Comparative Studies of Rare-Earth Element Y-Doped In2O3 by First-Principles Calculations

In2O3 doped with rare-earth element yttrium shows improved optoelectronic efficiency. Here the structural properties and electronic structures of Y-doped In2O3 are investigated by using a first-principles approximation. For In1.9375 Y0.062503, the d site is the more stable site. The Y^3＋ interstitial has a low formation energy and is a possible interstitial defect, which would lead to shallow and abundant donors without sacrificing optical transparency. Since defects are universally distributed in In2O3 or doped In2O3, complex defect configurations are also calculated.     

Re effects in model Ni-based superalloys investigated with first-principles calculations and atom probe tomography

The phase partition and site preference of Re atoms in a ternary Ni-Al-Re model alloy,including the electronic structure of different Re configurations,are investigated with first-principles calculations and atom probe tomography.The Re distribution of single,nearest neighbor(NN),next-nearest neighbor(NNN),and cluster configurations are respectively designed in the models withγandγphases.The results show that the Re atoms tend to enteringγphase and the Re atoms prefer to occupy the Al sites inγphase.The Re cluster with a combination of NN and NNN Re-Re pair configuration is not preferred than the isolated Re atom in the Ni-based superalloys,and the configuration with isolated Re atom is more preferred in the system.Especially,the electronic states are analyzed and the energetic parameters are calculated.The electronic structure analyses show there exists strong Ni-Re electronic interaction and it is mainly contributed by the d-d hybridization.The characteristic features of the electronic states of the Re doping effects are also given.It is also found that Re atoms prefer the Al sites inγside at the interface.The density of states at or near the Fermi level and the d-d hybridizations of NN Ni-Re are found to be important in the systems.     

Electronic structure of hexagonal quantum—disc clusters

Within the effective-mass approximation,we investigate the electronic structure of hexagonal quantum-disc clusters using the finite element method.With an increasing amount of quantum dots in the cluster,the electronic energy levels quickly expand into mini-bands.each consisting of discrete,unevenly distributed energy levels,The corresponding electronic eigenfunctions are linear combinations of the electron orbits in each quantum dot.The spatial symmetry of the combination is the same as the electronic eigenfunctioin of a single quantum dot.     

Electronic effect of doped oxygen atoms in Bi2201 superconductors determined by scanning tunneling microscopy

Oxygen dopants are essential for tuning the electronic properties of the cuprate superconductors Bi_2Sr_2Ca_(n-1)Cu_nO_(2n+4+δ).Here,we study an optimally doped Bi_2Sr_(2-x)La_xCuO_(6+δ)and an overdoped Bi_(2-y)Pb_ySr_2CuO_(6+δ)by scanning tunneling microscopy and spectroscopy(STM/STS).Based on the characteristic features of local STS,three forms of oxygen dopants are identified:interstitial oxygen atoms on the SrO layers,oxygen vacancies on the SrO layers,and interstitial oxygen atoms on the BiO layers.In both samples,the first form dominates the number of oxygen dopants.From the extracted spatial distribution of the oxygen dopants,we calculate the dopant concentrations and estimate the average hole carrier density.The magnitudes of the electronic pseudogap state in both samples are inhomogeneously distributed in space.The statistical analysis on the spatial distributions of the oxygen dopants and the pseudogap magnitude demonstrates that the doped oxygen atoms on the SrO layers tend to suppress the nearby pseudogap magnitude.     

Electronic transmission of three-terminal pyrene molecular bridge

This paper investigates theoretically the electronic transmission spectra of the three terminal pyrene molecular bridge and the quantum current distribution on each bond by the tight-binding model based on nonequilibrium Green’s function and the quantum current density approach, in which one π molecular orbital is taken into account per carbon atom when the energy levels and HOMO-LUMO gap are obtained. The transmission spectra show that the electronic transmission of the three terminal pyrene molecular bridge depends obviously on the incident electronic energy and the pyrene eigenenergy. The symmetrical and oscillation properties of the transmission spectra are illustrated. A novel plus-minus energy switching function is found. The quantum current distribution shows that the loop currents inside the pyrene are induced, and some bond currents are much larger than the input and the output currents. The reasons why the loop currents and the larger bond currents are induced are the phase difference of the atomic orbits and the degeneracy of the molecular orbits. The calculations illustrate that the quantum current distributions are in good agreement with Kirchhoff quantum current conservation law.     

First-principles study of the optical properties of defect electronic structure and chalcopyrite CdGa2Te4

<正>The electronic and optical properties of the defect chalcopyrite CdGa₂Te₄ compound are studied based on the first-principles calculations.The band structure and density of states are calculated to discuss the electronic properties and orbital hybridized properties of the compound.The optical properties,including complex dielectric function,absorption coefficient,refractive index,reflectivity,and loss function,and the origin of spectral peaks are analysed based on the electronic structures.The presented results exhibit isotropic behaviours in a low and a high energy range and an anisotropic behaviour in an intermediate energy range.     

Quantum fluctuation of mesoscopic distributed parameter circuits

Under the Born－von-Karmann periodic boundary condition, we propose a quantization scheme for a non-dissipative distributed parameter circuit (a uniform transmission line). Quantum fluctuations of charge and current in the vacuum state are investigated by adopting the canonical transformation and unitary transformation method. Our results indicate that in distributed parameter circuits, quantum fluctuations, which also have distributed properties, are related to both the circuit parameters and the positions and the mode of signals.     

Electronic structure of twinned ZnS nanowires

The electronic properties of twinned ZnS nanowires (NWs) with different diameters were investigated based on first-principles calculations. The energy band structures, projected density of states and the spatial distributions of the bottom of conduction band and the top of the valence band were presented. The results show that the twinned nanowires exhibit a semiconducting character and the band gap decreases with increasing nanowire diameter due to quantum confinement effects. The valence band maximum and conduction band minimum originate mainly from the S-p and Zn-s orbitals at the core of the nanowires, respectively, which was confirmed by their spatial charge density distribution. We also found that no heterostructure is formed in the twinned ZnS NWs since the valence band maximum and conduction band minimum states are distributed along the NW axis uniformly. We suggest that the hexagonal (2H) stacking inside the cubic (3C) stacking has no effect on the electronic properties of thin ZnS NWs.     

Unusual electronic structure of Dirac material BaMnSb_2 revealed by angle-resolved photoemission spectroscopy

High resolution angle resolved photoemission measurements and band structure calculations are carried out to study the electronic structure of BaMnSb_2. All the observed bands are nearly linear that extend to a wide energy range. The measured Fermi surface mainly consists of one hole pocket around Γ and a strong spot at Y which are formed from the crossing points of the linear bands. The measured electronic structure of BaMnSb_2 is unusual and deviates strongly from the band structure calculations. These results will stimulate further efforts to theoretically understand the electronic structure of BaMnSb_2 and search for novel properties in this Dirac material.     

Electronic Transmission Properties of Two—Dimensional Quasi—Lattice

In the framework of the tight binding model,the electronic transmission properties of two-dimensional Penrose lattices with free boundary conditions are studied using the generalized eigenfunction method (Phys.Rev.B 60(1999)13 444).The electronic transmission coefficients for Penrose lattices with different sizes and widths are calculated,and the result shows strong energy dependence because of the quasiperiodic structure and quantum coherent effect.Around the Fermi level E=0,there is an energy region with zero transmission amplitudes,which suggests that the studied systems are insulating.The spatial distributions of several typical electronic states with different transmission coefficients are plotted to display the propagation process.