We present an angle-resolved photoelectron spectroscopy study of YBa(2)Cu(3)O(7-delta) films in situ grown by pulsed laser deposition. We have successfully produced underdoped surfaces with ordered oxygen vacancies within the CuO chains resulting in a clear ortho-II band folding of the Fermi surface. This indicates that order within the CuO chains affects the electronic properties of the CuO(2) planes. Our results highlight the importance of having not only the correct surface carrier concentration, but also a very well ordered and clean surface in order that photoemission data on this compound be representative of the bulk.

We describe some general features in the transient behaviour of strongly correlated transition metal oxides, following ultrafast excitation by a femtosecond laser pulse. Our analysis is based on time-resolved reflectivity measurements on (V1-x Cr x )2O3, a prototype Mott-Hubbard material, and the manganite compound (La0.67Sr0.33)MnO3, performed over a time window of several tenths of ps. We point out the contribution of coherent lattice oscillations-both optical and acoustic-to the overall signal, and show how they can depend on the crystallographic orientation of the material with respect to the laser beam wavevector and polarisation. In particular, an acoustic wave is always found to be present in our measurements, and we show that its oscillating behaviour is superposed to the average time evolution of the material, which can be instead related in different ways to its electronic properties and thermodynamic phase. All these effects are to be taken into account in any further analysis leading to the estimation of relevant physical parameters for correlated materials, and they appear to play a significant role not only for reflectivity techniques, but also in other kinds of ultrafast pump-probe experiments.

In this study a metal oxide sensor array is exposed to a time-dependent amount of gas inside the sensor chamber of negligible "dead" volume. Special parameters of the response kinetics are used for multi-parametric featuring of volatile organic compounds (VOCs). The composition of the atmosphere in the chamber varies due to the time-dependent release of the VOCs from a solid phase micro-extraction (SPME) fiber into the flow of synthetic air. Four types of volatile compounds, namely acetone, acetic acid, acetaldehyde and butyric acid, that are known being frequently emitted from infected wounds, are tested in this study. The explorative data analysis (EDA) of the features is performed for the sensor outputs obtained at different carrying gas flow rates and the VOC amounts. Influence of specific aspects of the SPME based sampling on the sensor outputs is estimated. It is demonstrated by the PCA results that the target compounds cannot be distinguished below 3-4 ppm if only the sensor outputs based on the signal magnitudes are used for the featuring of VOCs (static-compatible features). The dynamic features add significant information and allow a better discrimination of the volatile compounds. The classification of the target volatile compounds can additionally be improved by precise control of the VOCs expansion in the chamber in the dynamic exposure approach. © 2009 Elsevier B.V. All rights reserved.

Ferroelectric domains were investigated using piezoresponse force microscopy in superlattices composed of multiferroic BiFeO3 and SrTiO3 layers. Compared to single BiFeO3 thin films, a reduction in the domains size and a suppression of the in-plane orientation of domains are observed in a superlattice of (BiFeO3)4(SrTiO3)8, suggesting a constrained ferroelectric domain orientation along the out-of-plane <001> direction. Such modification of domain size and orientation in BiFeO3-based heterostructures could play a vital role on engineering the domains and domain wall mediated functional properties necessary for device applications.

In order to analyze the effect of strain on the magnetic properties of narrow-band manganites, temperature-and field-dependent susceptibilities of about 8.5-nm-thick epitaxial Pr(0.7)Ca(0.3)MnO(3) films, respectively, grown on (001) and (110) SrTiO(3) substrates, have been compared. For ultrathin samples grown on (001) SrTiO(3), a bulklike cluster-glass magnetic behavior is found, indicative of the possible coexistence of antiferromagnetic and ferromagnetic phases. On the contrary, ultrathin films grown on (110) substrates show a robust ferromagnetism with a strong spontaneous magnetization of about 3.4 mu(B)/Mn atom along the easy axis. On the base of high-resolution reciprocal space mapping analyses performed by x-ray diffraction, the different behaviors are discussed in terms of the crystallographic constraints imposed by the epitaxy of Pr(0.7)Ca(0.3)MnO(3) on SrTiO(3). We suggest that for growth on (110) SrTiO(3), the tensile strain on the film c axis, lying within the substrate plane, favors the ferromagnetic phase, possibly by allowing a mixed occupancy and hybridization of both in-plane and out-of-plane e(g) orbitals. Our data allow to shed some physics of inhomogeneous states in manganites and on the nature of their ferromagnetic insulating state.

The possibility of multiband conductivity and multigap superconductivity is explored in oriented V(3)Si thin films by means of reflectance and transmittance measurements at terahertz frequencies. The temperature dependence of the transmittance spectra in the normal state gives evidence of two bands contributing to the film conductivity. This outcome is consistent with electronic structure calculations performed within density functional theory. On this basis, we performed a detailed data analysis and found that all optical data can be consistently accounted for within a two-band framework, with the presence of two optical gaps in the superconducting state corresponding to 2 Delta/kT(c) values close to 1.8 and 3.8.

The dissolution of interstitial-type end-of-range (EOR) damage in preamorphized Ge is shown to induce a transient enhanced diffusion of an epitaxially grown boron delta at temperatures above 350 °C that saturates above 420 °C. The B diffusion events are quantitatively correlated with the measured positive strain associated with the EOR damage as a function of the annealing temperature with an energy barrier for the EOR damage dissolution of 2.1±0.3 eV. These results unambiguously demonstrate that B diffuses in Ge through a mechanism assisted by self-interstitials, and impose considering the interstitial implantation damage for the modeling of impurity diffusion in Ge. © 2010 American Institute of Physics.

We present a comprehensive investigation of nonideal continuous-variable quantum teleportation implemented with entangled non-Gaussian resources. We discuss in a unified framework the main decoherence mechanisms, including imperfect Bell measurements and propagation of optical fields in lossy fibers, applying the formalism of the characteristic function. By exploiting appropriate displacement strategies, we compute analytically the success probability of teleportation for input coherent states and two classes of non-Gaussian entangled resources: two-mode squeezed Bell-like states (that include as particular cases photon-added and photon-subtracted de-Gaussified states), and two-mode squeezed catlike states. We discuss the optimization procedure on the free parameters of the non-Gaussian resources at fixed values of the squeezing and of the experimental quantities determining the inefficiencies of the nonideal protocol. It is found that non-Gaussian resources enhance significantly the efficiency of teleportation and are more robust against decoherence than the corresponding Gaussian ones. Partial information on the alphabet of input states allows further significant improvement in the performance of the nonideal teleportation protocol.

We demonstrate that the growth of Fe/(Ga,Mn)As heterointerfaces can be efficiently controlled by epitaxy and that robust ferromagnetism of the interfacial Mn atoms is induced at room temperature by the proximity effect. X-ray magnetic circular dichroism and x-ray resonant reflectivity data, supported by theoretical calculations, were used to monitor both temperature and magnetic field dependence of the Mn magnetic moment in the semiconducting host. We identify distinct Mn populations, each of them with specific magnetic character.

We present a new technique, differential ghost imaging (DGI), which dramatically enhances the signalto- noise ratio (SNR) of imaging methods based on spatially correlated beams. DGI can measure the transmission function of an object in absolute units, with a SNR that can be orders of magnitude higher than the one achievable with the conventional ghost imaging (GI) analysis. This feature allows for the first time, to our knowledge, the imaging of weakly absorbing objects, which represents a breakthrough for GI applications. Theoretical analysis and experimental and numerical data assessing the performances of the technique are presented.

A new insertion device beamline is now operational on straight section 8 at the SOLEIL synchrotron radiation source in France. The beamline and the experimental station were developed to optimize the study of the dynamics of electronic and magnetic properties of materials. Here we present the main technical characteristics of the installation and the general principles behind them. The source is composed of two APPLE II type insertion devices. The monochromator with plane gratings and spherical mirrors is working in the energy range 40-1500 eV. It is equipped with VLS, VGD gratings to allow the user optimization of flux or higher harmonics rejection. The observed resonance structures measured in gas phase enable us to determine the available energy resolution: a resolving power higher than 10000 is obtained at the Ar 2p, N 1s and Ne K-edges when using all the optical elements at full aperture. The total flux as a function of the measured photon energy and the characterization of the focal spot size complete the beamline characterization.

We report on structural, magnetic, and transport properties of La(x)MnO(3-delta) thin films, epitaxially grown on SrTiO(3) substrates by molecular beam epitaxy deposition technique. We varied the La/Mn ratio by changing the evaporation rate of the single-element diffusive cells. However, the oxygen content of La(x)MnO(3-delta) thin films was varied by post-annealing them in air and/or vacuum, by changing the annealing temperature and the time of post-annealing process. Optimal oxygenated La(0.88)MnO(3-delta) (LMO) films show extremely high metal insulator transitions temperature T(MI) similar to 380K and magneto-transport similar to those found in strontium-doped La(1-x)Sr(x)MnO(3) manganites compounds. Magnetic measurements confirm the formation of a ferromagnetic phase at Curie temperature T(c) of about 360K. All these findings clearly demonstrate that the lanthanum deficiency, with respect to bivalent cation-substitution, is a very efficient way to hole-dope manganites.

An important goal in cluster analysis is the internal validation of results using an objective criterion. Of particular relevance in this respect is the estimation of the optimum number of clusters capturing the intrinsic structure of your data. This paper proposes a method to determine this optimum number based on the evaluation of fuzzy partition stability under bootstrap resampling. The method is first characterized on synthetic data with respect to hyper-parameters, like the fuzzifier, and spatial clustering parameters, such as feature space dimensionality, clusters degree of overlap, and number of clusters. The method is then validated on experimental datasets. Furthermore, the performance of the proposed method is compared to that obtained using a number of traditional fuzzy validity rules based on the cluster compactness-to-separation criteria. The proposed method provides accurate and reliable results, and offers better generalization capabilities than the classical approaches. © 2009 Elsevier Ltd. All rights reserved.

The fields of plasmonics, Raman spectroscopy and atomic force microscopy have recently undergone considerable development, but independently of one another. By combining these techniques, a range of complementary information could be simultaneously obtained at a single molecule level. Here, we report the design, fabrication and application of a photonic-plasmonic device that is fully compatible with atomic force microscopy and Raman spectroscopy. Our approach relies on the generation and localization of surface plasmon polaritons by means of adiabatic compression through a metallic tapered waveguide to create strongly enhanced Raman excitation in a region just a few nanometres across. The tapered waveguide can also be used as an atomic force microscope tip. Using the device, topographic, chemical and structural information about silicon nanocrystals may be obtained with a spatial resolution of 7 nm

We report a comprehensive study of ordered MnSi films grown on Si111 which provides clear proofs that these MnSi films have the same magnetic and electronic properties of bulk MnSi compound, so closing a long-standing question. Furthermore, our measurements show the presence of a room-temperature ferromagnetic transition consistent with the ferromagnetic ground state predicted for Mn atoms with reduced coordination near surfaces and interfaces of silicon by recent calculations of Hortamani et al. Phys. Rev. B 78, 104402 2008. The possibility of growing layers on semiconductors which are ferromagnetic at room temperature RT is of paramount importance for nonvolatile memories and spintronic devices based on the injection of spin-polarized current from a ferromagnetic metal into a semiconductor. In this perspective MnSi films grown on Si substrates represent an interesting case study.

We present a line-shape analysis based on atomic single configuration Mn 3d6 multiplet calculations of core-level and valence-band spectroscopy data from metallic ferromagnetic Mn5Ge3. We show that atomic calculations can fit most of the spectral features measured in Mn 2p-3d x-ray absorption and circular dichroism, in Mn 2p and Mn 3s core-level photoemission, as well as for the delocalized electrons in valence-band photoemission. This indicates that, in spite of the metallic nature of the compound, atomic effects can play a relevant role to determine the physical properties of the Mn5Ge3 system.

The action of dopamine on the aggregation of the unstructured alpha-synuclein (alpha-syn) protein may be linked to the pathogenesis of Parkinson's disease. Dopamine and its oxidation derivatives may inhibit alpha-syn aggregation by non-covalent binding. Exploiting this fact, we applied an integrated computational and experimental approach to find alternative ligands that might modulate the fibrillization of alpha-syn. Ligands structurally and electrostatically similar to dopamine were screened from an established library. Five analogs were selected for in vitro experimentation from the similarity ranked list of analogs. Molecular dynamics simulations showed they were, like dopamine, binding non-covalently to alpha-syn and, although much weaker than dopamine, they shared some of its binding properties. In vitro fibrillization assays were performed on these five dopamine analogs. Consistent with our predictions, analyses by atomic force and transmission electron microscopy revealed that all of the selected ligands affected the aggregation process, albeit to a varying and lesser extent than dopamine, used as the control ligand. The in silico/in vitro approach presented here emerges as a possible strategy for identifying ligands interfering with such a complex process as the fibrillization of an unstructured protein.

The mechanism of superconductivity and magnetism and their possible interplay have recently been under debate in pnictides. A likely pairing mechanism includes an important role of spin fluctuations and can be expressed in terms of the magnetic susceptibility chi. The latter is therefore a key quantity in the determination of both the magnetic properties of the system in the normal state and of the contribution of spin fluctuations to the pairing potential. A basic ingredient to obtain chi is the independent-electron susceptibility chi(0). Using LaO(1-x)F(x)FeAs as a prototype material, in this report we present a detailed ab initio study of chi(0)(q, omega) as a function of doping and of the internal atomic positions. The resulting static chi(0)(q, 0) is consistent with both the observed M-point-related magnetic stripe phase in the parent compound and with the existence of incommensurate magnetic structures predicted by ab initio calculations upon doping.

We study excitonic condensation in an electron-hole bilayer system with unequal layer densities at zero temperature. Using mean-field theory we solve the Bardeen-Cooper-Schrieffer (BCS) gap equations numerically and investigate the effects of intralayer interactions. The electron-hole system evolves from BCS in the weak coupling limit to Bose-Einstein condensation (BEC) in the strong coupling limit. We analyze the stability of the Sarma phase with k,-k pairing by calculating the superfluid mass density and also by checking the compressibility matrix. We find that with bare Coulomb interactions the superfluid density is always positive in the Sarma phase, due to a peculiar momentum structure of the gap function originating from the singular behavior of the Coulomb potential at zero momentum and the presence of a sharp Fermi surface. Introducing a simple model for screening, we find that the superfluid density becomes negative in some regions of the phase diagram, corresponding to an instability toward a Fulde-Ferrel-Larkin-Ovchinnikov-type superfluid phase. Thus, intralayer interaction and screening together can lead to a rich phase diagram in the BCS-BEC crossover regime in electron-hole bilayer systems.

We report on transport properties of oxide manganite La(0.7)Ba(0.3)MnO(3-delta) (LBMO) thin films deposited by pulsed laser deposition (PLD) technique. Detailed analysis of heavy-ion stoichiometric composition has been carried out as a function of laser-pulse fluence and ambient oxygen pressure. Depositions using high-fluence (6 J/cm(2)) and low oxygen pressure (10(-2) mbar) provide the optimal heavy-ion stoichiometric ratio in the LBMO samples. Deviations from the optimal LBMO stoichiometry are observed when decreasing the laser fluence or increasing the background oxygen pressure. This behavior is interpreted by considering the influence of the experimental deposition conditions on the plume dynamics. All these findings provide clear insights on the PLD-growth of manganites and, more in general, of complex oxide materials