A5076197506- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Organic and Molecular Conductors Research
- Magnetism in coordination complexes
- Inorganic Chemistry and Materials
- Multiferroics and related materials
- Perovskite Materials and Applications
- Nonlinear Dynamics and Pattern Formation
- Cold Atom Physics and Bose-Einstein Condensates
- Magnetic Properties of Alloys
- Crystallization and Solubility Studies
- Random lasers and scattering media
- Advanced NMR Techniques and Applications
- Heusler alloys: electronic and magnetic properties
- Nonlinear Optical Materials Research
- Iron-based superconductors research
- Thermal and Kinetic Analysis
- nanoparticles nucleation surface interactions
- Quantum and electron transport phenomena
- Advanced Physical and Chemical Molecular Interactions
- X-ray Diffraction in Crystallography
- Topological Materials and Phenomena
- Advanced Sensor and Energy Harvesting Materials
- Polymer Nanocomposite Synthesis and Irradiation
Goethe University Frankfurt
2013-2023
Recent studies have brought $\alpha$-RuCl$_3$ to the forefront of experimental searches for materials realizing Kitaev spin-liquid physics. This material exhibits strongly anisotropic exchange interactions afforded by spin-orbit coupling 4d Ru centers. We investigate dynamical response at finite temperature and magnetic field a realistic model in $\alpha$-RuCl$_3$. These regimes are thought host unconventional paramagnetic states that emerge from suppression order. Using exact...
The description of quantized collective excitations stands as a landmark in the quantum theory condensed matter. A prominent example occurs conventional magnets, which support bosonic magnons-quantized harmonic fluctuations ordered spins. In striking contrast is recent discovery that strongly spin-orbital-coupled such α-RuCl3, may display broad excitation continuum inconsistent with magnons. Due to incomplete knowledge underlying interactions unraveling nature this remains challenging. most...
Motivated by the recent wealth of exotic magnetic phases emerging in two-dimensional frustrated lattices, we investigate origin possible magnetism monolayer family triangular lattice materials $MX_2$ ($M$={V, Mn, Ni}, $X$={Cl, Br, I}). We first show that consideration general properties such as filling and hybridization enables to formulate trends for most relevant interaction parameters. In particular, observe effects spin-orbit coupling (SOC) can be effectively tuned through ligand...
Abstract Motivated by reports of metallic behavior in the recently synthesized RuI 3 , contrast to Mott-insulating nature actively discussed α -RuCl as well RuBr we present a detailed comparative analysis electronic and magnetic properties this family trihalides. Using combination first-principles calculations effective-model considerations, conclude that similarly other two members, is most probably on verge Mott insulator, but with much smaller moments strong frustration. We predict ideal...
We investigate the spin-orbit coupling (SOC) effects in $\alpha$- and $\kappa$-phase BEDT-TTF BEDT-TSF organic salts. Contrary to assumption that SOC organics is negligible due light C, S, H atoms, we show relevance of such an interaction a few representative cases. In weakly correlated regime, manifests primarily opening energy gaps at degenerate band touching points. This effect becomes especially important for Dirac semimetals as $\alpha$-(ET)$_2$I$_3$. Furthermore, magnetic insulating...
We theoretically investigate the low-temperature phase of recently synthesized ${\mathrm{Lu}}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{5}{\mathrm{N}}_{2}$ material, an extraordinarily rare realization a $S=1/2$ three-dimensional pyrochlore Heisenberg antiferromagnet in which ${\mathrm{Mo}}^{5+}$ are magnetic species. Despite Curie-Weiss temperature (${\mathrm{\ensuremath{\Theta}}}_{\mathrm{CW}}$) $\ensuremath{-}121(1)$ K, experiments have found no signature ordering $\mathit{or}$ spin freezing down...
In the quest for materials with unconventional quantum phases, organic triangular-lattice antiferromagnet κ-(ET)
In Kitaev materials the spin-orbital entangled nature of magnetic moments suggests an intricate magnetoelastic coupling. For case $\ensuremath{\alpha}$-RuCl${}_{3}$, authors investigate this effect via first-principles methods. Exact diagonalization studies on calculated model reproduce and explain recent magnetostriction Gr\"uneisen parameter measurements, validating parameters. Their structure predicts that compressive uniaxial strain between honeycomb planes will strongly strengthen...
Abstract Motivated by recent reports of a quantum-disordered ground state in the triangular lattice compound NaRuO 2 , we derive j eff = 1/2 magnetic model for this system means first-principles calculations. The pseudospin Hamiltonian is dominated bond-dependent off-diagonal Γ interactions, complemented ferromagnetic Heisenberg exchange and notably antiferromagnetic Kitaev term. In addition to bilinear find sizable four-spin ring contribution with strongly anisotropic character, which has...
Implicit in the study of magnetic materials is concept spin Hamiltonians, which emerge as low‐energy theories correlation‐driven insulators. In order to predict and establish such Hamiltonians for real materials, a variety first principles ab initio methods have been developed, based on density functional theory wavefunction methodologies. this Feature Article, basic introduction essential concepts provided, with focus their practical capabilities limitations. Furthermore, recent efforts...
In spin-orbit-coupled magnetic materials, the usually applied Curie-Weiss law can break down. This is due to potentially sharp temperature dependence of local moments. We therefore propose a modified formula suitable for analysis experimental susceptibility. show octahedrally coordinated materials ${d}^{5}$ filling that Weiss constant obtained from improved in excellent agreement with calculated microscopic exchange interactions. Reanalyzing measured susceptibility several Kitaev candidate...
The so-called "Kitaev candidate" materials based on $4d^5$ and $5d^5$ metals have recently emerged as magnetic systems displaying strongly anisotropic exchange interactions reminiscent of the Kitaev's honeycomb model. Recently, these been shown to commonly display a distinct saw-tooth angular dependence torque over wide range fields. While higher order chiral spin considered source this observation, we show here that bilinear and/or $g$-anisotropy are each sufficient explain observed...
In this combined theoretical and experimental research, the authors investigate anisotropic magnetic magnetoelastic properties of quantum spin-liquid candidate $\ensuremath{\alpha}$-RuCl${}_{3}$. They find that magnetostriction anisotropy is unusually large compared to magnetization, which they relate strong \ensuremath{\Gamma}'-type coupling. also observe nonsymmetric for fields canted out honeycomb plane in opposite directions, relative orientation field with respect RuCl${}_{6}$ octahedra.
We present a general framework for deriving effective spin Hamiltonians of correlated magnetic systems based on combination relativistic ab initio density functional theory calculations (DFT), exact diagonalization generalized Hubbard Hamiltonian finite clusters and projections onto the low-energy subspace. A key motivation is to determine anisotropic bilinear exchange couplings in materials interest. As an example, we apply this method pyrochlore Lu$_2$V$_2$O$_7$ where vanadium ions form...
We report a detailed experimental and theoretical study on the effect of hydrostatic pressure structural magnetic aspects layered honeycomb antiferromagent $\alpha$-RuCl$_{3}$. Magnetic susceptibility measurements performed under almost ideal hydrostatic-pressure conditions yield that phase transition to zigzag-type antiferromagnetic order at $T_N$ = 7.3 K can be rapidly suppressed about 6.1 K. A further suppression with increasing is impeded due occurrence pressure-induced $p \geq$ 104 MPa,...
Organic salts represent an ideal experimental playground for studying the interplay between magnetic and charge degrees of freedom, which has culminated in discovery several spin-liquid candidates, such as $\kappa$-(ET)$_2$Cu$_2$(CN)$_3$ ($\kappa$-Cu). Recent theoretical studies indicate possibility chiral spin liquids stabilized by ring-exchange, but parent states with order have not been observed this material family. In work, we discuss properties recently synthesized...
Significance A better understanding of quantum spin liquids (QSLs), where dimer configurations are fluctuating even at the lowest temperatures, could be use in information, superconducting or other technologies. This macroscopic collective state typically arises from geometrical frustration low dimensionality. In layered EDT-BCO, we report a QSL state, which is generated, on different bases, with intrinsic disorder. The spins EDT plane despite weak would magnetically order but disorder...
We show that in the two-component Bose gas with Rashba spin-orbit coupling an arbitrarily small attractive interaction between bosons opposite spin induces spontaneous ferromagnetism below a finite critical temperature ${T}_{c}$. In ferromagnetic phase single-particle spectrum exhibits unique minimum momentum space direction of magnetization. For sufficiently temperatures ${T}_{c}$ eventually condense into state at bottom spectrum, forming Bose-Einstein condensate.