependence, respectively, more than decade temperature. ascribe this NFL behavior to presence (presumably) quasi-2D antiferromagnetic spin fluctuations related very weak phase transition...
Two series of randomly cross-linked poly(dimethylsiloxane) (PDMS) networks with systematically varying and well-defined dangling chain defect content were investigated by 1H double-quantum low-field NMR (DQ NMR), equilibrium swelling, high-resolution magic-angle spinning (MAS NMR) experiments in order to obtain information about the absolute molecular weight polymer chains between two cross-links, Mc, its distribution. A comparison experimental results from swelling DQ Miller–Macosko...
We present a study of the structure Tetra-PEG model networks, using proton multiple-quantum NMR at low field in combination with computer simulations. is novel high-performance hydrogel designed by two symmetric tetra-arm macromonomers. In contrast to conventional hydrogels, which are highly heterogeneous due fixed concentration fluctuations, exhibits much less microstructure as indicated previous light and small-angle neutron scattering studies. Here, local-scale connectivity...
The natural mineral azurite Cu(3)(CO(3))(2)(OH)(2) is a frustrated magnet displaying unusual and controversially discussed magnetic behavior. Motivated by the lack of unified description for this system, we perform theoretical study based on density functional theory as well state-of-the-art numerical many-body calculations. We propose an effective generalized spin-1/2 diamond chain model which provides consistent experiments: low-temperature magnetization, inelastic neutron scattering,...
We investigate the structural properties of model amphiphilic conetworks made by heterocomplementary end-linking tetra-poly(ethylene glycol) tetra-poly(ϵ-caprolactone) PCL star polymers in selective and nonselective solvents using small-angle X-ray scattering, nuclear magnetic resonance (NMR) diffusometry, double-quantum magic-angle spinning (DQ MAS) NMR techniques. The scattering experiments reveal correlation lengths our networks, including postcuring effects, microphase separation (MPS)...
We report resistivity, $\ensuremath{\rho}(T)$, and specific-heat, $C(T)$, results on near stoichiometric $\mathrm{CeCu}{}_{2}{\mathrm{Si}}_{2}$ samples, in the vicinity of a quantum critical point (QCP). The latter is defined by ${T}_{A}\ensuremath{\rightarrow}0$, where ${T}_{A}\ensuremath{\lesssim}0.8\mathrm{K}$ marks transition into spin-density--wave-type ``phase $A$'' which competes with heavy-fermion superconductivity below ${T}_{c}\ensuremath{\approx}0.65\mathrm{K}$. Upon approaching...
We present high-resolution measurements of the coefficient thermal expansion $\ensuremath{\alpha}(T)=\ensuremath{\partial}\mathrm{ln}l(T)/\ensuremath{\partial}T$ quasi-two-dimensional (quasi-2D) salts $\ensuremath{\kappa}\ensuremath{-}(\mathrm{BEDT}\ensuremath{-}\mathrm{TTF}{)}_{2}X$ with $X=\mathrm{Cu}(\mathrm{NCS}{)}_{2},$ $\mathrm{Cu}[\mathrm{N}(\mathrm{CN}{)}_{2}]\mathrm{Br},$ and $\mathrm{Cu}[\mathrm{N}(\mathrm{CN}{)}_{2}]\mathrm{Cl}$ in temperature range $T<~150 \mathrm{K}.$ Three...
Elastic constant and thermal expansion data for a high quality single crystal of ${\mathrm{CeCu}}_{2}$${\mathrm{Si}}_{2}$ are presented. The yield detailed B-T phase diagram exhibiting previously unknown high-field phase. From the unusual behavior elastic constants on entering superconducting we deduce that, in contrast to other heavy-fermion superconductors, does not coexist with surrounding
We present a specific heat and inelastic neutron scattering study in magnetic fields up into the $1/3$ magnetization plateau phase of diamond chain compound azurite ${\mathrm{Cu}}_{3}({\mathrm{CO}}_{3}{)}_{2}(\mathrm{OH}{)}_{2}$. establish that is dimer-monomer state, i.e., consisting $S=1/2$ monomers, which are separated by $S=0$ dimers on backbone. The effective spin couplings ${J}_{\mathrm{mono}}/{k}_{B}=10.1(2)\text{ }\text{ }\mathrm{K}$ ${J}_{\mathrm{dimer}}/{k}_{B}=1.8(1)\text{ derived...
The spin-liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3 has been studied by measuring the uniaxial expansion coefficients alpha(i), specific heat, and magnetic susceptibility. Special emphasis was placed on mysterious anomaly around 6 K--a potential instability. Distinct strongly anisotropic lattice effects have observed at K, clearly identifying this feature as a second-order phase transition. Owing to large anomalies in application of Grüneisen scaling enabled us determine corresponding heat...
In this work we explore the overall structural behaviour of [(CH3)2NH2][Mn(HCOO)3] multiferroic compound across temperature range where its ferroelectric transition takes place by means calorimetry, thermal expansion measurements and variable powder single crystal X-ray diffraction. The results clearly prove presence a phase at Tt ~ 187 K (the which dielectric occurs) that involves symmetry change from Rc to Cc, twinning crystals, discontinuous variation unit cell parameters volume, sharp...
Inelastic neutron scattering measurements of magnetic excitations in the charge-ordered state ${\mathrm{Yb}}_{4}{\mathrm{As}}_{3}$ have been performed under field up to about 6 T. By applying a field, spectrum at one-dimensional wave vector $q\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ [ $\ensuremath{\pi}/d$] changes drastically from broad one corresponding spinon excitation continuum $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\frac{1}{2}$ spin system sharp finite energy,...
We present results of low-temperature calorimetric and resistive measurements on the isostructural heavy-fermion compounds . `Non-Fermi-liquid' effects are established which suggest nearness an antiferromagnetic quantum critical point (QCP) in both systems. The observed deviations from properties a Landau Fermi liquid (FL) may be related to anomalous energy dependences quasiparticle mass - scattering cross section. For , moderately heavy FL can recovered by application moderate values either...
Dilatometric and magnetic experiments on high-quality single crystals of the superconducting compounds UP${\mathrm{d}}_{2}$A${\mathrm{l}}_{3}$ CeR${\mathrm{u}}_{2}$, which have enhanced spin susceptibilities, demonstrate a first-order transition between weak strong pinning at $T<{0.9T}_{c}$ ( $H>10$ kOe). This is compatible with staggered order parameter due to formation ``Fulde-Ferrell-Larkin-Ovchinnikov'' state.
Scale formation, the deposition of certain minerals such as CaCO3, MgCO3, and CaSO4·2H2O in industrial facilities household devices, leads to reduced efficiency or severe damage. Therefore, incrustation is a major problem everyday life. In recent years, double hydrophilic block copolymers (DHBCs) have been focus interest academia with regard their antiscaling potential. this work, we synthesized well-defined blocklike PAA-PAMPS consisting acrylic acid (AA) 2-acrylamido-2-methyl-propane...
The bond fluctuation method is used to simulate both non-concatenated entangled and interpenetrating melts of ring polymers. We find that the swelling rings upon dilution follows same laws as for linear chains. Knotting linking probabilities polymers in semi-dilute solution are analyzed using HOMFLY polynomial. an exponential decay knotting probability rings. correlation length can be superimpose data at different concentrations. A power law dependence $f_{n}\sim\phi R^{2}\sim\phi^{0.77}N$...
We investigate the effect that temperature dependence of crystal structure a two-dimensional organic charge-transfer salt has on low-energy Hamiltonian representation electronic structure. For that, we determine $\ensuremath{\kappa}$-(BEDT-TTF)${}_{2}$Cu${}_{2}$(CN)${}_{3}$ for series temperatures between $T=5$ and 300 K by single X-ray diffraction analyze evolution with using density functional theory tight binding methods. find considerable corresponding triangular lattice Hubbard...
The gel point of end-linked model networks is determined from computer simulation data. It shown that the difference between true conversion, pc, and ideal mean field prediction for point, pc,id, a function average number cross-links per pervaded volume network strand, P, thus, exhibits an explicit dependence on junction functionality, f. In contrast, amount intramolecular reactions at independent f in first approximation different power-law overlap elastic strands as compared to delay, pc –...
The coupling of the critical electronic system to a compressible lattice is found drastically alter Mott criticality.
Based upon the resistor analogy and using ideal loop gas approximation (ILGA), it is shown that only pending loops reduce modulus of an otherwise perfect network made monodisperse strands junctions identical functionality. Thus, cycle rank with structures removed (cyclic branched) sufficient to characterize modulus, if can be employed. It further impossible incorporate finite cycles into a polymer such individual are at equilibrium conformations while maintaining simultaneously force balance...