Ubiquitous Order-Disorder Transition in the Mn Antisite Sublattice of the (MnBiTe)(BiTe) Magnetic Topological Insulators.

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.

Stacking-Order-Dependent Excitonic Properties Reveal Interlayer Interactions in Bulk ReS.

Rhenium disulfide, a member of the transition metal dichalcogenide family of semiconducting materials, is unique among 2D van der Waals materials due to its anisotropy and, albeit weak, interlayer interactions, confining excitons within single atomic layers and leading to monolayer-like excitonic properties even in bulk crystals. While recent work has established the existence of two stacking modes in bulk, AA and AB the influence of the different interlayer coupling on the excitonic properties has been poorly explored. Here, we use polarization-dependent optical measurements to elucidate the nature of excitons in AA and AB-stacked rhenium disulfide to obtain insight into the effect of interlayer interactions.

Intermixing-Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi Te.

The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi Te and MnBi Te benchmark the (MnBi Te )(Bi Te ) family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi Te septuple layers (SLs). However, the QAHE realization is complicated in MnBi Te and MnBi Te due to the substantial antiferromagnetic (AFM) coupling between the SLs.

Metamagnetism of Weakly Coupled Antiferromagnetic Topological Insulators.

The magnetic properties of the van der Waals magnetic topological insulators MnBi_{2}Te_{4} and MnBi_{4}Te_{7} are investigated by magnetotransport measurements. We evidence that the relative strength of the interlayer exchange coupling J to the uniaxial anisotropy K controls a transition from an A-type antiferromagnetic order to a ferromagneticlike metamagnetic state. A bilayer Stoner-Wohlfarth model allows us to describe this evolution, as well as the typical angular dependence of specific signatures, such as the spin-flop transition of the uniaxial antiferromagnet and the switching field of the metamagnet.

Visualizing coexisting surface states in the weak and crystalline topological insulator BiTeI.

Dual topological materials are unique topological phases that host coexisting surface states of different topological nature on the same or on different material facets. Here, we show that BiTeI is a dual topological insulator. It exhibits band inversions at two time reversal symmetry points of the bulk band, which classify it as a weak topological insulator with metallic states on its 'side' surfaces.

Crystal Chemistry and Bonding Patterns of Bismuth-Based Topological Insulators.

Bismuth is gaining importance as a key element of functional quantum materials. The effects of spin-orbit coupling (SOC) are at the heart of many exciting proposals for next-generation quantum technologies, including topological materials for efficient information transmission and energy-saving applications. The "heavy" element bismuth and its compounds are predestined for SOC-induced topological properties, but materials design is challenged by a complex link between them and the chemical composition and crystal structure.

Detuning the Honeycomb of the α-RuCl Kitaev Lattice: A Case of Cr Dopant.

Fine-tuning chemistry by doping with transition metals enables new perspectives for exploring Kitaev physics on a two-dimensional (2D) honeycomb lattice of α-RuCl, which is promising in the field of quantum information protection and quantum computation. The key parameters to vary by doping are both Heisenberg and Kitaev components of the nearest-neighbor exchange interaction between the J = / Ru spins, depending strongly on the peculiarities of the crystal structure. Here, we present crystal growth by chemical vapor transport and structure elucidation of a solid solution series RuCr Cl (0 ≤ x ≤ 1), with Cr ions coupled to the Ru Kitaev host.

A bismuth triiodide monosheet on BiSe(0001).

A stable BiI monosheet has been grown for the first time on the (0001) surface of the topological insulator BiSe as confirmed by scanning tunnelling microscopy, surface X-ray diffraction, and X-ray photoemision spectroscopy. BiI is deposited by molecular beam epitaxy from the crystalline BiTeI precursor that undergoes decomposition sublimation. The key fragment of the bulk BiI structure, [Formula: see text][I-Bi-I] layer of edge-sharing BiI octahedra, is preserved in the ultra-thin film limit, but exhibits large atomic relaxations.

Synthesis and Characterization of the New Manganese Hydroxide Chloride γ-Mn(OH)Cl.

A new modification of Mn(OH)Cl was obtained under high-pressure/high-temperature conditions in a Walker-type multianvil device. The pale pink, hygroscopic compound crystallizes in the orthorhombic space group (no. 62) with = 602.

Unusual Phonon Heat Transport in α-RuCl_{3}: Strong Spin-Phonon Scattering and Field-Induced Spin Gap.

The honeycomb Kitaev-Heisenberg model is a source of a quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. Here we unveil the highly unusual low-temperature heat conductivity κ of α-RuCl_{3}, a prime candidate for realizing such physics: beyond a magnetic field of B_{c}≈7.5  T, κ increases by about one order of magnitude, both for in-plane as well as out-of-plane transport.

The Intermetalloid Cluster Cation (CuBi ).

The reaction of Bi, BiCl , and CuCl in the ionic liquid [BMIm]Cl⋅4 AlCl (BMIm=1-n-butyl-3-methylimidazolium) at 180 °C yielded air-sensitive shiny black crystals of (CuBi )[AlCl ] [Al Cl ] and (CuBi )[AlCl ] . For both compounds X-ray diffraction on single crystals revealed monoclinic structures that contain the intermetalloid cluster (CuBi ) . It is the first pure bismuth cluster with a 3d metal and the first with a metal that does not form binary intermetallics with bismuth under ambient pressure.

Synthesis of a Cu-Filled RhS Framework: Microwave Polyol Process Versus High-Temperature Route.

Metal-rich, mixed copper-rhodium sulfide CuRhS that represents a new Cu-filled variant of the RhS structure has been synthesized and structurally characterized. Copper content in the [CuRh] cubic cluster was found to vary notably dependent on the chosen synthetic route. Full site occupancy was achieved only in nanoscaled CuRhS obtained by a rapid, microwave-assisted reaction of CuCl, Rh(CHCO) and thiosemicarbazide at 300 °C in just 30 min; whereas merely Cu-deficient CuRhS (2.

The Triply Deprotonated Acetonitrile Anion CCN Stabilized in a Solid.

The unprecedented, fully deprotonated form of acetonitrile, the acetonitriletriide anion CCN , is experimentally realized for the first time in the stabilizing bulk host framework of the Ba [TaN ][C N] nitridometalate via a one-pot synthesis from the elements under moderate conditions (920 K). The molecular structure of this long-sought acetonitrile derivative is confirmed by X-ray diffraction, as well as NMR, IR, and Raman spectroscopy. The anion is isoelectronic to the CO molecule, and, in contrast to acetonitrile (H C-C≡N), the electron pairs are shifted towards two double bonds, that is, [C=C=N] .

Correlation between topological band character and chemical bonding in a Bi14Rh3I9-based family of insulators.

Recently the presence of topologically protected edge-states in Bi14Rh3I9 was confirmed by scanning tunnelling microscopy consolidating this compound as a weak 3D topological insulator (TI). Here, we present a density-functional-theory-based study on a family of TIs derived from the Bi14Rh3I9 parent structure via substitution of Ru, Pd, Os, Ir and Pt for Rh. Comparative analysis of the band-structures throughout the entire series is done by means of a unified minimalistic tight-binding model that evinces strong similarity between the quantum-spin-Hall (QSH) layer in Bi14Rh3I9 and graphene in terms of Pz-molecular orbitals.

A novel quasi-one-dimensional topological insulator in bismuth iodide β-Bi4I4.

Recent progress in the field of topological states of matter has largely been initiated by the discovery of bismuth and antimony chalcogenide bulk topological insulators (TIs; refs ,,,), followed by closely related ternary compounds and predictions of several weak TIs (refs ,,). However, both the conceptual richness of Z2 classification of TIs as well as their structural and compositional diversity are far from being fully exploited. Here, a new Z2 topological insulator is theoretically predicted and experimentally confirmed in the β-phase of quasi-one-dimensional bismuth iodide Bi4I4.

Neuroprotective activity of creatylglycine ethyl ester fumarate.

Background: We have recently shown neuroprotective activity of the creatine amides in the focal cerebral ischemia in rats on the 280 mg/kg administration. In the present study, neuroprotective properties of creatylglycine ethyl ester fumarate (CrGEt) in rats with focal cerebral ischemia were explored in a wide dosage range (30-280 mg/kg, intravenous and intragastric).

Methods: Focal cerebral ischemia was induced by the middle cerebral artery occlusion (MCAO).

Low-temperature topochemical transformation of Bi13Pt3I7 into the new layered honeycomb metal Bi12Pt3I5.

Ordered single-crystals of the metallic subiodide Bi13 Pt3 I7 were grown and treated with n-butyllithium. At 45 °C, complete pseudomorphosis to Bi12 Pt3 I5 was achieved within two days. The new compound is air-stable and contains the same ${{{\hfill 2\atop \hfill \infty }}}$[(PtBi8/2 )3 I](n+) honeycomb nets and iodide layers as the starting material Bi13 Pt3 I7 , but does not include ${{{\hfill 1\atop \hfill \infty }}}$[BiI2 I4/2 ](-) iodidobismuthate strands.

Structure and bonding of Bi4Ir: a difficult-to-access bismuth iridide with a unique framework structure.

Crystals of Bi(4)Ir, a new intermetallic compound, were obtained by the reaction of an iridium-containing intermetallic precursor with liquid bismuth. X-ray diffraction on a single crystal revealed a rhombohedral structure [R3̅m, a = 2656.7(2) pm, and c = 701.

A metallic room-temperature oxide ion conductor.

Nanoparticles of Bi3 Ir, obtained from a microwave-assisted polyol process, activate molecular oxygen from air at room temperature and reversibly intercalate it as oxide ions. The closely related structures of Bi3 Ir and Bi3 IrOx (x≤2) were investigated by X-ray diffraction, electron microscopy, and quantum-chemical modeling. In the topochemically formed metallic suboxide, the intermetallic building units are fully preserved.

Stacked topological insulator built from bismuth-based graphene sheet analogues.

Commonly, materials are classified as either electrical conductors or insulators. The theoretical discovery of topological insulators has fundamentally challenged this dichotomy. In a topological insulator, the spin-orbit interaction generates a non-trivial topology of the electronic band structure dictating that its bulk is perfectly insulating, whereas its surface is fully conducting.

[Ru2Bi14Br4](AlCl4)4 by mobilization and reorganization of complex clusters in ionic liquids.

Two polymorphs of the new cluster compound [Ru(2)Bi(14)Br(4)](AlCl(4))(4) have been synthesized from Bi(24)Ru(3)Br(20) in the Lewis acidic ionic liquid [BMIM]Cl/AlCl(3) ([BMIM](+) : 1-n-butyl-3-methylimidazolium) at 140 °C. A large fragment of the precursor's structure, namely the [(Bi(8))Ru(Bi(4)Br(4))Ru(Bi(5))](5+) cluster, dissolved as a whole and transformed into a closely related symmetrical [(Bi(5))Ru(Bi(4)Br(4))Ru(Bi(5))](4+) cluster through structural conversion of a coordinating Bi(8)(2+) to a Bi(5)(+) polycation, while the remainder was left intact. Both modifications have monoclinic unit cells that comprise two formula units (α form: P2(1)/n, a=982.

Resonant scattering and absorption in the titanate-based nanoplatelet dispersions in near ultraviolet region.

Extinction enhancement and nonlinear near-resonant absorption of potassium polytitanate nanoplatelets were experimentally studied in the near-UV region. Phenomenological models such as the one-oscillator Lorentz model for dielectric function and the two-level model with the depleted ground state were used to interpret the experimental data. The introduced model parameters demonstrate the adequately high sensitivity to variations in nanoplatelet morphology and chemical environment.

Analysis of the scatter growth in dispersive media with the use of dynamic light scattering.

Analysis of the structure functions of intensity fluctuations of scattered laser light was applied to monitor the phase separation in probed disperse media. UV-cured mixtures of a liquid crystal and prepolymer were studied during the formation of the structure of dispersive polymer-liquid crystal (DPLC) composites. The experimentally observed features of light beating induced by dynamic light scattering in DPLC systems (the scaling properties of the structure functions, the narrowing of the beating spectrum for certain weight fractions of the liquid-crystalline component) were interpreted in terms of the discrete scattering model using the results of statistical modeling.