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The electronic structure and magnetic property of the Mn doped β-Ga2O3
摘要： Ga2O3 is a promising candidate for high power, high voltage devices. In this work, the band structure of the pure β-Ga2O3 and the impact of orbital coupling on the Mn doped β-Ga2O3 electronic structure are analyzed based on density functional theory. The Mn dopant induces impurity bands near the band edge, resulting in the decrease of the band gap of the Ga2O3. When the Mn dopants only substitute the octahedrally coordinated Ga atoms, the doped systems possess the most stable structure and the ferromagnetism, the Monte Carlo simulation predicts that the Curie temperature is 421K. The room temperature ferromagnetism can be ascribed to the strong p-d coupling and the delocalization of O-2p orbital. The oxygen vacancy and gallium vacancy can induce the deep donor level and acceptor level into the band gap, respectively. Due to the valence change of Mn dopant, the Mn dopant undergoes a transition from donor to acceptor when the substrate obtains more carriers. Our results not only explain the observed electronic and magnetic properties in experiment, but also provide a theoretical model for designing high performance Ga2O3 based devices.
关键词： β-Ga2O3,Density Functional Theory,Electronic Structure,Ferromagnetism
更新于2025-09-10 09:29:36
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Fingerprinting electronic structure of heme iron by ab initio modeling of metal L-edge X-ray absorption spectra
摘要： The capability of the multiconfigurational restricted active space approach to identify electronic structure from spectral fingerprints is explored by applying it to iron L-edge X-ray absorption spectroscopy (XAS) of three heme systems that represent the limiting descriptions of iron in the Fe-O2 bond, ferrous and ferric [Fe(P)(ImH)2]0/1+ (P = porphine,ImH = imidazole), and FeII(P). The level of agreement between experimental and simulated spectral shapes is calculated using the cosine similarity, which gives a quantitative and unbiased assignment. Further dimensions in fingerprinting are obtained from the L-edge branching ratio, the integrated absorption intensity, and the edge position. The results show how accurate ab initio simulations of metal L-edge XAS can complement calculations of relative energies to identify unknown species in chemical reactions.
关键词： multiconfigurational restricted active space,branching ratio,integrated absorption intensity,iron L-edge X-ray absorption spectroscopy,electronic structure,cosine similarity,edge position,heme systems,spectral fingerprints
更新于2025-09-10 09:29:36
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Single Crystal Growth and Characterization of the Chalcopyrite Semiconductor CuInTe2 for Photoelectrochemical Solar Fuel Production
摘要： Transition metal chalcogenides are a promising family of materials for applications as photocathodes in photoelectrochemical (PEC) H2 generation. A long-standing challenge for chalcopyrite semiconductors is characterizing their electronic structure—both experimentally and theoretically—due to their relatively high energy bandgaps and spin orbit coupling (SOC), respectively. In this work, we present single crystals of CuInTe2, whose relatively small optically measured bandgap of 0.9 ± 0.03 eV enables electronic structure characterization by angle-resolved photoelectron spectroscopy (ARPES) in conjunction with first-principle calculations incorporating SOC. ARPES measurements reveal bands that are steeply dispersed in energy with a band velocity of 2.5-5.4 x 105 m/s, almost 50% of the extremely conductive material graphene. Additionally, CuInTe2 single crystals are fabricated into electrodes to experimentally determine the valence band edge energy and confirm the thermodynamic suitability of CuInTe2 for water redox chemistry. The electronic structure characterization and band edge position presented in this work provide kinetic and thermodynamic factors that support CuInTe2 as a strong candidate for water reduction.
关键词： photoelectrochemical H2 generation,electronic structure,spin orbit coupling,chalcopyrite semiconductors,band velocity,valence band edge energy,Transition metal chalcogenides,angle-resolved photoelectron spectroscopy,water redox chemistry,CuInTe2
更新于2025-09-10 09:29:36
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Optical Properties of Graphene/MoS2 Heterostructure: First Principles Calculations
摘要： The electronic structure and the optical properties of Graphene/MoS2 heterostructure (GM) are studied based on density functional theory. Compared with single-layer graphene, the bandgap will be opened; however, the bandgap will be reduced significantly when compared with single-layer MoS2. Redshifts of the absorption coefficient, refractive index, and the reflectance appear in the GM system; however, blueshift is found for the energy loss spectrum. Electronic structure and optical properties of single-layer graphene and MoS2 are changed after they are combined to form the heterostructure, which broadens the extensive developments of two-dimensional materials.
关键词： optical properties,graphene/MoS2 heterostructure,electronic structure
更新于2025-09-10 09:29:36
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Electronic structures and spectroscopic signatures of silicon-vacancy containing nanodiamonds
摘要： The presence of midgap states introduced by localized defects in wide-band-gap-doped semiconductors can strongly affect the electronic structure and optical properties of materials, generating a wide range of applications. Silicon-divacancy defects in diamond have been recently proposed for probing high-resolution pressure changes and performing quantum cryptography, making them good candidates to substitute for the more common nitrogen-vacancy centers. Using group-theory and ab initio electronic structure methods, the molecular origin of midgap states, zero-phonon line splitting, and size dependence of the electronic transitions involving the silicon-vacancy center is investigated in this paper. The effects of localized defects on the Raman vibrational and carbon K-edge x-ray absorption spectra are also explored for nanodiamonds. This paper presents an important analysis of the electronic and vibrational structures of nanosized semiconductors in the presence of midgap states due to localized defects, providing insight into possible mechanisms for modulating their optical properties.
关键词： midgap states,electronic structure,optical properties,nanodiamonds,Raman vibrational spectra,quantum cryptography,x-ray absorption spectra,silicon-vacancy defects
更新于2025-09-10 09:29:36
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First-principles many-body study of the electronic and optical properties of CsK <sub/>2</sub> Sb, a semiconducting material for ultra-bright electron sources
摘要： We present a comprehensive first-principles investigation of the electronic and optical properties of CsK2Sb, a semiconducting material for ultra-bright electron sources for particle accelerators. Our study, based on density-functional theory and many-body perturbation theory, provides all the ingredients to model the emission of this material as a photocathode, including band gap, band dispersion, and optical absorption. An accurate description of these properties beyond the mean-field picture is relevant to take into account many-body effects. We discuss our results in the context of state-of-the-art electron sources for particle accelerators to set the stage towards improved modeling of quantum efficiency, intrinsic emittance, and other relevant quantities determining the macroscopic characteristics of photocathodes for ultra-bright beams.
关键词： theoretical spectroscopy,electronic structure,alkali antimonides,density-functional theory
更新于2025-09-09 09:28:46
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Spin orbit coupling induced band gap in gemanene modulated by external field
摘要： We investigate the electronic band structure of germanene crystal by using the sixteen band tight-binding calculation. We focus on the modulation of its band gap with spin–orbit coupling (SOC), perpendicular electric ?eld and magnetic ?eld. Our calculation shows that the SOC opens a tunable band gap in the Dirac-type electronic structures, and plays a crucial rule in the formation of the energy band gap. The in?uence of SOC on the gap in germanene is much larger than that in graphene, which makes germanene an ideal candidate to exhibit the quantum spin Hall effect at room temperature. We also ?nd that the electronic structure and topological property of germanene can be tuned by the external ?eld signi?cantly. Thus the electronic structure of germanene can be controlled to produce metallic, semiconducting, or insulating properties by applying an appropriate external ?eld. In addition, the key features of the band structure induced by the electrical ?eld and magnetic ?eld are quite different. For the electric ?eld applied, two spin-up states produce a gap at K point, in contrast, two spin-down states do it at K′ points. While for the magnetic ?eld present, the band gaps are formed by the spin-up states from the conduction band and spin-down state from the valance band at both the K and K′ points. This modulation behavior of the band gap by the external ?eld paves a way to the realization of germanene based spintronic devices.
关键词： topological insulator,electronic structure,tight-binding model,germanene,spin-orbit coupling
更新于2025-09-09 09:28:46
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The Vacancy-Induced Electronic Structure of the SrTiO <sub/>3?δ</sub> Surface
摘要： The emergence of a 2D electron gas (2DEG) on the (001) surface of oxygen-deficient strontium titanate (SrTiO3?δ) is investigated. Using in situ soft X-ray spectroscopy and effective mass modeling, a series of quantitative band diagrams are developed to describe the evolution of near-surface and bulk carrier concentrations, downward band bending, and Fermi level along a lateral gradient of oxygen vacancies formed on SrTiO3?δ by direct-current resistive heating under ultrahigh vacuum conditions. Electrons are accumulated over a 3 nm region near the surface, confined within a potential well with saturated 300 meV downward band bending. The relation between Fermi levels and carrier concentrations near the surface suggests the density of states near the surface is much lower than the bulk density of states, which is consistent with the quantum-confined subbands of a 2DEG. The quantitative relationship between the surface and bulk electronic structures developed in this work provides a guide for precise engineering of the oxygen-vacancy-induced 2DEG in SrTiO3.
关键词： oxygen vacancies,electronic structure,in-situ x-ray spectroscopy,SrTiO3 surface,effective mass modeling
更新于2025-09-09 09:28:46
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across the quantum phase transition from topological to trivial insulator
摘要： Using spin- and angle-resolved photoemission spectroscopy and relativistic many-body calculations, we investigate the evolution of the electronic structure of (Bi1?xInx )2Se3 bulk single crystals around the critical point of the trivial to topological insulator quantum-phase transition. By increasing x, we observe how a surface gap opens at the Dirac point of the initially gapless topological surface state of Bi2Se3, leading to the existence of massive fermions. The surface gap monotonically increases for a wide range of x values across the topological and trivial sides of the quantum-phase transition. By means of photon-energy-dependent measurements, we demonstrate that the gapped surface state survives the inversion of the bulk bands which occurs at a critical point near x = 0.055. The surface state exhibits a nonzero in-plane spin polarization which decays exponentially with increasing x, and which persists in both the topological and trivial insulator phases. Our calculations reveal qualitative agreement with the experimental results all across the quantum-phase transition upon the systematic variation of the spin-orbit coupling strength. A non-time-reversal symmetry-breaking mechanism of bulk-mediated scattering processes that increase with decreasing spin-orbit coupling strength is proposed as explanation.
关键词： quantum-phase transition,topological insulator,electronic structure,photoemission spectroscopy,spin-orbit coupling
更新于2025-09-09 09:28:46
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First-principles study on the mechanics, optical, and phonon properties of carbon chains
摘要： Besides graphite, diamond, graphene, carbon nanotubes, and fullerenes, there is another allotrope of carbon, carbyne, existing in the form of a one-dimensional chain of carbon atoms. It has been theoretically predicted that carbyne would be stronger, stiffer, and more exotic than other materials that have been synthesized before. In this article, two kinds of carbyne, i.e., cumulene and polyyne are investigated by the ?rst principles, where the mechanical properties, electronic structure, optical and phonon properties of the carbynes are calculated. The results on the crystal binding energy and the formation energy show that though both are dif?cult to be synthesized from diamond or graphite, polyyne is more stable and harder than cummulene. The tensile stiffness, bond stiffness, and Young’s modulus of cumulene are 94.669 eV/ ?A, 90.334 GPa, and 60.62 GPa, respectively, while the corresponding values of polyyne are 94.939 eV/ ?A, 101.42 GPa, and 60.06 GPa. The supercell calculation shows that carbyne is most stable at N = 5, where N is the supercell number, which indicates that the carbon chain with 10 atoms is most stable. The calculation on the electronic band structure shows that cumulene is a conductor and polyyne is a semiconductor with a band gap of 0.37 eV. The dielectric function of carbynes varies along different directions, consistent with the one-dimensional nature of the carbon chains. In the phonon dispersion of cumulene, there are imaginary frequencies with the lowest value down to ?3.817 THz, which indicates that cumulene could be unstable at room temperature and normal pressure.
关键词： first-principles calculation,physical properties,electronic structure,carbyne
更新于2025-09-09 09:28:46