bluuebunny/crossref_metadata_2025 huggingface dataset:
CHAOTIC DYNAMICS OF HIGH DENSITY PHOTON AND EXCITON SYSTEM
Authors: DAN NGUYEN TRUNG , AN NGUYEN BA , MINH LE NGOC
Published: November 2004

We consider nonlinear dynamics of a system of interacting photons and excitons driven by a resonantly exciting light field. Using the linear stability analysis for nonlinear coupled equations of photon and exciton operators we investigated that, besides the usual unstable domain which is a negative slope branch, there are other unstable ones in the leftmost and rightmost sides of the lower and upper branches of the frequency-density bistable curves. Numerical study shows that the system has very rich information on the instability nature and a self-oscillation process leading to chaos can occur in these unstable domains.
TILINGS OF TRIACONTAHEDRA
Authors: ABRAMOVICI GILLES
Published: November 2004

We propose to prove rigorously a general result about bidimensional tilings made of triacontahedra. There exist exactly four kinds of perfect tilings, one of them being closed. These objects can be used in the geometrical construction of quasicrystals in particular with twins or clusters.
LINEAR RESPONSE THEORY: A HISTORICAL PERSPECTIVE
Authors: NAKANO HUZIO
Published: November 2004

A survey is given of the development of the linear response theory of transport processes in Japan in a short period between early 1955 and late 1956, immediately after the discovery of the formula for electrical conductivity. Although the article gives a historical account, it also provides sufficient pedagogical material for those who wish to study linear response theory. The conventional theory based on the Boltzmann-Bloch equation is also briefly reviewed for the sake of pedagogical completeness. To clarify the origin of irreversibility, variational principles of transport processes are described including Onsager’s thermostatistical theory, which are well known in conjunction with the reciprocity relations of transport coefficients. These variational principles correspond to various levels of the description of nonequilibrium systems. Contraction of microscopic to a macroscopic information transforms one variational principle into another. A reflection upon the foundation of linear response theory is given through the comparison of two different traditional theories of transport processes, Thomson’s theory of thermoelectricity and Onsager’s thermostatistical theory.
STATISTICAL MEMORY MODEL FOR POLYMER CHAIN SHAPES
Authors: DOROTHEYEV E.A. , DOTSENKO V.S. , TIROZZI B.
Published: November 2004

We study the equilibrium configurations of heteropolymer chains in the infinite-dimensional space. The number of sorts of monomers composing the chains is finite. The interactions between pairs of monomers are defined (using Hebbian learning rule) in such a way that in the thermodynamic limit the equilibrium configurations of the polymers are some preassigned shapes. The phase diagram of the model is obtained and the memory capacity is computed.
SOLUTION OF THE COOPER-BCS EQUATIONS WITH AN ENERGY-DEPENDENT ELECTRON-BOSON INTERACTION
Authors: DALLACASA V. , PAIUSCO M. , MANES L.
Published: November 2004

A numerical solution of the Cooper-BCS model is given, taking into account the energy dependence of the pair interaction U(ε) in the form suggested by Fröhlich.

At energies corresponding to scales Δx≈100 A this model is found to predict a high Tc≈100 K, with absence of isotope effect, in the weak to moderate coupling limit, and to reduce to the usual BCS model with constant interaction at macroscopic scales.
QUALITY CONTROLS ON HIGH-Tc BASED TUNNEL JUNCTIONS
Authors: CUCOLO A.M.
Published: November 2004

We report on systematic studies to perform quality controls on planar tunnel junctions realized on high-T c superconductors (HTS). Tunneling spectra of the orthorhombic 90 K and 60 K YBa2 Cu 3O7−δ phases, of the magnetically doped, tetragonal YBa 2( Cu 0.96 Fe 0.04)3 O 7 compound and of the Bi 2 Sr 2 CaCu 2O8 system are analyzed. The traditional, low-bias barrier analysis as well as a number of tests useful to investigate the “status” of the HTS surface layer are carried out. Evidence is given that some anomalous tunneling data can be understood in terms of a Kondo-type scattering between tunneling electrons and magnetic impurities at the interface. The reproducibility of the tunneling spectra for different junction fabrication conditions is also discussed.
MAN-MADE LOW-DIMENSIONAL SOLIDS: NEW CHALLENGES IN MICROSTRUCTURE MATERIALS SCIENCE
Authors: NÖTZEL RICHARD , PLOOG KLAUS H.
Published: November 2004

Size quantization in man-made semiconductor structures of less than three-dimensions leads to exciting new electronic properties which are important for fundamental physics and for development of novel device concepts. Fundamental research as well as device applications based on these low-dimensional semiconductor structures require methods to fabricate the structures and to control their geometrical size on the nanometer scale in a reproducible manner. We introduce a new concept to directly synthesize III-V semiconductor quantum-wire and quantum-dot structures. The concept is based on the evolution of well ordered macrosteps (facets) on non-(100)-oriented GaAs surfaces during molecular beam epitaxy which allows us to produce arrays of alternating narrow and wide regions of GaAs in an AIAs matrix. This arrangement forms symmetric and asymmetric GaAs quantum-dot structures on (111) and (211) surfaces, respectively, and quantum-wire structures on (311) substrates. The accumulation of steps by step bunching on (210) GaAs makes possible the fabrication of mesoscopic step arrays in GaAs/AlAs multilayer structures having a periodicity of 230 Å. This periodicity is comparable to the exciton Bohr radius and thus of particular importance for the modulation of the electronic properties of GaAs based heterostructures. The existence of all these quantum-wire and quantum-dot structures is confirmed by high-resolution transmission-electron microscopy and atomic-force microscopy. The quantum confinement of carriers is revealed by the distinct electronic properties.
COLLECTIVE EXCITATIONS IN DISORDERED SYSTEMS
Authors: SUCK JENS-BOIE
Published: November 2004

After an introduction into the field of collective excitations in disordered matter and into neutron inelastic scattering (NIS) techniques used for their investigation, results obtained by NIS experiments on classical fluids and amorphous solids are reviewed. It is concluded that a reasonably good understanding has been acquired during the years concerning the dispersion of excitations in liquid metals and rare gas fluids and partly also in metallic glasses. However, the damping of these modes and the collective excitations in fluids and in amorphous solids with other than metallic or pure molecular bonds still need to be investigated experimentally in more detail until a comparable understanding of the collective movements and their decay in these systems has been gained and theoretical predictions can be tested on a quantitative basis. With a few exceptions systematic studies under favorable experimental conditions (dedicated instruments) and high quality data are lacking up to now.
MAGNETIZATION DISTRIBUTIONS
Authors: BROWN P.J.
Published: November 2004

The determination of magnetization distributions using neutron scattering is not a new technique but one that has developed over the last 30 years. In the present article a brief introduction to the technique is given, methods used for the analysis of the data obtained are critically reviewed, and some of the new results which have been obtained in the last five years are presented. Attention is concentrated on examples for which the results obtained have helped to answer questions in areas of high current interest.
ROTATIONAL TUNNELLING SPECTROSCOPY WITH NEUTRONS
Authors: CARLILE C.J. , PRAGER M.
Published: November 2004

Neutron tunnelling spectroscopy has been a very fruitful field for almost two decades and is still expanding into new areas, both experimentally and theoretically. The development of the topic is reviewed from the theoretical point of view, highlighting new approaches, and selected examples of more recent experimental work are presented. A brief discussion of instrument performance and experimental requirements is given.
ELECTRICAL AND MAGNETIC MEASUREMENTS IN K DOPED GdBa2Cu3O7−d HIGH TEMPERATURE SUPERCONDUCTORS
Authors: VIDYALAL V. , RAJASREE K. , VALLABHAN C.P.G. , THOMAS PREETHI CICILY , NAYAR V. UNNIKRISHNAN
Published: November 2004

Stable and reproducible superconducting transition between 92 K and 100 K has been observed both resistively and magnetically in potassium doped GdBa 2 Cu 3 O 7−δ ceramic material. It has been found that the sintering temperature as well as stoichiometry plays an important role in determining the value of T c . Subtle changes in T c occur for certain weight % of K. The effect of changing composition on the superconducting transition temperature is also reported here.
THE ROLE OF MICROGEOMETRY IN THE ELECTRICAL BREAKDOWN OF METAL-INSULATOR MIXTURES
Authors: YAGIL YOAD , DEUTSCHER GUY , BERGMAN DAVID J.
Published: November 2004

The breakdown phenomena of percolative metal-insulator composites and their extreme sensitivity to fine details of the microgeometry are discussed, for three different cases: the critical current of superconductor-insulator mixtures (or superconductor-normal metal); the dielectric breakdown of metal-insulator composites below the percolation threshold (insulating regime); and the electrical breakdown above the metal-insulator transition (metallic regime). Two experimental techniques for characterizing the microgeometry are described: (a) 1/f noise measurements, which provide the fourth moment of the current distribution; (b) the harmonic generation method, where the weakly nonlinear electrical response due to local Joule heating provides information on the fourth (and higher) moment of the current distribution.
CHARGE TRANSPORT AND CONDUCTION MECHANISM OF COPPER SUBSTITUTED MAGNESIUM ALUMINIUM FERRITES
Authors: PURUSHOTHAM Y. , REDDY V. DEVENDER , MULAY V.N. , REDDY K. BHUPAL , REDDY P. VENUGOPAL
Published: November 2004

Electrical conductivity (σ) and thermopower (S) studies of polycrystalline copper substituted magnesium aluminium ferrites of different composition were investigated in the temperature range 300–800 K. Plots of log (σT) versus 103/T are almost linear and show a clear transition near the Curie temperature. On the basis of the sign of Seebeck coefficient, all the samples under investigation have been classified as n-type semiconductors. The temperature variation of Seebeck coefficient curves also exhibited a well defined magnetic transition at the Curie temperature. Using the temperature variation of charge carrier mobility a conduction mechanism in these ferrites is suggested.
EXACT SPECTRUM OF THE INTEGRABLE 3-STATE POTTS CHAIN
Authors: ALBERTINI G. , DASMAHAPATRA S. , McCOY B.
Published: November 2004

From a system of Bethe-Ansatz equations, the spectrum of low-lying excitations is found for the 3-state Potts chain in its ferromagnetic and antiferromagnetic version. In both cases, only massless excitations appear and their dispersion relations are computed.
CHIRAL POTTS MODEL: CORNER TRANSFER MATRICES AND PARAMETRIZATIONS
Authors: BAXTER R.J.
Published: November 2004

We consider the star-triangle relation and the form of its solutions. We present some simple parametrizations of the weight functions of the three-state chiral Potts model. This model does not have the “difference property”: we discuss the resulting difficulties in attempting to use the corner transfer matrix method for this model.
INVERSION AND SYMMETRY RELATIONS FOR A THREE-DIMENSIONAL SOLVABLE MODEL
Authors: BAZHANOV V.V.
Published: November 2004

The solvable sl(n)-chiral Potts model can be interpreted as a three-dimensional lattice model with local interactions. To within a minor modification of the boundary conditions it is an Ising type model on the body centered cubic lattice with two- and three-spin interactions. We discuss the spatial symmetry properties of the model and show that its partition function per site obeys the inversion relation. The connection with the free boson model is also discussed.
QUANTUM TOPS
Authors: REYMAN A.G.
Published: November 2004

We shall discuss here the problem of quantization of integrals of motion for completely integrable Hamiltonian systems decribed by Lax equations with a spectral parameter. Multi-dimensional tops and their analogs are the most interesting examples of such systems, which motivates the title. The construction of these systems and their quantization procedure are based on a Lie-algebraic scheme which for finite-dimensional Lie algebras is due essentially to Kostant [1]. The extension to loop algebras, i.e. to Lax equations with a spectral parameter, was proposed by Reyman and Semenov-Tian-Shansky [2] ; quantization in this case is obstructed by the absence of Casimir elements in the corresponding universal enveloping algebra. To some extent the situation is remedied by the reappearance of central elements for the associated Kac-Moody algebra at the critical value of the central charge (Sugawara operators), as shown by Malikov [3]. Thus, the Lie-algebraic approach to quantization has given so far only partial results. We shall try to describe here the current state of the problem.

The author would like to thank L.P.T.H.E. of the University Paris-VI and the Mathematics Department of the University of Montpellier II for their hospitality.
A CRITICAL ISING MODEL IN A MAGNETIC FIELD
Authors: WARNAAR S. OLE , NIENHUIS BERNARD , SEATON KATHERINE A.
Published: November 2004

Generalising ideas developed by Owczarek and Baxter and by Pasquier, we establish an equivalence between restricted solid-on-solid models and loop models. Application to the O (n) model leads to a new family of solvable A-D-E models. For the models related to the classical A L algebra we present an off-critical extension and show that the A 3 model thus obtained can be viewed as a critical spin-1 Ising model in a magnetic field. For this Ising model we calculate the critical exponent δ=15 without the use of scaling relations.
CONDUCTION ELECTRON IN THE ANISOTROPIC MEDIUM
Authors: SAFONOV VLADIMIR L.
Published: November 2004

A new model for describing free electrons and holes in crystals in the long-wavelength approximation is proposed. The crystalline anisotropy in the framework of this model is introduced by means of corresponding space-time geometry. The generalized Dirac’s equation is constructed and non-relativistic Hamiltonian containing energy terms of the order of c–2 is calculated. It is shown that the spin magnetic components depend on corresponding effective cyclotron masses. Applicability of the results of the proposed model to different experiments is discussed. For the one-dimensional case, a hypothesis of para-Fermi statistics is suggested which may appear to explain one more mechanism of high-T c superconductivity.
NONSTATIONARY JOSEPHSON EFFECT AND QUASIPARTICLE TUNNELING BETWEEN PARTIALLY-DIELECTRIZED SUPERCONDUCTORS WITH CHARGE-DENSITY WAVES
Authors: GABOVICH A.M.
Published: November 2004

The tunnel junctions between superconductors where the Fermi surface (FS) is partially dielectrized are considered. The dielectrization due to Coulomb- and (or) electron-phonon interactions leads to the emergence of the dielectric gap Σ on nested FS sections and the existence of the charge-density waves below temperature T=T d . When T<T c <T d the partially-dielectrized metals become superconductors with a corresponding gap ∆. The voltage dependences of the nonstationary Josephson current and quasiparticle current are calculated for such junctions. The current-voltage (I–V) characteristics involve several Riedel-type singularities and jumps for voltages equal to definite combinations of gaps ∆ and Σ in the fermion excitation spectrum. So, I–V curves are much more complex than the ones for usual BCS-type superconductors. The results for quasiparticle tunneling agree with the experimental data available for oxides.
NIOBIUM PHOSPHATE BRONZES — STRUCTURAL RELATIONSHIPS WITH PURE OCTAHEDRAL OXYGEN TUNGSTEN BRONZES
Authors: RAVEAU B. , BOREL M.M. , LECLAIRE A. , GRANDIN A.
Published: November 2004

The phosphate niobium bronzes form a large family of structures characterized by pentagonal or hexagonal tunnels. The host lattices of these oxides, involving a mixed valency of niobium Nb(V)-Nb(IV) are described here. The close relationships with pure octahedral structures, mainly perovskites, hexagonal tungsten bronzes (HTB) and tetragonal tungsten bronzes (TTB), and K 3 Nb 8 O 21 are studied.
TUNGSTEN OXIDES AND BRONZES: SYNTHESIS, DIFFUSION AND REACTIVITY
Authors: GUO JING-DONG , WHITTINGHAM M. STANLEY
Published: November 2004

The tungsten oxides and bronzes have been extensively studied since their discovery in the last century, because of their brilliant colors and high electrical conductivity. More recently the driving interest resulted from their potential use in electrochromic displays and other electrochemical systems. Their crystalline structures are generally based on the corner sharing of WO 6 octahedra giving tunnels of variable size and shape leading to exciting intercalation chemistry. These structures readily undergo redox reactions, and in the last quarter century these reactions have often involved soft chemistry. Most recently hydrothermal techniques have been used to prepare new sodium tungstates with the hexagonal tungsten bronze and the pyrochlore structures. The phase formed is a function of the pH of the reaction medium. The pyrochlore phase readily undergoes ion-exchange with a wide range of monovalent cations giving the compounds, M x W 2 O 6+x/2 · y H 2 O ; the value of y is strongly dependent on the identity of the cation, M. WO 3 with the pyrochlore structure could be formed from the hydronium and ammonium complexes. Lithium can be readily intercalated either chemically and electrochemically into both these phases, just as in the previously-known bronze phases. Surprisingly more lithium is incorporated in most cases in the hexagonal than in the pyrochlore phase. The ions in the pyrochlore structure show rapid ionic mobility, with the hydronium ion showing the greatest mobility.
ELECTRON-OPTICAL PHONON INTERACTIONS IN POLAR SEMICONDUCTOR QUANTUM WELLS
Authors: TSEN K.T.
Published: November 2004

Electron-optical phonon interactions in polar semiconductor quantum wells are reviewed. Three macroscopic and one microscopic models for electron-optical phonon interactions are compared with experimental results in GaAs-AlAs polar semiconductor quantum wells recently obtained by picosecond time-resolved Raman spectroscopy. The macroscopic model of Huang and Zhu as well as the microscopic model of Rucker et al. are found to be in good agreement with the experimental data. Direct measurements of electron-optical phonon scattering rates in GaAs-AlAs polar semiconductor quantum wells carried out by subpicosecond time-resolved Raman scattering technique are also presented. These experimental results are explained with the model of Huang and Zhu.
EFFECT OF AL ON ELECTRIC CONDUCTIVITY AND SUPERCONDUCTIVITY OF NB-Si-AL-O CERAMIC
Authors: KOBA S. , HIGO S. , HAKURAKU Y. , KAWANO I. , OGUSHI T. , NAKAO A.
Published: November 2004

Metal-insulator transition and superconductivity with changing Al composition were observed in the Nb-Si-Al-O system. Semiconductor-like characteristic and normal conductive characteristic were observed for Al <40% and Al >50% respectively. Super-conductive compositions are distributed around the boundary between those two types of conductivity, such as Nb x SiAl (α–x) O z((α, x)=(1.5, 0.7), (2.0,0.8), (3.0, 0.7~1.4)). The superconductivity was confirmed by resistive transitions and diamagnetic transitions. The superconductors in this study have T c =10.0~11.5 K with resistive transitions, and the amplitudes of the diamagnetism reach 30~58% of that of pure Nb powder. X-ray diffraction patterns of any other superconducting Nb-systems such as Nb , Nb 3 Al , Nb 3 Si , NbN , and NbC , have not been observed in Nb-Si-Al-O .
QUANTUM TUNNELING EFFECTS IN THE SSH MODEL OF ELECTRON-PHONON INTERACTIONS
Authors: QUÉMERAIS PASCAL , CAMPBELL DAVID K. , RAIMBAULT JEAN-LUC , AUBRY SERGE
Published: November 2004

We examine the Su-Schrieffer-Heeger (SSH) model of electron-phonon (e-p) interactions as an example of a theory in which commensurate and incommensurate bond-order wave (BOW) ground states are generated (in the quasi-one-dimensional (quasi 1-D) case) by an intersite e-p coupling. We focus primarily on the two-fold commensurate situation, in view of its applicability to the important quasi 1-D conducting polymer trans-polyacetylene (trans — (CH) x). Using a coherent state formalism to model the quantum fluctuation corrections to the adiabatic ground state, we study the quantum tunneling of the SSH “solitons” (viewed as discommensurations created in the two-fold commensurate ground state) and show that, as a result of this tunneling, the energy of the discommensurations can become negative for e-p couplings below a certain critical coupling. We argue that this negative defect energy is an indication of the instability of the underlying adiabatic commensurate BOW state. The critical e-p coupling for this transition depends on the phonon frequency and, for general commensurability, on the commensurability ratio. Thus, in real trans — (CH) x chains where the e-p coupling and the bare phonon frequency are fixed, the transition we describe can occur as a function of doping (which can change the effective commensurability) and may explain the BOW-to-quasimetal transition in doped (CH) x. For quasi-1-D systems, we also estimate the critical e-p couplings for the three-fold commensurate and incommensurate cases. We conclude by mentioning possible extensions of our approach and results to the new family of “fullerenes”, C n(n≥60).
NNN-ISING MODEL SIMULATION OF NANODOMAIN TEXTURES IN RELAXOR-TYPE LEAD SCANDIUM TANTALATE
Authors: QIAN H. , PENG J.L. , BURSILL L.A.
Published: November 2004

Chemical domain textures for lead scandium tantalate (PST) are modelled using Monte Carlo (MCS) and next-nearest-neighbor Ising (NNNI) models. A wide range of degrees of short- and long-range ordering of the (Ta, Sc) atoms occur in ceramic specimens, depending on processing routes. The simulations help us understand and quantify the chemical domain textures, chemical domain wall configurations and other chemical defects which may occur in certain relaxor-type perovskite-type oxides. The results are compared to dark-field transmission electron microscopic observations.

Some new types of small defects were discovered. These are described and classified. The results provide a first step towards the development of a microscopic statistical physics framework for analytical theories of the dielectric response of relaxor-type ceramics, where the frequency and temperature variation of the permittivity are due essentially to dipolar-type fluctuations on nanometer scales.
SECOND-ORDER AND AMPLITUDE-SQUARED SQUEEZING OF THE TWO TWO-LEVEL ATOMS WITH SUPERPOSITION STATE PREPARATION
Authors: MIR MUBEEN A.
Published: November 2004

An analysis of the second-order and amplitude-squared (AS) squeezing is presented for the two atoms prepared in a two-atom squeezed state using coherent and squeezed field inputs. The system produce strong sqeezing and superposition angle (θ) is more effective for small values of average photon number [Formula: see text] as compared to that of large one. The degree of squeezing of both types increases as θ increases for coherent field input with small [Formula: see text]. Some values of θ for the initial field in a squeezed-vacuum state with any value of input squeezing can make one of the quadrature of the both types of squeezing permanently squeezed for T≥0. For the initial field in a more general squeezed state, the second-order and AS squeezing behave randomly for different values of θ.
TWO COMPONENT ANYON SUPERFLUID WITH COMPLEMENTARY STATISTICS: A MODEL WITH SUPPRESSED PARITY VIOLATION
Authors: GOITY J.L. , SOTO J.
Published: November 2004

We analyze an anyon superfluid of the standard kind. The model is composed of equal number density of two types of anyons carrying complementary statistics and interacting via a repulsive hard-core potential. This system shows a suppression of parity violation. The analysis is carried out in the limit of quasi-bosonic statistics, where we show that the interactions induced by the statistics tend to suppress the condensate. We argue that a phase transition occurs as the hard-core interaction becomes sufficiently weak and give an estimate of the critical coupling.
SLATER DECOMPOSITION OF LAUGHLIN STATES
Authors: DUNNE GERALD V.
Published: November 2004

The second-quantized form of the Laughlin states for the fractional quantum Hall effect is discussed by decomposing the Laughlin wavefunctions into the N-particle Slater basis. A general formula is given for the expansion coefficients in terms of the characters of the symmetric group, and the expansion coefficients are shown to possess numerous interesting symmetries. For expectation values of the density operator it is possible to identify individual dominant Slater states of the correct uniform bulk density and filling fraction in the physically relevant N→∞ limit.
QUANTUM PHASE GATING WITH SEMICONDUCTOR QUANTUM DOTS IN A MICROCAVITY
Authors: FENG MANG
Published: November 2004

We propose a scheme to carry out quantum phase gate in one step by bichromatic radiation method with semiconductor quantum dots (QDs) embedded in a single mode microcavity. The spin degrees of freedom of the only excess conduction band electron are employed as qubits and excitonic states are used as auxiliary states. The nearest-neighbor coupling is not required because the cavity mode plays the role of data bus. We show how to perform quantum computing with properly tailored laser pulses and Pauli-blocking effect, without exciting the cavity mode.
RECONSTRUCTING THE WIGNER FUNCTION OF FIELD-MODES IN TWO SPATIALLY-SEPARATED CAVITIES
Authors: YUAN CHUN-HUA , ZHANG ZHI-MING
Published: November 2004

We suggest a scheme for reconstructing the Wigner function of two-mode fields. The scheme is based on the interaction between a Λ-type three-level atom and two field-modes in spatially-separated cavities. The two field-modes are displaced with two classical coherent fields and the atom passes through the two cavities successively. We find that there is a simple relation between the Wigner function of the cavity fields and the atomic populations. Therefore, we can reconstruct the Wigner function of cavity fields by measuring the atomic populations in the micromaser experiments.
LEVEL STATISTICS TRANSITIONS IN THE TWO-SPIN CLUSTERS
Authors: JIANG YIMIN , LIAO JIZHI
Published: November 2004

The nearest neighbour distribution (NND) and Δ3 statistics for the two-spin model are studied numerically. As one of the model parameters w increases from zero, the results show a standard Poisson–Wigner (GOE)–Poisson transition in the NND. In the integrable case w = 0, the NND of the model shows a remarkable deviation from the Poisson prediction, so gives a novel example of non-generic NND.
SHELLS AND SUPERSHELLS IN METAL CLUSTERS
Authors: GENZKEN O.
Published: November 2004

We analyze the shell and supershell structure of valence electrons in large metal clusters. For this purpose we use the spherical jellium model for the ions, treat the many-body problem of the interacting valence electrons selfconsistently in local-density approximation and solve numerically the Kohn-Sham equations for up to N ~ 6000 electrons. We investigate the influence of temperature effects on the shell structure and compare our results to experimental data and other calculations performed with phenomenological Woods–Saxon potentials.
DETECTING PHASE EQUILIBRIA IN MODELS OF THERMOTROPIC AND LYOTROPIC LIQUID CRYSTALS
Authors: ZHANG ZHENGPING , MOURITSEN OLE G. , ZUCKERMANN MARTIN J.
Published: November 2004

New ways are discussed of numerically detecting the nature of phase transitions and the position of phase equilibria in models of thermotropic and lyotropic liquid crystals where the phase transitions are dominated by strong fluctuations. The cases of continuous transitions (critical points), first-order transitions, as well as the absence of transitions, are considered. It is shown how computer-simulation techniques, which operate on a free-energy level by using reweighting (histogram) techniques in combination with finite-size scaling theory, provide an effective tool for unambiguously determining the nature of the transition and the position of associated phase equilibria. Three specific models are considered: the Lebwohl–Lasher model of the nematic–isotropic transition in thermotropic liquid crystals, the mismatch model of the main chain-melting phase transition in lipid-bilayer lyotropic liquid crystals, and a model for critical mixing in a lipid-bilayer lyotropic liquid crystal incorporated with trans-bilayer polypeptides.
XANES AND EPR SPECTROSCOPIC PROOFS FOR EXISTENCE OF PAIRING HOLES IN HIGH-Tc SUPERCONDUCTORS
Authors: ASATURIAN R. A.
Published: November 2004

XANES and EPR spectra data are presented which prove the existence of holes with 3d9L configuration in YBa 2 Cu 3 O 7 − δ at 293 K. With a growth of concentration of these holes, the absorption intensity in XANES spectra near the absorption of the formally trivalent copper at T < T c grows with the increase of T c . When this absorption appears in XANES spectra at T < T c , disappearance of EPR signal is observed under the same conditions. Such absorption is also observed in the bismuth ceramics at T < T c . The data obtained prove that pairing holes make a contribution to this absorption.
VARIOUS CONDENSED MATTER HAMILTONIANS IN TERMS OF U(2/2) OPERATORS AND THEIR SYMMETRY STRUCTURES
Authors: OKUMURA KO
Published: November 2004

We rewrite various lattice Hamiltonians in condensed matter physics in terms of U(2/2) operators that we introduce. In this representation the symmetry structure of the models becomes clear. Especially, the Heisenberg, the supersymmetric t-J and a newly proposed high-T c superconducting Hamiltonian reduce to the same form [Formula: see text]. This representation also gives us a systematic way of searching for the symmetries of the system.
CONFINEMENT OF STATES ABOVE POTENTIAL BARRIERS IN SEMICONDUCTOR SUPERLATTICES
Authors: LUO H. , FURDYNA J. K.
Published: November 2004

We discuss the localization of states whose energy exceeds potential barriers in a semiconductor superlattice. Although there are no confining potentials for such states, the potential discontinuities reflect the electron waves in such a way as to impose constructive interference conditions on the electron states, leading to significant confinement effects.
VARIATIONAL APPROACH TO THE THEORY OF ELASTICITY: AN INTRODUCTION
Authors: ALEXE-IONESCU A. L.
Published: November 2004

An alternative approach to the elastic theory is presented. Starting with a variational principle the bulk differential equation and the boundary conditions of the basic problem of the elastic theory are deduced. The elastic potential energy and the stress tensor are obtained in a simple way. The total force and torque acting on a deformed elastic body are evaluated.
PHASE ORDERING SIMULATION OF VECTOR ORDER-PARAMETERS WITHOUT SINGULAR DEFECTS
Authors: TOYOKI HIROYASU
Published: November 2004

Cell dynamical study of phase ordering dynamics is presented for vector order-parameter systems without singular defects. The structure factor satisfies the scaling relation; S (k, t) = l (t)2 g(kl(t)), whose tail at kl ≫ 1 is characterized by a single power as g (x) ~ x −χ. The exponent χ is larger than an analytical value χ = d + n where n and d are the dimensionality of order-parameter and space respectively. The characteristic length varies as l (t) ~ t0.5 for n ≥ 4 while the growth for n = 3 is slower than that.
AC LOSSES IN YBa2Cu3O6+x WITH TRAPPED MAGNETIC FLUX
Authors: CISZEK M. , OLEJNICZAK J. , ZALESKI A. J.
Published: November 2004

Results of measurements of low frequency ac losses in a cylindrical YBa 2 Cu 3 O 6+x sample subjected to a sinusoidally varying magnetic field are presented. Magnetic history effects are not observed if only the ac field is cycling. A quite different behavior is observed if dc magnetic field is trapped in the sample. In such a case, a significant increase, above one order of magnitude, of intergranular losses is observed, whereas the dissipation in granules remains practically unchanged. Moreover, there exists a threshold value of the applied dc magnetizing field below which changes of the ac losses connected with the magnetic history of the sample are not observed. Its value is approximately equal to the first penetration field for the grains.
CAPACITANCE PROPERTY OF A RESONANT TUNNELING DIODE
Authors: SHENG HANYU , CHUA SOO-JIN , SINKKONEN JUHA
Published: November 2004

A simple capacitance formula based on a semiclassical electron transport theory is given. The results show that the charges stored in the quantum well of a resonant tunneling diode have a considerable effect on the capacitance in the resonant region. The calculated capacitance is consistent with the experimental results.
DISTRIBUTION OF ELECTROLYTES WITH EXCLUDED VOLUME AROUND A CHARGED DNA MOLECULE
Authors: WIEGEL F. W. , STRATING P. , GARCÍA A. E.
Published: November 2004

In this paper we evaluate the distribution of ions around a charged cylinder, in thermal equilibrium, taking into account the main effects of the excluded volume of the counterions. The cylinder is a model of a DNA molecule. There are major corrections to the standard Gouy-Chapman theory when the electrostatic energy due to the charge of the cylinder is large as compared to the thermal energy. The concentration shows a distinct saturation effect over a finite region, which may be interpreted as the Stern layer of immobilized ions. The known saturation of the electrostatic potential at the surface of the cylinder is removed.
HIGH METALLIC RESISTIVITIES AND RESISTIVITY SATURATION: HIGH-PRESSURE AND THERMAL EXPANSION EFFECTS
Authors: SUNDQVIST BERTIL
Published: November 2004

Some recent developments in the field of resistivity saturation in metallic materials are discussed, concentrating on effects of thermal expansion and high pressures. It is shown that thermal expansion effects can significantly modify the measured temperature dependence of the resistivity, and that high pressure studies are an important, but little used, source of information. Examples are shown for transition metals and alloys, high transition temperature superconductors, and graphite intercalation compounds.
ELECTRICAL TRANSPORT PROPERTIES OF Nb-DOPED SrTiO3 FABRICATED ON MgO(100) AND SrTiO3(100) SUBSTRATES BY REACTIVE EVAPORATION METHOD
Authors: NAGATA M. , MIZUNO Y. , NOJIMA H. , SUGAWARA K. , KOBA M.
Published: November 2004

Undoped and Nb-doped SrTiO 3 films have been fabricated on SrTiO 3(100) and MgO(100) substrates at temperatures between 500°C and 800°C by a reactive evaporation method. The single-crystallinity of these films was confirmed by X-ray diffraction and RHEED studies. Better crystallinity was obtained for films fabricated at substrate temperatures of 700°C and 800°C. Metallic behavior was found in the resistivity vs. temperature relation for all the films with Nd concentration between ~ 0.5 wt.% and ~ 5wt.%. Hall mobility measurements revealed that the carriers are electrons in all the Nb-doped films. The mobility decreases with increasing temperature for all the Nb-doped samples. The Hall mobility measurements for the highly Nb-doped (~ 5 wt.%) film revealed that a larger mobility is obtained for films grown at higher substrate temperatures.
THE VAN DER WAALS INTERACTION BETWEEN ALKALI MICROCLUSTERS
Authors: PACHECO J. M. , EKARDT W.
Published: November 2004

The nonretarded van der Waals coefficients C6 and C8 are determined for all pairs of neutral sodium and potassium microclusters with 1, 2, 8 and 20 atoms. The spherical jellium approximation is used to replace their ionic cores, and the valence electrons are treated in the local density approximation of density functional theory. The dynamical polarizabilities of these systems are computed making use of three different methods, two microscopic and quantum mechanical linear response formulations and one classical. It is found that quantum size effects, in particular Landau fragmentation, play a crucial role in the determination of these coefficients. Furthermore, we find that self-interaction errors present in standard microscopic approximations lead to sizeable effects in the strength of the van der Waals coefficients. On the other hand, we find that the vibrational temperature of these clusters has a very small effect in the van der Waals interaction which can be disregarded within the range of temperatures presently reachable experimentally.
THREE-DIMENSIONAL TlBaCaCuO THICK FILM DC SQUID
Authors: HUO YUHUA , ZHAO SHOUZHEN , SHAO FANGWU , WEI CHANGCHUN , ZENG LINGWEN , ZHAO WEILI , XUE SHOUQING
Published: November 2004

TlBaCaCuO thick films were fabricated by the method of screen printing. Zero resistance temperature of 110 K–118 K and critical current density of about 102 A/cm 2 at 77 K were obtained. The thickness of the film was about 30 μm. Using the thick film we have fabricated three-dimensional DC SQUID. The flux modulated V–I curve, V–H curve, and triangular patterns in response to flux applied at the different dc bias current were measured. The results showed that not only TlBaCaCuO thick film DC SQUID was like that from TlBaCaCuO thin film in good microwave behaviour but also the processes of fabricating thick film DC SQUID were easy.
FERROELECTRIC PROPERTIES OF ENDOHEDRAL COMPLEXES OF C60 WITH POLAR MOLECULES
Authors: NANAYAKKARA ASIRI
Published: November 2004

The recent wealth of experimental data provides conclusive evidence for encapsulation of atoms, ions, and molecules inside carbon clusters like C 60. In this paper, we review ferroelectric properties of endohedral fullerites which are composed of endohedral complexes with polar molecules trapped inside C 60 cluster. The derivation of approximate expressions for dipole moments of endohedral complexes is given. Estimation of transition temperatures and dipole moments of endohedral fullerites with LiF, LiCl, NaF, and NaCl as guest molecules are presented.
SOME COMMENTS ABOUT ATOMS INTERACTING WITH LASER
Authors: GRADO CAFFARO M.A. , GRADO CAFFARO M.
Published: November 2004

The interaction of a single atom with a laser field is investigated. In particular, various new results on the time-dependent dipole moment induced in a single atom by the laser are obtained. These results are, in principle, applicable to atomic structures corresponding to certain solids, for instance, amorphous semiconductors. In addition, time-dependent Schrödinger equation is considered with respect to our problem and the interaction Hamiltonian involved in this equation is studied.
THE ${\rm{Si}} (111)\mbox{-}(\sqrt{3} \times \sqrt{3})$R30°-Ag AND -Au SURFACE STRUCTURES FROM FIRST PRINCIPLES CALCULATIONS
Authors: DING Y.G. , CHAN C.T. , HO K.M.
Published: November 2004

The electronic and structural properties of the [Formula: see text]R30°- Ag and Au surfaces are investigated using first-principles total energy calculations. The structures of Au and Ag are in fact quite similar and belong to the same class of structural models. However, small variation in the structural details can give rise to quite different observed STM images, as revealed in the theoretical calculations.
PREDATION AND STEADY STATES IN HIGH-TC SUPERCONDUCTORS
Authors: MOTA RONALDO
Published: November 2004

A study of the role played by predation in a population dynamical model previously considered for spin-polaron-pairs in high-Tc superconductors is presented. A practical model which exhibits two positive linearly stable steady state populations is considered. A discussion of various aspects and implications of the model is given.
THEORETICAL STUDIES OF MODEL COMPOSITES
Authors: MON K.K.
Published: November 2004

We study the application and convergence of the continuum approximation to discret composite as a function of the number of Fourier components. A discret model composite with alternating parallel slabs of different constituents and exact solution is considered. The direct method of solving the related eigensystem problem is used to calculate the sound velocity. We show that rather accurate results can be obtained from the continuum approximation with only a small number of Fourier components. The dependence on the number of components is consistent with a power law. Our model results also confirm recent arguments that the sound velocity is independent of density modulations.
SUB-keV ATOM INDUCED SPUTTERING OF CONDENSED N2: A MOLECULAR DYNAMICS STUDY
Authors: KAFEMANN HEINO , URBASSEK HERBERT M.
Published: November 2004

By molecular dynamics, the sputtering of a condensed N 2 sample due to 100 eV N atom bombardment is studied. The features observed in general parallel those of previous studies of Ar sputtering. Time- and space-resolved measurements give novel information on the original position of sputtered molecules and the time dependence of their energy distribution. Rotational and vibrational degrees of freedom are underpopulated with respect to center-of-mass translational motion.
ELECTRONIC STRUCTURE AND RECONSTRUCTION OF THE Mo(001) SURFACE
Authors: CHUNG J.W. , SHIN K.S. , HONG S.C.
Published: November 2004

Recent developments in understanding the nature of surface electronic structure focused on illuminating the electronic origin of reconstruction of the Mo (001) surface have been reviewed. The long-standing disputes between two competing theoretical models, the charge density wave model and the local bonding model, for the driving mechanism of the reconstructional transition seem to be resolved by recent experimental evidences favoring the Peierls-type 2kF instabilities with significant matrix element effects. Details of recent experimental and theoretical findings for the surface electronic bands are discussed briefly with an emphasis placed on characterizing the surface states and their roles in the reconstruction.
POPULATION RELAXATION TIME OF OPTICAL PHONONS IN GaAs-AlAs MULTIPLE QUANTUM WELL STRUCTURES
Authors: TSEN K.T. , CHIA C. , WEST J. , MORKOC H.
Published: November 2004

Population relaxation time of confined as well as interface optical phonons in a series of GaAs-AlAs multiple quantum well structures has been measured by picosecond time-resolved Raman spectroscopy. Our experimental results have shown that (1) within the experimental accuracy, the population relaxation time of confined optical phonons in GaAs-AlAs multiple quantum well structures is independent of GaAs well-width and is given by 6±1 ps at T=10 K; (2) the population relaxation times of both GaAs -like and AlAs -like interface optical phonons increase as GaAs well-width increases from 20 Å to 100 Å. These experimental results are compared with theoretical calculations recently carried out by Gupta and Ridley (Ref. 3).
CHIRAL SPIN LIQUID STATES IN 3-SPACE DIMENSIONS AND TOPOLOGICAL ASPECTS OF MONOPOLE SUPERCONDUCTIVITY
Authors: BASU B. , BANDYOPADHYAY P.
Published: November 2004

We have studied here the topological aspects of monopole superconductivity in 3+1 dimensions. It is pointed out that Heisenberg spin system may be associated with non-Abelian gauge fields. When the spin and charge become separated, spinons and holons emerge and holons interacting with such a gauge field associate a magnetic flux giving rise to nonzero Berry phase and causes the existence of chiral spin liquid. This also suggests that these holons are much heavier than their free counterpart and the pair of such holons forms a bosonic state respecting rotational invariance. Superconductivity arises out of this pair condensation.
ELASTICITY STUDIES OF SOME Bi-Pb-Sr-Ca-Cu-O HIGH-Tc SUPERCONDUCTING MATERIALS
Authors: SHEKAR S. , REDDY P. VENUGOPAL
Published: November 2004

Longitudinal and shear wave velocities of lead-substituted Bi-Sr-Ca-Cu-O (2223) super-conducting materials prepared by the three-step matrix solid state reaction method have been measured by the pulse transmission technique. Using the data, several elasticity parameters like Young’s modulus, rigidity modulus, Poisson’s ratio, Debye temperature, etc. have been evaluated. Variation of elasticity parameters with lead concentration has been explained in terms of binding forces between various atoms. It has been observed that these materials are behaving like any other oxide materials.
NON-ADIABATIC TRANSPORT IN QUANTUM POINT CONTACTS
Authors: BRATAAS A. , CHAO K.A.
Published: November 2004

We have performed an exact numerical calculation on the conductance of a narrow constriction in a two-dimensional electron gas and discovered a novel sum rule that the conductance is invariant with respect to the channel mixing. This feature explains why the adiabatic approximation results fit the experimental data quantitatively. A similar sum rule has been found for the excess noise. These important conclusions remain to be derived analytically.
TWO-DIMENSIONAL BOSE GAS AT LOW DENSITY
Authors: OVCHINNIKOV A.A.
Published: November 2004

We propose a new method to describe the interacting bose gas at zero temperature. For three-dimensional system, the correction to the ground state energy in density is reproduced. For the two-dimensional dilute bose gas, the ground state energy in the leading order in the parameter | ln α2ρ|−1, where α is a two-dimensional scattering length, is obtained.
DERIVATION OF THE EXACT ENERGY FUNCTIONAL OF THE GROUND STATE OF LARGE POLARONS
Authors: ONOOCHIN V.V.
Published: November 2004

The functional of the ground-state energy of large polarons is considered. After a canonical transformation and elimination of the field oscillators variables, the functional is presented in form convenient for further analysis. One can conclude that the type of ground state of each field oscillator is the coherent state.
DIELECTRIC MEASUREMENT OF SEMICONDUCTING RARE EARTH (Y–Ba–Cu–O)-BASED CERAMIC IN RADIO FREQUENCY RANGE
Authors: TIWARI D. C. , GUPTA RASHMI
Published: November 2004

In this paper, some of our measured experimental results on Y–Ba–Cu–O-based semiconducting ceramic are reported. The range of temperature and frequency variation are from 300 K to 473 K and 100 kHz to 12 MHz respectively. The measured experimental results are also theoretically modelled. We found that modified Debye theory can possibly explain the measured experimental behavior.
EXACT KINETIC ENERGY FUNCTIONAL OF NONINTERACTING FERMIONS
Authors: SHAO JIUSHU
Published: November 2004

The exact expression of kinetic energy as a functional of the density for a system of noninteracting fermions, which has been searched for many years, is derived based on the direct method.
FRACTAL DIMENSION ANALYSIS OF YBaCuO THIN FILM CLUSTERS
Authors: CHOW LEE , CHEN JUN , BOUWENS MARK
Published: November 2004

In a recent paper, we reported the observation of the growth of YBaCuO thin film clusters on SiTi 3 O substrate. These clusters were formed in the sputter-deposited YBaCuO thin film with strong composition variation. Here we will give an auto-correlation function analysis of the fractal dimension of these clusters at different growth stages. The results will be compared with diffusion limited aggregation model, and implications of the cluster growth of the YBaCuO thin film will be discussed.
SPINON PAIR EMISSION IN LUTTINGER LIQUID: A NEW MECHANISM OF NMR RELAXATION IN THE NORMAL STATE OF HIGH Tc MATERIALS
Authors: BASKARAN G. , SARDAR MANAS
Published: November 2004

The ubiquitous large T = 0 intercept of the normal state NMR relaxation rate of the Cu nuclei of the high-Tc superconductors is shown to arise from the process of two spinon emission by the Cu nuclei which is possible in a Luttinger liquid (long-range RVB). Quantitative estimates are made for both Cu (in plane and in chain) relaxation rates. Scaling of the constant intercept with doping is of the form [Formula: see text], which agrees with experiments.