bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and electronic properties of defect and intramolecular junctions for single‐walled carbon nanotube
Authors: Liu Hong , Chen Jiangwei , Yang Huatong 
Published: December 2003

AbstractThe influences of different distributions of defects in (5, 5) single‐walled carbon nanotube (SWCNT) on the electronic structure of SWCNT are considered. Furthermore, we suggest one way to connect two perfect semi‐infinite tubes with different chiralities, such as four different (5, 5)/(n, 0) (n = 8, 9, 10) intramolecular junctions. Their electronic local density of states (LDOS) and quantum conductance are studied. It is found that the conductance gap of the metal/semiconductor heterojunction is not determined only by the electronic structure of semiconductor tube, and the defect distribution mainly change the step behavior of conductance, which is particularly obvious in (5, 5)/(9, 0) metal/metal junctions. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐pressure stability and structural properties of CdS and CdSe
Authors: Benkhettou N. , Rached D. , Soudini B. , Driz M. 
Published: December 2003

AbstractThe structural phase transformations of CdS and CdSe under high pressure are studied by using the local approximation to the density functional theory, and the one‐electron equations are solved by means of the full‐potential linear muffin‐tin‐orbital method FP‐LMTO. CdS and CdSe are found to have nearly similar structural systematics under high pressure. In CdS, the Pmmn phase is predicted after the rocksalt structure, and in CdSe the Cmcm structure is thermodynamically stable after the rocksalt structure. We also find a thermodynamic stability range for the CsCl phase of CdSe. The structural properties of the zincblende, wurtzite, rocksalt, Pmmn, and Cmcm phases are presented. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The proton diffusivity of amorphous tantalum oxide thin films
Authors: Yu G. T. 
Published: December 2003

AbstractProton diffusion in tantalum oxide thin film is of significant interest because of its importance in barrier, sensor, and catalytic‐coating applications. In this study, a novel method based on potential‐pH response measurement was used to determine proton diffusivity of amorphous tantalum oxide thin films. This technique is based on the model of diffusion‐controlled proton transport in the oxide surface, measures the potential‐pH response in a thermostatic measurement set‐up. The proton diffusivity of amorphous tantalum oxide films obtained from this method was 4 × 10–21 cm2/s. The novel method is a relatively simple experimental procedure, which eliminates complications arising from surface‐related effects and/or the presence of hydrogen traps in the metal such as those found in the conventional permeation method. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of the behaviour of magnitude m with magnetic field in corrective term “mT1/2”of the metallic electrical conductivity in n‐type InP
Authors: El kaaouachi A. , Nafidi A. , Biskupski G. 
Published: December 2003

AbstractWe present measurements of the electrical conductivity of barely metallic n‐type indium phosphide (InP) that are driven to the metal‐insulator transition (MIT) by a magnetic field. The experiments are carried out at low temperature in the range 4.2−0.066 K and in magnetic fields up to 11 T. The analysis of the low‐temperature correction to the Boltzmann conductivity due to electron–electron interaction as a function of the magnetic field allowed us to study the influence of exchange and Hartree interactions on the change of the sign of the electron–electron interaction correction. When the magnetic field is increased, several phenomena contribute to this corrective term “mT1/2” among which are the spin‐splitting effect, the electron–electron interaction effect, and weak localisation effect. Not too close to the MIT, both the inelastic diffusion length LI and the interaction length LT contribute to a T1/2 corrective term of the metallic electrical conductivity σ. It is convenient to develop a criterion to distinguish their contribution. This is based on the relation between the magnitude m and the zero temperature σ (T = 0). (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Four‐sublattice ferrimagnetic systems: I. Quantum fluctuations of spins at zero temperature
Authors: Qiu Rong‐ke , Zhang Zhi‐dong 
Published: December 2003

AbstractWithin the framework of the linear spin wave approximation, the quantum fluctuations of spins at zero temperature in four‐sublattice ferrimagnetic systems are studied by employing retard Green's functions. The effects of exchange constants on the quantum fluctuations of spins are discussed for three different spin‐configurations. The magnetic properties of these spin configurations are related to their magnetically structural symmetry. When the parameters of the exchange couplings are adjusted, the crossover of the spin configurations results in the strong quantum fluctuations, owing to the behaviors of the non‐three‐dimensional magnetically system. When two of the four exchange‐constants in the present four‐sublattice bulk systems are set to be zero, the system behaves as a non‐three‐dimensionally magnetic system, although the structure of the system is still three‐dimensional. All the exchange couplings involve in the quantum competition of the systems, but the effects of antiferromagnetic and ferromagnetic exchange couplings are different evidently. The antiferromagnetic exchange couplings play an important role in a balance of the quantum competition. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Four‐sublattice ferrimagnetic systems: II. Effects of the spin quantum number
Authors: Qiu Rong‐ke , Zhang Zhi‐dong 
Published: December 2003

AbstractThe effects of the spin quantum number of each sublattice on the quantum fluctuations are discussed for different spin configurations in four‐sublattice ferrimagnetic systems. In multi‐sublattice ferrimagnets, although the individual sublattice magnetization vectors do not offset each other, but their deviations vectors can cancel out. Namely, the sum of the deviations of magnetization of sites with same initiate spin direction, equals to that of sites with opposite initiate spin direction Σi Δ = Σj Δ, i and j denote respectively the spins along the up and down initiate spin directions). The role of the spin quantum number of each site on magnetic properties of the system is correlative with properties of the exchange couplings surrounding the site. The results show that the proportion of ferromagnetic and antiferromagnetic exchange couplings, the spin quantum number of each sublattice and the magnetically structural symmetry of the system all play important roles on the quantum fluctuations of the systems. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Field‐induced carrier redistribution in double‐quantum‐well superlattices
Authors: Kleinert P. , Bryksin V. V. 
Published: December 2003

AbstractThe field‐induced carrier redistribution in double‐quantum‐well superlattices is treated on the basis of the density‐matrix approach. The Hamiltonian of the three‐level system is simplified by a canonical transformation. Two different types of the field‐mediated carrier redistribution are identified, which refer to intra‐cell and inter‐cell transitions. On the one hand, the occupation numbers of the three levels cross each other, when the levels of different wells of a given superlattice cell are aligned due to the electric field. These intra‐cell transitions lead to a formal population inversion. On the other hand, there is a redistribution of carriers mediated by inter‐cell transitions giving rise to a tunneling resonance characterized by extrema in the distribution function. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comment on “Tunable spin‐injection and magnetoconductance in a novel 2DEG‐ferromagnet structure” [phys. stat. sol. (b) 235, No. 1, 157–161 (2003)]
Authors: Papp G. , Peeters F. M. 
Published: December 2003

AbstractWe point out that the predicted strong spin‐injection effect by Jiang and Jalil [phys. stat. sol. (b) 235, 157 (2003)] for a double magnetic barrier structure is based on a wrong calculation of the transmission probability. We corrected the result and found no significant spin‐injection. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
‘Tunable spin‐injection and magnetoconductance in a novel 2DEG‐ferromagnet structure’” [phys. stat. sol. (b) 241, No. 1, 222 (2004)]
Authors: Jiang Y. , Jalil M. B. A. 
Published: December 2003

AbstractIn this reply, we agree with the comments from Papp et al. that a symmetric (S) double barrier induces only a weak spin‐polarization (P). But the main objective of us was to propose a practical arrangement to achieve a symmetric double barrier because P vanishes for any antisymmetric configuration. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase transitions detection by means of a contact electrode
Authors: Matlak M. , Pietruszka M. 
Published: December 2003

AbstractWe investigate theoretically and next experimentally a new possibility to detect critical temperatures of solids by means of a very simple electrical circuit consisting of an analyzed sample (exhibiting phase transitions) and a contact electrode (hereafter reference electrode) where the constant voltage is applied only to the latter one. The measured system is placed into a thermostat and the electric current flow through the reference electrode is measured as function of temperature. By assuming a model Hamiltonian for the probed sample describing ferromagnetic, superconducting or reentrant phase transitions and a one‐band model for the contact electrode we calculate d.c. conductivity of the reference electrode. The temperature dependence of the conductivity of this electrode clearly indicates (in the form of kinks) the transition temperatures connected with phase transitions occurring in the investigated material. This is due to the fact that the chemical potential of the whole system in contact should equal at equilibrium. Our considerations suggest straightforward application of such a circuit in a direct laboratory praxis, especially because (beyond simplicity) the applied method possesses unlimited temperature range and can be considered as noninvasive with respect to the investigated sample. To verify the effect experimentally we have used as an investigated sample an antiferromagnetic Cr material and Cu as the reference electrode. The measurements of the resistivity R(Cr + Cu) and R(Cu) alone as functions of temperature made a possibility to plot the difference R(Cr + Cu) − R(Cu) vs temperature. This plot enabled to identify the critical Neel temperature of the Cr sample corresponding to the profound minimum in this curve. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
IUPAP Workshop on Scientific Misconduct and the Role of Physics Journals in its Investigation and Prevention, London, UK, 13–14 October 2003
Authors: Hildebrandt Stefan 
Published: December 2003

AbstractConference Reports are meant to offer an authoritative view on a recently held scientific meeting rather than a comprehensive list of the conference presentations. Authors are invited to describe what they feel were the most interesting contributions.Changing the culture of science and publication was the tenor at the IUPAP Workshop on Scientific Misconduct and the Role of Physics Journals in its Investigation and Prevention, recently held in London. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge transfer and charge transport on the double helix
Authors: Armitage N. P. , Briman M. , Grüner G. 
Published: December 2003

AbstractWe present a short review of various experiments that measure charge transfer and charge transport in DNA. Some general comments are made on the possible connection between various ‘chemistry‐style’ charge transfer experiments that probe fluorescence quenching and remote oxidative damage and ‘physics‐style’ measurements that measure transport properties as defined typically in the solid‐state. We then describe measurements performed by our group on the millimeter wave response of DNA. By measuring over a wide range of humidity conditions and comparing the response of single strand DNA and double strand DNA, we show that the appreciable AC conductivity of DNA is not due to photon assisted hopping between localized states, but instead due to dissipation from dipole motion in the surrounding water helix. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relaxation of non‐equilibrium charge carriers in the hopping regime
Authors: Bleibaum O. , Haba E. , Böttger H. , Bryksin V. V. 
Published: December 2003

AbstractWe discuss a kinetic model for glass‐like relaxation processes in a strongly localized electron system. In our hopping model we assume that the charge carriers can exchange maximally an amount ω of energy in one hop. The investigation of the system shows that the energy scale ω discriminates between two different relaxation modes. If the thermal energy is large compared to ω the relaxation is percolation like. In this regime the relaxation is determined by the same paths as the close‐to‐equilibrium conductivity in a transport problem. If the thermal energy is small compared to ω then the relaxation becomes Miller‐Abraham like. In this relaxation mode the charge carriers always jump to the next closest site. The differences between these transport regimes manifest themselves in the typical time scales governing the relaxation and in the structure of the transport coefficients. To discuss them we focus on energy relaxation processes. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Long‐time relaxation of conductivity in hopping regime
Authors: Efros A. L. , Tsigankov D. N. , Pazy E. , Laikhtman B. D. 
Published: December 2003

AbstractUsing numerical simulations we studied the long‐time relaxation of the hopping conductivity. We perturbed the system through insertion of electrons and monitored the conductivity as a function of time. Even though employing numerical simulations one can only follow the system for very short time scales we have shown that during such available times we can reach an apparent saturation of conductivity and energy. In order to investigate the long‐time relaxation of the system we studied the difference between the saturated values of the conductivities obtained by the short‐time relaxation from initial excited states with different electron distribution. We have related these two typical time scales to relaxation in one pseudoground state and to very slow transitions between pseudoground states. By employing two different two‐dimensional models with electron–electron interactions we were able to show the effect of disorder on the relaxation of conductivity. In the strong‐disorder case the universality of the Coulomb gap, which is responsible for the universal Efros–Shklovskii law for the conductivity, suppresses the long‐time relaxation of conductivity since the universality strongly decreases the dispersion of conductivities of the pseudoground states. In the second model with a weak external disorder we found a difference between saturated values of conductivity in agreement with the experimental data. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wigner approach to quantum dynamics simulations of the interacting carriers in disordered systems
Authors: Filinov V. , Thomas P. , Bonitz M. , Fortov V. , Varga I. , Meier T. 
Published: December 2003

AbstractThe new method for solving Wigner–Liouville's type equations and studying dynamics of quantum particles has been developed within the Wigner formulation of quantum statistical mechanics. This approach combines both molecular dynamics and Monte Carlo methods and computes traces and spectra of the relevant dynamical quantities. Considering, as an application, the quantum dynamics of an ensemble of interacting electrons in an array of random scatterers clearly demonstrates that the many‐particle interaction between the electrons can lead to an enhancement of the electrical conductivity. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the mechanism of superionic conduction in the zero‐dimensional hydrogen‐bonded crystals M3H(XO4)2 with M = K, Rb, Cs and X = S, Se
Authors: Kamimura Hiroshi , Matsuo Yasumitsu , Ikehata Seiichiro , Ito Takuo , Komukae Masaru , Osaka Toshio 
Published: December 2003

AbstractIn this paper we first present recent experimental results related to superionic conduction in the zero‐dimensional hydrogen‐bonded crystals of alkali‐hydrosulfates or hydroselenates, M3H(XO4)2 [M = K, Rb, Cs and X = S, Se]. Then a novel approach to the mechanism of proton conduction in the paraelastic phase is described. The key features of the conduction mechanism in the high temperature paraelastic phase which we call the superionic phase are: (1) Two kinds of ionic states, H2XO4(+e) and XO4(−e) are formed by breaking a hydrogen‐bond thermally; (2) H2XO4(+e) and XO4(−e) ionic states move coherently from an XO4 tetrahedron to a distant XO4 as the result of successive proton tunneling among the hydrogen bonds. We calculate the density of states for the coherent motions of these ionic states by the recursion formula. From this result we show that a characteristic feature of the band‐like states obtained from itinerancy of H2XO4(+e) and XO4(−e) ionic states is that of the Bethe lattice; that is the appearance of the twin peak structure due to self‐similarity. The calculated conductivity is very high such as the order of 10−2 S/cm at and above Tc, consistent with experiment. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric‐field‐induced hopping transport in superlattices
Authors: Kleinertand P. , Bryksin V. V. 
Published: December 2003

AbstractA strong electric field applied parallel to the superlattice axis leads to Wannier–Stark localization. There are two formally equivalent pictures for the drift velocity and the diffusion coefficient, the hopping model, which is most suitable for localized states, and the band picture, which is applicable to extended states. Complete localization of carriers is achieved by strong electric and magnetic fields. In these molecule‐like systems, there is a strong interdependence between the carrier spectrum and its statistical properties, the description of which requires a new approach. The related double‐time character of the transport gives rise to interesting quantum effects in the current–voltage characteristics. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Are the interaction effects responsible for the temperature and magnetic field dependent conductivity in Si‐MOSFETs?
Authors: Pudalov V. M. , Gershenson M. E. , Kojima H. , Brunthaler G. , Bauer G. 
Published: December 2003

AbstractWe compare the temperature and in‐plane magnetic field dependences of resistivity ρ (T, B∥) of Si MOSFETs with the recent theories. In the comparison we use the effective mass m* and g*‐factor determined independently. An anomalous increase of ρ with temperature, which has been considered a signature of the “metallic” state, for high conductivities (σ > e2/h) can be described quantitatively by the interaction effects in the ballistic regime. ρ(B∥) is consistent with the theory only qualitatively; it is found to be more susceptible than ρ(T) to details of disorder, possibly associated with magnetic moments of localized states. Description of the transport in the “critical” regime of ρ ∼ h/e2 is still lacking. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic ordering in doped semiconductors near the metal–insulator transition
Authors: Zabrodskii A. G. 
Published: December 2003

AbstractExperiment clearly shows a certain extent of ordering of localized magnetic moments in doped semiconductors near the metal–insulator transition. An antiferromagnetic spin glass structure is revealed in a number of n‐type materials (Ge:As, 6H‐ and 4H‐SiC:N) by Electron Spin Resonance spectroscopy as a sharp decrease in the density of paramagnetic centres, observed when approaching the transition from its insulator side. In a p‐type material (Ge:Ga), the macroscopic magnetization and residual magnetization, as well as hole coupling in pairs or clusters with uncompensated moment, follow from the recently discovered hysteresis of variable range hopping magnetoresistance, accompanied by sharp drops in resistance on reversing the magnetization of the system. The location of the magnetically ordered phases is established. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Possibility of superconductivity in intercalation compound related to MgB2
Authors: Kato Nobuhiko , Nagao Hidemi , Nishikawa Kiyoshi , Nishidate Kazume , Endo Kazunaka 
Published: December 2003

AbstractWe investigated the electronic structure of MgB2 and intercalation compounds, MgBX (X = Li, Be, C), with fully relaxed crystal structure by using density functional theory. The compounds MgBLi and MgBBe could be similar two‐band superconductors to MgB2 because the Fermi surface crosses σ and π bands. Our results indicate that changing the lattice constants, hole or electron doping, and stacking of BX effect the energy levels of the σ and π bands in MgBX compounds. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Semiclassic approach within the He atom sphere model
Authors: Kiselyov A. A. 
Published: December 2003

AbstractThe helium atom doubly excited‐states energy levels are calculated for the 1S‐state. The He atom is considered as the three‐atomic molecule. The electrons are supposed to move on the sphere of the equal radius. The rotation is described by the Euler angles, which can be divided in a standard way. Then, the hyperspherical coordinates are introduced. The adiabatic approach allows us to solve the equation on interelectron angle θ. We used the contour integral method for this equation. The equation on the hyperradius R was solved according to the semiclassic approach. The obtained results are in good agreement with those of some other works. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Mean‐field potential approach to the quasiharmonic theory of solids
Authors: Wang Y. , Ahuja R. , Johansson B. 
Published: December 2003

AbstractAdopting the quasiharmonic approximation, a newly developed classical mean‐field potential (MFP) approach is extended to the quantum case. Two new Debye temperature expressions, which are in accordance with the thermodynamic theory of Dugdale and MacDonald and with the free volume theory, respectively, are derived in addition to the well‐known expression of Slater. The Grüneisen law is now implied explicitly in the Debye temperature expression, and therefore no additional conditions for the Grüneisen constant are needed for realistic thermodynamic calculations. The thermal expansion and specific heat of Na, Cu, Mo, Ta, and Th have been calculated from 10 K up to the melting point. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Approximate on‐top pair density into one‐body functions for CAS‐DFT
Authors: Takeda R. , Yamanaka S. , Yamaguchi K. 
Published: December 2003

AbstractWe have derived the new expression of the on‐top pair density of CAS [2,2] by one‐body functions of natural orbitals and these occupation numbers, which we call one‐body representation of second‐order density (ORSOD). The expression allows us to drastically reduce the computational cost of complete‐active‐space density functional theory. Furthermore, we define the ionic density as an approximation of ORSOD for description of potential surfaces exhibiting ionic character. We have applied these schemes for the dissociation curves of H2 and F2 molecules. The relation between the ORSOD, the ionic‐density, and the radical‐electron density that is defined in our previous work is also discussed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004