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Recently, LiGa 5 O 8 was identified as a cubic spinel type ultra-wide-bandgap semiconductor with a gap of about 5.36 eV and reported to be unintentionally p -type. Here, we present first-principles calculations of native defects and their various complexes to try to explain the occurrence of p -type doping. Although we find Li vacancies (0.74 eV above VBM) to be shallower acceptors than in LiGaO 2 (1.63 eV above VBM), and becoming slightly shallower in complexes with donors such as V O (0.58 eV above VBM) and Ga Li antisites (0.65 eV above VBM), these V Li based defects are not sufficiently shallow to explain p -type doping. The dominant defects are donors and, in equilibrium, the Fermi level would be determined by compensation between donors and acceptors and pinned deep in the gap. [ABSTRACT FROM AUTHOR]

Terahertz (THz) light, probing electronic responses near the Fermi level, is closely linked to DC transport. In this study, we investigate the in situ THz and DC conductivity of epitaxial VO 2 films near the heating-induced insulator–metal transition. We find that the THz conductivity transition occurs at lower temperatures than the DC conductivity transition, with the separation increasing with film thickness and crystallization quality. Analysis of the complex conductivity spectra attributes this separation to released carrier confinement at THz frequencies. Our findings contribute to a deeper understanding of electron dynamics in VO 2 films. [ABSTRACT FROM AUTHOR]

Amorphous molybdenum disulfide has shown potential as a hydrogen evolution catalyst, but the origin of its high activity is unclear, as is its atomic structure. Here, we have developed a classical inter-atomic potential using the charge equilibration neural network method, and we have employed it to generate atomic models of amorphous MoS2 by melting and quenching processes. The amorphous phase contains an abundance of molybdenum and sulfur atoms in low coordination. Besides the 6-coordinated molybdenum typical of the crystalline phases, a substantial fraction displays coordinations 4 and 5. The amorphous phase is also characterized by the appearance of direct S–S bonds. Density functional theory shows that the amorphous phase is metallic, with a considerable contribution of the 4-coordinated molybdenum to the density of states at the Fermi level. S–S bonds are related to the reduction of sulfur, with the excess electrons spread over several molybdenum atoms. Moreover, S–S bond formation is associated with a distinctive broadening of the 3s states, which could be exploited for experimental characterization of the amorphous phases. The large variety of local environments and the high density of electronic states at the Fermi level may play a positive role in increasing the electrocatalytic activity of this compound. [ABSTRACT FROM AUTHOR]

A generalized quantum master equation approach is introduced to describe electron transfer in molecular junctions that spans both the off-resonant (tunneling) and resonant (hopping) transport regimes. The model builds on prior insights from scattering theory but is not limited to a certain parameter range with regard to the strength of the molecule–electrode coupling. The framework is used to study the simplest case of energy and charge transfer between the molecule and the electrodes for a single site noninteracting Anderson model in the limit of symmetric and asymmetric coupling between the molecule and the electrodes. In the limit of elastic transport, the Landauer result is recovered for the current by invoking a single active electron Ansatz and a binary collision approximation for the memory kernel. Inelastic transport is considered by allowing the excitation of electron–hole pairs in the electrodes in tandem with charge transport. In the case of low bias voltages where the Fermi levels of the electrodes remain below the molecular state, it is shown that the current arises from tunneling and the molecule remains neutral. However, once the threshold is reached for aligning the fermi level of one electrode with the molecular orbital, a small amount of charge transfer occurs with a negligible amount of hopping current. While inelasticity in the current has a minimal impact on the shape of the current–voltage curve in the case of symmetric electrode coupling, the results for a slight asymmetry in coupling demonstrate complete charge transfer and a significant drop in current. These results provide encouraging confirmation that the framework can describe charge transport across a wide range of electrode–molecule coupling and provide a unique perspective for developing new master equation treatments for energy and charge transport in molecular junctions. An extension of this work to account for inelastic scattering from electron–vibrational coupling at the molecule is straightforward and will be the subject of subsequent work. [ABSTRACT FROM AUTHOR]

Plasmonic catalysis triggers the dissociation of H 2 or adsorbed O 2 (sluggish processes) under continuous wave excitation via plasmon decay. This is coupled to interband or intraband excitation of d-band or sp-band, respectively, to levels above fermi level of metals. Here, we have studied the plasmonic and photocatalytic behavior in an environment friendly medium with AM 1.5 G sunlight of CuO/ Cu 2 O thin films fabricated by pulsed laser deposition technique in vacuum with varying thickness. We have achieved ∼ 0.59 kmol h − 1 g − 1 H 2 production in the CuO/ Cu 2 O film with a thickness of ∼ 27 nm. The role of plasmons with metal–dielectric and semiconductor–semiconductor interfaces is conducted through both experimental and theoretical approaches. The results suggest that the impact of plasmonic catalysis/synthesis is subject to the dimension, composition, and band alignment of two interface materials. [ABSTRACT FROM AUTHOR]

In this work, spin transport in ferroelectric tunnel junctions with composite barriers and magnetic electrodes is investigated theoretically using spin-dependent screening theory. The shape of the insulator barrier and the electronic structure of the ferromagnetic electrode inevitably affect the spin transport properties. Interestingly, we find that when the Fermi level approaches the bottom of the minority-spin band of the electrode, an approximately ±100% bidirectional spin-filtering effect can be realized due to the included exchange potential with an appropriate electronic band structure of electrodes. Additionally, electrically induced magnetic reconstruction would occur on the electrode surface due to spin-dependent band bending. Our study significantly deepens the current understanding of spin-dependent screening on metal surfaces and at metal/ferroelectric interfaces and provides a feasible method for achieving the interface magnetoelectric effect. [ABSTRACT FROM AUTHOR]

The coupling of an electron gas confined by a harmonic potential and submitted to a strong magnetic field tilted in relation to the confining direction creates an excitation called here magneto-polariton. This work describes the origin of this excitation and calculates the energy eigenvalues for different tilted angles. It presents the reasons leading to the crossings and repulsions of the energy bands, the degeneracy of the states, the way the Fermi levels change with the magnetic field, the influence of an external electric field, and how the Hall resistance plateaus change with the change in the tilted angle. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal dichalcogenides (TMDs) hold immense promise as ultrathin-body semiconductors for cutting-edge electronics and optoelectronics. In particular, their sustained charge mobility even at atomic-level thickness as well as their absence of surface dangling bonds, versatile band structures, and silicon-compatibility integration make them a prime candidate for device applications in both academic and industrial domains. Despite such high expectations, group-VI TMDs reportedly exhibit a range of enigmatic properties, such as substantial contact resistance, Fermi level pinning, and limited unipolar charge transport, which are all rooted in their inherent defects. In other words, intrinsic physical properties resulting from their native defects extend their influence beyond the material level. Bridging point-defect-induced material properties and their behavior at the device level, this Perspective sheds light on the significance of crystalline defects beyond a rather simple defect–property relationship. As a distinctive approach, we briefly review the well-established defect model of conventional III–V semiconductors and further apply it to the emergent defect behaviors of 2D TMDs such as their defect-induced gap states. Within the main discussion, we survey a range of behaviors caused by the most prevalent intrinsic defect, namely, vacancies, within 2D TMDs, and their implications for electronic and optoelectronic properties when employed at the device level. This review presents an in-depth summary of complexities in material properties as well as device characteristics arising from intrinsic point defects and provides a solid foundation for the cross-links among native defects and material/device properties. [ABSTRACT FROM AUTHOR]

Ag-doping treatment is a popular method for enhancing the performance of kesterite-structured Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Among the various methods, incorporating a high concentration of Ag+ into an absorber surface has proven to be particularly effective. However, the exact mechanisms behind this improvement are still unclear. This study aims to investigate the key factors that improve device performance through simulation. Specifically, the influence of the change in the carrier density, CuZn antisite defects, interface defect density, and formation of an n-type AZTSSe surface after heavy surface Ag doping have been examined. The simulation results indicate that the formation of an n-type AZTSSe layer on an absorber surface can significantly improve the open circuit voltage (VOC) and overcome the efficiency saturation problem induced by severe interface recombination for CZTSSe devices with a negative conduction band offset (CBO), compared to other affecting factors. This is because the modified conduction band alignment and the realization of interface-type inversion reduce interface recombination and retard the Fermi level pinning. However, the formation of interface-type inversion does not significantly improve CZTSSe devices with a positive CBO, as these devices already have weaker interface recombination. This work implies that the formation of an n-type AZTSSe layer is crucial for further improving the performance of CZTSSe devices with a negative CBO and can pave the way for improving the performance of thin film solar cells with severe interface recombination. [ABSTRACT FROM AUTHOR]

The massive amount of wasted heat energy from industry has pushed the development of thermoelectric (TE) materials that directly convert heat into electricity to a new level of concern. Recently, multicomponent alloys such as GeTe-based and PbSe-based high-entropy (HE) chalcogenides have attracted a great deal of attention due to their potential application as TE materials. The nature of the interatomic bonding, lattice distortion (LD), and the electronic structure in this class of materials is not fully understood. Herein, we report a comprehensive computational investigation of nine GeTe-based HE alloys with eight metallic elements (Ag, Pb, Sb, Bi, Cu, Cd, Mn, and Sn) with large supercells of 1080 atoms each; seven PbSe-based HE solid solutions: Pb0.99−ySb0.012SnySe1−2xTexSx (x = 0.1, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, with y = 0) with supercells of 1000 atoms each; and five Pb0.99−ySb0.012SnySe1−2xTexSx (y = 0.05, 0.1, 0.15, 0.2, 0.25 with x = 0.25) solid solutions with supercells of 1000 atoms each. All these HE models are theoretically investigated for the first time. The electronic structure, interatomic bonding, charge transfer, and lattice distortion (LD) are investigated by first-principles calculations based on density functional theory. Multicomponent HE alloys can cause a significant LD, which affects their mechanical, thermal, and TE properties. The calculations for the GeTe-based HE chalcogenides showed that they are semiconductors with a narrow bandgap, except for m8, which has a semi-metallic characteristic, and this makes them good candidates for TE applications. For most of these models, the Fermi level shifts upward and locates deeply in the conduction bands, resulting in the enhancement of the electrical conductivity (σ). The bonding properties showed that most bonds in m5 are more dispersed, indicating highest LD and lower lattice thermal conductivity. For PbSe-based HE solid solutions, the LD calculations showed that the models Pb0.99Sb0.012Se0.5Te0.25S0.25 and Pb0.89Sb0.012Sn0.1Se0.5Te0.25S0.25 have the higher LD, and thus a lower lattice thermal conductivity. Such investigations are in high demand since it enables us to design new HE chalcogenides for TE applications. We use the novel concept of total bond order density as a single quantum mechanical metric to characterize the internal cohesion of these HE alloys and correlate with calculated properties, especially the mechanical properties. This work provides a solid database for HE chalcogenides and a road map for many potential applications. Moreover, the computational procedure we developed can be used to design new HE chalcogenides for specific TE applications. [ABSTRACT FROM AUTHOR]

In this study, the basic properties of Ba2AgSi3 were investigated in detail from both experimental and computational viewpoints. Polycrystalline Ba2AgSi3 formed by an arc-melting apparatus under an argon atmosphere was ground into powders, and then powder samples were sintered using the spark plasma sintering method. Both n-type and p-type samples were obtained. This may be due to a slight deviation from the stoichiometric composition. The energy bandgap of Ba2AgSi3 was measured to be around 0.17 eV from the temperature dependence of electrical conductivity and was in agreement with that by first-principles calculations. Sintered samples exhibited a high Seebeck coefficient of −273 μV K−1 and a high power factor of 0.38 mW m−1 K−2 at 307 K for n-type samples. They were 217 μV K−1 and 0.23 mW m−1 K−2, respectively, at 320 K for p-type samples. The electronic structures of impurity-doped Ba2AgSi3 were also discussed using first-principles calculations to investigate the insertion site of impurity atoms. The calculations suggest that the substitution of B (P) at any Si site shifts the Fermi level and transforms it into p-type (n-type) semiconductors. On the other hand, substitution of Ba or Ag sites with B or P is unlikely to occur in terms of formation energy. [ABSTRACT FROM AUTHOR]

The study of van der Waals (vdW) materials has seen increased interest in recent years due to the wide range of uses for these materials because of their unique mechanical, electronic, and optical properties. This area has recently expanded further into studying the behavior of vdW nanomaterials as decreasing dimensions open up opportunities to interact with these materials in new ways. However, measuring the band structures of nanomaterials, which is key to understanding how confinement affects material properties and interactions, comes with several challenges. In this review, we survey a range of techniques for synthesizing and characterizing vdW nanomaterials, in order to outline the key material and characterization challenges. This includes controlling the Fermi level in vdW nanoparticles, preparing these particles for either ensemble or individual particle measurement, as well as protecting the pristine surface from oxidation. [ABSTRACT FROM AUTHOR]

The effect of high temperature annealing under O2 and N2 atmospheres on the electrical properties and defect formation on Sn doped n-type β-Ga2O3 bulk samples was investigated by electron paramagnetic resonance (EPR) spectroscopy. EPR, being a volume sensitive technique, probes the entire sample volume. Our results show an electrical compensation being correlated with the formation of a negatively charged Ga vacancy defect VGa2−. This VGa center is different from the one observed after particle irradiation. The associated shift of the Fermi level reveals the presence of Fe3+, Cu2+, and Cr3+, which are residuals related to the growth conditions. The 1100 °C N2 annealed sample is fully compensated, and the neutral donor resonance is no longer observed. Our results directly confirm the thermal instability of Ga and Sn in n-type conducting samples. No oxygen vacancy related centers were detected. We discuss the various Ga vacancy centers reported previously. [ABSTRACT FROM AUTHOR]

The characteristic polytype behaviors of SiC and accompanying low stacking fault energies are known to cause engineering issues, including polytype inclusions and bipolar degradation. The dependence of the relative stability of SiC polytypes and stacking fault energies on excess carrier concentration was investigated using first-principles calculations. The relative energy of 2H-, 4H-, and 6H-SiC to 3C-SiC increased with the excess electrons over 2 × 1019 cm−3, while the energy variation with excess holes was small. The stacking fault energies in 4H-SiC also exhibited a significant decrease with excess electrons over 1.0 × 1019 cm−3, whereas this change was minor with excess holes. These excess carrier dependencies were attributed to variations in the bandgap between polytypes. The energy level of the excess electrons was at the conduction band minimum; this was lowest in 3C-SiC, which had the lowest bandgap energy. Consequently, the energy of 3C-SiC with excess electrons was lower than that of other polytypes. Conversely, the valence band maximum lacked electrons when excess holes were present, resulting in a small difference among the Fermi levels of the polytypes. Hence, the energy difference between the SiC polytypes was similar for excess holes. Similarly, the stacking faults in SiC exhibited quantum-well structures by incorporating other polytypes with different bandgaps. With excess electrons, the Fermi level within the stacking faults was lower than that in the bulk crystals. Consequently, the stacking fault energy decreased for the same reason that the energy in 3C-SiC decreased under excess electron conditions. [ABSTRACT FROM AUTHOR]

Optically active spin defects in semiconductors can serve as spin-to-photon interfaces, key components in quantum technologies. Silicon carbide (SiC) is a promising host of spin defects thanks to its wide bandgap and well-established crystal growth and device technologies. In this study, we investigated the oxygen-vacancy complexes as potential spin defects in SiC by means of ab initio calculations. We found that the OCVSi defect has a substantially low formation energy compared with its counterpart, OSiVC, regardless of the Fermi level position. The OCVSi defect is stable in its neutral charge state with a high-spin ground state (S = 1) within a wide energy range near the midgap energy. The zero-phonon line (ZPL) of the OCVSi0 defect lies in the near-infrared regime, 1.11–1.24 eV (1004–1117 nm). The radiative lifetime for the ZPL transition of the defect in kk configuration is fairly short (12.5 ns). Furthermore, the estimated Debye–Waller factor for the optical transition is 13.4%, indicating a large weight of ZPL in the photoluminescence spectrum. All together, we conclude that the OCVSi0 defect possesses desirable spin and optical properties and thus is potentially attractive as a quantum bit. [ABSTRACT FROM AUTHOR]

The lattice mismatch, defect, and weak interlayer coupling severely constrain the practical application of van der Waals heterojunctions (vdWHs) in the field of optoelectronic devices. Here, we introduced the 2D ferroelectric (FE) material AgBiP2Se6 to construct defect-free, low lattice-mismatched AgBiP2Se6/MoSe2 heterojunctions with different polariton directions (I, II, III). The AgBiP2Se6 layer can provide an excellent FE electric field to enhance the interlayer coupling and stiffness. The larger interlay stiffness reduces the probability of electron–phonon scattering and then results in significant carrier mobility (∼0.5 × 104 cm2 V−1 s−1) for configurations I and II. Phase transition of FE to paraelectric AgBiP2Se6 in the AgBiP2Se6/MoSe2 heterojunctions can be achieved under specific biaxial strain, which can effectively regulate the electronic structure. Applying the strain and electric field can regulate the bandgap and band alignment of configurations I and II. The photoelectric conversion efficiency of configuration I can reach as high as 20.54% under 2% biaxial strain. Furthermore, configuration II holds a nearly free electron state near the Fermi level under an electric field, which can act as a favorable electron transport channel. A design to strengthen interlayer coupling in the FE-based AgBiP2Se6/MoSe2 heterojunction has been proposed, and it can provide a new way to break through the traditional bottleneck in the development of optoelectronic devices. [ABSTRACT FROM AUTHOR]

We present computational results on electronic, magnetic, and structural properties of CoVMnSb, a quaternary Heusler alloy. Our calculations indicate that this material may crystallize in two energetically close structural phases: inverted and regular cubic. The inverted cubic phase is the ground state, with ferrimagnetic alignment, and around 80% spin polarization. Despite having a relatively large bandgap in the minority-spin channel close to the Fermi level, this phase does not undergo a half-metallic transition under pressure. This is explained by the "pinning" of the Fermi level at the minority-spin states at the Γ point. At the same time, the regular cubic phase is half-metallic and retains its perfect spin polarization under a wide range of mechanical strain. Transition to a regular cubic phase may be attained by applying uniform pressure (but not biaxial strain). In practice, this pressure may be realized by an atomic substitution of non-magnetic atoms (Sb) with another non-magnetic atom (Si) of a smaller radius. Our calculations indicate that 25% substitution of Sb with Si results in a half-metallic regular cubic phase being the ground state. In addition, CoVMnSb0.5Si0.5 retains its half-metallic properties under a considerable range of mechanical pressure, as well as exhibits thermodynamic stability, thus making this alloy attractive for potential spintronic applications. We hope that the presented results will stimulate experimental efforts to synthesize this compound. [ABSTRACT FROM AUTHOR]

We apply an Ising-type model to estimate the bandgaps of the polytypes of group IV elements (C, Si, and Ge) and binary compounds of groups: IV–IV (SiC, GeC, and GeSi), and III–V (nitride, phosphide, and arsenide of B, Al, and Ga). The models use reference bandgaps of the simplest polytypes comprising 2–6 bilayers calculated with the hybrid density functional approximation, HSE06. We report four models capable of estimating bandgaps of nine polytypes containing 7 and 8 bilayers with an average error of ≲0.05 eV. We apply the best model with an error of < 0.04 eV to predict the bandgaps of 497 polytypes with up to 15 bilayers in the unit cell, providing a comprehensive view of the variation in the electronic structure with the degree of hexagonality of the crystal structure. Within our enumeration, we identify four rhombohedral polytypes of SiC—9R, 12R, 15R(1), and 15R(2)—and perform detailed stability and band structure analysis. Of these, 15R(1) that has not been experimentally characterized has the widest bandgap (> 3.4 eV); phonon analysis and cohesive energy reveal 15R(1)-SiC to be metastable. Additionally, we model the energies of valence and conduction bands of the rhombohedral SiC phases at the high-symmetry points of the Brillouin zone and predict band structure characteristics around the Fermi level. The models presented in this study may aid in identifying polytypic phases suitable for various applications, such as the design of wide-gap materials, that are relevant to high-voltage applications. In particular, the method holds promise for forecasting electronic properties of long-period and ultra-long-period polytypes for which accurate first-principles modeling is computationally challenging. [ABSTRACT FROM AUTHOR]

Bipolar magnetic semiconductor (BMS) has special electronic structures; i.e., its conduction band minimum (CBM) and valence band maximum (VBM) are completely spin-polarized in opposite directions. In this work, the band structures of 2H-VX2 (X = S, Se, and Te) are examined through first-principles calculations, and the results show that both 2H-VS2 and 2H-VSe2 are BMSs, while 2H-VTe2 is a unipolar magnetic semiconductor (UMS); i.e., its CBM and VBM show the same spin direction. Most interestingly, we find that electronic orbitals near the Fermi level of 2H-VX2 are occupied by d z 2 and d x y orbitals, which can be effectively modulated by the biaxial strain. With appropriate strain modulations, 2H-VX2 can be BMS, UMS, or half-metal (HM). Our investigation reveals strain effects on the band structure of 2H-VX2, which greatly enhances their significance in spintronics. [ABSTRACT FROM AUTHOR]

The combined feature of high thermal conductivity and high carrier mobility makes cubic boron arsenide (c-BAs) promising for high power and high frequency applications. In BAs-based electronics, the interaction between metals and BAs is crucial, as it significantly affects the electronic properties. One particular parameter is the Schottky barrier height (SBH), which plays a critical role in determining the transmission properties. The interfacial contact effects of BAs (110), (111), and (100) surfaces with a variety of metals have been carefully explored using first-principles calculations in order to characterize their electrical characteristics. For p-type SBHs, over different terminations, there is a strong linear trend with increasing metal work function, with a relatively steeper pinning coefficient of ∼0.2. The results show that the SBHs follow a relation of ϕ n (110) > ϕ n (111) > ϕ n (100). Clear metal induced gap states can be observed at the interfacial BAs, resulting in an enhanced Fermi level pinning effect. The Sc is excellent at generating Schottky contacts with relatively higher SBHs (∼0.9 eV). Pt has the smallest barrier height of ∼0.3 eV, making it ideal for ohmic electrodes with low contact resistance. This work provides insight into the properties at metal–BAs contact interfaces and provides a theoretical basis for the selection of suitable electrodes for high power BAs devices. [ABSTRACT FROM AUTHOR]

Indium phosphide is widely used in electronics and photovoltaic devices due to its high electro-optical conversion efficiency, high electron mobility, and good radiation resistance. Defects are the main limitation for the performance of InP devices. In this work, based on hybrid functional with finite size correction, electronic properties of intrinsic and H-related defects have been investigated in InP. We found that PIn defect is the most stable intrinsic defect with the lowest formation energy. Defect signals detected experimentally are defined by our calculated results. Experimentally observed electron traps with the energy level of EC −0.66 eV and EC −0.68 eV are ascribed to the transition level ɛ(−1/−2) and ɛ(−2/−3) of In vacancies. The hydrogenated vacancies in InP have been systematically reported in the present work. Formation energies of H-related defects indicate that hydrogen atoms prefer to bind to In vacancy than P vacancy. The formation energy of In vacancy decreases with the addition of H, while that of P vacancy increases. For hydrogenated In vacancies, it captures fewer electrons than bare In vacancies when the Fermi level is close to CBM. Especially for the VIn −3H structure, it is 0 charge state in all Fermi levels so that it will not tend to capture electron or hole. Our work is helpful to explain experimental phenomena and radiation-induced damages and improve the performance of InP devices. [ABSTRACT FROM AUTHOR]

Matrix diagonalization is almost always involved in computing the density matrix needed in quantum chemistry calculations. In the case of modest matrix sizes (≲4000), performance of traditional dense diagonalization algorithms on modern GPUs is underwhelming compared to the peak performance of these devices. This motivates the exploration of alternative algorithms better suited to these types of architectures. We newly derive, and present in detail, an existing Chebyshev expansion algorithm [Liang et al., J. Chem. Phys. 119, 4117–4125 (2003)] whose number of required matrix multiplications scales with the square root of the number of terms in the expansion. Focusing on dense matrices of modest size, our implementation on GPUs results in large speed ups when compared to diagonalization. Additionally, we improve upon this existing method by capitalizing on the inherent task parallelism and concurrency in the algorithm. This improvement is implemented on GPUs by using CUDA and HIP streams via the MAGMA library and leads to a significant speed up over the serial-only approach for smaller (≲1000) matrix sizes. Finally, we apply our technique to a model system with a high density of states around the Fermi level, which typically presents significant challenges. [ABSTRACT FROM AUTHOR]

Frustrated lattices with dispersionless band structures and fully localized states are an exciting platform for exploring many-body physics. In this work, we identify X 3 MnN 3 (X = Ca, Sr, Ba) as a frustrated lattice and investigate its physical properties in the ferromagnetic (FM) and antiferromagnetic (AFM) states based on first-principles calculations. Our results show that all three materials in FM and A-type AFM configurations have flatbands with band touching in the k z ∼ 0 and k z ∼ π planes with bandwidths less than 0.2 eV. Intriguingly, the flatband is tuned to the Fermi level when X 3 MnN 3 is transformed into the FM state. Furthermore, we find the two-dimensional dice model hidden in X 3 MnN 3 by treating the coupled Mn and N atoms as a basic site, revealing that the compact localized state is generated by destructive interferences between the hopping amplitudes, and the dice models stack the system staggered along the c -axis. Our work provides new candidate materials for exploring strong correlation physics and reveals the mechanism of their localized state. [ABSTRACT FROM AUTHOR]

This paper is concerned with a theoretical analysis of the behavior of optically excited spin currents in bilayer and multilayer systems of ferromagnetic and normal metals. As the propagation, control, and manipulation of the spin currents created in ferromagnets by femtosecond optical pulses is of particular interest, we examine the influence of different thicknesses of the constituent layers for the case of electrons excited several electronvolts above the Fermi level. Using a Monte-Carlo simulation framework for such highly excited electrons, we first examine the spatiotemporal characteristics of the spin current density driven in a Fe layer, where the absorption profile of the light pulse plays an important role. Further, we examine how the combination of light absorption profile, spin-dependent transmission probabilities, and iron layer thickness affects spin current density in a Fe/Au bilayer system. For high-energy electrons studied here, the interface and secondary electron generation have a small influence on spin transport in the bilayer system. However, we find that spin injection from one layer to another is most effective within a certain range of iron layer thicknesses. [ABSTRACT FROM AUTHOR]

Different from conventional ferromagnetic methods, producing a spin-polarized current through electrical ways in spintronic devices can greatly increase operating speed, reduce power consumption, and improve device integration. Inspired by recent experimental progress on the synthesis of a heptauthrene molecule, we investigate its spin-dependent transport contacted with Au electrodes through first-principles calculations. By applying a gate voltage, the transmission can be switched between completely spin-up and spin-down polarized states, achieving an electrically controlled dual-spin filter. Furthermore, a fine tuning on the spin polarization, between 100% and − 100%, can also be realized, where the transport with any ratio of spin-up to spin-down electron quantities can be realized beyond the traditional devices. The peculiar transmission spectra and their shift are found to play crucial roles, where transmission peaks distribute on both sides of the Fermi level with opposite spin components. Such a spin-polarization modulating effect is found to be robust to the molecule-electrode contacting site, indicating it is an intrinsic feature of such systems. Moreover, the dimension of the device is at the single-molecule level, suggesting great application potential. [ABSTRACT FROM AUTHOR]

An efficient carrier compensation mechanism in semiconductor layers by Fermi-level engineering is demonstrated using the modulation-doping of a deep acceptor and a shallow donor. The punch-through of the depletion region across the whole stack of modulation-doped layers shifts the Fermi level closer toward the midgap position, resulting in the compensation of residual background free carriers. The method represents an alternative to achieve semi-insulating properties in semiconductor materials where a suitable deep acceptor or donor state at the midgap position is not available. We demonstrate the applicability of the concept with a commercially important GaN case study using carbon (deep acceptor) and Si (shallow donor) doping. A strong enhancement of breakdown field strength and reduced charge pileup effects are observed due to the efficient pinning of the Fermi level. [ABSTRACT FROM AUTHOR]

Control of the charge state of the nitrogen-vacancy (NV) center is crucial because of its instability and its transitions between the negative (NV–) and neutral (NV0) NV charge states under laser irradiation In this study, we fabricated an n-i-n junction, with an i-layer sandwiched between two phosphorus-doped n-layers; then, we measured the charge state of NV centers under steady state and laser irradiation in a known band structure where the Fermi energy changes gradually. The steady-state charge state measured by a nondestructive single shot exhibited stable NV– and NV0 signals when the Fermi level was even slightly above and below the transition level, respectively. This result indicates that the charge state can be significantly stabilized through band engineering. Both charge-state populations were observed only when the Fermi level was close to the transition level. Under continuous green laser irradiation, the ratio of NV– measured by the photoluminescence spectra changed gradually with the Fermi level in the depletion layer because of the balance between excitation from the laser and the supply of charge from the band. This outcome agrees reasonably with the calculated bands. Furthermore, we measured the PL spectra of the ensemble NV centers and discovered that their charge state can be well-controlled, as in the single NV center. The charge state of the i-layer at the interface can be stabilized by depositing a thin n-layer on the surface. These results would contribute significantly to improve sensor performance. [ABSTRACT FROM AUTHOR]

We report the in-plane electron transport in the MXenes (i.e., within the MXene layers) as a function of composition using the density-functional tight-binding method, in conjunction with the non-equilibrium Green's functions technique. Our study reveals that all MXene compositions have a linear relationship between current and voltage at lower potentials, indicating their metallic character. However, the magnitude of the current at a given voltage (conductivity) has different trends among different compositions. For example, MXenes without any surface terminations (Ti3C2) exhibit higher conductivity compared to MXenes with surface functionalization. Among the MXenes with –O and –OH termination, those with –O surface termination have lower conductivity than the ones with –OH surface terminations. Interestingly, conductivity changes with the ratio of –O and –OH on the MXene surface. Our calculated I–V curves and their conductivities correlate well with transmission functions and the electronic density of states around the Fermi level. The surface composition-dependent conductivity of the MXenes provides a path to tune the in-plane conductivity for enhanced pseudocapacitive performance. [ABSTRACT FROM AUTHOR]

One significant aspect that affects the performance of high‐ferrite cement is the incorporation of iron (Fe) atoms and its stabilization into the cement phases. However, the influence of Fe doping on the stability of key phases, particularly on the ettringite, remains largely unexplored requiring deeper insights into the fundamental mechanisms. The present study explored the stability of Fe‐doped AFt structure based on density functional theory calculations at different Fe dosage. The obtained results showed that the stability of AFt structure decreases by increasing Fe dosage, which is in good agreement with the previous experimental observations. The incorporation of Fe into ettringite induced a series of changes in AFt structural and electronic properties. Bond order analysis underscored stronger covalent Fe–O bonds compared to Al–O, further emphasizing changes in the material's bonding network. Notably, density of states (DOS) analysis highlights the emergence of new occupied states near the Fermi level, primarily contributed by Fe and O atoms. This increased DOS, coupled with higher electron mobility, correlates with a reduction in material stability, as observed through shifts in bonding interactions and alterations in the bonding network. These findings point toward a complex interplay of factors, including altered bonding characteristics, increased electron mobility, and changes in the electronic structure, contributing to the observed instability of Fe‐doped ettringite. [ABSTRACT FROM AUTHOR]

Possible conversion mechanism of S on the surface of N -CoP. [Display omitted] • Theoretical simulation results uncover that an introduced N element into CoP could form a shorter Co-N bond, create a higher charge number of the Co central atom, bring new defect levels, and induce the Co 3d band closer to Fermi level. • Further atomic level analysis revealed that N -CoP could form shorter Co-S bonds with sulfur species and simultaneously weaken the S S bridged bond of Li 2 S 4 and Li-S bond of Li 2 S. • The doping of CoP eventually facilitates the polysulfides conversion reaction in the discharge process and the Li 2 S oxidation in the charge process. Lithium polysulfide (LiPSs) shuttle effect and difficulties with Li 2 S oxidation are hinder the marketization of lithium-sulfur batteries. We suggest using a bidirectional catalyst in the sulfur host to solve these problems. We produced a nitrogen-doped cobalt phosphide (N -CoP@NC) as a sulfur carrier in this work. The introduction of nitrogen into cobalt phosphide enhances the electron transmission speed and forms shorter Co-N bonds. As a result, new defect energy levels are introduced, leading to an increase in the charge number of Co central atoms, which abate the Li-S and S S bonds in Li 2 S and Li 2 S 4 , thereby promoting the oxidation of Li 2 S during charging, as well as the alteration process of LiPSs during charge and discharge. Additionally, the crystal flaws that result in increased Co-S bond formation help to boost polysulfides' adsorption ability. The Li-S batteries shows outstanding cyclability when paired with this electrocatalyst, demonstrating a minimal capacity degradation rate of only 0.07 % per cycle over 500 cycles at a rate of 0.5C. As a result, incorporating anion doping in the host emerges as a promising method for crafting materials tailored for Li-S batteries. [ABSTRACT FROM AUTHOR]

Atomic‐level tailoring of active sites is an efficient strategy for designing high‐performance photocatalysts for clean energy. Asymmetric atomic sites (AAS) like MSA‐Ov‐M2 created through hetero‐metal single atoms (MSA) doping on defect‐rich metal oxides (M2‐Ov‐M2) are favored for better activation of targeted molecules. However, creating AAS typically demands high energy input, hindering their widespread use in photocatalytic H2 production. Furthermore, precise control over surface defects to create AAS remains challenging. Here, CuSA‐Ov‐Ti3c highly asymmetric atomic sites catalyst (HAASC) is constructed by strategically trapping Cu single atoms on high‐index (111) faceted TiO2. This material combines single‐atom catalysis and facet engineering, achieving unprecedented H2 production rates (8.3 mmol h−1 g−1 in pure water and 784.5 mmol h−1 g−1 in water/methanol mixture). Experimental and theoretical analyses reveal CuSA substituting five‐coordinated Ti atoms (Ti5c) next to three‐coordinated (Ti3c) ones, forming CuSA‐Ov‐Ti3c HAAS. HAAS plays multiple roles in i) improving light harvesting, charge‐transfer dynamics, and redox capability of photoexcited electrons; ii) enhanced adsorption and polarization of H2O molecules; iii) facilitating electron transfer from CuSA‐Ov‐Ti3c to H2O molecules, and iv) raising d‐band center toward Fermi level resulting in ≈250‐fold enhanced H2 production than Ti5c‐O‐Ti3c AASC. This work opens new avenues for future structural designs in heterogeneous catalysis for energy‐related applications. [ABSTRACT FROM AUTHOR]

Chalcogenide cathodes with multi‐electron transfer characteristics are indispensable to aluminum‐ion batteries (AIBs). Nevertheless, their grievous capacity degradation and sluggish reaction kinetics remain fundamental challenges for the practical application. Herein, a Cu2S/Ni3S2 multiphase structure within the metal‐organic frame (MOF) derived carbon decoration layer (CNS@MC) is constructed to elevate the intrinsic electronic properties of chalcogenide cathode and realize high‐performance AIBs. The existence of outer carbon layer and strong orbital interaction at inner heterointerfaces eliminates the bandgap and arises more electrons at Fermi level, efficiently reducing the energy barrier for electron transfer and achieving high reactivity within cathodes. The CNS@MC also presents a strong electronic interaction with active solvent groups, which is beneficial to capture Al3+ and facilitate the three‐electron charge‐storage reactions. Experimental results demonstrate that the tailored CNS@MC cathode possesses superior redox kinetics due to the sufficient surface area and rapid Al‐ion diffusion during cycling. Meanwhile, the robust CNS@MC delivers ultra‐high electrochemical stability (131.1 mAh g−1 over 3500 cycles) with high coulombic efficiency and outstanding rate performance. This work offers new opportunities for optimizing the intrinsic properties of the chalcogenide electrodes based on MOF derivatives and heterostructure, providing novel thoughts for designing high‐performance AIBs. [ABSTRACT FROM AUTHOR]

The heterostructure of electrode materials can improve conductivity and ion transport efficiency, thereby enhanced capacitance performance. In this study, we prepared FeMn-LDH by a hydrothermal method and then obtained FeMn-LDH/Ni(OH)2 with a flower-like heterostructure by electrodeposition. This unique heterostructure greatly improves the electrochemical properties of the electrode material, which exhibits a specific capacitance of 2380.5 F g−1 at a current density of 1 A g−1, much higher than that of FeMn-LDH (1109.5 F g−1). Even at a current density of 20 A g−1, the specific capacitance of FeMn-LDH/Ni(OH)2 can still reach 1660 F g−1 with a capacitance retention of 69.9%, which is better than that of FeMn-LDH (46.2%). We then assembled FeMn-LDH/Ni(OH)2 with activated carbon (AC) to form a capacitor. The excellent energy density (49.7 Wh kg−1) and power density (750 W kg−1) proves the potential application of FeMn-LDH/Ni(OH)2. The cycling stability of capacitors is remarkably good, after 10000 cycles, its capacitance still remains 79%. Furthermore, we conducted energy band and density of states (DOS) calculations for FeMn-LDH and FeMn-LDH/Ni(OH)2. The results indicated that the inclusion of Ni(OH)2 enhanced the conductivity of the FeMn-LDH/Ni(OH)2 materials by boosting the transmission of electrons near the Fermi energy level. [ABSTRACT FROM AUTHOR]

Coking is bottleneck problem during steam cracking processes, so strategies for online catalytic conversion of coke are vitally important for ethylene production. In this work, a method for regulating the band bap of perovskites to enhance hydroxyl radical generation is proposed to promote the catalytic conversion of coke. A series of ternary La 1- x Sr x FeO 3 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) perovskites were successfully prepared by sol-gel method. Experimental and DFT calculations show that Sr doped at A sites facilitates a reduction in the band gap and the promotion of electronic transitions in the perovskites. Moreover, water molecule adsorption, decomposition, and intermediate transition state desorption are improved. Using 10 wt % LSF-0.6 catalyst, a water flow rate of 0.167 mL/min, reaction temperature of 900 °C, and reaction time of 120 min, a coke conversion rate of 85.56% is achieved. This work provides a theoretical basis for in-situ high-efficiency coke removal. Perovskite LaFeO 3 is doped with s-block metal strontium (Sr) to regulated band gap of perovskite and move the O 2 p -band center up relative Fermi level, which enhances the generation of free ·OH radicals and the efficient in-situ conversion of coke. [Display omitted] [ABSTRACT FROM AUTHOR]

Asymmetric‐type UV photodetectors have attracted extensive interest for their applications in modern optoelectronics. Conventional fabrication approaches for asymmetric metal contacts typically cause damage at the metal‐semiconductor interface, leading to Fermi level pinning and further limiting barrier height adjustability and functionality. Herein, for the first time, van der Waals (vdW) asymmetric metal contact on wide bandgap semiconductor gallium‐nitride (GaN) is successfully fabricated and achieve the mitigation of Fermi level pinning effect through the formation of a damage‐free metal‐semiconductor interface. Scanning transmission electron microscopy reveals an atomically clean and sharp interface with a distinct vdW gap between the semiconductor and metal electrode. More importantly, the absence of interface damage effectively suppresses charge recombination and results in substantial enhancement in photoresponse characteristics, demonstrating an increased responsivity from 1.8 to 56.7 A W−1 along with a significantly improved response/recovery time from 545/115 to 420/20 ms and an ultralow dark current at the picoampere‐level compared to that of the photodetector with electrodes fabricated with traditional e‐beam evaporated technique. Such simultaneously enhanced responsivity and response speed overcome the responsivity‐speed trade‐off in asymmetric photodetectors and mark a milestone in integrating asymmetric metal contacts with semiconductors through a non‐destructive manner, offering unparalleled opportunities for developing high‐performance asymmetric optoelectronic systems. [ABSTRACT FROM AUTHOR]

In the realm of materials science, a fascinating class of substances known as topological nodal line semimetals have garnered significant attention. These materials possess distinctive quantum states, characterized by topologically nontrivial conduction and valence bands that intricately intersect with the Fermi level. Such unique band structures give these materials a plethora of surprising properties, including the emergence of flat Landau levels and the appearance of long‐range Coulomb interactions. Notably, certain bulk materials, namely PbTaSe2, ZrSiS, PtSn4, and Cu2Si, exhibit these intriguing topological nodal lines. However, the theoretical investigation pertaining to CuSe and its Dirac nodal line properties remains relatively limited. In this work, we have employed simulations on CuSe to elucidate its distinctive physical properties such as a Dirac matter. There exist Dirac bands and band inversion in the vicinity of Fermi levels, and Fermi surface holds a Horn‐like structure. We pointed out the occurrence of mirror reflection symmetry‐protected Dirac nodal line fermions in copper selenide (CuSe) that make CuSe a candidate for Dirac nodal line fermion started by the Se 4p and Cu 3d orbitals. The nontrivial topological edge states further verify our proposal of the mirror reflection symmetry is broken by spin‐orbit coupling. These findings provide a new perspective that advances our comprehension of the remarkable properties exhibited by these materials, thereby paving the way for the development of high‐speed and low‐dissipation devices in the future. [ABSTRACT FROM AUTHOR]

Calcium oxide (CaO) is a promising host for quantum defects because of its ultrawide bandgap and potential for long spin coherence times. Using hybrid functional calculations, we investigate the intrinsic point defects and how they limit Fermi-level positions and doping in CaO. We find calcium and oxygen vacancies to be the most common intrinsic defects, acting as compensating acceptors and donors, respectively. Oxygen interstitials are also prevailing under O-rich conditions and act as compensating donors. Due to compensation by these defects, O-poor conditions are required to dope CaO n-type, while O-rich conditions are required for p-type doping. We find that, at room temperature, intrinsic CaO can only achieve Fermi-level positions between 1.76 eV above the valence-band maximum (VBM) and 1.73 eV below the conduction-band minimum (CBM). If suitable shallow dopants are found, the allowed range of Fermi levels would increase to between VBM + 0.53 eV and CBM − 0.27 eV and is set by the compensating intrinsic defects. Additionally, we study hydrogen impurities, and show that hydrogen will not only limit p-type doping but can also act as shallow donor when substituting oxygen ( H O defects). [ABSTRACT FROM AUTHOR]

The composite MoO 3 / Me MoO 4 (Me = Cu, Ni, Co, Fe, and Mn) ceramics were obtained by standard high-temperature sintering. Their structure was tested using XRD, SEM, EDS, and XPS. The occurrence of two phases was determined. The main MoO 3 phase exhibited an orthorhombic Pnma space group related to the ceramic grain of micrometre size. The second phase was induced by doping with the Me atom. It showed various monoclinic structures and a smaller grain size. The XPS test confirmed the coexistence of the phases, which was reflected in several lines in the patterns. The valence band of the undoped MoO 3 was located ∼3.3 eV below the Fermi level. An additional subband attributed to the Me 3d state was detected within the energy gap. The MoO 3 / Me MoO 4 composites showed a valence band shifted toward the Fermi level and overlapped with the subband, originating from hybridized Mo 4d – Me 3d states. Magnetic susceptibility showed an antiferromagnetic state below ∼20 K for the Ni- and Fe-doped composites. The estimated magnetic moment magnitudes indicated the contribution from Me 2+ and Me 3+ ions that marked the occurrence of oxygen vacancies. Diffuse reflectance spectra exhibited anomalies in the Vis (∼500–650 nm) and the NIR (∼700–850 nm) ranges and tails in the ∼900–1000 nm range. The estimated magnitudes of energy gaps were attributed to defect-induced states. They corresponded to deduced oxygen vacancies (2.05–2.38 eV) and states or subbands induced by the introduced Me atoms (1.34–1.89 eV). Electric dc resistivity temperature dependence showed thermally activated dependence. The estimated activation energy varied from 0.27 eV to 0.58 eV, depending on the doping of the Me atom. The electric features were consistent with the electronic structure determined using XRD and XPS tests. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, we report the design and fabrication of self-powered binary response PDs based on II-type heterostructures consisting of SnS x nanoflakes (NFs) and rutile TiO 2 nanorod arrays (NRs). The TiO 2 NRs effectively block light with wavelengths below 400 nm from reaching SnS x. Under 385 nm light, the photoelectrons in TiO 2 recombine with holes in SnS x at the interface due to the energy band bending, resulting in a positive photocurrent. Under 410 nm light, the photoelectrons in SnS x and the photogenerated holes in TiO 2 accumulate at the interface, overcoming the interfacial potential barriers induced by the higher Fermi levels of SnS x and inducing a negative photocurrent. Based on the bipolar response, the dual-band imaging capability without external filters and the light-encrypted OR, AND, and NOT logic gates using a single device are demonstrated. This work provides a blueprint for the development of multifunctional self-powered PDs that can simplify system architecture, reduce the energy consumption, and improve accuracy for applications, such as visual systems, light-controlled logic circuits, and encrypted optical communications. [ABSTRACT FROM AUTHOR]

Tunable electromagnetically induced transparency-like (EIT-like) metamaterials exhibit extremely high modulation depth and sensitivity, and are widely applied in sensors, modulators and filters. However, frequency shift may occur in the process of regulation, and this law has not been discovered yet. In this work, we reveal the law of frequency shift in tunable EIT-like metamaterials. Based on bright-dark coupling mode and bright-bright coupling mode, two EIT-like metamaterials with simple structures are proposed. The transmission amplitude and frequency of EIT-like effect can be dynamically controlled by tuning the Fermi level of graphene. The law reveals that the frequency of EIT-like effect shifts only when the damping rates of both coupling modes change and the change of one damping rate cannot shift the EIT-like effect. The conclusion can be verified by two-particle model. Due to the universality in tunable EIT-like metamaterials, the law can reduce the blindness of building models in metamaterials and improve the efficiency of structural design. Our work shows great practical prospect in terahertz modulators, optical switches and buffers. [ABSTRACT FROM AUTHOR]

In this paper, we propose a tunable metal-graphene hybrid metamaterial modulator based on the electromagnetically induced transparency (EIT) effect, which can be applied in the terahertz modulation field. The device consists of a U-shaped sliver strip and a rectangular sliver ring. The proposed structure is coupled by bright-bright EIT mode to generate a narrow-band electromagnetically induced transparent window. In the modulation process, the transparent window only changes in amplitude, keeping the resonant frequency constant and improving the device's resistance to interference. Active tunability is achieved by adjusting the bias voltage to alter the Fermi level of the graphene film layer, thereby facilitating modulation performance adjustment. The transparent window has a narrow bandwidth of 0.053 THz, with the transparent peak located at 0.773 THz. The maximum modulation depth of the proposed device is 74.1% and the maximum positive group delay in the transparent window can reach 0.01 ns. The designed structure has the advantages of terahertz modulation and slow light field due to its narrow-band tunability. This work provides a potential solution for electromagnetic wave control for 6G wireless communication. [ABSTRACT FROM AUTHOR]

In this study CoZrMnSb, a quaternary Heusler alloy has been explored utilizing the density functional theory based simulation package WIEN2k. The structural analysis exhibits an X1-type structure with a relaxed lattice constant of 6.27 Å in ferromagnetic phase. The band structure calculations show its half-metallic nature with full spin polarization states around the Fermi level at 0.56 eV energy. In addition, the magnetic moment is calculated to be 1.0 μB, which is in accordance with the Slater Pauling rule (Mtot = (Ztot–24) μB). The study shows the d-d hybridization of the transition metals Co, Zr, and Mn elements. Further, optoelectronic performances in terms of dielectric function, reflectivity, energy loss function, absorption coefficient have been determined for a range of photon energy up to12 eV (ultraviolet region). In optoelectronic applications, absorption of this material in visible light enhances its significance. The thermoelectric properties with chemical potential and thermodynamic properties in the pressure range of 0–40 GPa and temperature range of 0–1200 K have been analysed. Specific heat capacity and Debye temperature authenticate similar metallic behaviour of CoZrMnSb alloy at temperature versus pressure variations. At room temperature, the chemical potential study suggests high figure of merit ~ 0.9, which makes it a potential thermoelectric material. The suggested material has a high Seebeck coefficient and low thermal conductivity, making it a better match for waste heat recovery and spintronic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] α -Sn is an elemental topological material, whose topological phases can be tuned by strain and magnetic field. Such tunability offers a substantial potential for topological electronics. However, InSb substrates, commonly used to stabilize α -Sn allotrope, suffer from parallel conduction, restricting transport investigations and potential applications. Here, the successful MBE growth of high-quality α -Sn layers on insulating, hybrid (001) CdTe/GaAs substrates, with bulk electron mobility approaching 20000 cm2V−1s−1 is reported. The electronic properties of the samples are systematically investigated by independent complementary techniques, enabling thorough characterization of the 3D Dirac (DSM) and Weyl (WSM) semimetal phases induced by the strains and magnetic field, respectively. Magneto-optical experiments, corroborated with band structure modelling, provide an exhaustive description of the bulk states in the DSM phase. The modelled electronic structure is directly observed in angle-resolved photoemission spectroscopy, which reveals linearly dispersing bands near the Fermi level. The first detailed study of negative longitudinal magnetoresistance relates this effect to the chiral anomaly and, consequently, to the presence of WSM. Observation of the π Berry phase in Shubnikov-de Haas oscillations agrees with the topologically non-trivial nature of the investigated samples. Our findings establish α -Sn as an attractive topological material for exploring relativistic physics and future applications. [ABSTRACT FROM AUTHOR]

The recent emergence of two-dimensional metal-organic framework (MOF) materials with nontrivial magnetic and electronic properties has attracted great interest in spintronics. Here, we theoretically demonstrate the synthesis of a coloring-triangle latticed 2D MOF by assembling 2,3,6,7,10,11-hexahydroxytriphenylene (H6HOTP) species and threefold coordinated Mn atoms, namely, 2D Mn-HOTP. The electronic structure calculations shown that 2D Mn-HOTP exhibits coexistence of bipolar magnetic semiconducting and topological behavior. 2D Mn-HOTP is an intrinsic bipolar magnetic semiconductor with a small spin-flip band gap of 0.21 eV and relatively large spin-conserving band gaps of 0.34 and 0.74 eV. Electrical/hole doping can induce the transformation of 2D Mn-HOTP into half-metal conduction with controllable spin polarization direction. In addition, the organic HOTP ligands containing coloring-triangle lattice enable the formation of p-orbital single polarized Dirac cones and flat bands, which exhibit the topological properties such as nonzero Chern number and nontrivial edge states near the Fermi level. The Dirac points and flat bands can be selectively detected at the Fermi level with experimentally achievable electron and hole concentrations of 5.19 and 0.91 × 1013 cm−2, respectively. These results not only highlight that 2D Mn-HOTP MOF is a promising candidate for developing spintronic devices but also provide an ideal platform to explore kagome-like correlated quantum states. [ABSTRACT FROM AUTHOR]

The valence band (VB) structure of an Al0.5TiZrPdCuNi high-entropy alloy (HEA) obtained using x-ray photoelectron spectroscopy has been compared to that recently calculated by Odbadrakh et al. [J. Appl. Phys. 126, 095104 (2019)]. Both the experimental and theoretical VBs show a split-band structure, typical for alloys consisting of the early (TE) and late (TL) transition metals. Accordingly, several electronic structure (ES) properties of this alloy, both in the glassy and crystalline state, are compared with those of similar TE-TL alloys. The comparison shows a strong effect of alloying with Al on the density of states at the Fermi level, N(EF), and on the magnetic susceptibility of Al0.5TiZrPdCuNi HEA, similar to that in conventional glassy alloys, such as Zr-Cu-Al ones. Despite some similarity in the theoretical and experimental density of states of the VBs, there are significant differences between them, which should be taken into account in any future studies of ES in HEAs and other compositionally complex alloys. [ABSTRACT FROM AUTHOR]

Recently, a three dimensional metal-organic framework (MOF) based on Dy(III) and the L-tartrate ligand was experimentally shown to exhibit a spin polarization (SP) power of 100% at room temperature. The material's spin filtering ability was ascribed to the chiral-induced spin selectivity (CISS) effect. In this work, we computationally characterize the electronic structure of this MOF, revealing that the high SP of the material is linked to the asymmetric arrangement, around the Fermi level, of the alpha- and beta-spin electron states arising from the 4f-states of the lanthanide Dy atom, which results in two different conduction channels (band gaps) for each spin state. Based on the understanding gathered in this work, we propose that the substitution of the hydroxyl groups of the ligand by mercaptan groups should boost the electrical conductivity, while retaining the spin filtering power of the material. Recently ideal spin filtering ability was demonstrated in the Dy-L-Tar metal-organic framework. In this work the authors show that this unusual effect emerges from the asymmetric display of alpha and beta spin states around the Fermi level, composed of the f states of the lanthanide. [ABSTRACT FROM AUTHOR]

Benefited from the lower dimensionality compared to their 3D counterpart, 2D flat‐band systems provide cleaner lattice models, easier experimental verification, and higher tunability, which make the 2D van der Waals (vdW) system an ideal playground for exploring flat‐band physics as well as their potential applications. Given the vast amount of research in the field of flat bands, a simple and efficient approach to search for realistic vdW materials with flat bands is still missing. Here, a two‐tier framework to filter and diagnose high‐quality flat‐band vdW materials by combining high‐throughput first‐principles calculations and the proposed 2D flat‐band score criterion is presented. Based on systematic geometrical analysis, 861 potential monolayer vdW materials are initially obtained amounting to 187,093 structures as stored in the Inorganic Crystal Structure Database. By applying the 2D flat‐band score criterion, 229 flat‐band candidates are efficiently identified, among which a sub‐catalog of 74 materials with flat bands right next to the Fermi level is further provided to facilitate experimental verification. All these efforts to screen experimentally available flat‐band candidates will certainly motivate continuing exploration toward the realization of this class of special materials and their applications in material science. [ABSTRACT FROM AUTHOR]

The Superatom Molecular Orbitals (SAMO) in fullerene derivatives are of great interests which gives a wide basement for many electronic applications. In this work, the Density Functional Theory reveals the SAMO states of endohedrally doped C80 derivatives with Li, Sc, Mn, Ti, Ca, Fe, and Co atoms in molecular and periodic structures. The choice and position of metal atoms in endohedrally doped C80 derivatives largely affects the orientation of SAMO energies and wavefunction distributions. Among various derivatives, the Co‐substituted C80 constitutes the lowest SAMO energy. The charge transfer study infers the influence of metal atoms inside the cage on SAMO energies. At higher energies, pz‐, 2s‐, and pxy‐ SAMO bands have been overlapped with higher dispersion bands which depict the increased intermolecular interaction in delocalized bands causing a larger dispersion. These results give new insights for future studies on lowering SAMO energy nearly to the fermi level in higher fullerenes. [ABSTRACT FROM AUTHOR]

The electronic structure of 7/9-AGNR superlattices with up to eight unit cells has been studied by means of state-of-the-art Density Functional Theory (DFT) and also by two model Hamiltonians, the first one including only local interactions (Hubbard model, Hu) while the second one is extended to allow long-range Coulomb interactions (Pariser, Parr and Pople model, PPP). Both are solved within mean field approximation. At this approximation level, our calculations show that 7/9 interfaces are better described by spin non-polarized solutions than by spin-polarized wavefunctions. Consequently, both Hu and PPP Hamiltonians lead to electronic structures characterized by a gap at the Fermi level that diminishes as the size of the system increases. DFT results show similar trends although a detailed analysis of the density of states around the Fermi level shows quantitative differences with both Hu and PPP models. Before improving model Hamiltonians, we interpret the electronic structure obtained by DFT in terms of bands of topological states: topological states localized at the system edges and extended bulk topological states that interact between them due to the long-range Coulomb terms of Hamiltonian. After careful analysis of the interaction among topological states, we find that the discrepancy between ab initio and model Hamiltonians can be resolved considering a screened long-range interaction that is implemented by adding an exponential cutoff to the interaction term of the PPP model. In this way, an adjusted cutoff distance λ = 2 allows a good recovery of DFT results. In view of this, we conclude that the correct description of the density of states around the Fermi level (Dirac point) needs the inclusion of long-range interactions well beyond the Hubbard model but not completely unscreened as is the case for the PPP model. [ABSTRACT FROM AUTHOR]