圆柱形散射子二维光子晶体的态密度与局域态密度

二维光子晶体只有赝带隙,因此能否利用二维光子晶体有效控制原子自发辐射是令人感兴趣也是有实际意义的问题。其中最重要的因素是态密度和局域态密度的性质。采用平面波展开结合晶体群论的方法计算了二维正方格子光子晶体的态密度和局域态密度。其中散射子为空气圆柱,放置在均匀的电介质背景上。结果显示两个特点:第一,总态密度和局域态密度在原来二维光子晶体赝带隙处虽然已经不为零,但是取值明显低于赝带隙范围之外的值,即存在一个准光子带隙。第二,局域态密度在空气散射子界面处发生突变,空气散射子区域的局域态密度相对较大,这可由电位移矢量的连续性来理解。由于这两个特点在其他二维光子晶体中也被发现过,它们可能是普遍存在的。     

硼烯纳米带能带结构和态密度的第一性原理研究

基于密度泛函理论,采用第一性原理的方法计算H修饰边缘不同宽度硼稀纳米带的电荷密度、电子能带结构、总态密度和分波态密度。结果表明,硼烯纳米带的宽度大小影响着材料的导电性能,宽度5的硼烯纳米带是间接带隙简并半导体,带隙值为0.674 eV,而宽度7的硼烯纳米带却具有金属材料的性质。分波态密度表明,宽度5的硼烯纳米带的费米能级附近主要是由B-2s、2p电子态贡献,H-1s主要贡献于下价带且具有局域性,消除了材料边缘的不稳定性。宽度7的B-2p和H-1s电子态贡献的导带和价带处于主导地位,费米能级附近B-2p和H-1s电子态的杂化效应影响材料的整体发光性能。     

氧化石墨烯纳米带能带结构和态密度的第一性原理研究

基于密度泛函理论,采用第一性原理方法,计算了氧化石墨烯纳米带的电荷密度、能带结构和分波态密度。结果表明,石墨烯纳米带被氧化后,转变为间接带隙半导体,带隙值为0.375 e V。电荷差分密度表明,从C原子和H原子到O原子之间有电荷的转移。分波态密度显示,在导带和价带中C-2s、2p,O-2p,H-1s电子态之间存在强烈的杂化效应。在费米能级附近,O-2p态电子局域效应的贡献明显,对于改善氧化石墨烯纳米带的半导体发光效应起到了主要作用。     

On the theory of the adsorption of atoms onto a metal surface in the presence of an external quantizing magnetic field

The Anderson-Newns model for the adsorption of atoms onto metals is generalized to the case of the presence of an external transverse quantizing magnetic field. Analytical expressions for the density of metal states in the external magnetic field are obtained. Analytical expressions for the density of adatom states are obtained in the approximation taking only the change in the density of substrate states into account. The charge exchange between the adatom and the metal is studied. The dependences of the density of adatom and transition-charge states on the magnetic field are studied for different values of the interaction constant. An analytical expression for the density of substrate states perturbed by adsorption is obtained.     

Charge densities and charge noise in mesoscopic conductors

We introduce a hierarchy of density of states to characterize the charge distribution in a mesoscopic conductor. At the bottom of this hierarchy are the partial density of states which represent the contribution to the local density of states if both the incident and the out-going scattering channel is prescribed. The partial density of states play a prominent role in measurements with a scanning tunneling microscope on multiprobe conductors in the presence of current flow. The partial density of states determine the degree of dephasing generated by a weakly coupled voltage probe. In addition the partial density of states determine the frequency-dependent response of mesoscopic conductors in the presence of slowly oscillating voltages applied to the contacts of the sample. The partial density of states permit the formulation of a Friedel sum rule which can be applied locally. We introduce the off-diagonal elements of the partial density of states matrix to describe charge fluctuation processes. This generalization leads to a local Wigner-Smith life-time matrix.     

Tunneling density of States of the interacting two-dimensional electron gas

We investigate the influence of electron-electron interactions on the density of states of a ballistic two-dimensional electron gas. The density of states is determined nonperturbatively by means of path integral techniques allowing for reliable results near the Fermi surface, where perturbation theory breaks down. We find that the density of states is suppressed at the Fermi level to a finite value. This suppression factor grows with decreasing electron density and is weakened by the presence of gates.     

The density of states in the mobility gap of amorphous-silicon films computed by a new analytical method

Summary The field effect technique has been used to measure the density of states in the mobility gap of silicon films. We used a new method to compute the density of states distribution. The method is based on an analytical solution of the Fredholm integral equation, which relates the space charge density to the density of states. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Density of states of degenerate n-type silicon from elastic constants

The density of states in heavily doped silicon can be derived from the electronic effect on a shear elastic constant. The density of states found in this way confirms the anomalous values obtained from specific heat measurements.     

碳纳米管的能隙特性和态密度特性

基于MATLAB语言数值模拟了碳纳米管的能隙特性和态密度特性,得出碳纳米管能隙的变化与碳纳米管的手性有关。数值模拟了碳纳米管的态密度表示,通过态密度表示与能隙对比,结果吻合的较好。结论为碳纳米管器件的制作提供参考。     

Photon Density of States in a Cholesteric Photonic Crystal

The photon density of states in a cholesteric photonic crystal in the region of the photon band has been determined from the measured polarized luminescence spectra. The orientational ordering of the transition dipole moment in luminescence, as well as the ellipticity of light eigenmodes in the photonic crystal, has been taken into account when determining the density of states. Maxima in the spectrum of the density of states on two sides of the photonic band are related to the displacement of states from the band. The group velocity of light inside the photonic band exceeds the speed of light in vacuum.     

On the effect of far impurities on the density of states of two-dimensional electron gas in a strong magnetic field

The effect of impurities situated at different distances from a two-dimensional electron gas on the density of states in a strong magnetic field is analyzed. Based on the entire result of Brezin, Gross, and Itzykson, we calculate the density of states in the entire energy range, assuming the Poisson distribution of impurities in the bulk. It is shown that, in the case of small impurity concentration, the density of states is qualitatively different from the model case when all impurities are located in the plane of the two-dimensional electron gas.     

二维缺陷GaAs电子结构和光学性质第一性原理研究

采用基于密度泛函理论的第一性原理方法计算了存在Ga空位缺陷和掺杂B原子的二维GaAs的能带结构、态密度和光学性质.计算结果表明空位缺陷二维GaAs显示出金属特性,B原子的引入使体系变为间接带隙半导体,禁带宽度为0.35 eV.态密度计算发现体系低能带主要由Ga的s态、p态、d态和As的s态、p态构成;高能带主要由Ga和As的s态、p态构成.掺杂B原子与存在空位缺陷的二维GaAs相比,静态介电常数相对较低,变为8.42,且易于吸收紫外光,在3.90～8.63 eV能量范围具有金属反射特性,反射率达到52%.     

YBa_2Cu_3O_7基面电子态特性计算

用散射理论描述了 YBa2 Cu3O7( 0 0 1)面的电子能带结构。用近似到第三近邻的紧束缚模型得到了 YBCO的体电子态密度 ,Cu O及 Cu O2 的表面态密度和表面投影能带 ,进而分析了 Cu O和 Cu O2 的表面态密度的特点及与体态密度的差别。     

About the deconvolution of XPS profiles

The generation of XPS profiles froma. density of states distributionb. spectral distribution of X-raysc. background increased. spectrometer function by means of convolution is discussed. Based on these considerations the density of states distribution is replaced by a sum of     

Spatial structure of an incompressible quantum Hall strip

The incompressible quantum Hall strip is sensitive to charging of localized states in the cyclotron gap. We study the effect of localized states by a density functional approach and find electron density and the strip width as a function of the density of states in the gap. Another important effect is electron exchange. By using a model density functional which accounts for negative compressibility of the QH state, we find electron density around the strip. At large exchange, the density profile becomes nonmonotonic. Both effects, localized states and exchange, lead to a substantial increase of the strip width.     

Mg和Zn掺杂CuAlS2电子结构的分析

从能带结构和态密度分析了黄铜矿CuAlS₂的电子结构.对比未掺杂CuAlS₂,从晶体结构、电子结构、电荷密度分布讨论了Mg和Zn替位Al掺杂对CuAlS₂的影响.结果表明:Mg和Zn掺杂CuAlS₂都导致晶格常数增大,Mg掺杂晶胞体积增大更多;掺杂在价带顶引入受主态,形成p型电导;Mg掺杂比Zn掺杂的受主能级电离能略小;而Zn掺杂CuAlS₂体系总能更低,晶格结构更稳定. 关键词： 2')" href="#">CuAlS₂ p型掺杂 电子结构 能带结构     

Density of states of two-dimensional aluminum nanoclusters in the Hubbard model

The density of states of a two-dimensional square nanosystem composed of N × N aluminum atoms (N = 3?30) is calculated in the framework of the Hubbard model. It is demonstrated that, at a small parameter N, the density of states depends substantially on the number of atoms and on the position of a particular atom in the lattice. As the parameter N increases, the density of states for the vertex and edge atoms tends to the value of the density of states for the bulk atoms. The temperature of the system is implicitly included by specifying the energy of hopping in the initial Hamiltonian.     

Calculation of electronic density of states using a self-consistent cluster-Bethe-lattice method

The electronic density of states for a periodic crystal is calculated by embedding a cluster of atoms in a Bethe-lattice medium. The structure of the Bethe-lattice Hamiltonian is determined by self-consistency requirements. The results for the density of states using this self-consistent cluster-Bethe-lattice method show excellent agreement with the exact density of states and significant improvement over previous calculations using the cluster-Bethe-lattice approach.     

Magnetic field effect on the density of states of a two-dimensional random system

The effect of the magnetic field on the single-particle density of states of a two-dimensional random system at finite temperatures is studied in the lowest order of a mutual interaction between electrons. We describe how the correction from the impurity-induced particle-particle correlation to the density of states is suppressed by the field.