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Electron–phonon coupling in single-layer MoS2
摘要： The electron–phonon coupling strength in the spin–split valence band maximum of single-layer MoS2 is studied using angle-resolved photoemission spectroscopy and density functional theory-based calculations. Values of the electron–phonon coupling parameter λ are obtained by measuring the linewidth of the spin–split bands as a function of temperature and fitting the data points using a Debye model. The experimental values of λ for the upper and lower spin–split bands at K are found to be 0.05 and 0.32, respectively, in excellent agreement with the calculated values for a free-standing single-layer MoS2. The results are discussed in the context of spin and phase-space restricted scattering channels, as reported earlier for single-layer WS2 on Au(111). The fact that the absolute valence band maximum in single-layer MoS2 at K is almost degenerate with the local valence band maximum at Γ can potentially be used to tune the strength of the electron–phonon interaction in this material.
关键词： Density functional theory,Angle-resolved photoemission spectroscopy,Transition metal dichalcogenides,Electron-phonon coupling
更新于2025-09-04 15:30:14
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Oxyfluoro-zinc-tellurite glasses – Part I: Predicting the elastic properties and glass transition temperature under the substitution of AlF3 by ZnO
摘要： An extensive study has been carried out to predict the elastic properties and glass transition temperature of oxyfluoro-zinc-tellurite (10-x)AlF3-xZnO-90TeO2 (1 ≤ x ≤ 9), (30-x)AlF3-xZnO-70TeO2 (5 ≤ x ≤ 25), (35-x)AlF3-xZnO-65TeO2 (10 ≤ x ≤ 30) and (40-x)AlF3-xZnO-60TeO2 (15 ≤ x ≤ 35) glass systems, for the first time. Changes in the elastic moduli, Poisson’s ratio and glass transition temperature due to the substitution of AlF3 by ZnO have been discussed in terms of molar volume, fractal bond connectivity, packing density and dissociation energy per unit volume of the glass. The correlation between theoretically calculated and experimentally measured elastic moduli and Poisson's ratio has also been studied on the basis of Makishima-Mackenzie’s theory and Rocherulle et al. model. The composition dependence of fractal bond connectivity suggested that the studied oxyfluoro-zinc-tellurite glasses have an intermediate dimensionality between three- and two-dimensional structures. Both AlF3 and ZnO are incorporated into the tellurite network as network modifiers. This results is the conversion of TeO4 trigonal bipyramids into TeO3+1 polyhedral and then to TeO3 trigonal pyramids through breaking of TeeOeTe linkages and creation of non-bridging oxygen atoms. In addition to this, both Makishima-Mackenzie's theory and Rocherulle et al. model appear to be applicable for all the investigated glass systems. The agreement between theoretical and experimental values of elastic moduli and Poisson's ratio is excellent for majority of the samples.
关键词： Rocherulle et al. model,Elastic properties,Makishima–Mackenzie’s theory,Oxyfluorotellurite glasses
更新于2025-09-04 15:30:14
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Photoelectron Spectroscopy and Theoretical Study of Cr <sub/><i>n</i> </sub> Si <sub/> 15– <i>n</i> </sub><sup>–</sup> ( <i>n</i> = 1–3): Effects of Doping Cr Atoms on the Structural and Magnetic Properties
摘要： CrnSi15?n? (n = 1?3) clusters were investigated by using size-selected anion photoelectron spectroscopy combined with density functional theory calculations. The results show that the most stable structure of CrSi14? is of C2v symmetry with the Cr atom encapsulated in a Si14 cage which can be viewed as a boat-shaped Si10 unit capped by four additional silicon atoms. A large HOMO?LUMO gap of neutral CrSi14 is confirmed based on the photoelectron spectrum of CrSi14?. Cr2Si13? has two isomers nearly degenerate in energy: one can be characterized as one Si atom interacting with a Cr2Si12 hexagonal prism while the other can be viewed as one Si atom capping a distorted Cr2Si12 hexagonal antiprism. Cr3Si12? has a D6d symmetric wheel structure in which three Cr atoms form an axle surrounded by 12 Si atoms. The magnetic moments of CrSi14?, Cr2Si13?, and Cr3Si12? increase from 1 to 3 μB and then to 7 μB with the increasing number of Cr atoms in the clusters. The magnetic moments of Cr2Si13? and Cr3Si12? are mainly contributed by the surface Cr atoms.
关键词： Photoelectron spectroscopy,Silicon clusters,Chromium doping,Density functional theory,Magnetic properties
更新于2025-09-04 15:30:14
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Facile Production of Mesoporous WO3-rGO Hybrids for High-Performance Supercapacitor Electrodes: An Experimental and Computational Study
摘要： This work explored a promising supercapacitor electrode material (WO3-rGO hybrids) synthesized by simplistic one-pot hydrothermal synthesis route. Various analytical studies (X-ray diffraction study, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray photo-electron spectroscopy, Brunauer-Emmett-Teller analysis) were employed in furtherance to explore the structural, morphological, compositional and surface areal property of the prepared materials. The enhancement in electrochemical supercapacitive properties were evaluated from pure hexagonal phased WO3 to the various hybrids depending upon the concentration of GO introduced into it, using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The WG-80 composite revealed the high-rise in capacitance value of 801.6 F/g overcoming the individual capacitance of rGO (71.11 F/g) and WO3 (94.22 F/g) at a current density of 4 A/g with a good cycling stability (75.7 %) over 5000 cycles. We have presented quantum capacitance from ab-initio calculations and provided theoretical explanation from the orbital interactions.
关键词： WO3-rGO hybrids,Density functional theory,Hydrothermal method,Supercapacitor
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Antenna Effective Area for Spherical Waves
摘要： Antenna power response to incident waves can be described with the effective area. While the effective area widely used is for uniform plane waves, the effective area can be de?ned also for uniform spherical waves. We introduce the effective area as a function of the direction and the curvature of an incident wave. The spherical-wave effective area is suitable for the antenna fundamental relation and the Friis transmission formula, and extends their interpretation.
关键词： antenna theory,reciprocity,antenna property
更新于2025-09-04 15:30:14
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Band Gap Control in Bilayer Graphene by Co-Doping with B-N Pairs
摘要： The electronic band structure of bilayer graphene is studied systematically in the presence of substitutional B and/or N doping, using density functional theory with van der Waals correction. We show that introduction of B-N pairs into bilayer graphene can be used to create a substantial band gap, stable against thermal fluctuations at room temperature, but otherwise leaves the electronic band structure in the vicinity of the Fermi energy largely unaffected. Introduction of B-N pairs into B and/or N doped bilayer graphene likewise hardly modifies the band dispersions. In semiconducting systems (same amount of B and N dopants), however, the size of the band gap is effectively tuned in the presence of B-N pairs.
关键词： density functional theory,van der Waals correction,band gap,B-N doping,bilayer graphene
更新于2025-09-04 15:30:14
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Controlling light in Airy and higher-order caustic photonic structures
摘要： Caustics form geometrically stable structures in light and are hierarchically categorized by the catastrophe theory. We embed higher-order cusp and swallowtail catastrophes in paraxial beams and investigate their dynamics. Utilizing high-intensity caustics that propagate on curved trajectories, we realize photonic caustic lattices in photosensitive media, and demonstrate waveguiding with a rich diversity of light guiding paths.
关键词： caustics,photonic structures,waveguiding,catastrophe theory,nonlinear photonics
更新于2025-09-04 15:30:14
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Charge transfer across monolayer/bilayer MoS<sub>2</sub> lateral interface and its influence on exciton and trion characteristics
摘要： The charge transfer phenomenon is identified to be a major factor determining exciton and trion characteristics of atomically thin MoS2 layers in various stacking configurations. We report photoluminescence (PL) from CVD-grown layered MoS2 in the presence of a skewed or a deformed triangular-shaped monolayer/bilayer (1L/2L) lateral interface. Integrated PL mapping images over the 1L and 2L MoS2 regions revealed that the neutral exciton emission was significantly enhanced and exhibited an oscillatory behavior in its intensity in the 1L region near the 1L/2L boundary, whereas the negative trion emission remained unchanged. The interplays among the number of MoS2 layers, a substrate, and a geometric boundary structure of the 1L/2L lateral interface turned out to be important in charge transfer due to a modulation in work functions. As a result, PL intensity profiles showed rich features such as a stacking dependent decomposition of excitons and trions, a sharp spectroscopic contrast along the 1L/2L boundary, and a charge transfer relevant to the work function difference at the lateral interface. Our results demonstrate that understanding the MoS2 PL is useful in characterizing the electronic properties in two-dimensional layered nanostructures and sheds light on possible new device applications.
关键词： density functional theory,work function,charge transfer,MoS2,exciton
更新于2025-09-04 15:30:14
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Resonant inelastic scattering of two x-ray photons by a many-electron atom
摘要： A nonrelativistic variant of the quantum theory for the resonant inelastic-scattering process of two x-ray photons in the deep 1s-shell ionization threshold energy region of a free many-electron atom is established. A quantitative estimate for the magnitude of the observed differential cross section is given.
关键词： differential cross section,quantum theory,resonant inelastic scattering,many-electron atom,x-ray photons
更新于2025-09-04 15:30:14
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Quantitative mobility evaluation of organic semiconductors using quantum dynamics based on density functional theory
摘要： We present an order-N methodology to evaluate mobilities of charge carriers coupled with molecular vibrations using quantum dynamics based on first-principles calculations that can be applied to micron-scale soft materials. As a demonstration, we apply it to several organic semiconductors and show that the calculated intrinsic hole mobilities and their temperature dependences are quantitatively in good agreement with those obtained in experiments. We also clarified which vibrational modes dominate the transport properties. The methodology paves the way for quantitative prediction of the transport properties of various soft materials.
关键词： quantum dynamics,density functional theory,charge-carrier mobility,organic semiconductors,molecular vibrations
更新于2025-09-04 15:30:14