Spin gap in quasi-one-dimensional S=3/2 antiferromagnet CoTi2O5

Quasi-one-dimensional(1D)antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra.Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi2O5 with highly ordered Co2+/Ti4+occupation,in which the Co2+ions with S=3/2 form a 1D spin chain along the a-axis.CoTi2O5 undergoes an antiferromagnetic transition at TN~24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region.Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins,by analyzing the specific heat,the thermal conductivity,and the spin-lattice relaxation rate(1/T1)as a function of temperature,we found that a spin gap is opened in the spin-excitation spectrum of CoTi2O5 around TN,manifested by the rapid decrease of magnetic specific heat to zero,the double-peak characteristic in thermal conductivity,and the exponential decay of 1/T1 below TN.Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi2O5,which induces the magnetic anisotropy in CoTi2O5,and then opens the spin gap at low temperature.

Quasi-one-dimensional characters in topological semimetal TaNiTe_(5)

One-dimensional(1D)topological insulators are superior for low-dissipation applications owing to the 1D character of surface states where scatterings other than prohibited backscattering are further restricted.Among the proposed candidates for 1D topological materials,TaNiTe_(5)has attracted intensive attention for its quasi-one-dimensional(quasi-1D)crystalline structure.In this study,we identify the chain-like construction and anisotropic electronic states on TaNiTe_5 surface with scanning tunneling microscopy.The electron scatterings are largely suppressed even with chromium impurities deposited on the surface and magnetic field applied normal to the surface,which endows TaNiTe_5 great potential for low-dissipation spintronic applications.

Magnetism in Quasi-One-Dimensional A2Cr3As3（A=K,Rb） Superconductors

We predict that the recently discovered quasi-one-dimensional superconductors, A2 Cr3As3 （A=K, Rb）, possess strong frustrated magnetic fluctuations and are nearby a novel in-out co-planar magnetic ground state. The frustrated magnetism is very sensitive to the c-axis lattice constant and can thus be suppressed by increasing pressure. Our results qualitatively explain strong non-Fermi liquid behaviors observed in the normal state of the superconductors as the intertwining between the magnetism and superconductivity can create a large quantum critical region in quasi-one-dimensional systems and also suggest that the materials share similar phase diagrams and superconducting mechanism with other unconventional superconductors, such as cuprates and iron-based superconductors.

Phonons near Peierls Structural Transition in Quasi-One-Dimensional Organic Crystals of TTF-TCNQ

The Peierls structural transition in quasi-one-dimensional organic crystals of TTF-TCNQ is investigated in the frame of a more complete physical model. The two most important electron-phonon interaction mechanisms are taken into account simultaneously. One is similar of that of deformation potential and the other is of polaron type. For simplicity, the 2D crystal model is considered. The renormalized phonon spectrum and the phonon polarization operator are calculated in the random phase approximation for different temperatures. The effects of interchain interaction on renormalized acoustic phonons and on the Peierls critical temperature are analyzed.

A Single-Crystal Neutron Diffraction Study on Magnetic Structure of the Quasi-One-Dimensional Antiferromagnet SrCo_2V_2O_8

The magnetic structure of the spin-chain antiferromagnet SrCo2 V208 is determined by single-crystal neutron diffraction experiment. The system undergoes a long-range magnetic order below the critical temperature TN=4.96 K. The moment of 2.16#B per Co at 1.6K in the screw chain running along the c axis Mternates in the c axis. The moments of neighboring screw chains are arranged antiferromagnetically along one in-plane axis and ferromagnetieally Monk the other in-plane axis. This magnetic configuration breaks the four-fold symmetry of the tetragonM crystal structure and leads to two equally populated magnetic twins with the antiferromagnetic vector in the a or b axis. The very similar magnetic state to the isostructural BaCo2 V~ 08 warrants SrCo2 V2 08 as another interesting half-integer spin-chain antiferromagnet for investigation on quantum antiferromagnetism.

CeAu_(2)In_(4):A candidate of quasi-one-dimensional antiferromagnetic Kondo lattice

Needle-like single crystals of CeAu_(2)In_(4)have been grown from In flux and characterized as a new candidate of quasi-one-dimensional Kondo lattice compound by crystallographic,magnetic,transport,and specific-heat measurements down to very low temperatures.We observe an antiferromagnetic transition at T_(N)≈0.9 K,a highly non-mean-field profile of the corresponding peak in specific heat,and a large Sommerfeld coefficientγ=369 mJ·mol^(-1)·K^(-2).The Kondo temperature T_(K)is estimated to be 1.1 K,being low and comparable to TN.While Fermi liquid behavior is observed deep into the magnetically ordered phase,the Kadowaki-Woods ratio is much reduced relative to the expected value for Ce compounds with Kramers doublet ground state.Markedly,this feature shares striking similarities to that of the prototypical quasi-one-dimensional compounds YbNi_(4)P_(2) and CeRh_(6)Ge_(4) with tunable ferromagnetic quantum critical point.Given the shortest Ce-Ce distance along the needle direction,CeAu_(2)In_(4)appears to be an interesting model system for exploring antiferromagnetic quantum critical behaviors in a quasi-one-dimensional Kondo lattice with enhanced quantum fluctuations.

Boosting ethanol oxidation over nickel oxide through construction of quasi-one-dimensional morphology and hierarchically porous structure

Quasi-one-dimensional NiO with a hierarchically porous structure was synthesized through a facile coordination−precipitation method with the coupling effect of ammonia and a post-calcination treatment.The electrocatalytic properties of NiO fibers for the oxidation of ethanol were compared with those of NiO spheres.The results show that the fibrous NiO possesses a larger specific surface area of 140.153 m2/g and a lower electrical resistivity of 4.5×105Ω·m,leading to an impressively superior electrocatalytic activity to spherical NiO for ethanol oxidation in alkaline media.The current decay on fibrous NiO at 0.6 V in 100−900 s was 0.00003%,which is much lower than that of spherical NiO,indicating its better stability.The unique morphology and hierarchically porous structure give the fibrous NiO great potential to be used as an anodic electrocatalyst for direct ethanol fuel cells.

Metal-Insulator Transition of Peierls Type in Quasi-One-Dimensional Crystals of TTT₂I₃

We investigate the metal-insulator transition in quasi-one-dimensional organic crystals of tetrathiotetracene-iodide, TTT2I3, in the 2D model. A crystal physical model is applied which takes into account two the most important hole-phonon interaction mechanisms. One is similar to that of deformation potential and the other is of polaron type. The scattering on defects is also considered and it is crucial for the explanation of the transition. The phonon polarization operator and the renormalized phonon spectrum are calculated in the random phase approximation for different temperatures applying the method of Green functions. We show that the transition is of Peierls type. The effect of lattice distortion on the dispersion of renormalized acoustic phonons is analyzed.

Mild Hydrothermal Synthesis,Crystal Structure and Magnetic Behavior of AgCu(IO_3)_3:a Quasi-one-dimensional S=1/2 Chain Compound

A new complex AgCu（IO3）3 is synthesized by mild hydrothermal method and characterized by single-crystal X-ray diffraction and magnetization measurement.AgCu（IO3）3 is triclinic,space group P1,with a = 7.3081（1）,b = 7.8089（1）,c = 8.2447（1）A,α = 67.159（1）,β = 74.982（1）,γ = 80.982（1）°,and Z = 2.AgCu（IO3）3 is isostructral with Ag Pb（IO3）3.The structure of Ag Cu（IO3）3 consists of CuO6 chain columns parallel to the c axis,formed by corner-sharing Cu（1） and Cu（2） octahedra and flanked by corner-sharing IO3 groups; these CuO6 columns are cross-linked into a three-dimensional framework through I–O and Ag–O bonds.I（1）,I（2） and I（3） are coordinated respectively with 3 oxygens on the same side to form trigonal pyramids confirming the presence of a stereochemically active lone pair of each I^5＋ cation.In the CuO6 chain columns,Cu（1）O6 and Cu（2）O6 octahedra are tetragonally distorted with four shorter bonds in the square planes and two longer apical bonds.Cu（1）O6 octahedra were corner sharing with Cu（2）O6 octahedra with a shorter Cu（1）–O（1） bond in the square planes and a longer apical Cu（2）–O（1） bond,which forms a Cu（1）–Cu（2） magnetic chain along the c direaction.Magnetization measurement shows weak antiferromagnetic property in low temperature range.Ag Cu（IO3）3 provides a new example of a quasi-one-dimensional magnetic system.

Comment on“Chemical vapor deposition synthesis and Raman scattering investigation of quasi-one-dimensional ZrS_(3) nanoflakes”

A fundamentally crucial suggestion to rectify the fits to the high-resolution X-ray photoemission spectroscopy(XPS)raw data for the S 2p core level published by Chen et al.(Nano Res.2023,16,10567-10572)is presented herein.

Chemical vapor deposition synthesis and Raman scattering investigation of quasi-one-dimensional ZrS_(3)nanoflakes

Quasi-one-dimensional ZrS_(3)nanoflakes attract intense interest attributed to their superior electrical and optical anisotropy,stemming from the low symmetry in the crystal structure.However,the conventional chemical vapor transport method for synthesizing bulk ZrS_(3)is limited by morphology and size controllability.It is highly desirable to propose a facile way to precisely synthesize ZrS_(3)nanoflakes.In this work,the chemical vapor deposition method is proposed as a feasible way to synthesize ZrS_(3)nanoflakes.The effects of various substrates and temperatures on ZrS_(3)synthesis have been investigated.For the as-grown ZrS_(3),good crystallinity is confirmed with X-ray diffraction and transmission electron microscopy.The structure and interlayer coupling are investigated with Raman scattering spectroscopy.The strong in-plane anisotropy and interlayer coupling of the ZrS_(3)nanoflakes are illustrated with angle-resolved Raman spectroscopy and temperature-dependent Raman characterization,respectively.This study demonstrates a feasible way for the synthesis of transition metal trisulfides,which may shed new light on the research of other two-dimensional anisotropic transition metal materials.

Selective substitution induced anomalous phonon stiffening within quasi-one-dimensional P–P chains in SiP2

Light-matter interactions in low-dimensional quantum-confined structures can dominate the optical properties of the materials and lead to optoelectronic applications.In anisotropic layered silicon diphosphide(SiP2)crystal,the embedded quasi-onedimensional(1D)phosphorus–phosphorus(P–P)chains directly result in an unconventional quasi-1D excitonic state,and a special phonon mode vibrating along the P–P chains,establishing a unique 1D quantum-confined system.Alloying SiP2 with the homologous element serves as an effective way to study the properties of these excitons and phonons associated with the quasi-1D P–P chains,as well as the strong interaction between these quasiparticles.However,the experimental observation and the related optical spectral understanding of SiP2 with isoelectronic dopants remain elusive.Herein,with the photoluminescence and Raman spectroscopy measurements,we demonstrate the redshift of the confined excitonic peak and the stiffening of the phonon vibration mode■of a series of Si(P1−xAsx)2 alloys with increasing arsenic(As)compositions.This anomalous stiffening of■is attributed to the selective substitution of As atoms for P atoms within the P–P chains,which is confirmed via our scanning transmission electron microscopy investigation.Such optical spectra evolutions with selective substitution pave a new way to understand the 1D quantum confinement in semiconductors,offering opportunities to explore quasi-1D characteristics in SiP2 and the resulting photonic device application.

Antiferromagnetic insulating state in quasi-one-dimensional K_(2)Cr_(3)As_(3)H

Quasi-one-dimensional(Q1D) Cr-based pnictide K_(2)Cr_(3)As_(3)exhibits superconductivity probably with spin-triplet pairing. It is of fundamental importance to explore the parent compound from which superconductivity emerges. Here we report the synthesis,crystal structure, physical properties, and density functional theory(DFT) calculations of(nearly) fully hydrogenized K_(2)Cr_(3)As_(3)H.It is found that the intercalation of hydrogen in K_(2)Cr_(3)As_(3)leads to absence of metallicity as well as superconductivity. An antiferromagnetic transition nearby room temperature is evidenced from the measurements of magnetic susceptibility and heat capacity.The antiferromagnetic insulating state can be reproduced by the DFT calculations, which show a novel non-collinear co-planar magnetic order. Our result sheds light on the mechanism of unconventional superconductivity in Q1D Cr-based superconductors.

A Quasi-One-Dimensional CFD Model for Multistage Turbomachines

The objective of this paper is to present a fast and reliable CFD model that is able to simulate stationary and transient operations of multistage compressors and turbines. This analysis tool is based on an adapted version of the Euler equations solved by a time-marching, finite-volume method. The Euler equations have been extended by including source terms expressing the blade-flow interactions. These source terms are determined using the ve- locity triangles and a row-by-row representation of the blading at mid-span. The losses and deviations undergone by the fluid across each blade row are supplied by correlations. The resulting flow solver is a performance pre- diction tool based only on the machine geometry, offering the possibility of exploring the entire characteristic map of a multistage compressor or turbine. Its efficiency in terms of CPU time makes it possible to couple it to an optimization algorithm or to a gas turbine performance tool. Different test-cases are presented for which the calculated characteristic maps are compared to experimental ones.

Superconductivity at 10.4 K in a novel quasi-one-dimensional ternary molybdenum pnictide K2Mo3As3

Here we report the discovery of the first ternary molybdenum pnictide based superconductor K2Mo3As3. Polycrystalline samples were synthesized by the conventional solid state reaction method. X-ray diffrac- tion analysis reveals a quasi-one-dimensional hexagonal crystal structure with （Mo3As3）2 linear chains separated by K^＋ ions, similar as previously reported K2Cr3As3, with the space group of P-6m2 （No. 187） and the refined lattice parameters a = 10.145（5） A and c = 4.453（8） A. Electrical resistivity, magnetic susceptibility, and heat capacity measurements exhibit bulk superconductivity with the onset Tc at 10.4 K in K2Mo3As3 which is higher than the isostructural Cr-based superconductors. Being the same group VIB transition elements and with similar structural motifs, these Cr and Mo based superconductors may share some common underlying origins for the occurrence of superconductivity and need more investigations to uncover the electron pairing within a quasi-one-dimensional chain structure.

The kink-soliton and antikink-soliton in quasi-one-dimensional nonlinear monoatomic lattice

The quasi-one-dimensional nonlinear monoatomic lattice is analyzed. The kink-soliton and antikink-soliton are presented. When the interaction of the lattice is strong in the x-direction and weak in the y-direction, the two-dimensional (2D) lattice changes to a quasi-one-dimensional lattice. Taking nearest-neighbor interaction into account, the vibration equation can be transformed into the KPI, KPII and MKP equation. Considering the cubic nonlinear potential of the vibration in the lattice, the kink-soliton solution is presented. Considering the quartic nonlinear potential and the cubic interaction potential, the kink-soliton and antikink-soliton solutions are presented.

A quasi-one-dimensional model for hypersonic reactive flow along the stagnation streamline

This study proposes a quasi-one-dimensional model to predict the chemical nonequilibrium flow along the stagnation streamline of hypersonic flow past a blunt body. The model solves reduced equations along the stagnation streamline and predicts nearly identical results as the numerical solution of the full-field Navier-Stokes equations. The high efficiency of this model makes it useful to investigate the overall quantitative behavior of related physical-chemical phenomena. In this paper two important properties of hypersonic flow, shock stand-off distance and oxygen dissociation, are studied using the quasi-one-dimensional model with the ideal dissociating gas model. It is found that the shock stand-off distance is affected by both chemical and thermal non-equilibrium.The shock stand-off distance will increase when the flow conditions are changed from equilibrium to non-equilibrium, because the average density of the shock-compressed gas will decrease as a result of the increase in translational energy. For oxygen dissociation, the maximum value of its dissociation degree along the stagnation line varies with the flight altitude. It is increased at first and decreased thereafter with the altitude, which is due to the combination effect of the equilibrium shift and chemical non-equilibrium relaxation. The overall variation of the maximum dissociation is then plotted in the speed and altitude coordinates as a reference for engineering application.

Molybdenum Nanoscrews:A Novel Non-coinage-Metal Substrate for Surface-Enhanced Raman Scattering

For the first time, Mo nanoscrew was cultivated as a novel non-coinage-metal substrate for surface-enhanced Raman scattering(SERS). It was found that the nanoscrew is composed of many small screw threads stacking along its length direction with small separations. Under external light excitation, strong electromagnetic coupling was initiated within the gaps, and many hot-spots formed on the surface of the nanoscrew, which was confirmed by high-resolution scanning near-field optical microscope measurements and numerical simulations using finite element method. These hotspots are responsible for the observed SERS activity of the nanoscrews. Raman mapping characterizations further revealed the excellent reproducibility of the SERS activity. Our findings may pave the way for design of low-cost and stable SERS substrates.

Physical criterion study on forward stagnation point heat flux CFD computations at hypersonic speeds

In order to evaluate uncertainties in computational fluid dynamics （CFD） computations of the stagnation point heat flux, a physical criterion is developed. Based on a quasi-one-dimensional hypothesis along the stagnation line, a new stagnation flow model is applied to obtain the governing equations of the flow near the stagnation point at hypersonic speeds. From the above equations, the compatibility relations are given at the stagnation point and along the stagnation line, which consist of the physical criterion for checking the accuracy in the stagnation point heat flux computations. The verification of the criterion is made with various numerical results.

Role of the spin anisotropy of the interchain interaction in weakly coupled antiferromagnetic Heisenberg chains

In quasi-one-dimensional(q1D) quantum antiferromagnets, the complicated interplay of intrachain and interchain exchange couplings may give rise to rich phenomena. Motivated by recent progress on field-induced phase transitions in the q1D antiferromagnetic(AFM) compound YbAlO3, we study the phase diagram of spin-1/2 Heisenberg chains with Ising anisotropic interchain couplings under a longitudinal magnetic field via large-scale quantum Monte Carlo simulations,and investigate the role of the spin anisotropy of the interchain coupling on the ground state of the system. We find that the Ising anisotropy of the interchain coupling can significantly enhance the longitudinal spin correlations and drive the system to an incommensurate AFM phase at intermediate magnetic fields, which is understood as a longitudinal spin density wave(LSDW). With increasing field, the ground state changes to a canted AFM order with transverse spin correlations. We further provide a global phase diagram showing how the competition between the LSDW and the canted AFM states is tuned by the Ising anisotropy of the interchain coupling.