ISRN Condensed Matter Physics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Projection-Reduction Approach to Optical Conductivities for an Electron-Phonon System and Their Diagram Representation Mon, 07 Apr 2014 13:37:45 +0000 Utilizing state-dependent projection operators and the Kang-Choi reduction identities, we derive the linear, first, and second-order nonlinear optical conductivities for an electron system interacting with phonons. The lineshape functions included in the conductivity tensors satisfy “the population criterion” saying that the Fermi distribution functions for electrons and Planck distribution functions for phonons should be combined in multiplicative forms. The results also contain energy denominator factors enforcing the energy conservation as well as interaction factors describing electron-phonon interaction properly. Therefore, the phonon absorption and emission processes as well as photon absorption and emission processes in all electron transition processes can be presented in an organized manner and the results can be represented in diagrams that can model the quantum dynamics of electrons in a solid. Nam Lyong Kang and Sang Don Choi Copyright © 2014 Nam Lyong Kang and Sang Don Choi. All rights reserved. Fractional Gradient Elasticity from Spatial Dispersion Law Thu, 03 Apr 2014 09:49:20 +0000 Nonlocal elasticity models in continuum mechanics can be treated with two different approaches: the gradient elasticity models (weak nonlocality) and the integral nonlocal models (strong nonlocality). This paper focuses on the fractional generalization of gradient elasticity that allows us to describe a weak nonlocality of power-law type. We suggest a lattice model with spatial dispersion of power-law type as a microscopic model of fractional gradient elastic continuum. We demonstrate how the continuum limit transforms the equations for lattice with this spatial dispersion into the continuum equations with fractional Laplacians in Riesz's form. A weak nonlocality of power-law type in the nonlocal elasticity theory is derived from the fractional weak spatial dispersion in the lattice model. The continuum equations with derivatives of noninteger orders, which are obtained from the lattice model, can be considered as a fractional generalization of the gradient elasticity. These equations of fractional elasticity are solved for some special cases: subgradient elasticity and supergradient elasticity. Vasily E. Tarasov Copyright © 2014 Vasily E. Tarasov. All rights reserved. On the Nature of Electronic Wave Functions in One-Dimensional Self-Similar and Quasiperiodic Systems Sun, 30 Mar 2014 12:48:40 +0000 The interest in the precise nature of critical states and their role in the physics of aperiodic systems has witnessed a renewed interest in the last few years. In this work we present a review on the notion of critical wave functions and, in the light of the obtained results, we suggest the convenience of some conceptual revisions in order to properly describe the relationship between the transport properties and the wave functions distribution amplitudes for eigen functions belonging to singular continuous spectra related to both fractal and quasiperiodic distribution of atoms through the space. Enrique Maciá Copyright © 2014 Enrique Maciá. All rights reserved. Growth and Analysis of NSH and KMNSH Crystals by Slow Evaporation Technique Mon, 24 Mar 2014 08:24:01 +0000 Nickel sulphate hexahydrate (NSH) and potassium magnesium nickel sulphate hexahydrate (KMNSH) single crystals were grown by slow evaporation method. The grown NSH crystal was found to crystallize in tetragonal system with space group P41 21 2 and KMNSH in monoclinic system with space group P121/c. The optical band gap energies of the grown crystals using UV-Vis spectral results for the doped and undoped NSH crystals were calculated. The presence of various functional groups in the crystal was identified by FTIR analysis. The thermal behaviour of the grown crystal has been studied by TGA/DTA analysis. V. Masilamani, J. Shanthi, and V. Sheelarani Copyright © 2014 V. Masilamani et al. All rights reserved. Study of the Nanomechanics of CNTs under Tension by Molecular Dynamics Simulation Using Different Potentials Thu, 13 Mar 2014 12:55:06 +0000 At four different strain rates, the tensile stress strain relationship of single-walled 12-12 CNT with aspect ratio 9.1 obtained by Rebo potential (Brenner, 1990), Airebo potential (Stuart et al., 2000), and Tersoff potential (Tersoff, 1988) is compared with that of Belytschko et al. (2002) to validate the present model. Five different empirical potentials such as Rebo potential (Brenner, 1990), Rebo potential (Brenner et al., 2002), Inclusion LJ with Rebo potential (Brenner, 1990), Airebo potential (Stuart et al., 2000), and Tersoff potential (Tersoff, 1988) are used to simulate CNT subjected to axial tension differing its geometry at high strain rate. In Rebo potential (Mashreghi and Moshksar, 2010) only bond-order term is used and in Rebo potential (Brenner et al., 2002) torsional term is included with the bond-order term. At high strain rate the obtained stress strain relationships of CNTs subjected to axial tension differing its geometries using five different potentials are compared with the published results and from the comparison of the results, the drawback of the published results and limitations of different potentials are evaluated and the appropriate potential is selected which is the best among all other potentials to study the elastic, elastic-plastic properties of different types of CNTs. The present study will help a new direction to get reliable elastic, elastic-plastic properties of CNTs at different strain rates. Effects of long range Van der Waals interaction and torsion affect the elastic, elastic-plastic properties of CNTs and why these two effects are really needed to consider in bond-order Rebo potential (Brenner, 1990) to get reliable elastic, elastic-plastic properties of CNTs is also discussed. Effects of length-to-diameter ratio, layering of CNTs, and different empirical potentials on the elastic, elastic-plastic properties of CNTs are discussed in graphical and tabular forms with published results as a comparative manner to understand the nanomechanics of CNTs under tension using molecular dynamics simulation. S. K. Deb Nath and Sung-Gaun Kim Copyright © 2014 S. K. Deb Nath and Sung-Gaun Kim. All rights reserved. Plateaus in the Hall Resistance Curve at Filling Factors Wed, 19 Feb 2014 07:46:20 +0000 The fractional quantum Hall (FQH) states with higher Landau levels have new characters different from those with . The FQH states at are examined by developing the Tao-Thouless theory. We can find a unique configuration of electrons with the minimum Coulomb energy in the Landau orbitals. Therein the electron (or hole) pairs placed in the first and second nearest Landau orbitals can transfer to all the empty (or filled) orbitals at , 14/5, 7/3, 11/5, and 5/2 via the Coulomb interaction. More distant electron (or hole) pairs with the same centre position have the same total momentum. Therefore, these pairs can also transfer to all the empty (or filled) orbitals. The sum of the pair energies from these quantum transitions yields a minimum at . The spectrum of the pair energy takes the lowest value at and a higher value with a gap in the neighbourhood of because many transitions are forbidden at a deviated filling factor from . From the theoretical result, the FQH states with are stable and the plateaus appear at the specific filling factors . Shosuke Sasaki Copyright © 2014 Shosuke Sasaki. All rights reserved. Theoretical Investigations of Structural Phase Transitions and Magnetic, Electronic and Thermal Properties of DyNi: Under High Pressures and Temperatures Tue, 04 Feb 2014 07:06:28 +0000 Present work is influenced by the requirement of investigation of rare earth intermetallics due to the nonavailability of theoretical details and least information from experimental results. An attempt has been made to analyse the structural, electronic, magnetic and thermal properties of DyNi using full potential linear augmented plane wave method based on density functional theory. DyNi differs from other members of lanthanides nickelates as in ground state it crystallizes in FeB phase rather than orthorhombic CrB structure. The equilibrium lattice constant, bulk modulus, and pressure derivative of bulk modulus are presented in four polymorphs (FeB, CrB, CsCl and NaCl) of DyNi. At equilibrium the cell volume of DyNi for FeB structure has been calculated as 1098.16 Bohr3 which is comparable well with the experimental value 1074.75 Bohr3. The electronic band structure has been presented for FeB phase. The results for thermal properties, namely, thermal expansion coefficient, Gruneisen parameter, specific heat and Debye temperature at higher pressure and temperatures have been reported. The magnetic moments at equilibrium lattice constants have also been tabulated as the rare earth ions associated with large magnetic moments increase their utility in industrial field for the fabrication of electronic devices due to their magnetocaloric effect used in magnetic refrigeration. Pooja Rana and U. P. Verma Copyright © 2014 Pooja Rana and U. P. Verma. All rights reserved. Optical Rectification and Second Harmonic Generation on Quasi-Realistic InAs/GaAs Quantum Dots: With Attention to Wetting Layer Effect Mon, 23 Dec 2013 12:01:56 +0000 In this paper, we have performed a theoretical study on nonlinear optical rectification (OR) and second harmonic generation (SHG) for three-level dome-shaped InAs/GaAs quantum dots (QDs) in the presence of wetting layer (WL). We used the compact density matrix framework and effective mass approximation to investigate the second order nonlinear phenomena on InAs/GaAs QD. It is demonstrated that second harmonic generation (SHG), optical rectification (OR), and their mutual absorption and refractive index changes are quite sensitive to the size of QDs. The size variations have profound irregular behavior owing to distribution of envelope function on WL and QD simultaneously. Moreover it is found that  nm is a critical radius where the regular variation takes place. It is shown that size variation causes blue shift until Critical radius ( nm) and after that, increasing the QD size lead to redshift in second order phenomena. A. Khaledi-Nasab, M. Sabaiean, M. Sahrai, and V. Fallahi Copyright © 2013 A. Khaledi-Nasab et al. All rights reserved. Spin Polarization Curve of Fractional Quantum Hall States with Filling Factor Smaller than 2 Mon, 07 Oct 2013 09:23:07 +0000 Kukushkin et al. have measured the electron spin polarization versus magnetic field in the fractional quantum Hall states. The polarization curves show wide plateaus and small shoulders. The 2D electron system is described by the total Hamiltonian (). Therein, is the sum of the Landau energies and classical Coulomb energies. is the residual interaction yielding Coulomb transitions. It is proven for any filling factor that the most uniform electron configuration in the Landau states is only one. The configuration has the minimum energy of . When the magnetic field is weak, some electrons have up-spins and the others down-spins. Then, there are many spin arrangements. These spin arrangements give the degenerate ground states of . We consider the partial Hamiltonian only between the ground states. The partial Hamiltonian yields the Peierls instability and is diagonalized exactly. The sum of the classical Coulomb and spin exchange energies has minimum for an interval modulation between Landau orbitals. Using the solution with the minimum energy, the spin polarization is calculated which reproduces the wide plateaus and small shoulders. The theoretical result is in good agreement with the experimental data. Shosuke Sasaki Copyright © 2013 Shosuke Sasaki. All rights reserved. Growth of Polycrystalline In2S3 Thin Films by Chemical Bath Deposition Using Acetic Acid as a Complexing Agent for Solar Cell Application Tue, 10 Sep 2013 15:43:32 +0000 In2S3 films have been successfully deposited on Corning glass substrates via chemical bath deposition (CBD) method using acetic acid as a novel complexing agent. The layers were grown by employing synthesis using indium sulphate and thioacetamide (TA) as precursors by varying TA concentration in the range of 0.1–0.5 M, keeping other deposition parameters constant. Energy dispersive X-ray analysis (EDAX) revealed an increase of S/In ratio in the films with the increase of TA concentration in the solution. The X-ray diffraction (XRD) analysis indicated a change in preferred orientation from (311) plane related to cubic structure to the (103) direction corresponding to the tetragonal crystal structure. The evaluated crystallite size varied in the range of 15–25 nm with the increase of TA concentration. Morphological analysis showed that the granular structure and the granular density decrease with the raise of TA concentration. The optical properties of the layers were also investigated using UV-Vis-NIR analysis, which indicated that all the In2S3 films had the optical transmittance >60% in the visible region, and the evaluated energy band varied in the range of 2.87–3.32 eV with the change of TA concentration. Further, a thin film heterojunction solar cell was fabricated using a novel absorber layer, SnS, with In2S3 as a buffer. The unoptimized SnS/In2S3/ZnO:Al solar cell showed a conversion efficiency of 0.6%. G. R. Gopinath and K. T. Ramakrishna Reddy Copyright © 2013 G. R. Gopinath and K. T. Ramakrishna Reddy. All rights reserved. Growth of Films by RF Magnetron Sputtering: Studies on the Structural, Optical, and Electrochromic Properties Mon, 09 Sep 2013 10:28:43 +0000 Molybdenum oxide (MoO3) films were deposited on glass and silicon substrates held at temperature 473 K by RF magnetron sputtering of molybdenum target at various oxygen partial pressures in the range mbar. The deposited MoO3 films were characterized for their chemical composition, crystallographic structure, surface morphology, chemical binding configuration, and optical properties. The films formed at oxygen partial pressure of mbar were nearly stoichiometric and nanocrystalline MoO3 with crystallite size of 27 nm. The Fourier transform infrared spectrum of the films formed at mbar exhibited the characteristics vibrational bands of MoO3. The optical band gap of the films increased from 3.11 to 3.28 eV, and the refractive index increased from 2.04 to 2.16 with the increase of oxygen partial pressure from to mbar, respectively. The electrochromic performance of MoO3 films formed on ITO coated glass substrates was studied and achieved the optical modulation of about 13% with color efficiency of about 20 cm2/C. S. Subbarayudu, V. Madhavi, and S. Uthanna Copyright © 2013 S. Subbarayudu et al. All rights reserved. Electron Transport Characteristics of Wurtzite GaN Mon, 09 Sep 2013 07:50:34 +0000 A three-valley Monte Carlo simulation approach was used to investigate electron transport in wurtzite GaN such as the drift velocity, the drift mobility, the average electron energy, energy relaxation time, and momentum relaxation time at high electric fields. The simulation accounted for polar optical phonon, acoustic phonon, piezoelectric, intervalley scattering, and Ridley charged impurity scattering model. For the steady-state transport, the drift velocity against electric field showed a negative differential resistance of a peak value of  m/s at a critical electric field strength  V/m. The electron drift velocity relaxes to the saturation value of  m/s at very high electric fields. The electron velocities against time over wide range of electric fields are reported. F. M. Abou El-Ela and A. Z. Mohamed Copyright © 2013 F. M. Abou El-Ela and A. Z. Mohamed. All rights reserved. Research of Nanosized Inhomogeneities in H-Bonded Liquids Using Sophisticated Light Scattering Techniques Sun, 01 Sep 2013 11:29:32 +0000 Hydrogen bonded (H-bonded) liquids can be considered as mediums that have nanosized heterogeneities. Previously, it was shown that the light scattering by acoustic phonons is accompanied by fluctuations of intensity of light with power spectral density   () that reflects the phonon energy fluctuations. In this work fluctuations of light scattering in H-bonded liquids have been investigated. We consider two mechanisms of -process forming: fluctuations of phonon energy and fluctuations caused by dynamical inhomogeneities, predicted by percolation model. The variability can be explained by different contributions of both scattering mechanisms, which form an overall picture of low-frequency fluctuations of scattering light intensity in complex liquids. Nataliia Kuzkova and Andrey Yakunov Copyright © 2013 Nataliia Kuzkova and Andrey Yakunov. All rights reserved. Temperature Variations Analysis for Condensed Matter Micro- and Nanoparticles Combustion Burning in Gaseous Oxidizing Media by DTM and BPES Sun, 01 Sep 2013 09:23:20 +0000 Combustion process for iron particles burning in the gaseous oxidizing medium is investigated using the Boubaker polynomial expansion scheme (BPES) and the differential transformation method (DTM). Effects of thermal radiation from the external surface of burning particle and alterations of density of iron particle with temperature are considered. The solutions obtained using BPES technique and DTM are compared with those of the fourth-order Runge-Kutta numerical method. Results reveal that BPES is more accurate and reliable method than DTM. Also the effects of some physical parameters that appeared in mathematical section on temperature variations of particles as a function of time are studied. M. Hatami, D. D. Ganji, and K. Boubaker Copyright © 2013 M. Hatami et al. All rights reserved. Sputter Power Influenced Structural, Electrical, and Optical Behaviour of Nanocrystalline CuNiO2 Films Formed by RF Magnetron Sputtering Sun, 25 Aug 2013 09:13:22 +0000 Copper nickel oxide (CuNiO2) films were deposited on glass and silicon substrates using RF magnetron sputtering of equimolar Cu50Ni50 alloy target at different sputter powers in the range of 3.1–6.1 W/cm2. The effect of sputter power on the chemical composition, crystallographic structure, chemical binding configuration, surface morphology, and electrical and optical properties of CuNiO2 films was investigated. The films formed at sputter power of 5.1 W/cm2 were of nearly stoichiometric CuNiO2. Fourier transform infrared spectroscopic studies indicated the presence of the characteristic vibrational bands of copper nickel oxide. The nanocrystalline CuNiO2 films were formed with the increase in grain size from 75 to 120 nm as the sputter power increased from 3.1 to 5.1 W/cm2. The stoichiometric CuNiO2 films formed at sputter power of 5.1 W/cm2 exhibited electrical resistivity of 27 Ωcm, Hall mobility of 21 cm2/Vsec, and optical bandgap of 1.93 eV. A. Sreedhar, M. Hari Prasad Reddy, S. Uthanna, and J. F. Pierson Copyright © 2013 A. Sreedhar et al. All rights reserved. On the Problem of Metal-Insulator Transitions in Vanadium Oxides Mon, 29 Jul 2013 11:45:17 +0000 The problem of metal-insulator transition is considered. It is shown that the Mott criterion is applicable not only to heavily doped semiconductors but also to many other materials, including some transition-metal compounds, such as vanadium oxides (particularly, VO2 and V2O3). The low-temperature transition (“paramagnetic metal—antiferromagnetic insulator”) in vanadium sesquioxide is described on the basis of this concept in terms of an intervening phase, between metal and insulator states, with divergent dielectric constant and effective charge carrier mass. Recent communications concerning a possible “metal-insulator transition” in vanadium pentoxide are also discussed. A. L. Pergament, G. B. Stefanovich, N. A. Kuldin, and A. A. Velichko Copyright © 2013 A. L. Pergament et al. All rights reserved. Thickness-Dependent Physical Properties of Coevaporated Cu4SnS4 Films Wed, 10 Jul 2013 11:59:53 +0000 Cu4SnS4 films of different thicknesses were prepared by thermal coevaporation technique on glass substrates at a constant substrate temperature of 400°C. The layer thickness was varied in the range 0.25–1 μm. The composition analysis revealed that all the evaporated films were nearly stoichiometric. The XRD patterns indicated the presence of a strong (311) peak as the preferred orientation, following the orthorhombic crystal structure corresponding to Cu4SnS4 films. Raman analysis showed a sharp peak at 317 cm−1, also related to Cu4SnS4 phase. The optical transmittance spectra suggested that the energy band gap decreased from 1.47 eV to 1.21 eV with increase of film thickness. The hot-probe test revealed that the layers had p-type electrical conductivity. A decrease of electrical resistivity was observed with the rise of film thickness. V. P. Geetha Vani, M. Vasudeva Reddy, and K. T. Ramakrishna Reddy Copyright © 2013 V. P. Geetha Vani et al. All rights reserved. Out-of-Equilibrium Dynamics of the Bose-Hubbard Model Wed, 12 Jun 2013 17:25:30 +0000 The Bose-Hubbard model is the simplest model of interacting bosons on a lattice. It has recently been the focus of much attention due to the realization of this model with cold atoms in an optical lattice. The ability to tune parameters in the Hamiltonian as a function of time in cold atom systems has opened up the possibility of studying out-of-equilibrium dynamics, including crossing the quantum critical region of the model in a controlled way. In this paper, I give a brief introduction to the Bose Hubbard model, and its experimental realization and then give an account of theoretical and experimental efforts to understand out-of-equilibrium dynamics in this model, focusing on quantum quenches, both instantaneous and of finite duration. I discuss slow dynamics that have been observed theoretically and experimentally for some quenches from the superfluid phase to the Mott insulating phase and the picture of two timescales, one for fast local equilibration and another for slow global equilibration, that appears to characterize this situation. I also discuss the theoretical and experimental observation of the Lieb-Robinson bounds for a variety of quenches and the Kibble-Zurek mechanism in quenches from the Mott insulator to superfluid. I conclude with a discussion of open questions and future directions. Malcolm P. Kennett Copyright © 2013 Malcolm P. Kennett. All rights reserved. Effect of pH on the Characteristics of Cu2ZnSnS4 Nanoparticles Mon, 03 Jun 2013 12:00:20 +0000 We have investigated the effect of pH on the structural and optical properties of chemical coprecipitated Cu2ZnSnS4 (CZTS) nanoparticles. The CZTS nanoparticles have been successfully synthesized at different pH values ranging from 6 to 9, keeping all other deposition parameters as constant. X-ray diffraction and Raman studies confirmed the Kesterite structure. The powders synthesized at a pH value of 8 exhibited preferred orientation along (112) and (220) with near stoichiometric ratio. The as synthesized nanoparticles exhibited direct band gap of 1.4 eV which is an optimum value for the absorber layer in the fabrication of photovoltaic cells. R. Lydia and P. Sreedhara Reddy Copyright © 2013 R. Lydia and P. Sreedhara Reddy. All rights reserved. The Possibility of Many Compensation Points in a Mixed-Spin Ising Ferrimagnetic System Mon, 27 May 2013 12:03:43 +0000 The magnetic properties of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising model with different anisotropies are investigated by using the mean-field approximation (MFA). In particular, the effect of magnetic anisotropies on the compensation phenomenon, acting on A-atoms and B-ones for the mixed-spin model, has been considered in a zero field. The free energy of a mixed-spin Ising ferrimagnetic system from MFA of the Hamiltonian is calculated. By minimizing the free energy, we obtain the equilibrium magnetizations and the compensation points. The phase diagram of the system in the anisotropy dependence of transition temperature has been discussed as well. Our results of this model predict the existence of many (two or three) compensation points in the ordered system on a simple cubic lattice. Hadey K. Mohamad Copyright © 2013 Hadey K. Mohamad. All rights reserved. Excitation Kinetics of Impurity Doped Quantum Dot Triggered by Gaussian White Noise Sat, 25 May 2013 14:03:46 +0000 We investigate the excitation kinetics of a repulsive impurity doped quantum dot initiated by the application of Gaussian white noise. In view of a comprehensive research we have considered both additive and multiplicative noise (in Stratonovich sense). The noise strength and the dopant location have been found to fabricate the said kinetics in a delicate way. Moreover, the influences of additive and multiplicative nature of the noise on the excitation kinetics have been observed to be prominently different. The investigation reveals emergence of maximization and saturation in the excitation kinetics as a result of complex interplay between various parameters that affect the kinetics. The present investigation is believed to provide some useful perceptions of the functioning of mesoscopic systems where noise plays some profound role. Suvajit Pal, Sudarson Sekhar Sinha, Jayanta Ganguly, and Manas Ghosh Copyright © 2013 Suvajit Pal et al. All rights reserved. Theoretical Analysis of the Faraday Effect in Carbon Nanotubes with Arbitrary Chirality Mon, 20 May 2013 18:33:03 +0000 Using tight-binding model with nearest neighbour interactions, the optical properties of carbon nanotubes under the influence of an external magnetic field are analyzed. First, dipole matrix elements for two cases of light polarized parallel as well as perpendicular to the nanotube axis are analyzed. A close form analytic expression for dipole matrix is obtained for carbon nanotubes with arbitrary chirality in the case of light polarized parallel to the nanotube axis. Then the diagonal and off-diagonal elements of the frequency-dependent susceptibility in the presence of an axial magnetic field are investigated. The off-diagonal elements are applied to calculate the interband Faraday rotation and the Verdet constant. These effects should be clearly detectable under realistic conditions using weak magnetic fields. Abbas Zarifi Copyright © 2013 Abbas Zarifi. All rights reserved. From Graphite to Graphene: The Confinement of the Fermi Surface to the Line KH Tue, 07 May 2013 09:00:39 +0000 The graphite structure is self-consistently calculated by use of the all electron Modified Augmented Plane Wave (MAPW) scheme with lattice constants considerably enlarged above the experimental value of graphite. Overall, the band structures of the series are found to be quite similar: the energy levels of the highly symmetric states K and H almost coincide, essentially fixing the Fermi level of the semimetallic solid. The dispersion along lines parallel to the atomic planes, already small in graphite at the experimental value of , continues to flatten with increasing value of . The structure with an interlayer distance enlarged by the factor 3 over the experimental value provides a good approximation of the behaviour of a monoatomic sheet. In this context, the unusual behaviour of graphene appears in a new light. Helmut Bross Copyright © 2013 Helmut Bross. All rights reserved. Topological Order: From Long-Range Entangled Quantum Matter to a Unified Origin of Light and Electrons Wed, 27 Mar 2013 10:43:42 +0000 We review the progress in the last 20–30 years, during which we discovered that there are many new phases of matter that are beyond the traditional Landau symmetry breaking theory. We discuss new “topological” phenomena, such as topological degeneracy that reveals the existence of those new phases—topologically ordered phases. Just like zero viscosity defines the superfluid order, the new “topological” phenomena define the topological order at macroscopic level. More recently, we found that at the microscopical level, topological order is due to long-range quantum entanglements. Long-range quantum entanglements lead to many amazing emergent phenomena, such as fractional charges and fractional statistics. Long-range quantum entanglements can even provide a unified origin of light and electrons; light is a fluctuation of long-range entanglements, and electrons are defects in long-range entanglements. Xiao-Gang Wen Copyright © 2013 Xiao-Gang Wen. All rights reserved. Solid Solutions of () Obtained via a Combustion Synthesis Route and Their Electrochemical Characteristics Mon, 11 Feb 2013 14:38:41 +0000 Pure, single-phase and layered materials with good cation ordering are not easy to synthesize. In this work, solid solutions of (x = 0, 0.1, …, 0.9) are synthesized using a self-propagating combustion route and characterized. All the materials are observed to be phase pure giving materials of hexagonal crystal system with R-3m space group. The RIR and R factor values of stoichiometries of (x = 0.1, 0.2, 0.3, 0.4, and 0.5) show good cation ordering. Their electrochemical properties are investigated by a series of charge-discharge cycling in the voltage range of 3.0 to 4.3 V. It is found that some of the stoichiometries exhibit specific capacities comparable or better than those of LiCoO2, but the voltage plateau is slightly more slopping than that for the LiCoO2 reference material. Kelimah Elong, Norlida Kamarulzaman, Roshidah Rusdi, Nurhanna Badar, and Mohd Hilmi Jaafar Copyright © 2013 Kelimah Elong et al. All rights reserved. Hexagonal Manganites—(RMnO3): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity Thu, 07 Feb 2013 09:57:04 +0000 Hexagonal manganites belong to an exciting class of materials exhibiting strong interactions between a highly frustrated magnetic system, the ferroelectric polarization, and the lattice. The existence and mutual interaction of different magnetic ions (Mn and rare earth) results in complex magnetic phase diagrams and novel physical phenomena. A summary and discussion of the various properties, underlying physical mechanisms, the role of the rare earth ions, and the complex interactions in multiferroic hexagonal manganites, are presented in this paper. Bernd Lorenz Copyright © 2013 Bernd Lorenz. All rights reserved. A Theoretical Approach to Pseudogap and Superconducting Transitions in Hole-Doped Cuprates Wed, 06 Feb 2013 09:16:24 +0000 We consider a two-dimensional fermion system on a square lattice described by a mean-field Hamiltonian involving the singlet id-density wave (DDW) order, assumed to correspond to the pseudo-gap (PG) state, favored by the electronic repulsion and the coexisting -wave superconductivity (DSC) driven by an assumed attractive interaction within the BCS framework. Whereas the single-particle excitation spectrum of the pure DDW state consists of the fermionic particles and holes over the reasonably conducting background, the coexisting states corresponds to Bogoliubov quasi-particles in the background of the delocalized Cooper pairs in the momentum space. We find that the two gaps in the single-particle excitation spectrum corresponding to PG and DSC, respectively, are distinct and do not merge into one “quadrature” gap if the nesting property of the normal state dispersion is absent. We show that the PG and DSC are representing two competing orders as the former brings about a depletion of the spectral weight available for pairing in the anti-nodal region of momentum space where the superconducting gap is supposed to be the largest. This indicates that the PG state perhaps could not be linked to a preformed pairing scenario. We also show the depletion of the spectral weight below at energies larger than the gap amplitude. This is an important hallmark of the strong coupling superconductivity. Partha Goswami Copyright © 2013 Partha Goswami. All rights reserved. Ab Initio Investigation of Nitride in Comparison with Carbide Phase of Superconducting InX (X = C, N) Mon, 14 Jan 2013 10:34:24 +0000 The structural, elastic, electronic, thermal, and optical properties of superconducting nanolaminates Ti2InX (X = C, N) are investigated by density functional theory (DFT). The results obtained from the least studied nitride phase are discussed in comparison with those of carbide phase having value half as that of the former. The carbide phase is found to be brittle in nature, while the nitride phase is less brittle. Elastic anisotropy demonstrates that the c-axis is stiffer in Ti2InN than in Ti2InC. The band structure and density of states show that these phases are conductors, with contribution predominantly from the Ti 3d states. The bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient are obtained as a function of temperature and pressure for the first time through the quasiharmonic Debye model with phononic effects. The estimated values of electron-phonon coupling constants imply that Ti2InC and Ti2InN are moderately coupled superconductors. The calculated thermal expansion coefficient is in fair agreement with the only available measured value for Ti2InC. Further the first time calculated optical functions reveal that the reflectivity is high in the IR-visible-UV region up to ~10 eV and 12.8 eV for Ti2InC and Ti2InN, respectively, showing these to be promising coating materials. M. Roknuzzaman and A. K. M. A. Islam Copyright © 2013 M. Roknuzzaman and A. K. M. A. Islam. All rights reserved. Characterization and Electrical Properties of [C6H9N2]2CuCl4 Compound Thu, 20 Dec 2012 17:28:54 +0000 We report measurements of X-ray powder diffraction, vibrational study, the differential scanning calorimetry (DSC), and the electric properties of a made-up [C6H9N2]2CuCl4 sample. The alternative current (ac) conductivity of the compound [C6H9N2]2CuCl4 has been measured in the temperature range 356–398 K and the frequency range 209 Hz–5 MHz. The Cole-Cole (the imaginer part () versus real part () of impedance complex) plots are well fitted to an equivalent circuit model which consists of a parallel combination of a bulk resistance () and constant phase elements (CPE). The single semicircle indicates only one primary mechanism for the electrical conduction within [C6H9N2]2CuCl4. The variation of the value of these elements with temperatures confirmed the result detected by DSC and dielectric measurements. Thus the conduction in the material is probably due to a hopping or a small polaron tunneling process. M. Hamdi, A. Oueslati, I. Chaabane, and F. Hlel Copyright © 2012 M. Hamdi et al. All rights reserved. Analysis of the Dielectric Constant as a Function of Temperature at Constant Electric Fields for the Smectic A-Smectic G Transition in A6 Tue, 20 Nov 2012 08:30:11 +0000 The temperature dependence of the dielectric constant is studied under some fixed electric fields for the smectic G- (tilted-) smectic A (orthogonal) transition of the ferroelectric liquid crystal of compound A6. For this study, a mean field model with the quadrupole-quadrupole interactions is introduced. By fitting the inverse dielectric susceptibility from the mean field model to the experimental data from the literature, the observed behaviour of the dielectric constant is described satisfactorily for the smectic AG transition in A6. The transition temperature induced by an external electric field is also discussed for this ferroelectric compound. H. Yurtseven and E. Kilit Copyright © 2012 H. Yurtseven and E. Kilit. All rights reserved.