In this study, we reanalyze the magnetic interactions in Kitaev spin liquid candidate materials Na$_2$IrO$_3$, $\alpha$-RuCl$_3$, and $\alpha$-Li$_2$IrO$_3$ using nonperturbative exact diagonalization methods. These methods are more appropriate given relatively itinerant nature of systems suggested previous works. We treat all up to third neighbours on equal footing. The computed terms reveal significant long range coupling, bond-anisotropy, and/or off-diagonal couplings which argue...

The layered honeycomb magnet alpha-RuCl3 has been proposed as a candidate to realize Kitaev spin model with strongly frustrated, bond-dependent, anisotropic interactions between spin-orbit entangled jeff=1/2 Ru4+ magnetic moments. Here we report detailed study of the three-dimensional crystal structure using x-ray diffraction on untwinned crystals combined structural relaxation calculations. We consider several models for stacking layers and find evidence monoclinic unit cell corresponding...

Abstract Rare-earth engineering is an effective way to introduce and tune magnetism in topological kagome materials, which have been acting as a fertile platform investigate the quantum interactions between geometry, topology, spin, correlation. Here, we report synthesis, structure, physical properties of titanium-based metals RETi 3 Bi 4 (RE = Yb, Pr, Nd) with various magnetic states. They all crystallize orthogonal space group Fmmm (No. 69), featuring distorted titanium lattices rare-earth...

Waveform-agile sensing is fast becoming an important technique for improving sensor performance in applications such as radar, sonar, biomedicine, and communications. The paper provided overview of research work on waveform-agile target tracking. From both control theoretic information perspectives, waveforms can be selected to optimize a tracking criterion minimizing the MSE or maximizing retrieval. designed directly based their estimation resolution properties, from class with varying...

In the pursuit of developing routes to enhance magnetic Kitaev interactions in α−RuCl3, as well probing doping effects, we investigate electronic properties α−RuCl3 proximity graphene. We study α−RuCl3/graphene heterostructures via ab initio density functional theory calculations, Wannier projection, and nonperturbative exact diagonalization methods. show that becomes strained when placed on graphene charge transfer occurs between two layers, making (graphene) lightly electron doped (hole...

By considering two {\it ab initio}-based complementary approaches, we analyze the electronic structure and extract effective spin models of BaCo$_2$(AsO$_4$)$_2$, a honeycomb material which has been proposed as candidate for Kitaev physics. Both methods show that dominant direct hopping makes bond-dependent term negligible averting away from sought-after spin-liquid regime. As result, present simple three-parameter exchange model to describe interactions lowest doublet cobaltate...

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...

A few <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>4</a:mn><a:mi>d</a:mi></a:mrow></a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mn>5</b:mn><b:mi>d</b:mi></b:mrow></b:math> transition metal compounds with various electron fillings were recently found to exhibit magnetic susceptibilities <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mi>χ</c:mi></c:math> moments that deviate from the well-established Kotani model. This model has...

Motivated by recent reports of H$_3$LiIr$_2$O$_6$ as a spin-orbital-entangled quantum liquid, we investigate via combination density functional theory and non-perturbative exact diagonalization the microscopic nature its magnetic interactions. We find that while interlayer O-H-O bond geometry strongly affects local couplings, these bonds are likely to remain symmetrical due large zero-point fluctuations H positions. In this case, estimated model lies close classical tricritical point between...

The influences of phonon frequency and unit cell volume on the superconductivity element-doped ${\mathrm{MgB}}_{2}$ are discussed with reference to a Raman study $\mathrm{SiC}$, C, Mn, $\mathrm{Al}\text{\ensuremath{-}}\mathrm{Ag}$-doped $\mathrm{Mg}\text{\ensuremath{-}}\mathrm{B}$ materials. A phenomenon has been found in doped samples, that changes counteract crystal lattice variation keep system stable within Gr\"uneisen parameter 2.0--4.0. chemical doping effects can be explained by...

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...

We present results for the optical conductivity of Na2IrO3 within density functional theory by including spin-orbit (SO) and correlation effects (U) as implemented in GGA+SO+U. identify various interband transitions show that underlying quasi-molecular-orbital nature electronic structure translates into distinct features conductivity. Most importantly, parity quasi-molecular orbitals appears to be main factor determining strong weak transitions. also calculations Li2IrO3 discuss similarities...

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...

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...

Muon spin rotation measurements have been performed on a powder sample of $\ensuremath{\alpha}\ensuremath{-}{\mathrm{RuCl}}_{3}$, layered material in which Ru ions are arranged honeycomb lattice and previously has proposed to be close quantum liquid ground state. Our data reveal two distinct transitions at 11 14 K, we interpret as originating from the onset three-dimensional order in-plane magnetic order, respectively. We identify, with help density functional theory calculations, likely...

A magnetic field of up to 12T was applied during the sintering process pure MgB2 and carbon nanotube (CNT) doped wires. The authors have demonstrated that processing results in grain refinement, homogeneity, enhancement Jc(H) Hirr. extent improvement Jc increases with increasing field. for a 10T processed CNT sample by factor 3 at 10K 8T 20K 5T, respectively. Hirr reached 9T 20K, which exceeded best value SiC 20K. Magnetic reduces resistivity MgB2, straightens entangled CNTs, improves...

Optical conductivity measurements are combined with density functional theory calculations in order to understand the electrodynamic response of frustrated Mott insulators herbertsmithite ${\mathrm{ZnCu}}_{3}{(\mathrm{OH})}_{6}{\mathrm{Cl}}_{2}$ and closely related kagome-lattice compound ${\mathrm{Y}}_{3}{\mathrm{Cu}}_{9}{(\mathrm{OH})}_{19}{\mathrm{Cl}}_{8}$. We identify these materials as charge-transfer rather than Mott-Hubbard insulators, similar high-${T}_{c}$ cuprate parent compounds....

We report results of Raman scattering experiments on twin-free BaFe$_{2}$As$_{2}$ with the main focus placed understanding influence electronic and spin degrees freedom lattice dynamics. In particular, we scrutinize $E_g$ modes As $A_{1g}$ mode. Each two phonons in tetragonal phase is observed to split into a $B_{2g}$ $B_{3g}$ mode upon entering orthorhombic stripe-magnetic phase. The splitting amounts approximately 10\,cm$^{-1}$ less than 5\,cm$^{-1}$ for low- high-energy mode,...

We have carried out a detailed first-principles study of ${d}^{4.5}$ quaternary iridate ${\mathrm{Ba}}_{3}{\mathrm{YIr}}_{2}{\mathrm{O}}_{9}$ both in its 6H-perovskite-type ambient pressure (AP) phase and also for the high (HP) cubic phase. Our analysis reveals that AP belongs to intermediate spin-orbit coupling (SOC) regime. This is further supported by identification spin moment as primary order parameter (POP) obtained from magnetic multipolar analysis. The large ${t}_{2g}$ bandwidth...

Distorting a crystal affects its magnetic properties; vice versa, interactions can influence the lattice and vibrations. By probing optical phonons -- quantized sound waves excited by infrared radiation we identify changes in symmetry related to ground state of widely studied quantum spin liquid candidate herbertsmithite. We determine atomic motion all 54 phonon modes specify possible breaking associated with slowest phonons, providing insight into coupling structural properties.

To realize the chemistry of a multicage organic molecule with excess electron, as model, by confining an electron inside double-cage single molecule, structures e−@C24F22(NH)2C20F18 (e−@AB) and e−@C20F18(NH)2C20F18 (e−@BB′) are obtained at B3LYP/6-31G(d) + 4s4p theory level. It is confirmed that mainly confined one cage larger interior electronic attractive potential (A for e−@AB B e−@BB′) in ground state, while localized other first excited state. Owing to such localizations, interesting...

Elastic properties of three high pressure polymorphs CaCO3 are investigated based on first principles calculations. The calculations conducted at 0 GPa–40 GPa for aragonite, 40 GPa–65 post-aragonite, and 65 GPa–150 the -h-CaCO structure, respectively. By fitting third-order Birch–Murnaghan equation state (EOS), values bulk modulus derivative 66.09 4.64 81.93 4.49 56.55 5.40 -h-CaCO, respectively, which in good agreement with previous experimental theoretical data. constants, wave velocities,...