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The X2MH6 family, consisting of an electropositive cation Xn+ and a main group metal M octahedrally coordinated by hydrogen, have been identified as promising templates for high‐temperature conventional superconductivity. Herein, we analyze the electronic structure of two members of this family, Mg2IrH6 and Ca2IrH6, showing why the former may possess superconducting properties rivaling those of the cuprates, whereas the latter does not. Within Mg2IrH6 the vibrations of the anions IrH64− anions are key for the superconducting mechanism, and they induce coupling in the eg* ${e_g^{\ast} }$ set of orbitals, which are antibonding between the H 1s and the Ir dx2-y2 ${d_{x^2 - y^2 } }$ or dz2 ${d_{z^2 } }$ orbitals. Because calcium possesses low‐lying d‐orbitals, eg* ${e_g^{\ast} }$ →Ca d back‐donation is preferred, quenching the superconductivity. Our analysis explains why high critical temperatures were only predicted for second or third row X metal atoms, and may provide rules for identifying likely high‐temperature superconductors in other systems where the antibonding anionic states are filled. [ABSTRACT FROM AUTHOR]

The highest ambient‐pressure Tc among binary compounds is 40 K (MgB2). Higher Tc is achieved in high‐pressure hydrides or multielement cuprates. Alternatively, are explored superconducting properties of binary, metastable sub‐oxides, that may emerge under extremely low oxygen partial pressure. The emphasis is on the rock‐salt structure, which is known to promote superconductivity, and exploring AlO, ScO, TiO, and NbO. Dynamic lattice stability is achieved by introducing metal and oxygen vacancies in the fashion of Nb1−xO1−x‐type structure (x = ¼). The electron‐phonon (e‐ph) coupling is remarkably large in Al1−xO1−x and Ti1−xO1−x (λ ≈ 2 at x = ¼), with Tc ≈ 35 K according to the Allen–Dynes equation. Significantly, the coupling strength is comparable to that in high‐pressure hydrides, yet, in contrast to hydrides and MgB2, the coupling is largely driven by low frequency phonons. Sc1−xO1−x and Nb1−xO1−x show significantly smaller λ and Tc. Further, hydrogen intercalation to boost λ and Tc is investigated. Only Ti1−x(O1−xHx) and Nb1−x(O1−xHx) are dynamically stable upon intercalation, where H, respectively, decreases and increases Tc. The effect of H doping on electronic structure and Tc is discussed. Altogether, the study suggests that metal sub‐oxides are promising compounds to achieve strong e‐ph coupling at ambient pressure. [ABSTRACT FROM AUTHOR]

In cuprates, the superconducting transition temperature (Tc) is closely related to the number n of CuO2 planes per unit cell. The studies on multi‐layered cuprates offer insights into the physical properties and pairing mechanisms of superconductivity. However, the synthesis and stability of ultra‐multilayered cuprates pose significant challenges. Here, a newly discovered seven‐layered cuprate CuBa2Ca6Cu7O17±δ grown under high pressure is reported. Magnetization and transport measurements confirm bulk superconductivity with Tc of ≈85 K. The magnetization hysteresis loops, critical current density (Jc), and irreversibility fields of CuBa2Ca6Cu7O17±δ are also investigated. The novel compound CuBa2Ca6Cu7O17±δ provides an ideal platform for studying the physics of multi‐layered cuprates. [ABSTRACT FROM AUTHOR]

In recent years, the electronic structures of organocuprates in general and the complex [Cu(CF3)4]− in particular have attracted significant interest. A possible key indicator in this context is the reactivity of these species. Nonetheless, this aspect has received only limited attention. Here, we systematically study the series of tetra‐alkyl cuprates [MenCu(CF3)4−n]− and their unimolecular reactivity in the gas phase, which includes concerted formal reductive eliminations as well as radical losses. Through computational studies, we characterize the electronic structures of the complexes and show how these are connected to their reactivity. We find that all [MenCu(CF3)4−n]− ions feature inverted ligand fields and that the distinct reactivity patterns of the individual complexes arise from the interplay of different effects. [ABSTRACT FROM AUTHOR]

The melt‐quenching technique is used to fabricate calcium sodium aluminum borate glasses (Sm: ANCB) doped with varying concentrations of Sm3+ ions. Characteristics of ANCBSm glasses, including density, molar volume, refractive index, absorption, emission (via visible light, X‐ray, and proton excitation), decay time, and CIE color coordinates, are analyzed. The density, molar volume, and refractive index of ANCBSm glass increased with Sm2O3 concentration. Sm3+ ions enabled photon absorption in both visible and NIR regions, with a strong reddish‐orange emission at 600 nm due to the 6H5/2 → 6P3/2 transition under various excitations. X‐ray excitation is also compared with BGO scintillation crystals. The J–O theory predicted the radiative properties of Sm3+ ion emission levels. Decay curves of the 6H5/2 levels showed a single exponential nature with a millisecond‐order lifetime. CIE chromaticity of ANCBSm glasses is in the reddish‐orange region. ANCBSm glasses have potential applications in orange laser medium material. [ABSTRACT FROM AUTHOR]

2D dilute magnetic semiconductors have been recently reported in transition metal dichalcogenides doped with spin‐polarized transition metal atoms, for example vanadium‐doped WS2 monolayers, which exhibit room‐temperature ferromagnetic ordering. However, a broadband characterization of the electronic band structure of these doped WS2 monolayers and its dependence on vanadium concentration is still lacking. Therefore, power‐dependent photoluminescence, resonant four‐wave mixing, and differential reflectance spectroscopies are performed here to study optical transitions close to the A exciton energy of vanadium‐doped WS2 monolayers at three different doping levels. Instead of a single A exciton peak, vanadium‐doped samples exhibit two photoluminescence peaks associated with transitions from a donor‐like level and the conduction band minima. Moreover, resonant Raman and second‐harmonic generation experiments reveal a blueshift in the B exciton energy but no energy change in the C exciton after vanadium doping. Density functional theory calculations show that the band structure is sensitive to the Hubbard U correction for vanadium, and several scenarios are proposed to explain the two photoluminescence peaks around the A exciton energy region. This work provides the first broadband optical characterization of these 2D dilute magnetic semiconductors, shedding light on the novel and tunable electronic features of V‐doped WS2 monolayers. [ABSTRACT FROM AUTHOR]

Recent developments in 2D magnetic materials have motivated the search for new van der Waals magnetic materials, especially Ising‐type magnets with strong magnetic anisotropy. Fe‐based MPX3 (M = transition metal, X = chalcogen) compounds such as FePS3 and FePSe3 both exhibit an Ising‐type magnetic order, but FePSe3 receives much less attention compared to FePS3. This work focuses on establishing the strategy to engineer magnetic anisotropy and exchange interactions in this less‐explored compound. Through chalcogen and metal substitutions, the magnetic anisotropy is found to be immune against S substitution for Se whereas tunable only with heavy Mn substitution for Fe. In particular, Mn substitution leads to a continuous rotation of magnetic moments from the out‐of‐plane direction toward the in‐plane. Furthermore, the magnetic ordering temperature displays non‐monotonic doping dependence for both chalcogen and metal substitutions but due to different mechanisms. These findings provide deeper insight into the Ising‐type magnetism in this important van der Waals material, shedding light on the study of other Ising‐type magnetic systems as well as discovering novel 2D magnets for potential applications in spintronics. [ABSTRACT FROM AUTHOR]

Despite the success of top-seeded melt growth (TSMG) and TSIG, some key aspects of their manufacture need to be addressed including the presence of microstructural defects, inhomogeneities in trapped field and the difficulty of growing large-diameter bulk monoliths. Recently, a promising new method single-direction melt growth (SDMG) appears to address the majority of the shortcomings of TSMG and TSIG. Single-grain EuBCO/Ag bulk with the highest peritectic temperature to date was grown by modified SDMG. This remarkable achievement was made possible by lowering the peritectic temperature of the precursor composition by the addition of silver and by using single-grain EuBCO fabricated by TSMG as a seed. The EuBCO/Ag bulk grown by SDMG has demonstrated significant improvements in comparison to a reference TSMG sample. A reduction of approximately 30% in defect area (associated primarily with porosity), as well as a significantly enhanced homogeneity of trapped field and critical temperature, was observed. Furthermore, the critical current density curves exhibit a considerable improvement, particularly in the 2-5 T field range. The SDMG technique has considerable potential for scale-up for the fabrication of large-diameter bulk single grains, with only growth along the c-axis involved during the thermal process. [ABSTRACT FROM AUTHOR]

Motivated by the physics literature on "photonic doping" of scatterers made from "epsilon‐near‐zero" (ENZ) materials, we consider how the scattering of time‐harmonic TM electromagnetic waves by a cylindrical ENZ region Ω×R$\Omega \times \mathbb {R}$ is affected by the presence of a "dopant" D⊂Ω$D \subset \Omega$ in which the dielectric permittivity is not near zero. Mathematically, this reduces to analysis of a 2D Helmholtz equation div(a(x)∇u)+k2u=f$\mathrm{div}\, (a(x)\nabla u) + k^2 u = f$ with a piecewise‐constant, complex valued coefficient a that is nearly infinite (say a=1δ$a = \frac{1}{\delta }$ with δ≈0$\delta \approx 0$) in Ω∖D¯$\Omega \setminus \overline{D}$. We show (under suitable hypotheses) that the solution u depends analytically on δ near 0, and we give a simple PDE characterization of the terms in its Taylor expansion. For the application to photonic doping, it is the leading‐order corrections in δ that are most interesting: they explain why photonic doping is only mildly affected by the presence of losses, and why it is seen even at frequencies where the dielectric permittivity is merely small. Equally important: our results include a PDE characterization of the leading‐order electric field in the ENZ region as δ→0$\delta \rightarrow 0$, whereas the existing literature on photonic doping provides only the leading‐order magnetic field. [ABSTRACT FROM AUTHOR]

The chemical interaction of Sn with H2 by X‐ray diffraction methods at pressures of 180–210 GPa is studied. A previously unknown tetrahydride SnH4 with a cubic structure (fcc) exhibiting superconducting properties below TC = 72 K is obtained; the formation of a high molecular C2/m‐SnH14 superhydride and several lower hydrides, fcc SnH2, and C2‐Sn12H18, is also detected. The temperature dependence of critical current density JC(T) in SnH4 yields the superconducting gap 2Δ(0) = 21.6 meV at 180 GPa. SnH4 has unusual behavior in strong magnetic fields: B,T‐linear dependences of magnetoresistance and the upper critical magnetic field BC2(T) ∝ (TC – T). The latter contradicts the Wertheimer–Helfand–Hohenberg model developed for conventional superconductors. Along with this, the temperature dependence of electrical resistance of fcc SnH4 in non‐superconducting state exhibits a deviation from what is expected for phonon‐mediated scattering described by the Bloch‐Grüneisen model and is beyond the framework of the Fermi liquid theory. Such anomalies occur for many superhydrides, making them much closer to cuprates than previously believed. [ABSTRACT FROM AUTHOR]

The BiS2‐based layered superconductors with structures similar to those of cuprates and iron‐based superconductors have stimulated much research interest. Here, a new quaternary compound is reported, Bi5O4S3Cl, which crystalizes in a tetragonal structure with P4/mmm (No. 123) space group having alternately stacking unique BiS3 layers and Bi2O2 layers along the c‐axis with a Cl atom located at the center of the unit cell. A superconducting transition above 3 K is observed for both electrical transport and magnetic measurements. Hall resistivity measurements show its multiband character with a conduction dominated by electron‐like charge carriers. The first‐principles calculations exhibit that the semiconducting parent phase Bi5O4S3Cl becomes metallic when sulfur vacancies are introduced, which hints the origin of superconductivity in Bi5O4S3Cl. The findings will inspire the exploration of new BiS‐based superconductors. [ABSTRACT FROM AUTHOR]

The presence of electron correlations in a system with topological order can lead to exotic ground states. Considering single crystals of LaAgSb2 which has a square net crystal structure, one finds multiple charge density wave transitions (CDW) as the temperature is lowered. Large planar Hall (PHE) signals are found in the CDW phase, which are still finite in the high‐temperature phase though they change sign. Optimizing the structure within first‐principles calculations, one finds an unusual chiral metallic phase. This is because as the temperature is lowered, the separation between the Ag/Sb atoms on different layers decreases, leading to stronger repulsions between electrons associated with atoms on different layers. This leads to successive layers sliding with respect to each other, thereby stabilizing a chiral structure in which inversion symmetry is also broken. The large Berry curvature associated with the low‐temperature structure explains the low‐temperature PHE. At high temperature, the PHE arises from the changes induced in the anisotropic Dirac cone in presence of a magnetic field. This work represents a route toward detecting and understanding the mechanism in a correlation‐driven topological transition through electron transport measurements, complemented by ab‐initio electronic structure calculations. [ABSTRACT FROM AUTHOR]

The discovery of superconductivity in hole‐doped infinite‐layer nickelates has fueled intense research to identify the critical factor responsible for high‐Tc superconductivity. Magnetism and superconductivity are closely entangled, and elucidating the magnetic interactions in hole‐doped nickelates is critical for understanding the pairing mechanism. Here, these calculations based on the generalized Bloch theorem (GBT) and magnetic force theorem (MFT) consistently reveal that hole doping stabilizes an incommensurate (IC) spin state and increases the IC wave vector continuously, in a way strikingly similar to hole‐doped cuprates. Going further, a nonlinear Heisenberg model including first‐neighbor and third‐neighbor in‐plane magnetic interactions is developed. The analytical solutions successfully reproduce GBT and MFT results and reveal that the competition between the two magnetic interactions is the decisive factor for the IC magnetic transition. Eventually, by analyzing the doping‐controlled spin splitting of dx2−y2${d}_{{x}^2 - {y}^2}$ band and orbital‐contributed exchange interactions, direct links between hole doping, magnetization, exchange constants, and magnetic order are established. This discovery of the IC spin state, new understanding of its electronic origin, and establishment of direct connection with the paring dx2−y2${d}_{{x}^2 - {y}^2}$ electrons radically change the current understanding of the magnetic properties in hole‐doped NdNiO2 and open new perspectives for the superconducting mechanism in nickelates superconductors. [ABSTRACT FROM AUTHOR]

The chemical interaction of Sn with H2 by X‐ray diffraction methods at pressures of 180–210 GPa is studied. A previously unknown tetrahydride SnH4 with a cubic structure (fcc) exhibiting superconducting properties below TC = 72 K is obtained; the formation of a high molecular C2/m‐SnH14 superhydride and several lower hydrides, fcc SnH2, and C2‐Sn12H18, is also detected. The temperature dependence of critical current density JC(T) in SnH4 yields the superconducting gap 2Δ(0) = 21.6 meV at 180 GPa. SnH4 has unusual behavior in strong magnetic fields: B,T‐linear dependences of magnetoresistance and the upper critical magnetic field BC2(T) ∝ (TC – T). The latter contradicts the Wertheimer–Helfand–Hohenberg model developed for conventional superconductors. Along with this, the temperature dependence of electrical resistance of fcc SnH4 in non‐superconducting state exhibits a deviation from what is expected for phonon‐mediated scattering described by the Bloch‐Grüneisen model and is beyond the framework of the Fermi liquid theory. Such anomalies occur for many superhydrides, making them much closer to cuprates than previously believed. [ABSTRACT FROM AUTHOR]

CrSe2 monolayer is a recently synthesized ferromagnetic material exhibiting remarkable environmental stability. By using first‐principles calculations, a comprehensive study on the magnetic phase diagram of CrSe2 monolayer under conditions of electron/hole doping and different strains is presented. It is demonstrated that applying compressive strain can induce a magnetic phase transition from the ferromagnetic order to a Hexagon ferrimagnetic order. Moreover, the results reveal that electron doping can attenuate the ferromagnetism in the monolayer. This work thus provides insights into the design of CrSe2‐based spintronic devices. [ABSTRACT FROM AUTHOR]

One of the unsolved problems for using high‐Tc superconducting cuprates for spintronic applications are the short coherence lengths of Cooper pairs in oxides (a few Å), which requires atomically sharp and defect‐free interfaces. This research demonstrates the presence of high‐Tc superconducting La1.84Sr0.16CuO4 in direct proximity to SrLaMnO4 and provides evidence for the sharpness of interfaces between the cuprate and the manganite layers at the atomic scale. These findings shed light on the impact of the chemical potential at the interface of distinct materials on highly sensitive physical properties, such as superconductivity. Additionally, this results show the high stability of ultrathin layers from the same K2NiF4‐type family, specifically one unit cell of Sr2−xLaxMnO4 and three unit cells of La1.84Sr0.16CuO4. This work advances both the fundamental understanding of the proximity region between superconducting cuprates and manganite phases and the potential use of oxide‐based materials in quantum computing. [ABSTRACT FROM AUTHOR]

As a low‐cost alternative to noble metals, Cu plays an important role in industrial catalysis, such as water‐gas shift reaction, methanol or ethanol oxidation, hydrogenation of oils, CO oxidation, among many others. An important step in optimizing Cu catalyst performance is control of nanoparticles size, distribution, and the interface with the support. While proton conducting perovskites can enhance the metal catalytic activity when acting as the support, there has been limited investigation of in situ growth of Cu metal nanoparticles from the proton conductors and its catalytic performance. Here, Cu nanoparticles are tracked exsolved from an A‐site‐deficient proton‐conducting barium cerate‐zirconate using scanning electron microscopy, revealing a continuous phase change during exsolution as a function of reduction temperature. Combined with the phase diagram and cell parameter change during reduction, a new exsolution mechanism is proposed for the first time which provides insight into tailoring metal particles interfaces at proton conducting oxide surfaces. Furthermore, the catalytic behavior in the CO oxidation reaction is explored and, it is observed that these new nanostructures can rival state of the art catalysts over long term operation. [ABSTRACT FROM AUTHOR]

Copper salts are a popular choice as p‐dopants for organic semiconductors, particularly in N2,N2,N2′,N2′,N7,N7,N7′,N7′‐octakis(4‐methoxyphenyl)‐9,9′‐spirobi[9H‐fluoren]‐2,2′,7,7′‐tetramine (Spiro‐MeOTAD) hole transport material for solar cells. While being exceptionally effective, no scientific consensus about their doping mechanism has been established so far. This study describes the thermodynamic equilibria of involved species in copper(II) bis(trifluoromethanesulfonyl)imide (Cu(TFSI)2) doped, co‐evaporated Spiro‐MeOTAD. A temperature‐independent formation of charge transfer states is found, followed by an endothermic release of free charge carriers. Impedance and electron paramagnetic resonance spectroscopy unravel low activation energies for hole release and hopping transport. As a result, (52.0 ± 6.4)% of the total Cu(TFSI)2 molecules form free, dissociated holes at 10 mol% and room temperature. CuI species arising out of doping are stabilized by formation of a [CuI(TFSI)2]‐ cuprate, inhibiting elemental copper formation. This CuI species presents a potent hole trap reducing their mobility, which can be averted by simple addition of a bathocuproine complexing agent. A nonlinear temperature‐dependent conductivity and mobility that contradicts current charge transport models is observed. This is attributed to a combination of trap‐ and charge transfer state freeze‐out. These insights may be adapted to other metal salts, providing guidelines for designing next‐generation ultra‐high efficiency dopants. [ABSTRACT FROM AUTHOR]

Superconducting proximity effects in graphene have received a great deal of attention for over a decade now. This has unveiled a plethora of exotic effects linked to the specificities of graphene's electronic properties. The vast majority of the related studies are based on conventional, low‐temperature superconducting metals with isotropic s‐wave pairing. Here recent advances made on the less studied case of unconventional high‐temperature superconducting cuprates are reviewed. These are characterized by an anisotropic d‐wave pairing, whose interplay with Dirac electrons yields very rich physics and novel proximity behaviors. A theoretical analysis is provided and the experiments reported so far are summarized. These unveil hints of proximity‐induced unconventional pairing and demonstrate the gate‐tunable, long‐range propagation of high‐temperature superconducting correlations in graphene. Finally, the fundamental and technological opportunities brought by the theoretical and experimental advances are discussed, together with the interest in extending similar studies to other Dirac materials. [ABSTRACT FROM AUTHOR]

This work describes a homometallic spin‐1/2 tetrabromocuprate adopting a bilayer structure. Magnetic‐susceptibility measurements show a broad maximum centred near 70 K, with fits to this data using a Heisenberg model consistent with strong antiferromagnetic coupling between neighbouring copper atoms in different layers of the bilayer. There are further weak intralayer ferromagnetic interactions between copper cations in neighbouring dimers. First‐principles calculations are consistent with this, but suggest there is only significant magnetic coupling within one direction of a layer; this would suggest the presence of a spin ladder within the bilayer with antiferromagnetic rung and weaker ferromagnetic rail couplings. [ABSTRACT FROM AUTHOR]

The intense absorption of light to covering a large part of the visible spectrum is highly desirable for solar energy conversion schemes. To this end, we have developed novel anionic bis(4H‐imidazolato)Cu(I) complexes (cuprates), which feature intense, panchromatic light absorption properties throughout the visible spectrum and into the NIR region with extinction coefficients up to 28,000 M−1 cm−1. Steady‐state absorption, (spectro)electrochemical and theoretical investigations reveal low energy (Vis to NIR) metal‐to‐ligand charge‐transfer absorption bands, which are a consequence of destabilized copper‐based donor states. These high‐lying copper‐based states are induced by the σ‐donation of the chelating anionic ligands, which also feature low energy acceptor states. The optical properties are reflected in very low, copper‐based oxidation potentials and three ligand‐based reduction events. These electronic features reveal a new route to panchromatically absorbing Cu(I) complexes. [ABSTRACT FROM AUTHOR]

Utilisation of CO2 as a chemical reagent is challenging, due to the molecule's inherent chemical stability. However, CO2 reacts promptly at high temperature (∼1000 °C) with alkaline‐earth oxides to form carbonates and such reactions are used towards capture and re‐utilisation. In this work, this concept is extended and CO2 is utilised as a reagent to modify the crystal structure of mixed‐metal inorganic solids. Modification of the crystal structure is a "tool" used by materials scientists to tailor the physical property of solids. CO2 gas was reacted with several isostructural mixed‐metal oxides Sr2CuO3, Sr1.8Ba0.2CuO3 and Ba2PdO3. These oxides are carefully selected to show anion vacancies in their crystal structure, to act as host sites for CO2 molecules, leading to the formation of carbonate anions, (CO3)2−. The corresponding oxide carbonates were formed successfully and the favourable formation of SrCO3 as secondary phase was minimised via an innovative, yet simple synthetic procedure involving alternating of CO2 and air. We also derived a simple model to predict the kinetics of the reactions for the cuprates, using first‐principles density functional theory and assimilating the reaction to a gas‐surface process. [ABSTRACT FROM AUTHOR]

A Bose-Einstein condensate (BEC) of a nonzero momentum Cooper pair constitutes a composite boson or simply a boson. We demonstrated that the quantum coherence of the two-component BEC (boson and fermion condensates) is controlled by plasmons. It has been proposed that plasmons, observed in both electron-doped and hole-doped cuprates, originates from the long-range Coulomb screening, where the transfer momentum q ⟶ 0. We further show that the screening mediates boson-fermion pairing at condensate state. While only about 1 % of plasmon energy mediates the charge pairing, most of the plasmon energy is used to overcome the modes that compete against superconductivity such as phonons, charge density waves, antiferromagnetism, and damping effects. Additionally, the dependence of frequency of plasmons on the material of a superconductor is also explored. This study gives a quantum explanation of the modes that enhance and those that inhibit superconductivity. The study informs the nature of electromagnetic radiations (EMR) that can enhance the critical temperature of such materials. [ABSTRACT FROM AUTHOR]

High‐temperature superconducting cuprates have the potential to be transformative in a wide range of energy applications. In this work, the corpus of historical data about cuprates is analyzed using materials informatics, re‐examining how their structures are related to their critical temperatures (Tc). The available data is highly clustered and no single database contains all the features of interest to properly examine trends. To work around these issues a linear calibration approach that allows the utilization of multiple data sources is employed, combining fine resolution data for which the Tc is unknown with coarse resolution data where it is known. The hybrid data set constructed enables the exploration of the trends in Tc with the apical and in‐plane copper–oxygen distances. It is shown that large regions of the materials space have yet to be explored. Novel experiments relying on the nano‐engineering of the crystal structure may enable the exploration of such new regions. Based on the trends identified it is proposed that single layer Bi‐based cuprates are good candidate systems for such experiments. [ABSTRACT FROM AUTHOR]

In the search for new high‐temperature superconductors, it has been proposed that there are strong similarities between the fluoroargentate AgF2 and the cuprate La2CuO4. We explored the origin of the possible layered structure of AgF2 by studying its parent high‐symmetry phase and comparing these results with those of a seemingly analogous cuprate, CuF2. Our findings first stress the large differences between CuF2 and AgF2. Indeed, the parent structure of AgF2 is found to be cubic, naturally devoid of any layering, even though Ag2+ ions occupy trigonal sites that, nevertheless, allow the existence of a Jahn‐Teller effect. The observed Pbca orthorhombic phase is found when the system is cooperatively distorted by a local E⊗e trigonal Jahn‐Teller effect around the silver sites that creates both geometrical and magnetic layering. While the distortion implies that two Ag2+−F− bonds increase their distance by 15 % and become softer, our simulations indicate that covalent bonding and interlayer electron hopping is strong, unlike the situation in cuprate superconductors, and that, in fact, exfoliation of individual planes might be a harder task than previously suggested. As a salient feature, these results prove that the actual magnetic structure in AgF2 is a direct consequence of vibronic contributions involved in the Jahn‐Teller effect. Finally, our findings show that, due to the multiple minima intrinsic to the Jahn‐Teller energy surface, the system is ferroelastic, a property that is strongly coupled to magnetism in this argentate. [ABSTRACT FROM AUTHOR]

The multicomponent approach has been successfully expanded to the Ruddlesden–Popper structure with the synthesis of two different high‐entropy cuprate compositions: (La0.2Nd0.2Gd0.2Tb0.2Dy0.2)2CuO4 and (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2CuO4. The effect of synthesis method is explored using both solid‐state reaction and polymeric steric entrapment (PSE) methods. It is found that PSE leads to more randomly distributed cation species, providing an advantageous method of synthesis for the growing field of high entropy oxides. In situ high‐temperature x‐ray diffraction tracks the amorphous to crystalline phase transformation in (La0.2Nd0.2Gd0.2Tb0.2Dy0.2)2CuO4 powder, synthesized using the PSE method. Using the High‐Temperature XRD data, a method for gaining information on the kinetic behavior is also applied. Magnetometry of both compositions indicates ferrimagnetic behavior at low temperatures. [ABSTRACT FROM AUTHOR]

Van der Waals heterostructures (vdWHs) allow the assembly of high‐crystalline 2D materials in order to explore dimensionality effects in strongly correlated systems and the emergence of potential new physical scenarios. In this work, the feasibility of integrating 2D materials in‐between 2D superconductors is illustrated. In particular, the fabrication and electrical characterization of vertical vdWHs based on air‐unstable atomically‐thin transition metal dichalcogenides formed by NbSe2/TaS2/NbSe2 stacks, with TaS2 being the insulator 1T‐TaS2 or the metal 2H‐TaS2, is presented. Phase transitions as 1T‐TaS2 charge density wave and NbSe2 superconductivity are detected. An enhancement of the vdWH resistance due to Andreev reflections is observed below the superconducting transition temperature of the NbSe2 flakes. Moreover, in the NbSe2 superconducting state, the field and temperature dependence of the normalized conductance is analyzed within the Dynes' model and the overall behavior is consistent with the Bardeen–Cooper–Schrieffer theory. This vdWH approach can be extended to other 2D materials, such as 2D magnets or topological insulators, with the aim of exploring the new emergent properties that may arise from such combinations. [ABSTRACT FROM AUTHOR]

Spin‐orbit‐coupled Mott iridates show great similarity with parent compounds of superconducting cuprates, attracting extensive research interest especially for their electron‐doped states. However, previous experiments have been largely limited within a small doping range due to the absence of effective dopants, and therefore the electron‐doped phase diagram remains elusive. Here, an ionic‐liquid‐gating‐induced protonation method is utilized to achieve electron‐doping into a 5d Mott‐insulator built with a SrIrO3/SrTiO3 superlattice (SL), and a systematic mapping of its electron‐doped phase diagram is achieved with the evolution of the iridium valence state from 4+ to 3+, equivalent to doping of one electron per iridium ion. Along increasing doping level, the parent Mott‐insulator is first turned into a localized metallic state with gradually suppressed magnetic ordering, and then further evolves into a nonmagnetic band insulating state. This work forms an important step forward for the study of electron‐doped Mott iridate systems, and the strategy of manipulating the band filling in an artificially designed SL structure can be readily extended into other systems with more exotic states to explore. [ABSTRACT FROM AUTHOR]

In a nearly‐filled energy band where scattering of electrons is hampered, a pairing interaction between two electrons and quanta in a solid (e.g., phonons or spin‐resonances or some other excitation of electronic origin) can still occur in the s‐channel where a field quantum mediates the coalescence of two fermions into a new composite particle. By describing the attractively‐interacting electrons as a gas mixture of individual electrons plus bosons made up of two electrons, the dependence on momentum of the energy of single electrons is investigated. When the net interaction BCS dimensionless coupling constant λ and the ratio with the maximum energy ℏωD of a quantum mediating the pairing to the Fermi energy EF increases, the coalescence of electrons at temperatures higher than the Bose–Einstein condensation (BEC) temperature Tc of bosons leads to the appearance of steep (waterfall‐like) changes in the high‐energy electron spectrum of the binary boson–fermion (BF) gas mixture. These waterfall‐like anomalies seen in high‐Tc superconductors (HTSCs) are in fact a characteristic property of a BF gas mixture and reflect the splitting of the conduction band into two subbands emerging as the number NB of two‐electron bosons increases. [ABSTRACT FROM AUTHOR]

We report on the development of a high‐resolution and highly efficient beamline for soft X‐ray resonant inelastic X‐ray scattering (RIXS) located at the Taiwan Photon Source. This beamline adopts an optical design that uses an active grating monochromator (AGM) and an active grating spectrometer (AGS) to implement the energy compensation principle of grating dispersion. Active gratings are utilized to diminish defocus, coma and higher‐order aberrations, as well as to decrease the slope errors caused by thermal deformation and optical polishing. The AGS is mounted on a rotatable granite platform to enable momentum‐resolved RIXS measurements with scattering angles over a wide range. Several high‐precision instruments developed in‐house for this beamline are described briefly. The best energy resolution obtained from this AGM–AGS beamline was 12.4 meV at 530 eV, achieving a resolving power of 4.2 × 104, while the bandwidth of the incident soft X‐rays was kept at 0.5 eV. To demonstrate the scientific impact of high‐resolution RIXS, we present an example of momentum‐resolved RIXS measurements on a high‐temperature superconducting cuprate, i.e. La2–xSrxCuO4. The measurements reveal the A1g buckling phonons in superconducting cuprates, opening a new opportunity to investigate the coupling between these phonons and charge‐density waves. [ABSTRACT FROM AUTHOR]

First‐principles calculations are performed to investigate the electronic states of 1/1 and 2/1 approximants with the composition Al15Zn40Mg45, which is close to the quasicrystal (QC) Al14.9Zn41.0Mg44.1 in which the superconductivity recently has been discovered. The density of states for the 1/1 approximant shows a wide pseudogap structure near the Fermi level as commonly observed in various approximants of the QCs, whereas those for the 2/1 approximant do not show such a wide pseudogap. Instead of the wide pseudogap, the 2/1 approximant shows a remarkable narrow pseudogap at the Fermi level in contrast to the 1/1 approximant, which shows a shallow hump at the Fermi level within the wide pseudogap. This seems to be consistent with the experimental observation of the electrical resistivity, which increases with decreasing temperature from room temperature down to around the superconducting transition temperature for the 2/1 approximant together with the QC, whereas it monotonically decreases for the 1/1 approximant. [ABSTRACT FROM AUTHOR]

Topological nodal‐line semimetal SrAs3 hosts a simple nodal loop on the verge of Fermi level without distracting trivial states, providing a good platform for further investigations of electronic quantum states. Here, a report on pressure‐driven superconductivity in SrAs3 single crystal is provided and the interplay between the crystal structure, electronic state, and superconductivity is clarified therein. The comprehensive high‐pressure experiments, i.e., synchrotron X‐ray diffraction, electrical transport, and Raman spectroscopy, consistently reveal a critical pressure Pc ≈ 25 GPa. Around Pc, a superconducting transition appears, concomitant with the formation of high‐pressure cubic Pm‐3m phase. Meanwhile, the superconducting transition temperature Tc and hole carrier density increase synchronously above Pc. This finding demonstrates that the emerging superconductivity in SrAs3 stems from the high‐pressure cubic phase on the one hand, and shows that the evolution of Tc(P) is intimately correlated with the enhanced density of states near the Fermi level on the other hand. [ABSTRACT FROM AUTHOR]

Fundamental understanding of interface mechanisms that generate unexpected physical properties in the cuprate/manganite heterostructures is essential for possible applications as spintronic devices. Here, CaCuO2/La1−xSrxMnO3 (CCO/LSMO) superlattices are investigated, where the infinite‐layer cuprate CCO does not have apical oxygen for Cu in the Ca‐plane so that the Mn–O–Cu superexchange coupling can be only present at the MnO2–(La,Sr)O–CuO2 interface. Two different doping states for the manganites are studied, namely x = 0.1 and x = 0.3, corresponding to the ferromagnetic insulating and ferromagnetic metallic states, respectively, in the manganite phase diagram. Linear and circular dichroism in X‐ray absorption by synchrotron radiation at Cu and Mn L‐edges clearly demonstrate that in the absence of apical oxygen in the cuprate block, the magnetic coupling between the LSMO and CCO is weakly ferromagnetic when LSMO is metallic, while it is antiferromagnetic when LSMO is insulating, along with an increased Cu 3d(3z2–r2) and Mn 3d(3z2–r2) orbital occupation. It is proposed that the Mn 3d valence band upward shift driven by the enhancement of Mn3+ content in the underdoped sample enhances the orbital hybridization. The stronger hybridization at the interface MnO2–(La,Sr)O–CuO2 gives rise to the antiferromagnetic coupling between cuprate and underdoped manganite. [ABSTRACT FROM AUTHOR]

Water (H2O) molecules are often used to depolymerize crystal structures. Conversely, polycondensation of basic building units of crystal structures can be realized by removing water molecules from hydrous compounds. Herein, we report our rational design and synthesis of a novel copper phosphate (NH4)Cu[PO4] from a hydrothermal route with minimal water used. The title compound keeps the layered structural feature of its hydrous analogue (NH4)Cu[PO4]·H2O, but the isolated centrosymmetric [Cu2O8] dimers in the latter further polymerize into a two‐dimensional (2D) corrugated honeycomb layer in the former. Interestingly, the layers of corrugated honeycomb arrangement of Cu atoms in the bc plane are composed of a relatively rare compressed [CuO5] trigonal bipyramid, rather than the axially elongated [CuO4(OH2)] square pyramid in (NH4)Cu[PO4]·H2O. Magnetic susceptibility χ(T) of the title compound increases steadily to a maximum at 58 K but falls off rapidly to almost zero with decrease in temperature, suggesting the existence of a spin gap and long range ordering for the 2D S = 1/2 corrugated honeycomb layer. [ABSTRACT FROM AUTHOR]

TlCu2O2, a mixed‐valence spin‐chain cuprate, was synthesized in a piston cylinder system starting from thallium sesquioxide Tl2O3, cuprous oxide Cu2O and copper powder. The main structural characteristics are edge‐sharing (CuO2)n zigzag chains, which are linked in the perpendicular crystallographic direction by Cu+ to form a three‐dimensional network. Data from magnetic susceptibility and specific heat measurements show features typical for low‐dimensional magnetic exchange interactions. The long‐range antiferromagnetic ordering is observed at TN = 19.7 K. No weak ferromagnetic component can be detected, suggesting a plain Néel‐type spin‐ordered structure. [ABSTRACT FROM AUTHOR]

TlCu2O2, a mixed‐valence spin‐chain cuprate, was synthesized in a piston cylinder system starting from thallium sesquioxide Tl2O3, cuprous oxide Cu2O and copper powder. The main structural characteristics are edge‐sharing (CuO2)n zigzag chains, which are linked in the perpendicular crystallographic direction by Cu+ to form a three‐dimensional network. Data from magnetic susceptibility and specific heat measurements show features typical for low‐dimensional magnetic exchange interactions. The long‐range antiferromagnetic ordering is observed at TN = 19.7 K. No weak ferromagnetic component can be detected, suggesting a plain Néel‐type spin‐ordered structure. [ABSTRACT FROM AUTHOR]

Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion‐exchange) is extremely challenging as these low‐temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition‐metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4−xNiRuO8 0.5

Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion‐exchange) is extremely challenging as these low‐temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition‐metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4−xNiRuO8 0.5

Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion‐exchange) is extremely challenging as these low‐temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition‐metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4−xNiRuO8 0.5

Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion‐exchange) is extremely challenging as these low‐temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition‐metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4−xNiRuO8 0.5

Detailed investigation into the CuX/base/phosphine modified Stephens–Castro syntheses of dehydrotriaryl[12]annulenes 1–3 have shown that cyclization is suppressed by excess CuX, strong donor ligands, high dilution conditions, and thermally unstable ethynylcuprate monomers. Surprisingly, intermediate dimer 16 plays only a minor role in the formation of 2 and 4. Overall, our findings are consistent with a cyclization pathway governed more by the nature of prior self‐association of the ethynylcuprate monomers. Crystallographic characterization of tetrameric by‐product 4, is also reported and revealed that it assembles into tubular stacks in the solid state. [ABSTRACT FROM AUTHOR]

Through regulating the pH values, a series of iodo‐argentate/cuprate hybrids, [Me3(4‐TPT)]4[Ag6I18] (1, Me3(4‐TPT)=N,N′,N′′‐trimethyl‐2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine), [Me3(4‐TPT)][M5I8] (M=Ag/2, Cu/2 a), [Me3(3‐TPT)][M5I8] (Me3(3‐TPT)=N,N′,N′′‐trimethyl‐2,4,6‐tris(3‐pyridyl)‐1,3,5‐triazine, M=Ag/3, Cu/4), which exhibit adjustable structural variations with different dimensional structures, have been obtained under solvothermal conditions. They are directed by two types of in situ N‐alkylation TPT‐derivatives (Me3(4‐TPT) for 1/2/2 a and Me3(3‐TPT) for 3/4) and represent the isolated units (1), 1D polymeric chain (4), 2D layered structures (2/2 a, 3) based on diverse metal iodide clusters. These compounds possess reducing band gaps as compared with the bulk β‐AgI and CuI and belong to potential semiconductor materials. Iodocuprates feature highly efficient photocatalytic activity in the sunlight‐induced degradation of organic dyes. The detailed study on the possible photocatalytic mechanism, including radical trapping tests and theoretical calculations, reveals that the N‐alkylation TPT moieties contribute to the narrow semiconducting behavior and effectively inhibit the recombination of photogenerated electron‐hole pairs, which result in an excellent visible‐light‐induced photocatalytic performance. Mind the band gap: By tuning pH values, four iodo‐argentate/cuprate hybrids with adjustable structural variations directed by in situ N‐alkylation tripyridine‐derivatives were solvothermally obtained, which exhibit narrow band gaps and highly efficient solar‐driven photocatalytic property. [ABSTRACT FROM AUTHOR]

The aim of the research is to create new high‐temperature superconductors (HTS) NdBa2Cu3O7−x, SmBa2Cu3O7−x, EuBa2Cu3O7−x, and Nd1/3Sm1/3Eu1/3Ba2Cu3O7−x based on light rare earth (LRE) metals. The superconducting materials are investigated for microstructural and physicochemical properties. The paper describes the preparation process of substrate powders and the granulation results of the raw material mixtures before the first calcination, as well as after the first and the second calcination. The granulation analysis of the raw materials are performed using a low‐angle laser light scattering (LALLS) method. Qualitative and quantitative phase analysis of the superconducting materials after the first and the second calcination and after annealing in oxygen atmosphere have been performed by X‐Ray diffraction (XRD) technique. A detailed structural investigations mainly shows the orthorhombic phase with small amounts of BaCuO2 and CuO compounds detected in all samples. A microstructural analysis of materials are carried out by using Raman spectroscopy and scanning electron microscopy (SEM), respectively. The magnetic properties of the superconducting materials are characterized by AC magnetic susceptibility as a function of temperature. The critical current densities at liquid nitrogen temperatures were also measured. [ABSTRACT FROM AUTHOR]

Sr2IrO4, known as the Jeff = 1/2 Mott insulator, was predicted to be an unconventional superconductor upon doping since it highly resembles the high‐temperature cuprates. However, recent work pointed out an enhanced insulating behavior in the Ir‐vacant Sr2Ir1–xO4 system. In this contribution, to investigate the microscopic mechanism of its enhanced insulating behavior, X‐ray absorption spectroscopy was applied to study the electronic structure and local structure distortion of Sr2Ir1–xO4. Due to the presence of Ir5+ ions, the preconceived holes are barely doped in the Ir‐vacant system. Nevertheless, Ir vacancies finely modulate the local atomic structure, i.e. the topology of IrO6 octahedra and the in‐plane Ir—O1—Ir bond angle. Combined with theoretical calculations, it is demonstrated that both the more distorted IrO6 octahedra and decreased Ir—O1—Ir angle contribute to the increment of the band gap, and then result in the enhanced insulating state for Sr2Ir1–xO4. [ABSTRACT FROM AUTHOR]

Abstract: X‐ray diffraction structure of two new bis [1‐methyl‐3‐(methoxycarbonylmethyl) benzimidazolium]2+ [CuBr4]2− and [ZnBr4]2− compounds has been determined. Zn‐crystal is monoclinic with perfect Td symmetry of the ZnBr4 tetrahedron, whereas the Cu‐compound is orthorhombic with D2d symmetry of CuBr4 tetrahedron. The difference in these structures is described as due to the static Jahn‐Teller effect. Vibrational spectroscopy (1800–3200 cm−1) identified hydrogen bond network. NIR‐UV‐Vis spectra (5000–50000 cm−1) are dominated by ligand‐to‐metal bands with d‐d transition contribution. EPR results (Q‐band) analyzed in terms of the MO‐theory showed a very strong delocalization of unpaired electron density on ligands accompanied by the Cu(II) 4pz orbital contribution. This effect is partially compensated by charge transfer transitions to the EPR g‐factor. [ABSTRACT FROM AUTHOR]

It may be argued that the remarkable properties of the high-temperature superconducting cuprates such as the insulator-metal transition (IMT) and the metal-superconductor transition (MST) originate from competition and interplay between the interlayer ionic interaction and the intralayer covalent bonds in these materials. It is proposed here that the microscopic order parameter is the local field estimated from the ionic polarization at the sub-unit cell level, and it is demonstrated that it shows a strong temperature as well as chemical doping dependence. The out-of-plane ionicity induces an interlayer electron transfer that reduces the ionicity of the layers and leads to IMT, while the in-plane covalency induces in-plane intersite hole transfer that increases the out-of-plane ionicity. It is suggested that this competition leads to a local field catastrophe at a critical temperature Tc that drives the compound to MST. The asymmetry of the free charge carrier density breaks locally the mirror reflection symmetry of the order parameter, leading to a pairing between the real current and the polarization current. [ABSTRACT FROM AUTHOR]

Pyridine ligand complexes of [Bu4N][BiI4] were prepared using chelating ligands 2,2'-bipyridyl (2,2'-Bpy), 1,10-phenanthroline (Phen), and 4-nitro-1,10-phenanthroline (NO2Phen), producing monomeric complexes [Bu4N][(2,2'-Bpy)BiI4], [Bu4N][(Phen)BiI4], and [Bu4N][(NO2Phen)BiI4], and bridging ligands 4,4'-bipyridyl (4,4'-Bpy), pyrazine (Pyz), and aminopyrazine (NH2Pyz) resulting in formation of polymers [Bu4N]n[(4,4'-Bpy)BiI4]n and [Bu4N]2n[(RPyz)Bi2I8]n (R=H,NH2). The latter contain edge-sharing Bi2I8 dimers. Organic ligand BiIII/CuI clusters [Bu4N]2[L2Bi2Cu2I10] {L = PPh3,P(OPh)3} and [Bu4N]2[PyBi2Cu2I10] (Py = pyridine) have been prepared. All bismuthate(III) centers are distorted octahedra and all cuprate(I) centers are tetrahedral, with organic ligands bonded to CuI.The first neutral BiI3/CuI organic ligand complex [BiCu3I6(PPh3)6] is reported. Diffuse reflectance spectroscopy measurements reveal strong absorption bands for both iodobismuthate(III) and iodocuprate(I)/bismuthate(III) complexes in the UV and visible range. Despite the similarity in absorption bands, DFT calculations support a distinct shift in transition from a mixed halide/ metal-to-ligand charge transfer (X/MLCT) to a metal--halide cluster-centered transition upon incorporation of copper(I) into the cluster. [ABSTRACT FROM AUTHOR]

A direct one-pot synthesis of asymmetric dehydrobenzopyrido[ 12]annulenes 2 and 3 containing one or two pyridine rings is reported that employs a Stephens-Castro mediated cross-coupling of mixtures of ethynylcuprate precursors. The spectroscopic and theoretical properties of 2 and 3 are compared to those of the threefold symmetric dehydrotribenzo[ 12]annulene 1, and dehydrotripyrido[12]annulenes 4 and 5 and dehydrodibenzodipyrido[16]annulene byproduct 6, and showed 1-5 to be essentially isoelectronic band gap materials whose electron accepting ability increases with increasing nitrogen incorporation. The structures of 2, 4 and 6 were also unambiguously characterized by X-ray crystallography. The results highlight the potential dehydroaryl[12]annulenes incorporating pyridines offer for the construction of high carbon content electronic materials. [ABSTRACT FROM AUTHOR]

Many approaches to introduce the CF2P(O)(OR)2 unit into organic molecules make use of CuI-catalyzed couplings between organic halides and BrZnCF2P(O)(OR)2. Despite the great importance of this process for the synthesis of α,α-difluoromethylenephosphonates, the constitution and molecular structures of the organozinc precursor and the catalytically relevant copper/zinc complex are still unknown. Here we report on the isolation of these two species, their spectroscopic characterization, and the determination of their structure by single-crystal X-ray diffraction. First orienting experiments on the stability of the cuprate reagent in solution at room temperature as well as its reactivity towards allyl bromides were subsequently performed. [ABSTRACT FROM AUTHOR]