A5066266534- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Multiferroics and related materials
- Quantum many-body systems
- Theoretical and Computational Physics
- Iron-based superconductors research
- Magnetism in coordination complexes
- Quantum and electron transport phenomena
- Magnetic properties of thin films
- High-pressure geophysics and materials
- Rare-earth and actinide compounds
- Atomic and Subatomic Physics Research
- Nuclear materials and radiation effects
- Nuclear Physics and Applications
- Crystal Structures and Properties
- Topological Materials and Phenomena
- Electronic and Structural Properties of Oxides
- Algebraic structures and combinatorial models
- Advanced NMR Techniques and Applications
- Magnetic Properties of Alloys
- Inorganic Fluorides and Related Compounds
- Superconducting Materials and Applications
- Quantum, superfluid, helium dynamics
- Inorganic Chemistry and Materials
Technische Universität Berlin
2016-2025
Helmholtz-Zentrum Berlin für Materialien und Energie
2016-2025
University of Copenhagen
2014
German Orient Foundation
2006-2011
Nagoya University
2008
Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute
2005-2008
Nagoya Institute of Technology
2008
Monash University
2008
Queensland University of Technology
2008
The University of Queensland
2008
Linear spin wave theory provides the leading term in calculation of excitation spectra long-range ordered magnetic systems as a function 1/√S. This is acquired using Holstein-Primakoff approximation operator and valid for small δS fluctuations moment. We propose an algorithm that allows ground states with general moment directions single-Q incommensurate ordering vector local coordinate transformation every rotating incommensurability. Finally we show, how our model can determine spectrum...
Neutron scattering is used to characterize the magnetism of vortices for optimally doped high-temperature superconductor La(2-x)Sr(x)CuO4 (x = 0.163) in an applied magnetic field. As temperature reduced, low-frequency spin fluctuations first disappear with loss vortex mobility, but then reappear. We find that state can be regarded as inhomogeneous mixture a superconducting fluid and material containing nearly ordered antiferromagnet. These experiments show many other properties cuprate...
The space- and time-dependent response of many-body quantum systems is the most informative aspect their emergent behaviour. dynamical structure factor, experimentally measurable using neutron scattering, can map this in wavevector energy with great detail, allowing theories to be quantitatively tested high accuracy. Here, we present a comparison between scattering measurements on one-dimensional spin-1/2 Heisenberg antiferromagnet KCuF3, recent state-of-the-art theoretical methods based...
${\mathrm{BaMn}}_{2}{\mathrm{As}}_{2}$ is unique among Ba${T}_{2}$As${}_{2}$ compounds crystallizing in the body-centered-tetragonal ${\mathrm{ThCr}}_{2}{\mathrm{Si}}_{2}$ structure, which contain stacked square lattices of $3d$ transition metal $T$ atoms, since it has an insulating large-moment ($3.9\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}/$Mn) G-type (checkerboard) antiferromagnetic (AF) ground state. We report measurements anisotropic magnetic susceptibility...
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 present synchrotron x-ray diffraction, neutron powder and time-of-flight inelastic scattering measurements on the rare earth pyrochlore oxide ${\mathrm{Nd}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ to study ordered state magnetic structure cystal-field states. The structural characterization by high-resolution diffraction confirms that has no detectable O vacancies or Nd/Zr site mixing. reveals long-range all-in/all-out antiferromagnetic order below ${T}_{\mathrm{N}}\ensuremath{\approx}0.4$...
We demonstrate how quantum entanglement can be directly witnessed in the quasi-1D Heisenberg antiferromagnet KCuF$_3$. apply three witnesses --- one-tangle, two-tangle, and Fisher information to its inelastic neutron spectrum, compare with spectra simulated by finite-temperature density matrix renormalization group (DMRG) classical Monte Carlo methods. find that each witness provides direct access entanglement. Of these, is most robust experimentally, indicates presence of at least bipartite...
High-resolution neutron scattering experiments on optimally doped ${\mathrm{L}\mathrm{a}}_{2\ensuremath{-}x}{\mathrm{S}\mathrm{r}}_{x}\mathrm{C}\mathrm{u}{\mathrm{O}}_{4}$ ($x=0.16$) reveal that the magnetic excitations are dispersive. The dispersion is same as in ${\mathrm{Y}\mathrm{B}\mathrm{a}}_{2}\mathrm{C}{\mathrm{u}}_{3}{\mathrm{O}}_{6.85}$, and quantitatively related to observed with charge sensitive probes. associated velocity only weakly dependent doping a value close spin-wave of...
We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41 as a starting point for investigating doped ladders and their tendency toward superconductivity. A key feature was separation of one-triplon two-triplon scattering. Two-triplon is observed quantitatively first time so access realized to important strong magnetic quantum fluctuations. The spin gap found be 26.4+/-0.3 meV. data are successfully modeled using continuous unitary transformation...
We present a unique study of the frustrated spinel MgV2O4 which possesses highly coupled spin, lattice and orbital degrees freedom. Using large single-crystal powder samples, we find distortion from at room temperature (space group F-43m) allows for greater trigonal VO6 octahedra low space (I-4m2) that maintains mirror plane symmetry. The magnetic structure develops below 42 K consists antiferromagnetic chains with strongly reduced moment while inelastic neutron scattering reveals...
Confinement is a process by which particles with fractional quantum numbers bind together to form quasiparticles integer numbers. The constituent are confined an attractive interaction whose strength increases increasing particle separation and as consequence, individual not found in isolation. This phenomenon well known physics where quarks baryons mesons. An analogous occurs certain magnetic insulators; weakly coupled chains of spins S=1/2. collective excitations these systems spinons...
We have investigated the physical properties of a pyrochlore hafnate Nd2Hf2O7 using ac magnetic susceptibility \chi_ac(T), dc \chi(T), isothermal magnetization M(H) and heat capacity C_p(T) measurements, determined ground state by neutron powder diffraction study. An upturn is observed below 6 K in C_p(T)/T, however both \chi(T) do not show any clear anomaly down to 2 K. The \chi_ac(T) shows well pronounced indicating an antiferromagnetic transition at T_N = 0.55 long range ordering...
Using high resolution THz spectroscopy, the authors study spinon confinement in weakly coupled antiferromagnetic chain compound SrCo${}_{2}$V${}_{2}$O${}_{8}$. The confined spinons appear a hierarchy that can be fully described by one dimensional Schr\"odinger equation with linear potential.
Abstract The quantum spin liquid is a highly entangled magnetic state characterized by the absence of static magnetism in its ground state. Instead, spins fluctuate correlated way down to lowest temperatures. Quantum liquids are very rare and confined few specific cases where interactions between ions cannot be simultaneously satisfied (known as frustration). Lattices with triangular or tetrahedral arrangements, which interact via isotropic antiferromagnetic interactions, can generate such...
Inelastic neutron scattering measurements are reported that show a new longitudinal mode in the antiferromagnetically ordered phase of spin- 1/2 quasi-one-dimensional antiferromagnet KCuF3. This signals crossover from one-dimensional to three-dimensional behavior and indicates reduction spin moment antiferromagnet. The compared with recent quantum field theory calculations found be excellent agreement. A feature data not predicted by is damping decay processes transverse spin-wave branches.