共查询到20条相似文献,搜索用时 15 毫秒
1.
The density of states for a system of interacting Ising dipoles in the presence of diagonal disorder is obtained by computer simulation. Two models are considered, one with the true dipole-dipole interaction and another in which the angular dependence of the interaction is not included. Results for different values of the disorder energy are obtained for the two models, fitting quite well to previous analytical calculations. 相似文献
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R. Salomon 《Zeitschrift für Physik B Condensed Matter》1987,65(4):443-451
The density of states of a two-dimensional, non-interacting electron gas under the influence of a strong perpendicular magnetic field and random impurities is examined. In the strong magnetic field the ensemble averaged Green's function can be restricted to a single Landau leveln. Using 1/n as expansion parameter we calculate first order corrections. The results for two models of disorder are compared: white-noise potential and uniformly distributed zero-range scatterers with a Lorentzian distribution of strength. 相似文献
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Y Liu CG Pappas M Shayegan LN Pfeiffer KW West KW Baldwin 《Physical review letters》2012,109(3):036801
Measurements on very low disorder two-dimensional electrons confined to relatively wide GaAs quantum well samples with tunable density reveal a close competition between the electron liquid and solid phases near the Landau level filling factor ν=1. As the density is raised, the fractional quantum Hall liquid at ν=4/5 suddenly disappears at a well-width dependent critical density, and then reappears at higher densities with insulating phases on its flanks. These insulating phases exhibit reentrant ν=1 integer quantum Hall effects and signal the formation of electron Wigner crystal states. Qualitatively similar phenomena are seen near ν=6/5. 相似文献
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A. A. Greshnov M. A. Kaliteevskiĭ R. A. Abram S. Brand G. G. Zegrya 《Physics of the Solid State》2007,49(10):1999-2003
An analytic theory of the density of states in one-dimensional disordered photonic crystals is proposed. It is shown that the problem of the density of optical modes can be reduced in the small dielectric contrast approximation to solving a generalized Fokker-Planck equation for the distribution function of the logarithmic derivative of the electric field (the wave phase). The exact analytic solution and density-of-states asymptotics deep in the band gap of the photonic crystal and close to the band gap edge are derived. The results obtained agree well with the empirical relations derived earlier from numerical experiments. 相似文献
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We study the local density of vibrational states of a disordered binary chain using a renormalization approach suitable for the alloy problem. We include isotopic and spring constant disorder. Short range order effects in the alloy are taken into account in the pair approximation. We present some numerical results for the case of spring constant disorder and discuss their relevance for the interpretation of neutron scattering experiments in some metallic amorphous systems. 相似文献
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Fernández LA Gordillo-Guerrero A Martín-Mayor V Ruiz-Lorenzo JJ 《Physical review letters》2008,100(5):057201
We present the first detailed numerical study in three dimensions of a first-order phase transition that remains first order in the presence of quenched disorder (specifically, the ferromagnetic-paramagnetic transition of the site-diluted four states Potts model). A tricritical point, which lies surprisingly near the pure-system limit and is studied by means of finite-size scaling, separates the first-order and second-order parts of the critical line. This investigation has been made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that plague the standard approach. Entropy, rather than free energy, is the basic object in this approach that exploits a recently introduced microcanonical Monte Carlo method. 相似文献
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S. V. Iordanski 《JETP Letters》2014,99(9):523-526
It is shown that the thermodynamic instability at the half filling of L1 leads to the vortex lattice formation with the electronic spectrum analogous to that of graphene with two Dirac-Fermi points on Brillouin cell boundary. This result is used for the explanation of the observed current generated by a surface acoustic wave in the heterostructure on the surface of piezoelectric GaAs. Using the existence of two Fermi points instead of a Fermi surface suggested in the previous theoretical works, permit the explanation of the experimental results. 相似文献
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Rolf Thürwächter 《Zeitschrift für Physik B Condensed Matter》1989,76(2):185-192
Wegner's gauge-invariant model of the localization problem is treated on ad-dimensional lattice. Borel-Padé methods are used to analyze the perturbation series for the averaged one-particle Green function. Results for the density of states are obtained. 相似文献
14.
We study the Anderson model of localisation at the
metal-insulator transition in the band centre of three-dimensional
disordered samples. For the critical disorder we determine a large
number of wave functions of the model and study the distribution of
the wave function amplitudes. Deviations from scaling of
multifractal correlation functions allow us to discriminate
anomalously localised states from the usual critical states. The
thus identified anomalously localised states lead to deviations of
the critical properties and should be eliminated from the ensemble
average for a characterisation of criticality. 相似文献
15.
We apply the modified-moments method to compute the density of states of the impurity band of a doped semi-conductor in the intermediate region of impurity concentrations. This method is used to correct the density of states obtained by interpolating between the high and low concentration limit asymptotic expressions. The calculation is based on the Hubbard model in the atomic limit without spin ordering. The overlap integral is assumed to be a Gaussian function of the impurity separation. Use is made of the first seven moments of the exact distribution and of the low and high concentration limit approximations previously calculated. The first six moments are employed to determine the orthogonal polynomial expansion of the density of states while the seventh moment is used as a check on the accuracy of the distribution obtained. The results are similar to the previous ones using a truncated Edgeworth series for the correction term but the present method has the advantage of being a more systematic approach. 相似文献
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Murthy G 《Physical review letters》2000,84(9):1954-1957
The structure and orientational ordering of N2O molecules physisorbed on graphite (0001) is investigated applying x-ray, neutron, and low-energy electron diffraction techniques. Combining the results of the three techniques, we find that N2O forms a highly ordered, hexagonal, commensurate (sqrt[21]xsqrt[21])R10.89 degrees phase. The unit cell contains seven molecules which are arranged in a seven-sublattice pinwheel structure, unexpected for linear molecules on a hexagonal lattice. Potential energy calculations corroborate these results. 相似文献
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D.V. Khveshchenko 《Zeitschrift für Physik B Condensed Matter》1996,103(2):275-278
Experiments show that at even denominator fractions (EDF) (7p = 1=2;3=4;3=2,...) the two-dimensional electron gas (2DEG) in a strong magnetic field becomes compressible, has no energy gap, and demonstrates the presence of an ostensible Fermi surface (FS). Since this phenomenon results from a minimization of the interaction, rather than the kinetic energy, the EDF states might well exhibit deviations from a conventional Fermi liquid (FL). We show that impurity scattering and its interference with electronelectron and electron-phonon interactions provide examples of intrinsically non-Fermi-liquid (NFL) transport at EDFs. 相似文献
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We investigate the effects of structural disorder on the exciton density of states of molecular crystals, utilizing an exact soluble model which involves correlated Lorentzian distributions of both the site-excitation energies and the transfer integrals. Off-diagonal disorder results in asymmetric density of states functions, the asymmetry being prominent for one-dimensional exciton band structure. 相似文献