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1.
It is shown that for a narrow band version of the Anderson Hamiltonian, the transformation of Schrieffer and Wolff can be carried out to all orders in the mixing parameter. The resulting Kondo-like Hamiltonian is in diagonal form. The results can be used to derive a systematic approximation scheme for the Anderson Hamiltonian, through use of the level shift operator of Primas. The resulting interaction parameters remain regular when the energy of the localized level approaches the Fermi level. 相似文献
2.
The integrated narrow band pass filter is an important photonic device. The performance of this device is limited by the two
problems, absorption coefficient and thickness homogeneous in the resonant cavity layer. We have developed a numerical simulation
method to analyze the factors’ influence on the behavior of integrated filters. It is found that the non-homogeneous of layer
thickness will play a dominance role in the property of band width of transmission spectra of the 32-chanels integrated narrow
band pass filter device in near infrared. 相似文献
3.
Deformed Hartree-Fock calculations are performed for some light nuclei in a large configuration space consisting of first
four major shells. The interaction employed is the modified Skyrme interaction in which the deformed density is replaced by
the band averaged scalar density that makes the Hamiltonian rotationally invariant rendering the spectroscopic calculations
feasible. It is shown that the introduction of density dependence spreads out the energy spectra and that the Skyrme variant
SIV which has a weak density dependence gives best overall agreement for energy spectra and the available data for the electromagnetic
properties of the nuclei studied. It is found that the maximum contribution to the energy of any state in the low lying spectrum
comes from thes-state attractive ands-state repulsive parts of the Skyrme interaction. It is also shown that when two-body density dependent version of Skyrme
interaction is used, the Koopmans theorem no longer holds. 相似文献
4.
Anupam Madhukar 《Solid State Communications》1973,13(11):1767-1770
A simple criterion for antiferromagnetic ordering versus lattice distortion in very narrow band materials is obtained. The model describing these narrow band materials contains the Hubbard Hamiltonian, short ranged interatomic Coulomb and exchange interactions, and the electron-phonon interaction. 相似文献
5.
Uday Ramesh Prabhu N. Suryaprakash 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,202(2):217-222
We report the application of z-COSY experiment and a band selected version of it by employing a selective 90° pulse entitled BASE-z-COSY for precise chiral discrimination, quantification of enantiomeric excess and the analyses of the 1H NMR spectra of chiral molecules aligned in the chiral liquid crystalline solvent poly-γ-benzyl-l-glutamate (PBLG). We have demonstrated their applicability for obtaining very high resolution in the 1H NMR spectra of small organic molecules. It is well known that the commonly employed z-COSY experiment disentangles the spectral complexity, provides pure phase spectra with high resolution, aids in the complete spectral analyses, in addition to yielding information on relative signs of the couplings. The BASE-z-COSY experiment possesses all these properties, permits the measure of enantiomeric excess, in addition to large saving of instrument time. 相似文献
6.
The concept of an effective magnon Hamiltonian is used to study magnon relaxation inthe band model of ferromagnetism. The 4-magnon processes of electrostatic and magnetic dipolar origin in a narrow single band are discussed. 相似文献
7.
Yoshinori Takahashi 《Zeitschrift für Physik B Condensed Matter》1989,73(4):419-423
The valence band photoemission spectrum of highT
c
-superconductors is discussed based on the half-filled single band Hubbard Hamiltonian with the strong Coulomb interaction. We discuss how to analyze these valence band and deep core level excitation spectra, concerning particularly with which orbital, Cud or Op state, a hole will occupy in the CuO2 plane. 相似文献
8.
Acef O Bordé CJ Clairon A Pierre G Sartakov B 《Journal of Molecular Spectroscopy》2000,199(2):188-204
An extended set of 321 frequencies of vibration-rotation lines of the nu(3) band of SF(6) has been measured by saturation spectroscopy using various isotopic species of CO(2). A least-squares fit of these data has been performed using an effective Hamiltonian written either with a spherical tensor or with a cubic tensor formalism. We have derived correspondence formulas between the parameters in the two approaches and checked that both formalisms give the same results up to the seventh order. Corrected parameters are given for the fit with a fifth-order Hamiltonian. An accurate representation of the band is obtained at the tenth order (standard deviation approximately 12 kHz) with a remarkable predictive power (better than 40 kHz) for J values = 100. The convergence properties of the Hamiltonian power expansion are discussed. Copyright 2000 Academic Press. 相似文献
9.
We derive a spin-dependent Hamiltonian that captures the symmetry of the zone edge states in silicon. We present analytical expressions of the spin-dependent states and of spin relaxation due to electron-phonon interactions in the multivalley conduction band. We find excellent agreement with experimental results. Similar to the usage of the Kane Hamiltonian in direct band-gap semiconductors, the new Hamiltonian can be used to study spin properties of electrons in silicon. 相似文献
10.
采用基于密度泛函理论的第一性原理平面波超软赝势方法,研究了闪锌矿CdTe及不同量Hg掺杂HgxCd1-xTe的电子结构,给出了相应的的能带结构、态密度、差分电荷分布及光吸收谱。计算结果表明,随着Hg掺杂含量的增加,体系禁带宽度逐渐变窄,并给出了禁带宽度变窄的微观机理。 相似文献
11.
We study the electronic structures and the optical absorption spectra of the multilayer graphenes in the effective mass approximation. We decompose the Hamiltonian of graphene with an arbitrary thickness into smaller subsystems effectively identical to monolayer or bilayer graphene, and express the optical spectrum as a summation over the subsystems. We include the full band parameters which compose the bulk graphite, and closely study their effects on the band structure. We found that the particular band parameters destroying the electron–hole symmetry can affect the optical spectrum through shift of the absorption edge. 相似文献
12.
Jin-ming DONG 《理论物理通讯》1989,11(2):231-234
Using the tunneling Hamiltonian method we have studied the Josephson type effect occuring in a junction composed of two weakly coupled CDW materials. We have found that the tunneling effect in CDW junction has great resemblance to the Josephson effect, but there are also basic differences between them. For example, in CDW junction there is a special pair-single particle tunneling current term which is absent in the superconducting tunneling junction. It is just this term that gives rise to the narrow band noise. This is a kind of contact effect, but its mechanism is probably different from the vortex theory. 相似文献
13.
Approximate radiative properties of methane at high temperature 总被引:1,自引:0,他引:1
Band model parameters for high-temperature methane have been generated up to 2000 K from an extended spectroscopic database. Part of the spectroscopic data are issued from calculations made in the framework of the effective Hamiltonian approach. These data have been completed by a statistical extrapolation. The calculations of global radiative properties such as band absorbtances and total emissivities are in good agreement with the available experimental data showing that the contribution of the hot bands is correctly taken into account. Finally, the degree of correlation between CH4, CO2 and H2O spectra in typical conditions of combustion applications is discussed. Band model parameters are available upon request. 相似文献
14.
15.
采用光学传输矩阵方法,研究了外磁场作用下一维光子晶体的光传输特性.在外磁场作用下,介质介电函数在回旋频率ω.附近受到强烈的调制,使组分材料的色散关系发生明显改变,导致光子晶体的能带发生变化,透射谱出现复杂结构.在光子带隙中出现窄通带,窄带中的光是局域的.这表明,在不改变光子晶体组分材料的条件下,可以通过改变外磁场的大小,调制光子晶体的能带及其光传输性质. 相似文献
16.
S. Ben Bouzid W. Zaghdoudi N. Ben Sedrine J.C. Harmand 《Applied Surface Science》2008,254(22):7122-7126
We study the effect of the GaAsN narrow QWs on the optical properties of the GaInNAsSb/GaAs QWs using photoluminescence spectroscopy. A drastic effect of the N-rich layers on the QW photoluminesecnec (PL) intensity was observed with a strong influence of the spacer thickness. In the PL spectra a broad band caused by excitonic transitions related with N-related clusters in GaAs barriers is found. Based on calculations from experimental data, we have identified the low QW peak energy to the E1-H1 transition using the shear deformation potentials report Δp/p = 0.24. 相似文献
17.
Energy spectra of the graphene-based Fibonacci superlattice (SL) in the presence of the band gap in graphene have been investigated. The lattice consists of rectangular barriers, which are arranged along axis Ox. The quasi-periodic modulation is performed due to the difference in the values of the mass term of the Hamiltonian in various SL elements. It is shown that effective splitting of allowed bands (and thereby the formation of a series of gaps) under the effect of the quasi-periodic factor is implemented with both oblique and normal incidence of the electron wave on the SL surface. The energy spectra have a clearly pronounced periodic character over the entire energy scale. The bands split in separate fragments of the spectrum (conventionally periods) according to the Fibonacci inflation rule in each new generation. The band gap associated with a new Dirac point is formed in all Fibonacci generations similarly to the periodic graphene-based SLs. The location of the Dirac point is independent of the SL period; it is very sensitive to the potential barrier height and to the width ratio between the quantum well and the barrier and depends weakly on the mass term in the Hamiltonian. The dependence of the spectra on the incidence angle of the electron wave is insignificant. 相似文献
18.
钡钇氟化物中Eu2+离子的激发光谱和发射光谱 总被引:1,自引:0,他引:1
在298和77K下分别研究BaYF5(BaF2·YF3)中Eu2+的激发和发射光谱。Eu2+的发射光谱中,除了一个属5d-4f跃迁的宽发射带外,还有一组6PJ→8S7/2的4f-4f跃迁窄谱线发射。它们的发射强度与Eu2+的浓度和温度有关。由於Eu2+从4f7基态跃迁到4f65d1态产生两个宽的激发带,4f65d(eg)和4f65d(t2g)。实验证实,Eu2+的6PJ→8S7/2的窄谱线发射主要来自高能级的t2g激发能弛豫的结果。 相似文献
19.
A technique for simulation of band spectra of compound crystals in the basis of states of their sublattices is developed.
The Hamiltonian of the crystal is written as a sum of sublattice Hamiltonians and a perturbation operator resulting from hybridization
of the sublattice states. The simplest models are proposed to account for the sublattice hybridization. The methods for calculating
the average crystal potential are discussed to represent the band spectra of sublattices in a common energy scale when calculating
band structures by the pseudopotential method. The band spectra of MgO and MgS crystals are calculated to show the application
of the methods under consideration.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 81–84, July, 2006. 相似文献
20.
New allotropic forms of carbon based on С60 and С20 fullerenes are considered. The most stable carbon compounds are found using an evolution algorithm, and their crystal structure (X-ray diffraction spectra) and electron (band structure) and mechanical (moduli of elasticity, hardness) characteristics are studied. The carbon phase with the tetragonal symmetry with mechanical properties close to those of a diamond crystal and having a narrow band gap is found. 相似文献