Advances in Condensed Matter Physics http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Half-Metallic Ferromagnetism in Chalcopyrite (AlGaMn)P2 Alloys Tue, 03 Mar 2015 14:00:00 +0000 http://www.hindawi.com/journals/acmp/2015/706957/ We studied the electronic and magnetic properties of (Al1−yMny)GaP2 (Ga-rich) and Al(Ga1−yMny)P2 (Al-rich) with y = 0.03125, 0.0625, 0.09375, and 0.125 by using the first-principles calculations. The ferromagnetic Mn-doped AlGaP2 chalcopyrite is the most energetically favorable one. The spin polarized Al(GaMn)P2 state (Al-rich system) is more stable than spin polarized (AlMn)GaP2 state (Ga-rich) with the magnetic moment of 3.8 /Mn. The Mn-doped AlGaP2 yields strong half-metallic ground states. The states of host Al, Ga, or P atoms at the Fermi level are mainly a P-3p character, which mediates a strong interaction between the Mn-3d and P-3p states. Byung-Sub Kang, Kwang-Pyo Chae, and Haeng-Ki Lee Copyright © 2015 Byung-Sub Kang et al. All rights reserved. The Chemistry of Bioconjugation in Nanoparticles-Based Drug Delivery System Sat, 28 Feb 2015 14:01:56 +0000 http://www.hindawi.com/journals/acmp/2015/198175/ Nanomedicine is, generally, the application of nanotechnology to medicine. The term nanomedicine includes monitoring, construction of novel drug delivery systems, and any possible future applications of nanotechnology and nanovaccinology. In this review, the most important ligand-nanocarrier and drug-nanocarrier bioconjugations are described. The detailed characterizations of covalently formed bonds between targeted ligand and nanocarrier, including amide, thioether, disulfide, acetyl-hydrazone and polycyclic groups, are described. Also, the coupling of small elements and heteroatoms in the form of R-X-R the “click chemistry” groups is shown. Physical adsorption and chemical bonding of drug to nanocarrier surface involving drug on the internal or external surfaces of nanocarriers are described throughout possibility of the formation of the above-mentioned functionalities. Moreover, the most popular nanostructures (liposomes, micelles, polymeric nanoparticles, dendrimers, carbon nanotubes, and nanohorns) are characterized as nanocarriers. Building of modern drug carrier is a new method which could be effectively applied in targeted anticancer therapy. Karolina Werengowska-Ciećwierz, Marek Wiśniewski, Artur P. Terzyk, and Sylwester Furmaniak Copyright © 2015 Karolina Werengowska-Ciećwierz et al. All rights reserved. Entanglement Area Law in Disordered Free Fermion Anderson Model in One, Two, and Three Dimensions Sat, 28 Feb 2015 07:59:31 +0000 http://www.hindawi.com/journals/acmp/2015/397630/ We calculate numerically the entanglement entropy of free fermion ground states in one-, two-, and three-dimensional Anderson models and find that it obeys the area law as long as the linear size of the subsystem is sufficiently larger than the mean free path. This result holds in the metallic phase of the three-dimensional Anderson model, where the mean free path is finite although the localization length is infinite. Relation between the present results and earlier ones on area law violation in special one-dimensional models that support metallic phases is discussed. Mohammad Pouranvari, Yuhui Zhang, and Kun Yang Copyright © 2015 Mohammad Pouranvari et al. All rights reserved. The THz Spectrum of Density Fluctuations of Water: The Viscoelastic Regime Thu, 26 Feb 2015 10:55:54 +0000 http://www.hindawi.com/journals/acmp/2015/137435/ Relevant advances in the knowledge of the water dynamics at mesoscopic scales are reviewed, while mainly focusing on the contribution provided by high resolution inelastic X-ray scattering (IXS). In particular it is discussed how the use of IXS has improved our understanding of viscoelastic properties of water at THz frequencies. This specifically involves some solid-like features such as the onset of shear wave propagation, a sound velocity surprisingly similar to the one of ice, and an anomalously low sound absorption coefficient. All these properties can be explained by assuming the coupling of THz density fluctuations with a structural relaxation process connected to the breaking and forming of hydrogen bonds (HBs). This review also includes more recent IXS results demonstrating that, upon approaching supercritical conditions, relaxation phenomena in water gradually lose their structural character becoming essentially collisional in character. Furthermore, GHz spectroscopy results on supercooled water, suggesting the occurrence of a structural arrest, are discussed. An overview of the new opportunities offered by next generation IXS spectrometers finally concludes this review. Alessandro Cunsolo Copyright © 2015 Alessandro Cunsolo. All rights reserved. Two-Dimensional Metallicity with a Large Spin-Orbit Splitting: DFT Calculations of the Atomic, Electronic, and Spin Structures of the Au/Ge(111)- Surface Wed, 25 Feb 2015 11:39:45 +0000 http://www.hindawi.com/journals/acmp/2015/531498/ Density functional theory (DFT) is applied to study the atomic, electronic, and spin structures of the Au monolayer at the Ge(111) surface. It is found that the theoretically determined most stable atomic geometry is described by the conjugated honeycomb-chained-trimer (CHCT) model, in a very good agreement with experimental data. The calculated electronic structure of the system, being in qualitatively good agreement with the photoemission measurements, shows fingerprints of the many-body effects (self-interaction corrections) beyond the LDA or GGA approximations. The most interesting property of this surface system is the large spin splitting of its metallic surface bands and the undulating spin texture along the hexagonal Fermi contours, which highly resembles the spin texture at the Dirac state of the topological insulator Bi2Te3. These properties make this system particularly interesting from both fundamental and technological points of view. Andrzej Fleszar and Werner Hanke Copyright © 2015 Andrzej Fleszar and Werner Hanke. All rights reserved. Hysteresis in Two-Dimensional Liquid Crystal Models Mon, 23 Feb 2015 08:51:09 +0000 http://www.hindawi.com/journals/acmp/2015/834867/ We make a numerical study of hysteresis loop shapes within a generalized two-dimensional Random Anisotropy Nematic (RAN) model at zero temperature. The hysteresis loops appear on cycling a static external ordering field. Ordering in these systems is history dependent and involves interplay between the internal coupling constant , the anisotropy random field , and the ordering external field . Here the external field is represented by a traceless tensor, analogous to extension-type fields in continuum mechanics. The calculations use both a mean field approach and full lattice simulations. Our analysis suggests the existence of two qualitatively different solutions, which we denote as symmetric and symmetry breaking. For the set of parameters explored, only the symmetric solutions are stable. Both approaches yield qualitatively similar hysteresis curves, which are manifested either by single or double loops. But the quantitative differences indicate that mean field estimates are only of limited predictive value. Slavko Buček, Samo Kralj, and T. J. Sluckin Copyright © 2015 Slavko Buček et al. All rights reserved. Nonequilibrium Quantum Systems: Divergence between Global and Local Descriptions Mon, 23 Feb 2015 08:37:25 +0000 http://www.hindawi.com/journals/acmp/2015/615727/ Even photosynthesis—the most basic natural phenomenon underlying life on Earth—involves the nontrivial processing of excitations at the pico- and femtosecond scales during light-harvesting. The desire to understand such natural phenomena, as well as interpret the output from ultrafast experimental probes, creates an urgent need for accurate quantitative theories of open quantum systems. However it is unclear how best to generalize the well-established assumptions of an isolated system, particularly under nonequilibrium conditions. Here we compare two popular approaches: a description in terms of a direct product of the states of each individual system (i.e., a local approach) versus the use of new states resulting from diagonalizing the whole Hamiltonian (i.e., a global approach). The main difference lies in finding suitable operators to derive the Lindbladian and hence the master equation. We show that their equivalence fails when the system is open, in particular under the experimentally ubiquitous condition of a temperature gradient. By solving for the steady state populations and calculating the heat flux as a test observable, we uncover stark differences between the formulations. This divergence highlights the need to establish rigorous ranges of applicability for such methods in modeling nanoscale transfer phenomena—including during the light-harvesting process in photosynthesis. Pedro D. Manrique, Ferney Rodríguez, Luis Quiroga, and Neil F. Johnson Copyright © 2015 Pedro D. Manrique et al. All rights reserved. Hydrostatic Pressure and Built-In Electric Field Effects on the Donor Impurity States in Cylindrical Wurtzite GaN/AlxGa1−xN Quantum Rings Thu, 19 Feb 2015 12:47:35 +0000 http://www.hindawi.com/journals/acmp/2015/594176/ Within the framework of the effective mass approximation, the ground-state binding energy of a hydrogenic impurity is investigated in cylindrical wurtzite GaN/ strained quantum ring (QR) by means of a variational approach, considering the influence of the applied hydrostatic pressure along the QR growth direction and the strong built-in electric field (BEF) due to the piezoelectricity and spontaneous polarization. Numerical results show that the donor binding energy for a central impurity increases inchmeal firstly as the QR radial thickness decreases gradually and then begins to drop quickly. In addition, the donor binding energy is an increasing (a decreasing) function of the inner radius (height). It is also found that the donor binding energy increases almost linearly with the increment of the applied hydrostatic pressure. Moreover, we also found that impurity positions have an important influence on the donor binding energy. The physical reasons have been analyzed in detail. Guangxin Wang, Xiuzhi Duan, and Rui Zhou Copyright © 2015 Guangxin Wang et al. All rights reserved. Impact of Nanoparticles on Nematic Ordering in Square Wells Wed, 18 Feb 2015 06:19:32 +0000 http://www.hindawi.com/journals/acmp/2015/532745/ Nematic liquid crystalline structures within square wells are studied numerically using both Lebwohl-Lasher lattice semimicroscopic and the Landau-de Gennes mesoscopic approach. At lateral boundary wall strong planar anchoring is enforced. The cell thickness h along the z Cartesian coordinate is assumed to be smaller than the characteristic square well size R. Using semimicroscopic modelling we restrict to effectively two-dimensional systems which we study in terms of the tensor nematic order parameter. We consider impact of appropriate nanoparticles (NPs) on nematic configuration for cases where R becomes comparable to the biaxial order parameter correlation length. In this case a star-like order reconstruction biaxial profile could be formed in absence of NPs. We demonstrate existence of a rich variety of different nematic structures, including topological defects, which are enabled by presence of appropriate NPs. M. Slavinec, E. Klemenčič, M. Ambrožič, and M. Krašna Copyright © 2015 M. Slavinec et al. All rights reserved. Low-Temperature DC Carrier Transport in (Fe0.45Co0.45Zr0.10)x(Al2O3)1−x Nanocomposites Manufactured by Sputtering in Pure Ar Gas Atmosphere Tue, 17 Feb 2015 13:47:37 +0000 http://www.hindawi.com/journals/acmp/2015/320187/ This presented work investigates the structure and temperature relationship/dependence of the DC conductivity in the (Fe0.45Co0.45Zr0.10)x(Al2O3)1−x nanocomposites deposited in Ar atmosphere with composition ( at.%) and temperature ( K). It is shown that VRH displayed crossover from Mott-like to Shklovskii-Efros regimes which occurred at temperatures of 100–120 K. It is also noted that the observed shift of the percolation threshold to higher concentrations of metallic fraction can be attributed to the disordering of the metallic nanoparticles due to the incorporation of the residual oxygen in the vacuum chamber during the deposition procedure. Ivan A. Svito, Alexander K. Fedotov, Anis Saad, Momir Milosavljević, Julia A. Fedotova, Tomasz N. Kołtunowicz, and Paweł Żukowski Copyright © 2015 Ivan A. Svito et al. All rights reserved. High-Density Physical Random Number Generator Using Spin Signals in Multidomain Ferromagnetic Layer Mon, 16 Feb 2015 13:42:36 +0000 http://www.hindawi.com/journals/acmp/2015/251819/ A high-density random number generator (RNG) based on spin signals in a multidomain ferromagnetic layer in a magnetic tunnel junction (MTJ) is proposed and fabricated. Unlike conventional spin-based RNGs, the proposed method does not require one to control an applied current, leading to a time delay in the system. RNG demonstrations are performed at room temperature. The randomness of the bit sequences generated by the proposed RNG is verified using the FIPS 140-2 statistical test suite provided by the NIST. The test results validate the effectiveness of the proposed RNGs. Our results suggest that we can obtain high-density, ultrafast RNGs if we can achieve high integration on the chip. Sungwoo Chun, Seung-Beck Lee, Masahiko Hara, Wanjun Park, and Song-Ju Kim Copyright © 2015 Sungwoo Chun et al. All rights reserved. Controlled Nanoparticle Targeting and Nanoparticle-Driven Nematic Structural Transition Mon, 16 Feb 2015 06:25:54 +0000 http://www.hindawi.com/journals/acmp/2015/803480/ We study experimentally and theoretically controlled targeting of specific nanoparticles (NPs) to different regions within nematic liquid crystal. Using a simple mesoscopic Landau-de Gennes-type model in terms of a tensor nematic order parameter, we demonstrate a general mechanism which could be exploited for controlled targeting of NPs within a spatially nonhomogeneous nematic texture. Furthermore, we experimentally demonstrate using polarising microscopy that even a relatively low concentration of localised appropriate NPs could trigger a nematic structural transition. A simple estimate is derived to account for the observed transition. A. V. Dubtsov, S. V. Pasechnik, D. V. Shmeliova, S. Kralj, and R. Repnik Copyright © 2015 A. V. Dubtsov et al. All rights reserved. Ab Initio Study of Strain Effects on the Quasiparticle Bands and Effective Masses in Silicon Sun, 15 Feb 2015 09:26:52 +0000 http://www.hindawi.com/journals/acmp/2015/453125/ Using ab initio computational methods, we study the structural and electronic properties of strained silicon, which has emerged as a promising technology to improve the performance of silicon-based metal-oxide-semiconductor field-effect transistors. In particular, higher electron mobilities are observed in n-doped samples with monoclinic strain along the [110] direction, and experimental evidence relates this to changes in the effective mass as well as the scattering rates. To assess the relative importance of these two factors, we combine density-functional theory in the local-density approximation with the approximation for the electronic self-energy and investigate the effect of uniaxial and biaxial strains along the [110] direction on the structural and electronic properties of Si. Longitudinal and transverse components of the electron effective mass as a function of the strain are derived from fits to the quasiparticle band structure and a diagonalization of the full effective-mass tensor. The changes in the effective masses and the energy splitting of the conduction-band valleys for uniaxial and biaxial strains as well as their impact on the electron mobility are analyzed. The self-energy corrections within lead to band gaps in excellent agreement with experimental measurements and slightly larger effective masses than in the local-density approximation. Mohammed Bouhassoune and Arno Schindlmayr Copyright © 2015 Mohammed Bouhassoune and Arno Schindlmayr. All rights reserved. Photoelectrochemical CO2 Conversion to Hydrocarbons Using an AlGaN/GaN-Si Tandem Photoelectrode Sun, 15 Feb 2015 07:11:04 +0000 http://www.hindawi.com/journals/acmp/2015/537860/ We report on a qualitatively improved photoelectrochemical CO2 reduction system which makes it possible to convert CO2 into hydrocarbons. The key is the tandem photoelectrode, which consists of AlGaN/GaN and Si device with p-n junction. The Si device is located on the back of AlGaN/GaN structure and acts as activation layer that raises cathode potential. Use of a Cu cathode results in change of the main reaction products from CO and HCOOH to hydrocarbons such as CH4 and C2H4. The energy conversion efficiency to hydrocarbons from CO2 is estimated to be 0.046% under irradiation with concentrated solar light. Masahiro Deguchi, Satoshi Yotsuhashi, Yuka Yamada, and Kazuhiro Ohkawa Copyright © 2015 Masahiro Deguchi et al. All rights reserved. Effect of Lidocaine and Epinephrine on Human Erythrocyte Shape and Vesiculability of Blood Cells Thu, 12 Feb 2015 09:58:57 +0000 http://www.hindawi.com/journals/acmp/2015/870602/ The effect of local anesthetic composed of lidocaine and epinephrine on vesiculability of blood cells and erythrocyte shape was studied. Whole blood and plasma were incubated with lidocaine/epinephrine. Extracellular vesicles were isolated by centrifugation and washing and counted by flow cytometry. Lidocaine/epinephrine and each component alone were added to diluted blood. Shape changes were recorded by micrographs. An ensemble of captured frames was analyzed for populations of discocytes, echinocytes, and stomatocytes by using statistical methods. Incubation of whole blood and blood plasma with lidocaine/epinephrine considerably increased concentration of extracellular vesicles in isolates (for an average factor 3.4 in blood and 2.8 in plasma). Lidocaine/epinephrine caused change of erythrocyte shape from mainly discocytic to mainly stomatocytic (higher than 50%). Lidocaine alone had even stronger stomatocytic effect (the percent of stomatocytes was higher than 95%) while epinephrine had echinocytic effect (the percent of echinocytes was higher than 80%). The differences were highly statistically significant with statistical power . Lidocaine/epinephrine induced regions of highly anisotropically curved regions indicating that lidocaine and epinephrine interact with erythrocyte membrane. It was concluded that lidocaine/epinephrine interacts with cell membranes and increases vesiculability of blood cells in vitro. Tanja Slokar, Carlos Lopez-Mariscal, Judita Lea Krek, Roman Štukelj, Oskar Zupanc, and Veronika Kralj-Iglič Copyright © 2015 Tanja Slokar et al. All rights reserved. On the Propagation of Waves in an Anisotropic Solid with Laser-Induced Atomic Defects Mon, 09 Feb 2015 13:59:28 +0000 http://www.hindawi.com/journals/acmp/2015/547521/ The behavior of plane waves in a linear, elastic anisotropic laser-excited solid has been investigated taking into account the effects of atomic defect generation. It is found that there are four types of dispersive waves in these crystals, namely, a quasilongitudinal (QL-mode), two quasitransverse (QT-mode), and a quasidefect concentration (N-mode) wave. The complex secular equations for cubic and transversely isotropic crystals are reduced as special cases. It is demonstrated that when waves propagate in one of the planes of transversely isotropic solid having defect concentration field, only one purely quasitransverse wave decouples from the rest of the motion and is not influenced by defect concentration changes. The other waves are coupled and get modified due to presence of defects. When waves propagate along the axis of the solid, only QT- and N-mode are coupled, whereas the two QT-modes get decoupled from the rest of the motion. The phase velocities and attenuation factors of waves have been obtained. Significant effect of defects and anisotropy on wave characteristics is observed in certain ranges of frequency. It is also shown that there is an appreciable variation in case of QL-mode as compared with QT- and N-mode. F. Kh. Mirzade Copyright © 2015 F. Kh. Mirzade. All rights reserved. (112) Surface of CuInSe2 Thin Films with Doped Cd Atoms Tue, 27 Jan 2015 07:25:05 +0000 http://www.hindawi.com/journals/acmp/2015/206501/ The doping behavior of Cd atoms in the CuInSe2 thin films and their influences on electronic structures are investigated. The doped Cd atoms replace Cu atoms and prefer to stay at the (112) surface of the thin films. They combine with Cu vacancies to form defect pairs due to low formation energy. The Cd atom does not by itself modify significantly the electronic structure of the surface, but the defect pairs have important influences. They result in a down shift of valence band maximum and form a hole barrier at the surface, which can prevent holes from reaching the surface and reduce the recombination of carriers. Bo Yin and Chaogang Lou Copyright © 2015 Bo Yin and Chaogang Lou. All rights reserved. Model of Reversible Breakdown in HfO2 Based on Fractal Patterns Thu, 22 Jan 2015 13:49:00 +0000 http://www.hindawi.com/journals/acmp/2015/136938/ We propose a model of the kinetics of reversible breakdown in metal-insulator-metal structures with afnia based on the growth of fractal patterns of defects when the insulator is subject to an external voltage. The probability that a defect is (or is not) generated and the position where it is generated depend on the electric field distribution. The new defect moves accordingly to fractal rules and attach to another defect in a tree branch. When the two electrodes sandwiching the insulating film are connected a conductive filament is formed and the breakdown takes place. The model is calibrated with experiments inducing metastable soft breakdown events in Pt/HfO2/Pt capacitors. P. Lorenzi, R. Rao, G. Romano, and F. Irrera Copyright © 2015 P. Lorenzi et al. All rights reserved. Collective Modes of an Ultracold 6Li-40K Mixture in an Optical Lattice Wed, 21 Jan 2015 06:30:21 +0000 http://www.hindawi.com/journals/acmp/2015/952852/ A low-energy theory of the Nambu-Goldstone excitation spectrum and the corresponding speed of sound of an interacting Fermi mixture of Lithium-6 and Potassium-40 atoms in a two-dimensional optical lattice at finite temperatures with the Fulde-Ferrell order parameter has been formulated. It is assumed that the two-species interacting Fermi gas is described by the one-band Hubbard Hamiltonian with an attractive on-site interaction. The discussion is restricted to the BCS side of the Feshbach resonance where the Fermi atoms exhibit superfluidity. The quartic on-site interaction is decoupled via a Hubbard-Stratonovich transformation by introducing a four-component boson field which mediates the Hubbard interaction. A functional integral technique and a Legendre transform are used to give a systematic derivation of the Schwinger-Dyson equations for the generalized single-particle Green’s function and the Bethe-Salpeter equation for the two-particle Green’s function and the associated collective modes. The numerical solution of the Bethe-Salpeter equation in the generalized random phase approximation shows that there exist two distinct sound velocities in the long-wavelength limit. In addition to low-energy (Goldstone) mode, the two-species Fermi gas has a superfluid phase revealed by two roton-like minima in the asymmetric collective-mode energy. Z. G. Koinov Copyright © 2015 Z. G. Koinov. All rights reserved. Selection Theory of Dendritic Growth with Anisotropic Diffusion Tue, 20 Jan 2015 08:28:39 +0000 http://www.hindawi.com/journals/acmp/2015/529036/ Dendritic patterns frequently arise when a crystal grows into its own undercooled melt. Latent heat released at the two-phase boundary is removed by some transport mechanism, and often the problem can be described by a simple diffusion model. Its analytic solution is based on a perturbation expansion about the case without capillary effects. The length scale of the pattern is determined by anisotropic surface tension, which provides the mechanism for stabilizing the dendrite. In the case of liquid crystals, diffusion can be anisotropic too. Growth is faster in the direction of less efficient heat transport (inverted growth). Any physical solution should include this feature. A simple spatial rescaling is used to reduce the bulk equation in 2D to the case of isotropic diffusion. Subsequently, an eigenvalue problem for the growth mode results from the interface conditions. The eigenvalue is calculated numerically and the selection problem of dendritic growth with anisotropic diffusion is solved. The length scale is predicted and a quantitative description of the inverted growth phenomenon is given. It is found that anisotropic diffusion cannot take the stabilizing role of anisotropic surface tension. Martin von Kurnatowski and Klaus Kassner Copyright © 2015 Martin von Kurnatowski and Klaus Kassner. All rights reserved. Phase Transitions of Binary Lipid Mixtures: A Combined Study by Adiabatic Scanning Calorimetry and Quartz Crystal Microbalance with Dissipation Monitoring Tue, 20 Jan 2015 06:52:26 +0000 http://www.hindawi.com/journals/acmp/2015/479318/ The phase transitions of binary lipid mixtures are studied by a combination of Peltier-element-based adiabatic scanning calorimetry (pASC) and quartz crystal microbalance with dissipation monitoring (QCM-D). pASC, a novel type of calorimeter, provides valuable and unambiguous information on the heat capacity and the enthalpy, whereas QCM-D is proposed as a genuine way of determining phase diagrams by analysing the temperature dependence of the viscosity. Two binary mixtures of phospholipids with the same polar head and differing in the alkyl chain length, DMPC + DPPC and DMPC + DSPC, are discussed. Both techniques give consistent phase diagrams, which compare well with literature results, showing their capability to map the phase behaviour of pure lipids as well as lipid mixtures. This work can be considered as a departure point for further investigations on more complex lipid mixtures displaying relevant phases such as the liquid-ordered phase and solid-lipid interfaces with biologically functional importance. P. Losada-Pérez, N. Mertens, B. de Medio-Vasconcelos, E. Slenders, J. Leys, M. Peeters, B. van Grinsven, J. Gruber, C. Glorieux, H. Pfeiffer, P. Wagner, and J. Thoen Copyright © 2015 P. Losada-Pérez et al. All rights reserved. Noise from Glauber Dynamics: Self-Consistent Interaction and Temperature Dependent Correlations Thu, 15 Jan 2015 11:20:38 +0000 http://www.hindawi.com/journals/acmp/2015/607021/ Low frequency flicker noise has been argued to occur in spatially extended metastable systems near a critical point (Bak et al., 1987). An Ising-Glauber model based method is suggested here to systematically obtain temperature dependent nth-order correlation functions for arbitrary interacting two-level systems (TLSs). This model is fully consistent with existing methods to calculate noise spectra from TLSs and complements them. However, with as such no a priori assumptions on the typical log normal distribution of fluctuation rates, it is shown that noise manifests in two different cases: first in the thermodynamic limit on a 2D lattice with long range antiferromagnetic interactions at low temperatures and second in the case of a statistical ensemble of finite-sized spin clusters representing disorder, but where each cluster is ordered due to ferromagnetic interactions. Amrit De Copyright © 2015 Amrit De. All rights reserved. Application of Ellipsometry to Control the Plasmachemical Synthesis of Thin TiONx Layers Tue, 13 Jan 2015 06:33:00 +0000 http://www.hindawi.com/journals/acmp/2015/709308/ Ellipsometry is often used to determine the characteristics of films. Ellipsometric studies may turn out to be ineffective because several solutions correspond to the same polarization angles. It is demonstrated that the ambiguity is not due to the physical limitations of the method but it has a purely mathematical character. So, additional information about the film is necessary to determine the absolute values of refractive index, attenuation, and thickness. F. N. Dultsev and E. A. Kolosovsky Copyright © 2015 F. N. Dultsev and E. A. Kolosovsky. All rights reserved. Tin-Doped Indium Oxide-Titania Core-Shell Nanostructures for Dye-Sensitized Solar Cells Tue, 30 Dec 2014 12:13:48 +0000 http://www.hindawi.com/journals/acmp/2014/903294/ Dye-sensitized solar cells (DSSCs) hold great promise in the pursuit of reliable and cheap renewable energy. In this work, tin-doped indium oxide (ITO)-TiO2 core-shell nanostructures are used as the photoanode for DSSCs. High-density, vertically aligned ITO nanowires are grown via a thermal evaporation method and TiO2 is coated on nanowire surfaces via TiCl4 treatment. It is found that high TiO2 annealing temperatures increase the crystallinity of TiO2 shell and suppress electron recombination in the core-shell nanostructures. High annealing temperatures also decrease dye loading. The highest efficiency of 3.39% is achieved at a TiO2 annealing temperature of 500°C. When HfO2 blocking layers are inserted between the core and shell of the nanowire, device efficiency is further increased to 5.83%, which is attributed to further suppression of electron recombination from ITO to the electrolyte. Open-circuit voltage decay (OCVD) measurements show that the electron lifetime increases by more than an order of magnitude upon HfO2 insertion. ITO-TiO2 core-shell nanostructures with HfO2 blocking layers are promising photoanodes for DSSCs. Luping Li, Cheng Xu, Yang Zhao, and Kirk J. Ziegler Copyright © 2014 Luping Li et al. All rights reserved. In and Ga Codoped ZnO Film as a Front Electrode for Thin Film Silicon Solar Cells Sun, 28 Dec 2014 07:03:35 +0000 http://www.hindawi.com/journals/acmp/2014/971528/ Doped ZnO thin films have attracted much attention in the research community as front-contact transparent conducting electrodes in thin film silicon solar cells. The prerequisite in both low resistivity and high transmittance in visible and near-infrared region for hydrogenated microcrystalline or amorphous/microcrystalline tandem thin film silicon solar cells has promoted further improvements of this material. In this work, we propose the combination of major Ga and minor In impurities codoped in ZnO film (IGZO) to improve the film optoelectronic properties. A wide range of Ga and In contents in sputtering targets was explored to find optimum optical and electrical properties of deposited films. The results show that an appropriate combination of In and Ga atoms in ZnO material, followed by in-air thermal annealing process, can enhance the crystallization, conductivity, and transmittance of IGZO thin films, which can be well used as front-contact electrodes in thin film silicon solar cells. Duy Phong Pham, Huu Truong Nguyen, Bach Thang Phan, Thi My Dung Cao, Van Dung Hoang, Vinh Ai Dao, Junsin Yi, and Cao Vinh Tran Copyright © 2014 Duy Phong Pham et al. All rights reserved. Laser and Ion Beams Interactions with Materials Mon, 22 Dec 2014 10:46:29 +0000 http://www.hindawi.com/journals/acmp/2014/890520/ Xiaotao Zu, Kai Sun, Wanguo Zheng, and Haiyan Xiao Copyright © 2014 Xiaotao Zu et al. All rights reserved. Theoretical Analysis and Computational Simulation of Advanced Structured Materials Thu, 18 Dec 2014 11:23:53 +0000 http://www.hindawi.com/journals/acmp/2014/367916/ Hanxing Zhu, Daniel Balint, and Zaoyang Guo Copyright © 2014 Hanxing Zhu et al. All rights reserved. Is There a Metamaterial Route to High Temperature Superconductivity? Thu, 04 Dec 2014 00:10:10 +0000 http://www.hindawi.com/journals/acmp/2014/479635/ Superconducting properties of a material such as electron-electron interactions and the critical temperature of superconducting transition can be expressed via the effective dielectric response function () of the material. Such a description is valid on the spatial scales below the superconducting coherence length (the size of the Cooper pair), which equals ∼100 nm in a typical BCS superconductor. Searching for natural materials exhibiting larger electron-electron interactions constitutes a traditional approach to high temperature superconductivity research. Here we point out that recently developed field of electromagnetic metamaterials deals with somewhat related task of dielectric response engineering on sub-100 nm scale. We argue that the metamaterial approach to dielectric response engineering may considerably increase the critical temperature of a composite superconductor-dielectric metamaterial. Igor I. Smolyaninov and Vera N. Smolyaninova Copyright © 2014 Igor I. Smolyaninov and Vera N. Smolyaninova. All rights reserved. Numerical Study of Membrane Configurations Sun, 30 Nov 2014 00:10:21 +0000 http://www.hindawi.com/journals/acmp/2014/373674/ We studied biological membranes of spherical topology within the framework of the spontaneous curvature model. Both Monte Carlo simulations and the numerical minimization of the curvature energy were used to obtain the shapes of the vesicles. The shapes of the vesicles and their energy were calculated for different values of the reduced volume. The vesicles which exhibit in-plane ordering were also studied. Minimal models have been developed in order to study the orientational ordering in colloids coated with a thin sheet of nematic liquid crystal (nematic shells). The topological defects are always present on the surfaces with the topology of a sphere. The location of the topological defects depends strongly on the curvature of the surface. We studied the nematic ordering and the formation of topological defects on vesicles obtained by the minimization of the spontaneous curvature energy. Luka Mesarec, Miha Fošnarič, Samo Penič, Veronika Kralj Iglič, Samo Kralj, Wojciech Góźdź, and Aleš Iglič Copyright © 2014 Luka Mesarec et al. All rights reserved. Field Induced Memory Effects in Random Nematics Sun, 30 Nov 2014 00:10:19 +0000 http://www.hindawi.com/journals/acmp/2014/423693/ We studied numerically external field induced memory effects in randomly perturbed nematic liquid crystals. Random anisotropy nematic-type lattice model was used. The impurities imposing orientational disorder were randomly spatially distributed with the concentration below the percolation threshold. Simulations were carried for finite temperatures, where we varied , interaction strength between LC molecules, and impurities and external field . In the plane we determined lines separating short range—quasi long range and quasi long range—long range order. Furthermore, crossover regime separating external field and random field dominated regime was estimated. We calculated remanent nematic ordering in samples at as a function of the previously experienced external field strength . Amid Ranjkesh, Milan Ambrožič, Samo Kralj, and T. J. Sluckin Copyright © 2014 Amid Ranjkesh et al. All rights reserved.