bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Bihole in Quantum Well Structures
Authors: Bobrysheva A. I. , Russu S. S. , Zaloj V. A. 
Published: July 2007

AbstractIn GaAs–Ga1−xAlxAsmany quantum well structures or superlattices the top valence subband VB1 of size quantization is heavy‐hole‐like HH1 and the effective mass m1 is positive. The second valence subband VB2 has a heavy‐hole – HH2 or light‐hole –LH1 character in dependence on the barrier and well layer thicknesses and the composition x. The effective mass m2 in VB2 is negative and the condition for bihole formation m1 > ‖m2| is fulfilled. The binding energy of the bihole is calculated. The bihole formation due to light absorption is studied. The oscillator strengths in the cases of inter‐ and intrasubband transitions of holes succeeded by bihole formation are obtained.
Anomalies in the Phonon Spectra and the Fermi Surface of the Random Substitutional Alloy Cu0.9Ni0.1
Authors: Rumyantsev A. Yu. , Mitrofanov N. L. , Ivanov A. S. , Chernoplekov N. A. , Weiss L. , Eschrig H. , Richter R. 
Published: July 2007

AbstractWith a full self‐consistent LCAO‐CPA‐calculation of the Bloch spectral function (representing the electronic bandstructure) of the random substitutional alloy Cu0.9Ni0.1, statements regarding the existence and the shape of the Fermi surface are given. The relation of the Fermi surface with various kinds of anomalies in the phonon dispersion curves as pointed out in previous papers is used to compare such anomalies as measured by neutron spectroscopy in the (110)‐plane of this alloy with the calculations. The experimental results show that the Fermi surface intersecting this plane is somewhat less extended than coming out from this calculation.
High‐Order Perturbation Formulae of the Spin‐Hamiltonian Parameters for the Ground State 3A2(F) of d8 Ions in Rhombic Symmetry
Authors: Chen Jia‐Jun , Zhao Min‐Guang 
Published: July 2007

AbstractHigh‐order perturbation formulae of the spin‐Hamiltonian parameters D and E and the g‐factor for the ground state 3A2(F) of d8 ions are obtained in the strong‐field coupling scheme. In the derivation, not only spin triplet states but also spin singlet states are considered. According to Zhao's μkα‐correlation ligand field model for the Ni2+−6X−(F−, Cl−, Br−, I−) complexes, the relationships between the spin‐Hamiltonian parameters and the crystalline ones of the Ni2+−6X− cluster are established and applied to ZnF2:Ni2+ and NiF2. In the calculation, no adjustable parameter is introduced. The results agree well with the experimental findings, indicating that the given relationships are reasonable.
On the Theory of Double Gamma Electronic Magnetic Resonance in Paramagnetic Systems
Authors: Sadykov E. K. , Skvortsov A. I. 
Published: July 2007

AbstractThe theoretical analysis is continued of the double gamma electronic magnetic resonance (DGEMR) phenomenon described previously. The possibility of essential modification of the hyperfine magnetic structure (HMS) in the nuclear gamma resonance (NGR) spectrum under coherent excitation of the electron spin system of the paramagnetic atom is demonstrated. The influence of the r.f. amplitude on the DGEMR spectrum form is considered. The nature of the r.f. collapse of the HMS taking place in these conditions is defined. For small values of r.f. amplitude the DGEMR spectrum form in presence of the inhomogeneous broadening of ESR line and optimal experimental conditions defined by this matter are investigated.
Optical Absorption of the Soliton Lattice
Authors: Puff H. , Streitwolf H. W. 
Published: July 2007

AbstractThe optical conductivity for the soliton‐lattice solution of the continuum approximation to the Su‐Schrieffer‐Heeger model of doped polyacetylene is calculated for different excess electron densities. The optical sum rule is verified in each case. The resulting shifts of the absorption maxima are compared with experiment. Implications of the finiteness of Δ0/W (gap/bandwidth) on the nature of the phase transition and the absorption are discussed.
Gauge Theory of Defect Systems and Equivalence Principle
Authors: Holz A. 
Published: July 2007

AbstractA gauge theory of solid and liquid systems is developed based on sets of point like particles using simplicial and differential geometric methods. The proper use of the equivalence principle in the context of describing defect systems by means of gauge theory is worked out. The break‐down of the equivalence principle in the liquid state or highly defected state as a consequence of change of local order is discussed and alternatives are pointed out. Some applications of the theory to two‐dimensional systems using complex function theory are given and simple extensions of such defect structures to three dimensions are compared to space‐time structures in 2 + 1‐dimensional gravitation.
The Kink Energy in Anisotropic Media
Authors: Schoeck G. , Püschl W. 
Published: July 2007

AbstractThe energy of a kink pair is calculated by approximating the configuration by piecewise straight segments and minimizing the total energy with respect to the geometrical parameters. The elastic energy and the core energy contribute both to the total energy by nearly the same amount. The expression for the elastic energy includes all interaction terms between the different segments and takes fully account of anisotropy. The increase in core energy corresponding to the Peierls energy enters as an open parameter which can be calculated realistically only by atomistic considerations but which may be determined experimentally from the results.
Die unterschiedliche Löslichkeit der Wasserstoffisotope Protium, Deuterium und Tritium in Vanadium
Authors: Bleichert H. , Wenzl H. 
Published: July 2007

AbstractAus Löslichkeitsmessungen im Temperaturbereich 40 ≦ T ≦ 800°C und Druckbereich 10−4 ≦ p ≦ 2 × 105 Pa wird die partielle Lösungsenthalpie ΔHH und ΔS Lösungsentropie (Nicht‐Konfigurationsanteil) der Wasserstoffisotopen Protium (P), Deuterium (D) und Tritium (T) bei der Einlagerung von Wasserstoff (H) aus der Gasphase in verdünnte VHr‐Legierungen (0,003 ≦ r ≦ 0,045) bestimmt. Bei 200°C ergeben sich folgende Werte (r → O): ΔH = 29,2 kJ mol−1, ΔS = 68,1 JK−1 mol−1, ΔH = 31,1 kJ mol−1, ΔS = 71,9 JK−1 mol−1, ΔH = 34,5 kJ mol−1, ΔS = 77,9 JK−1 mol−1. Bei T < 400°C steigt bei gleichem Gasdruck die Löslichkeit mit steigender Isotopenmasse, bei T > 400°C sinkt sie mit steigender Isotopenmasse. Die Isotopieabhängigkeit in der Löslichkeit läßt sich durch ein harmonisches Oszillatormodell für die lokalisierten Schwingungen des Wasserstoffs auf Tetraederplätzen beschreiben, wobei die charakteristischen Anregungsenergien von Protium E1 = 120 meV und E2 = 180 meV (2‐fach entartet) betragen. Die Anregungsenergien der anderen Isotope ergeben sich durch Herabskalieren mit √2 für D und √3 für T.
The Surface Superconductivity of Layered Metals
Authors: Shapiro B. Ya. , Efimova L. V. 
Published: July 2007

AbstractAn investigation of the surface influence on superconducting parameters (critical temperature and upper critical magnetic field) of the metallic superlattices is made. The dependence of the critical temperature on superlattice parameters (distance L between the layers with better superconducting properties and distance D between the former from these layers and surface) is obtained. The temperature dependence of the upper critical field parallel and perpendicular to the superlattice surface is found for different ratio between L and D. The dependence of the critical parameters on number n of the layers of the superlattice is calculated. It is shown that the surface of the metallic superlattice induced superconducting state contrary to that of homogeneous superconductors.
The Thermodynamic Properties of Liquid Transition and Rare‐Earth Metals Based on CHS Model
Authors: Joarder R. N. , Das T. 
Published: July 2007

AbstractThe thermodynamic properties of liquid transition and rare‐earth metals are discussed on the basis of CHS model. The validity of the Gibbs‐Bogolyubov inequality within the thermodynamic perturbation theory is assumed. The small perturbation term is approximated by s‐d hybridisation energy in the atomic sphere approximation. The results indicate that the method yields thermodynamic quantities quite in agreement with the OCP model and much better than corresponding hard sphere results. Unlike the OCP model the expressions are obtainable analytically and in this sense the model is advantageous. The role of charge and packing on entropy calculation is also discussed in some length.
Heat Capacity and Lattice Anharmonicity in Cu‐III‐VI2 Chalcopyrite Compounds
Authors: Neumann H. , Kühn G. , Möller W. 
Published: July 2007

AbstractThe molar heat capacity at constant pressure is measured for CuGaS2 in the temperature range from 300 to 600 K and for CuGaTe2, CuInS2, CuInSe2, and CuInTe2 from 300 to 500 K with an estimated accuracy of ±1 J/mol K. The anharmonic contributions to the heat capacity at constant pressure and at constant volume are estimated and analysed in terms of perturbation theory. The volume Grüneisen functions of the compounds are evaluated and compared with existing literature data.
Electronic and Vibrational Properties of One‐Dimensional Quasi‐Crystals
Authors: He H. 
Published: July 2007

AbstractThe electronic structure of a one‐dimensional quasi‐crystal in the form of a Fibonacci sequence in tight‐binding model is extended to include next nearest neighbor couplings in addition to the nearest neighbor couplings previously included. The vibrational properties are also studied using negative eigenvalue theorem. The results of density of electronic states and square phonon frequencies are presented.
Material Constants of Composites. III. Development of the General Theory and Application to Alloys with Off‐Diagonal Disorder
Authors: Monecke J. 
Published: July 2007

AbstractIt is shown that the fourth order differential equation for the determination of effective material constants of composites or alloys from those of their constituents, derived for special cases in two previous papers, is universal in the sense that it can be applied to a wide class of physical properties. It is proved that the solution of this equation avoids multiple occupancies. Especially it can be applied to alloys with off‐diagonal disorder, too.
The Metal‐Semiconductor Transition in Amorphous Si1−xCrx Films Detection of the Transition by Room‐Temperature Measurements
Authors: Möbius A. 
Published: July 2007

AbstractThe relation between σ and dσ/dT is studied at room‐temperature. All samples investigated, which show activated conduction at low temperatures, fulfil σ(293 K) < 360 Ω−1 cm−1, whereas all samples with metallic conduction at low temperatures fulfil σ(293 K) > 440 Ω−1 cm−1. Within the regions 100 to 360 Ω−1 cm−1 and 440 to 1400 Ω−1 cm−1 nearly linear relations between σ and dσ/dT are observed. It seems likely that dσ/dT as a function of σ exhibits a knee at about 420 Ω−1 cm−1 indicating the presence of a sharp metal‐semiconductor transition at room‐temperature. The experimental results confirm quantitatively a phenomenological model of σ(T, x) in the semiconducting region, which is developed mainly on the basis of low temperature measurements in two preceding papers. On the other hand, doubts arise on the physical meaning of the ansatz α + βT1/2 + γT often used to analyse the metallic region at low T.
Optical Band Edge Absorption in CuInSe2
Authors: Medvedkin G. A. , Rud Yu. V. , Tairov M. A. 
Published: July 2007

AbstractOptical properties are studied of (100) oriented CuInSe2 (D) crystals near the absorption edge. While the edge absorption spectra in the range 80 to 370 K are found to follow Urbach's rule, there are two regions in α(ħω) differing in the temperature dependence of Urbach's parameter. The results obtained suggest that the optical band edge absorption in CuInSe2 is dominated by electron–phonon interaction. Linear optical dichroism of the edge absorption in chalcopyrite‐structure CuInSe2 is revealed and investigated. CuInSe2 is established to differ from the other chalcopyrite crystals in a negative linear dichroism near the absorption edge.
Study of the Environment of Copper in Some Ternary Chalcogenides by EXAFS Spectroscopy
Authors: Deshpande A. P. , Sapre V. B. , Mande C. 
Published: July 2007

AbstractThe EXAFS data of the K absorption discontinuity of copper in some ternary chalcogenides obtained earlier are reanalysed using the graphical method originally proposed by Lytle, Sayers, and Stern. It is shown that the graphical method gives useful information about bond lengths, and also the environment of the absorbing atom. While the phase parameters of the first coordination shell α1 and β1 provide information about the forward and backscattering atoms, respectively, the total phase shift δ1 gives an idea about the periodicity of the EXAFS function. It is also shown that the periodicity is affected by the presence of the other atoms in the second coordination shell in the ternary compounds studied. The potentiality of the graphical method to probe the environment of atoms is demonstrated.
Theory of Higher‐Order Corrections to the Electronic Stopping Power of Solids
Authors: Shindo S. , Minowa H. 
Published: July 2007

AbstractHigher‐order perturbation corrections are considered to the stopping power formula, i.e., the Bloch correction and the Barkas effect, which causes a difference of the stopping power for positive and negative charged particles. For this purpose, a semiclassical harmonic oscillator model is presented for the theory of the stopping power. It is shown that the contributions from the close collision is more important than those from the distant collision for the Barkas effect.
Mean Square Displacements of Neighbours and Phonon Resonance Due to a Vacancy in HgTe and CdTe
Authors: Madhavan Y. , Ramachandran K. , Haridasan T. M. 
Published: July 2007

AbstractThe mean square displacements (MSD) of the neighbours around a vacancy in HgTe and CdTe are worked out using Green's function technique and scattering wave formalism. The results are compared with the values of the perfect systems. The phonon resonance due to the vacancy for the above systems are also simultaneously worked out.
The Optical Absorption Edge in Thin Amorphous Oxide Films Based on Cerium Dioxide
Authors: Al‐Dhhan Z. T. , Hogarth C. A. , Riddleston N. 
Published: July 2007

AbstractMeasurements of optical absorption of thin film samples of CeO2/SnO2 and CeO2/GeO2 prepared by a co‐evaporation process at a pressure in the range 1.06 to 1.33 mPa, and having a thickness of ≈300 nm are reported. It is found that the fundamental optical absorption edge is sharp, much more like that expected for a crystalline material rather than the usual form for amorphous material, and the optical gap is increased by the addition of CeO2 to SnO2 and GeO2 films.
Temperature Dependence of Exciton Linewidth in CsI and CsBr
Authors: Beerwerth F. , Fröhlich D. , Leinweber V. 
Published: July 2007

AbstractThe temperature dependence of the linewidth of the lowest two Γ excitons in CsI and in CsBr and of a very narrow Γ exciton in CsI is reported. All spectra are measured by three‐photon spectroscopy. The analysis of the experimental results allows conclusions about the decay mechanism of excitons in alkali halides. The temperature dependent broadening is quantitatively described by taking into account exciton—phonon interaction.
Optical Properties of InS under High Pressure
Authors: Takarabe K. 
Published: July 2007

AbstractPressure effects are studied on the fundamental indirect gap (Eg), direct gap (B0), and next higher critical point (B) in InS single crystals by using a diamond‐anvil cell for the first time. A synchronized decrease of their energies is observed with pressure increasing up to 2 GPa. This unusual behavior is inferred partly due to a softening of InIn bond under pressure.
Theoretical Study of the Optical Absorption, Mössbauer, and EPR Spectra of Fe2+ Ion in Orthopyroxene
Authors: Zhou Yi‐Yang 
Published: July 2007

AbstractThe optical absorption, Mössbauer, and EPR spectra of Fe2+ ion in orthopyroxene, (Mg, Fe)SiO3, are theoretically studied using the approximated SCF d‐orbit of Fe2+ proposed by Zhao and Du. Most of the optical absorption spectra, especially the bands which have not been considered in past works, are assigned uniformly, and the Mössbauer data are fitted satisfactorily using these calculated values of the spectra. In addition, a comparison of EPR zero‐field splitting between the theoretical results and the experimental value shows that the contribution of the triplet of the Fe2+ ion in crystal is important for the zero‐field splitting.
The Faraday Effect Approach to a Study of AIVBVI Narrow‐Gap Semiconductor Band Structure
Authors: Martynchuk E. K. , Sizov F. F. 
Published: July 2007

AbstractThe magnetooptical Faraday effect in the transparency range ħhω ≦ Eg of Pb1−xSnxTe (0 ≦ x ≦ 0.23) and PbSe single crystals with carrier concentrations from 2 × 1016 to 2 × 1018 cm−3 is investigated under applied magnetic fields up to 6 T over the temperature range T = 4.2 to 300 K. g‐factors and effective masses of carriers are determined within the range of T = 4.2 to 300 K. It is shown that the experimental results with or without quantization of the energy spectrum may be interpreted only under condition ∣gc∣ > ∣gv∣, where gc and gv are the g‐factors of electrons and holes. Some new values of Dimmock six‐band model parameters g and g are obtained taking into account ∣gc∣ > ∣gv∣ condition.
The Role of Diffuse Scattering on Microdefects in the Precise Lattice Parameter Measurement
Authors: Holý V. , Härtwig J. 
Published: July 2007

AbstractDiffuse scattering of X‐rays on microdefects play a substantial role in the interpretation of the results of lattice parameter measurements according to the Bond method. A lattice parameter can be defined on the basis of the elastically quasiperfect reference crystal. To determine this lattice parameter a diffuse scattering correction must be used.
Double‐Valued Band Representations of Monoclinic and Orthorhombic Space Groups
Authors: Evarestov R. A. , Smirnov V. P. 
Published: July 2007

AbstractThe simple double‐valued band representations of the space groups C, C, C, C, D, D, D‐D are generated. These space groups describe the symmetry of the most widely spread low‐symmetry crystal structures. The dependence of the band representations on the choice of origin and setting in the space group description is discussed.
Single Electron Tunneling
Authors: Apell P. , Tagliacozzo A. 
Published: July 2007

AbstractSome of the most basic physical ingredients are discussed characterizing the observation of single particle tunneling in ultra small tunnel junctions. This includes charging energy versus image interaction and temperature, normal resistance of tunneling compared to the quantum resistance, and tunneling time versus time scale of introducing charges into the junction. Bounds are obtained for the resistance and capacitance of the junction to observe single particle tunneling and particularly the use of the recently developed scanning tunneling microscope to monitor this fundamental tunneling process is investigated.
Rigorous Ground State Energy of a Linearized Model of a Polaron in a Magnetic Field
Authors: Brosens F. , Devreese J. T. 
Published: July 2007

AbstractAn explicit analytical expression is derived for the ground state energy of a linearized polaron model in a constant and uniform magnetic field. In this model, the validity of the Feynman inequality in a magnetic field is investigated. In a fixed magnetic field, it is shown that even for arbitrarily small electron—phonon coupling, the presence of a magnetic field is prohibitive for the application of the Feynman inequality.
Density of States of a Binary Alloy with Short‐Range Order in a Bethe Lattice
Authors: Nazareno H. N. , Moreno I. Fonseca , Ribeiro‐Teixeira R. M. , Iglesias J. R. 
Published: July 2007

AbstractA study is made of the electronic structure of a binary alley in a Bethe lattice with coordination number 4. The basis set of orbitals sp3 was chosen thinking in the tetrahedral structure shown by most semiconductors. Short range order (SRO) correlation is included in the occupancy in the lattice. The results show a strong dependence of the density of states on the assumed values of the SRO parameter.
The Size‐Quantized States of the Wannier‐Mott Exciton in Structures with Superthin Films
Authors: Pokatilov E. P. , Beril S. I. , Fomin V. M. , Litovchenko V. G. , Korbutyak D. V. , Lashkevich E. G. , Mikhailovskaya E. V. 
Published: July 2007

AbstractResults are given of the experimental investigation of exciton absorption spectra in superthin films of PbI2 deposited on various substrates (glass, mica, metal). A theory of exciton states in thin polar films is developed, on the basis of which excitonic and band size effects are analyzed. The theory is in qualitative and quantitative agreement with the experiment.
Impurity Binding Energies in Heterostructures
Authors: Costa W. B. , Albuquerque E. L. 
Published: July 2007

AbstractThe transfer‐matrix theory for a one‐dimensional heterostructure is discussed. The applicability of effective‐mass approximation to the calculation of impurity binding energy is also presented. It is shown that both treatments lead to almost the same results which indicates the suitability of this approximation. Numerical results of the density of states are performed and their features discussed.
Low‐Temperature Conductivity of a Weakly Disordered, Strongly Anisotropic Two‐Dimensional System with Electron—Electron Interaction. Application to Germanium Bicrystals and to Surface Superlattices
Authors: Firsov Yu. A. , Nakhmedov E. P. , Prigodin V. N. , Weller W. 
Published: July 2007

AbstractIn the framework of a simple model for the electron gas in the grain boundary (inversion layer) of a semiconductor bicrystal or in a surface superlattice the quantum corrections to the conductivity tensor due to the electron—electron interaction are calculated. The results have a typical two‐dimensional form for w ≫ kBTħ/τ and show a crossing‐over to typical one‐dimensional behaviour for w ≪ kBTħ/τ. Here w⟂ is the transverse overlap integral betwween neighbouring dislocation tubes, τ the relaxation time due to scattering on the disorder. Also the weak localization corrections are calculated.
Spin Coherent States, Holstein‐Primakoff Transformations for Heisenberg Spin Chain Models, and Status of the Landau‐Lifshits Equation
Authors: Makhankov A. V. , Makhankov V. G. 
Published: July 2007

AbstractThe XXZ Heisenberg spin chain is considered. Following results are obtained: for the Bosonization of the spin Hamiltonians widely used Holstein‐Primakoff transformations are very sensitive to the way of breaking an initial system symmetry by the ground state. In the case of easy‐axis models only such transformations may be applied without previous analysis (at any rate when an external magnetic field vanishes). Others are subjected to the corresponding symmetry analysis.
Theory of Two‐Step Spectral Hole Burning by Pulses
Authors: Rebane I. K. 
Published: July 2007

AbstractA two‐step spectral hole burning (SHB) is considered, where the selective excitation of the first step is fixed by a photochemical transformation through the second excitation step. It is shown that in a three‐level system excited by two consecutive pulses, the kinetics of the forming spectral hole differs essentially from the one on stationary irradiation. In the case of a short second pulse the shape of the hole in the inhomogeneous distribution function (IDF) of the purely electronic line frequency Ω01 is dependent on the time interval T between the first and second excitation steps and under certain conditions a hole can be obtained which is narrower than in the one‐step SHB with monochromatic light. It is considered how the hole in IDF is manifested in the absorption and two‐step pulse excitation spectra. It is shown that the hole in the absorption spectrum may be narrower than 2γ1 and in the two‐step pulse excitation, −γ1 (γ1 is the energy relaxation constant of the first excited level).