bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling the electric field effect in superconducting films
Authors: Pavlenko N. 
Published: June 2022

AbstractWe present a phenomenological model of periodic ferroelectric‐superconductor (FE‐S) heterostructures containing two alternating ferroelectric and superconducting layers. The interaction at the FE‐S contacts is described as a coupling of the local carrier density of the superconductor with the spontaneous ferroelectric polarization near the FE‐S interface. For the stronger coupling, we find a stable symmetric domain‐type phase exhibiting the ferroelectric domain structure. With a further increase of the coupling energy, we obtain the complete suppression of the superconducting state in the S‐film. The behavior of the system is discussed for different thicknesses of the S‐films.
Pulsed laser deposited SrBi2Nb2O9 thin films grown on various substrates compatible with microwaves applications
Authors: Rousseau A. , Duclère J.‐R. , Guilloux‐Viry M. , Bouquet V. , Perrin A. 
Published: June 2022

AbstractSrBi2Nb2O9 (SBN) films were grown by pulsed laser deposition on various substrates suitable for microwaves applications. Pure c‐axis oriented SBN films on (100) MgO and (100) LaAlO3 are epitaxially grown. The crystalline quality evaluated by the rocking curves width is strongly correlated to the film‐substrate mismatch (Δohgr; = 0.9–2° on MgO and Δω = 0.3–0.4° on LaAlO3). SBN growth on sapphire is more complex. In fact, on R‐plane as well as on C‐plane, XRD evidences the coexistence of various orientations of the SBN films. In spite of the coexistence of several orientations epitaxial growth was evidenced, strongly influencing the microstructure.
Advances of pulsed laser deposition of ZnO thin films
Authors: Lorenz M. , Hochmuth H. , Schmidt‐Grund R. , Kaidashev E.M. , Grundmann M. 
Published: June 2022

AbstractAdvances in Pulsed Laser Deposition (PLD) equipment and process design for the epitaxy of ZnO thin films on a‐, and c‐oriented sapphire substrates are reported. The achieved improvement of device relevant ZnO layer properties is directly related to our equipment design and novel process schemes. First results on growth and reflectivity of ZnO‐MgO based dielectric Bragg resonators for future ZnO‐based light emitter devices are shown.
Electro‐optical properties of ZnO‐BaTiO3‐ZnO heterostructures grown by pulsed laser deposition
Authors: Schubert M. , Ashkenov N. , Hofmann T. , Lorenz M. , Hochmuth H. , v. Wenckstern H. , Grundmann M. , Wagner G. 
Published: June 2022

AbstractElectro‐optical birefringence measurements by spectroscopic ellipsometry on ZnO‐BaTiO3‐ZnO heterostructures, grown by pulsed laser deposition on (0001) sapphire are reported. Wurtzite‐structure ZnO layers serve as transparent conducting electrodes. An interesting hysteresis is observed, tentatively assigned due to coupling between wurtzite and ferroelectric polarization, and ferroelectric phase transition.
Making the transition temperature of cuprate superconductors higher by using the field‐effect‐transistor geometry
Authors: Hayashi M. 
Published: June 2022

AbstractWe present a possibility to raise the transition temperature of cuprate superconductors by using the field‐effect‐transistor type devices. The basic mechanism is based on the proximity effect of the two off‐diagonal‐long‐range‐orders in the superconducting phase of the cuprates, namely, the singlet resonating‐valence‐bond order and the bose condensation. Our model is based on the mean field theory of the t‐J model.
Magnetism of SrRuO3 thin films under high hydrostatic pressure
Authors: Demuer A. , Jaccard D. , Reiner J.W. , Ahn C.H. , Triscone J.‐M. 
Published: June 2022

AbstractWe report on resistivity and Hall measurements performed on epitaxial thin films of the weak ferromagnet SrRuO3 under hydrostatic pressure up to 21.4 GPa. In the low pressure range (< 13GPa), we observe a linear pressure dependence of the Curie temperature with a rate ‐6K GPa‐1 similar to that found in the bulk material. At higher pressures, the hysteretic loop observed in the Hall measurement, related to the magnetization via the extraordinary Hall effect, supports our previous observation concerning the unexpected persistence of ferromagnetic order above 70 K.
Influence of film thickness and strain on magnetic properties of epitaxial La0.7A0.3CoO3 (A = Ca, Sr, Ba) thin films
Authors: Morán O. , Fuchs D. , Adelmann P. , Schneider R. 
Published: June 2022

AbstractWe prepared La0.7A0.3CoO3 (A=Ca, Sr, Ba) films with a thickness ranging from 50 up to 1000 monolayers (∼ 20–400 nm) by pulsed laser deposition (PLD) on (001)‐oriented single crystal substrates of SrTiO3, (LaAlO3)0.3(Sr2AlTaO6)0.7 and LaAlO3 and studied the in‐plane and out‐of‐plane magnetization as function of thickness and of the strain provided by the substrate‐film lattice mismatch. The Curie temperature TC decreases slightly with thickness according to the finite size scaling 1 – TC / T∞ = (N0 / N)λ, where T∞ is the bulk Curie temperature and N is the number of monolayers. We obtain a critical exponent λ = 0.9 ± 0.2, consistent with the theoretical mean field value, and a spin‐spin coupling range N0 = 2–3.
Surface electronic structure and Verwey‐transition of magnetite studied by photoemission spectroscopy
Authors: Schrupp D. , Sing M. , Tsunekawa M. , Fujiwara H. , Kasai S. , Sekiyama A. , Suga S. , Muro T. , Brabers V.A.M. , Claessen R. 
Published: June 2022

AbstractWe report on a detailed study of single crystal surfaces with (111) and (100) orientations by means of photoemission spectroscopy (PES). The surfaces were prepared by sputtering, annealing, and post‐oxidizing and characterized using LEED, XPS, and STM. The surface electronic structure turns out to be strongly dependent on the surface orientation and preparation conditions. This also holds for more bulk sensitive PES measurements using photons with an energy at the Fe 2p resonance threshold. Thus we conclude that the surface region extends much deeper into the bulk than the topmost atomic layer.
The microstructure of La0.67Sr0.33MnO3 grain boundaries on SrTiO3 bicrystal substrates
Authors: Liljenfors T. , Gunnarsson R. , Ivanov Z. , Olsson E. 
Published: June 2022

AbstractThe aim of this study is to characterize the grain boundary microstructure of artificial La0.67Sr0.33MnO3 (LSMO) grain boundaries obtained by epitaxial growth on SrTiO3 (STO) bicrystal substrates. The films were deposited on STO bicrystal substrates using pulsed laser deposition. The substrates were (001) oriented and the boundaries were symmetrical [001]‐tilt boundaries with nominal tilt angle 24° and 37° respectively. The microstructures were characterized using a transmission electron microscope. The thickness of the LSMO films was 32 and 37 nm respectively. The films were relatively smooth and the interface between the substrate and the films was sharp without any evidence of chemical reaction or interdiffusion.
Correlation of the electrical transport in epitaxial La2/3Ca1/3MnO3 thin films with magnetization
Authors: Morán O. , Fuchs D. , Hott R. , Grube K. , Schneider R. , Bacca E. , Prieto P. 
Published: June 2022

AbstractWe measured the magnetization M(T,H) and resistivity ρ(T,H) of epitaxial c‐axis oriented films of the metallic ferromagnetic perovskite La2/3Ca1/3MnO3 as function of temperature and external magnetic field. The films were prepared by dc‐sputtering at high oxygen pressure onto (001) SrTiO3 substrates without additional oxygen annealing. Ferromagnetic ordering was observed below a temperature TC ≈ 260 K where a negative magnetoresistance ratio of 50% was achieved in a magnetic field of 6 T. Above TC, the zero field resistivity exhibits polaron‐hopping like activated conduction. The relation ρ(T,H) ∝ exp[‐M(H,T)/M0] observed below TC suggests a direct connection between magnetization and resistivity.
Novel effects observed in heavy ion irradiated Bi2Sr2‐xLaxCuOy thin films
Authors: Raffy H. , Murrills C. , Pomar A. , Li Z.Z. 
Published: June 2022

AbstractThe superconducting properties of Bi2Sr2‐xLaxCuOy thin films irradiated by 1 GeV heavy ions have been investigated. Firstly, irradiation produces dramatic changes in Tc and in R(T). This fact is attributed to a self‐doping effect of the sample by oxygen liberated from the ion tracks. Secondly, the pinning properties of the columnar defects allowed us to probe different vortex behaviours for films with increasing La content (0 ≤ x ≤ 0.4). From the angular dependence of R(H) and Jc(H) in the mixed state, for a given column density, a directional pinning effect, or linear vortex behaviour, is observed for low x values, whereas no directional effect is seen for large x values and 2D scaling properties, characteristic of pancake vortices, are then observed. Importantly this reveals that changes in x induce large changes in the material anisotropy.
Strain dependence of transport critical exponent in RuO2‐glass systems
Authors: Vionnet S. , Grimaldi C. , Maeder T. , Ryser P. , Strässler S. 
Published: June 2022

AbstractA vast class of disordered conducting‐insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponents. The lack of universality implies that critical indexes may depend on material properties such as microstructure, composition etc., and that in principle they can be influenced by suitable applied perturbations leading to important informations about the origin of nonuniversality. Here we show that RuO2‐glass compounds can have nonuniversal values of transport critical exponents which can be altered by an applied mechanical strain leading to a logarithmically divergent piezoresistive response at the percolation threshold. This finding supports the tunneling‐percolation theory of nonuniversality proposed several years ago.
Behavior of the APSG electronic wavefunction near the electron‐electron coalescence point
Authors: Pernal K. , Cioslowski J. 
Published: June 2022

AbstractThe behavior of electronic wave functions within the antisymmetrized product of strongly orthogonal geminals (APSG) approximation at the point of the electron‐electron coalescence is examined. Its elucidation allows one to understand the origins of the previously reported satisfactory performance of APSG wavefunctions as reference states in the connected moments expansion method (CMX). It is shown that the failure to satisfy the electron‐electron cusp condition causes divergence of certain type of integrals that enter the CMX formulae, which in turn brings about significant deterioration of the quality of the resulting estimates for the ground‐state energy in finite basis sets.
Local information‐distance thermodynamics of molecular fragments
Authors: Nalewajski R.F. 
Published: June 2022

AbstractThe Fisher information contained in a probability distribution is summarized. The corresponding measures of the information distance, relative to the reference probability density, are introduced and discussed. These concepts are designed as analogues of the Kullback‐Leibler directed divergence and Kullback's divergence. For these alternative measures of the missing information the equilibrium (“stockholder”) scheme of Hirshfeld, of a division of the molecular electron density into the subsystem components, is derived from the minimum principle of the local or global entropy deficiency relative to the free‐subsystem (“promolecule”) reference. The local information distance densities are used to describe instantaneous electron distributions in molecular subsystems within a thermodynamic‐like approach to the density fluctuations and irreversible processes. The key concepts of such a local irreversible “thermodynamics” are introduced. They include the corresponding local affinities (forces) and the conjugate fluxes (responses), which together determine the local entropy deficiency source. These quantities depend on the adopted measure of the information distance and selected state‐parameters. For each such representation the relevant Onsager‐type reciprocity relations can be derived, which reflect the symmetries between the linear effects of affinities on fluxes.
Electric/magnetic flux tube on the background of magnetic/electric field
Authors: Dzhunushaliev V. 
Published: June 2022

AbstractIt is argued that the phenomenon of a flux tube in quantum chromodynamics is closely connected with a spontaneously symmetry breakdown of gauge theory. It is shown that in the presence of a mass term in the SU(2) gauge theory the Nielsen‐Olesen equations describe the flux tube surrounded by an external field.
Electronic structure and transport properties of quantum dots
Authors: Tews M. 
Published: June 2022

AbstractThe subject of this paper are electronic properties of isolated quantum dots as well as transport properties of quantum dots coupled to two electronic reservoirs. Thereby special focus is put on the effects of Coulomb interaction and possible correlations in the quantum dot states. First, the regime of sequential tunneling to the reservoirs is investigated. It is shown that in case degenerate states participate in transport, the resonance positions in the differential conductance generally depend on temperature and the degree of degeneracy. This effect can be used to directly probe degeneracies in a quantum dot spectrum. A further effect, characteristic for sequential tunneling events, is the complete blocking of individual channels for transport. A generalisation of the well known spin blockade is found for correlated dot states transitions through which are not directly spin‐forbidden. In the second part, the electronic structure of spherical quantum dots is calculated. In order to account for correlation effects, the few‐particle Schrödinger equation is solved by an exact diagonalization procedure. The calculated electronic structure compares to experimental findings obtained on colloidal semiconductor nanocrystals by Scanning Tunneling Spectroscopy. It is found that the electric field induced by the tunneling tip is gives rise to a Stark effect which can break the spherical symmetry of the electronic ground state density which is in agreement with wave‐function mapping experiments. The symmetry breaking depends on the competition between exchange energy and the Stark energy. Moreover, a systematic dependence on particle number is found for the excitation energies of optical transitions which explains recent experimental findings on self‐organized quantum dots. In the last part, co‐tunneling in the Coulomb blockade regime is studied. For this end the tunneling current is calculated up to the forth order perturbation theory in the tunnel coupling by a real‐time Green's function approach for the non‐equilibrium case. The differential conductance calculated for a quantum dot containing up to two interacting electrons shows complex signatures of the excitation spectrum which are explained by a combination of co‐tunneling and sequential tunneling processes. Thereby the calculations show a peak structure within the Coulomb blockade regime which has also been observed in experiment.
QCD universality recovered via the Total Available Quadri‐Scalar
Authors: Appignani C. 
Published: June 2022

AbstractAfter presenting a brief review of the phenomenology of the Leading Effect, we define a new variable, the “Total Available Quadri‐Scalar” (ATOT) and propose it as the invariant quantity effectively available for the production of the multihadronic final states. The introduction and definition of this new varaible is justified by means of simple geometrical‐kinematical considerations and we show that ATOT reduces to the so‐called effective energy in the single specific situation where the use of the latter applies. Using ATOT to re‐plot existing data, the quantity <nch> is shown to be a “Universality Feature” – that is, independent from the colliding particles, the collider nominal energy, and even from the hadronic invariant mass – as imposed by QCD universality.
Electron excitation cross section of atomic transitions in the two‐state approximation
Authors: Kamli A. , Bougouffa S. 
Published: June 2022

AbstractThe cross section of the 3s → 3p transition of sodium produced by electron impact has been calculated by performing a numerical integration of the coupled differential equations. The potential functions have been calculated exactly using the hydrogen‐like wave functions for the valence electron of the sodium with an effective charge adjusted to fit the experimental 3s → 3p line strength. The results compare very well with experimental data and with those obtained using more elaborate and sophisticated models.
Novel properties of wave propagation in biaxially anisotropic left‐handed materials
Authors: Shen J.Q. 
Published: June 2022

AbstractSome physically interesting properties and effects (including the quantum effects) of wave propagation in biaxially anisotropic left‐handed materials are investigated in this paper: (i) we show that in the biaxially gyrotropic left‐handed material, the left‐right coupling of circularly polarized light arises due to the negative indices in permittivity and permeability tensors of gyrotropic media; (ii) it is well known that the geometric phases of photons inside a curved fiber in previous experiments often depend on the cone angles of solid angles subtended by a curve traced by the direction of wave vector of light, at the center of photon momentum space. Here, however, for the light propagating inside certain anisotropic left‐handed media we will present a different geometric phase that is independent of the cone angles; (iii) the extra phases of electromagnetic wave resulting from the instantaneous helicity inversion at the interfaces between left‐ and right‐handed (LRH) media is also studied in detail by using the Lewis‐Riesenfeld invariant theory. Some interesting applications (e.g., controllable position‐dependent frequency shift, detection of quantum‐vacuum geometric phases and helicity reversals at the LRH interfaces etc.) of above effects and phenomena in left‐handed media is briefly discussed.
Current‐density patterns induced by avalanche injection phenomena in high‐voltage diodes during turn‐off
Authors: Niedernostheide F.‐J. , Falck E. , Schulze H.‐J. , Kellner‐Werdehausen U. 
Published: June 2022

AbstractThe turn‐off behavior of two types of high‐voltage diodes is investigated by means of numerical simulations. Basic self‐organized structures appearing as transient patterns during the turn‐off period are quasi‐stationary or traveling current‐density filaments and periodic current‐density distributions. Additionally, we find evolution of more complex patterns that can be considered to be a superposition of basic structures. Examples of such complex structures are presented and mechanisms leading to their evolution are discussed.
Pattern formation in a reaction‐advection model with delay: a continuum approach to myxobacterial rippling
Authors: Börner U. , Bär M. 
Published: June 2022

AbstractStanding wave oscillations of the cell density (rippling) are observed in premature aggregates of developing myxobacteria. Recently the underlying pattern formation mechanism was shown to be based on the interplay between active cell motion and local interactions triggering reversals in the cells' direction of motion. The propagation of information through the system is mediated by the internal state of moving cells rather than by diffusible chemical signals. Discrete cellular automata and coupled‐map lattices have been investigated earlier and indicate the importance of a minimum refractory period between subsequent reversals of a cell. In this paper we consider the continuum limit of the process, that yields a set of hyperbolic partial differential equations with a a single discrete time delay. The time delay corresponds to the duration of the mentioned refractory period of the cells. According to linear stability analysis a minimal time delay is required for a wave instability to occur. The results of the continuum model are in reasonable agreement with the findings in the discrete models adding credibility to the earlier studies.
Reaction‐diffusion waves in neuronal tissue and the window of cortical excitability
Authors: Dahlem M.A. , Müller S.C. 
Published: June 2022

AbstractSpreading depression (SD) is a dynamic wave phenomenon occurring in all gray matter regions of the central nervous systems (CNS). It is characterized by a sudden breakdown of neuronal activity and accompanied by a massive influx and efflux of ions across the membrane of neurons. The retina is a constituent of the CNS in which one can easily observe the dynamic behavior of the SD wave fronts, because SD changes the optical properties of the tissue. There is ample evidence that SD belongs to the self‐organization processes due to the coupling of reaction with diffusion in excitable medium. It is assumed that the occurrence of SD is associated with some neurological symptoms of migraine with aura. A frequently reported aura symptom is a traveling visual blind region (scotoma) with a preceding figure of scintillating line segments. The characteristic form and development of the scotoma suggests that the underlying phenomenon is a wave propagating through the primary visual cortex, most likely the cortical spreading depression. In this article we discuss similarities between SD waves and the migraine aura on the basis of properties of reaction‐diffusion waves known from other excitable media. In particular, the propagation velocities, the shape and the dynamics of the waves are compared with each other. We find that the assumption of the neuronal tissue to be in a state of only weak excitability explains some properties of the migraine aura, such as the confined appearance and its propagation with a stable velocity.
Anomalous statistics in turbulence, financial markets and other complex systems
Authors: Peinke J. , Böttcher F. , Barth St. 
Published: June 2022

AbstractThe meaning of non‐Gaussian statistics of disordered systems is discussed. The risks of heavy tailed probability distributions of wind gusts are presented together with the discussion of an eventual power law behavior of such heavy tailed distributions. We summarize the argumentation connecting such probability distributions with Levy processes and the meaning of non‐existing moments. Based on turbulence and financial market data, stochastic cascade processes are presented, which lead to anomalous statistics with heavy tails, too. Finally we show how for disordered complex systems with an underlying hierarchical structure, like the cascade structure in turbulence, a stochastic equation can be estimated directly from the data. The numerical solution of this reconstructed stochastic process gives back the anomalous statistics.
The vanadium Magnéli phases VnO2n‐1
Authors: Schwingenschlögl U. , Eyert V. 
Published: June 2022

AbstractTo compare the metal‐insulator transitions (MITs) of VO2 and V2O3 we analyze the relations between the structural and electronic properties of the vanadium Magnéli phases. These materials set up the homologous series VnO2n‐1 (3 ≤ n ≤ 9) and have crystal structures comprising typical dioxide‐like and sesquioxide‐like regions. As the MITs of the vanadium Magnéli phases are accompanied by structural transformations, we are able to discuss the effects of characteristic changes in the local atomic environments. The systematic investigation of the transport properties is based on a new and unifying description of the crystal structures of the Magnéli phases including VO2 and V2O3. Our results lead to a comprehensive understanding of the MITs in the Magnéli class and shed new light on the role of particular electronic states for the MIT of V2O3.