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排序方式: 共有302条查询结果,搜索用时 331 毫秒
1.
Alejandro Cabo-Bizet 《Physics letters. A》2009,373(21):1865-1869
Special solutions of the Hartree-Fock (HF) problem for Coulomb interacting electrons described by a simple model of the Cu-O planes in La2CuO4 are presented. One of the mean field states obtained, is able to predict some of the most interesting properties of this material, such as its insulator character and the antiferromagnetic order. The natural appearance of pseudogaps in some states of this material is also indicated by another of the HF states obtained. These surprising results follow after eliminating spin and crystal symmetry restrictions usually imposed on the single particle HF orbitals, by employing the rotational invariant formulation of the HF scheme originally introduced by Dirac. Therefore, it is exemplified here, how up to know considered strong correlation effects, can be described by improving the HF solution of the considered system. In other words, it has been argued, that defining correlation effects as the ones shown by the system and not predicted by the HF best (lowest energy) solution, allows to explain important, up to know considered as strong correlation properties, as simple mean field ones. The discussion also helps to clarify the role of the antiferromagnetism and pseudogaps in the physical properties of the HTSC materials and indicates a promising way to start conciliating the Mott and Slater pictures in the physics of the transition metal oxides and other strongly correlated electron systems. 相似文献
2.
E.L. Pankratov 《Physics letters. A》2008,372(6):893-897
It has been shown, that inhomogeneity of a multilayer structure leads to decreasing of depth of a p-n-junction, which was produced in the multilayer structure. In the Letter we determined some conditions for decreasing depth of an implanted-junction rectifier. 相似文献
3.
T. Jacob B. Fricke J. Anton S. Varga T. Baştuğ S. Fritzsche W.-D. Sepp 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):257-260
In order to describe processes which are localized on a surface or inside the bulk of a solid, molecular calculations of an
inner cluster may be adequate as long as the effect of the outer environment is taken into account via an embedding-method. Using a relativistic density functional method for the self-consistent cluster calculation we have developed
a new cluster-embedding scheme here. As an example we have studied the adsorption of Al on an Al(100) surface and we get significant
agreement with different methods. This indicates that this embedding-method is reliable enough to simulate an unlimited solid.
Received 29 November 2000 相似文献
4.
D. Dobrev J. Vetter N. Angert R. Neumann 《Applied Physics A: Materials Science & Processing》2001,72(6):729-733
Pulse reverse electrolysis in an ultrasonic field is used to grow iron single crystals of micron size in templates formed
by etching the tracks of swift ions in polymer foils. High-grade crystals are produced from high-temperature ferrous chloride
baths. The crystals are oriented along their <110>, <100>, and <111> crystallographic axes. Their orientation turns out to
depend on supersaturation during the growing process. At low overvoltages of deposition, <110> and <100> orientations are
observed. The crystals of <111> orientation appear more frequently at higher cathode pulse current density. The crystals possess
prominent resistance to corrosion.
Received: 20 February 2001 / Accepted: 21 February 2001 / Published online: 3 May 2001 相似文献
5.
R. Nevado C. Sada F. Segato F. Caccavale A. Kling J.C. Soares E. Cantelar F. Cussó G. Lifante 《Applied physics. B, Lasers and optics》2001,73(5-6):555-558
Rutherford backscattering (RBS) and secondary-ion mass spectrometry techniques have been used to investigate the two-step
process involved during waveguide fabrication in LiNbO3 using Zn-vapour diffusion. Compositional analysis (O, Nb, Li and Zn) in the two steps has been characterised. RBS analysis
reveals that the first step, involving a heating of the substrate under a metallic Zn atmosphere, gives rise to a partial
exchange between the Nb and Li ions from the crystals and the Zn from the vapour source. The second treatment at higher temperature
in an open atmosphere diffuses the Zn deeper into the substrate, thus forming an optical waveguide, while the Nb and Li ions
recover their bulk values.
Received: 16 May 2001 / Revised version: 7 September 2001 / Published online: 30 October 2001 相似文献
6.
J. Zhang L. Zhang X. Peng X. Wang 《Applied Physics A: Materials Science & Processing》2001,73(6):773-775
MgO nanobelts have been fabricated by chemical vapor deposition using MgCl3 as starting material. The products consist of a large quantity of belt-like nanostructures with typical lengths in the range
of several tens to several hundreds of micrometers; some of them even have lengths on the order of a millimeter. The typical
thickness and width-to-thickness ratio of the MgO nanobelts are in the range of 20 to 100 nm and about 5 to 10, respectively.
The size and morphology of the MgO nanobelts were measured by transmission electron microscopy. Investigations of X-ray diffraction
patterns and using high-resolution transmission electron microscopy indicate that the nanobelts have a cubic structure and
are single-crystalline.
Received: 23 August 2001 / Accepted: 27 August 2001 / Published online: 2 October 2001 相似文献
7.
It has recently been claimed that the dynamics
of long-wavelength phason fluctuations has been observed in
i-AlPdMn quasicrystals [S. Francoual et al.
Phys. Rev. Lett. 91, 225501 (2003);
A. Létoublon et al. 54, 753 (2001)]. We will show that
the data reported call for a more detailed development of
the elasticity theory of Jarić and Nelsson [M.V. Jarić and D.R. Nelsson, Phys. Rev. B 37,
4458 (1988)]
in order to determine the nature of small phonon-like atomic displacements
with a symmetry that follows the phason elastic constants.
We also show that a simple model with a single diffusing tile is sufficient
to produce a signal that (1) is situated at a “satellite position”
at a distance q from each Bragg peak; that (2) has an intensity that
scales with the intensity of the corresponding Bragg peak;
(3) falls off as 1/q2; and (4) has a time decay constant that is proportional to 1/Dq2.
It is thus superfluous to call for a picture of “phason waves” in order to explain such data, especially as such “waves” violate
many physical principles. 相似文献
8.
M. Hinczewski A. N. Berker 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):461-472
The anisotropic d=3 tJ model is studied by
renormalization-group theory, yielding the evolution of the system
as interplane coupling is varied from the isotropic
three-dimensional to quasi-two-dimensional regimes.
Finite-temperature phase diagrams, chemical potential shifts, and
in-plane and interplane kinetic energies and antiferromagnetic
correlations are calculated for the entire range of electron
densities. We find that the novel τ phase, seen in earlier
studies of the isotropic d=3 tJ model, persists even for
strong anisotropy. While the τ phase appears at low
temperatures at 30–35% hole doping away from 〈
ni〉=1, at smaller hole dopings we see a complex lamellar
structure of antiferromagnetic and disordered regions, with a
suppressed chemical potential shift, a possible marker of
incommensurate ordering in the form of microscopic stripes. An
investigation of the renormalization-group flows for the isotropic
two-dimensional tJ model also shows a clear pre-signature of the
τ phase, which in fact appears with finite transition
temperatures upon addition of the smallest interplane coupling. 相似文献
9.
F.-J. Zhang Z. Xu Y.-G. Lv J.-C. Zhang S. L. Zhao J.-Z. Huang Y. Wang G.-C. Yuan D.-W. Zhao X.-R. Xu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):245-248
The organic-inorganic combined structural device (ITO/PVK:Eu/ZnS/Al) is
fabricated based on layered optimization scheme. II–VI semiconductor
material ZnS is acted as an electron function (transporting and
acceleration) layer. The hot electrons which have been accelerated in the
ZnS layer directly impact excitation europium ions through resonant energy
transfer and then recombine with injected holes to form excitons in PVK or
EuTTA2(N-HPA)Phen. Europium (Eu) ions may also be excited by
intramolecular energy transfer from ligands. There are two kinds of
excitation mechanisms: impacted excitation and injected recombination for
the combined structural device. The electroluminescence (EL) intensity of
the combined structural device is strongly improved and reaches up to
381 cd/m2 at 20 V compared with the pure organic structural device. It
may be an effective method to improve the EL intensity of the lanthanide
complex by using electric characteristics of inorganic semiconductor
materials. 相似文献
10.
S. N. Paul K. Roychowdhury S. Burman A. Roychowdhury B. Paul 《Czechoslovak Journal of Physics》2006,56(12):1453-1460
Theoretical investigation on the propagation of ion-acoustic waves in an unmagnetized self-gravitating plasma has been made
for the existence of solitary waves using the reductive perturbation method. It is observed that nonlinear excitations follow
a coupled third-order partial differential equation which is slightly different from the usual case of coupled Korteweg-de
Vries (K-dV) system. It appears that the system so deduced is a two-component generalization of the previous one derived by
Paul et al. (1999) in which it was shown that ion-acoustic solitary waves can not exist in such system. 相似文献