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The 12th International Workshop on Desorption Induced by Electronic Transitions (DIET XII) took place from 19–23 April 2009 in Pine Mountain, Georgia, USA. This was the 12th conference in a strong and vibrant series, which dates back to the early 1980s. DIET XII continued the tradition of exceptional interdisciplinary science and focused on the study of desorption and dynamics induced by electronic excitations of surfaces and interfaces. The format involved invited lectures, contributed talks and a poster session on the most recent developments and advances in this area of surface physics.

The Workshop International Steering Committee and attendees wish to dedicate DIET XII to the memory of the late Professor Theodore (Ted) Madey. Ted was one of the main pioneers of this field and was one of the primary individuals working to keep this area of science exciting and adventurous. His overall contributions to surface science were countless and his contributions to the DIET field and community were enormous. He is missed and remembered by many friends and colleagues throughout the world.

The papers collected in this issue cover many of the highlights of DIET XII. Topics include ultrafast electron transfer at surfaces and interfaces, quantum and spatially resolved mapping of surface dynamics and desorption, photon-, electron- and ion-beam induced processes at complex interfaces, the role of non-thermal desorption in astrochemistry and astrophysics and laser-/ion-based methods of examining soft matter and biological media.

Although the workshop attracted many scientists active in the general area of non-thermal surface processes, DIET XII also attracted many younger scientists (i.e., postdoctoral fellows, advanced graduate students, and a select number of advanced undergraduate students). This field has had an impact in a number of areas including nanoscience, device physics, astrophysics, and now biophysics. We believe that this special issue of Journal of Physics: Condensed Matter will help foster further progress in the study of DIET processes. Since the field remains vibrant and exciting, the workshop series will continue with DIET XIII. Professor Richard Palmer (University of Birmingham, UK) will chair DIET XIII in the UK in early summer 2012.

We gratefully acknowledge financial support from SPECS, HIDEN Analytical, BRUKER, The United States National Science Foundation, Georgia Institute of Technology and The State University of New Jersey, Rutgers.

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Multichannel analysis of graphene nanoribbons (GNR), often required for describing applications to practical devices, constitutes a heavy computational task, even in a simplified framework like that provided by discrete or nearest neighbour models. Scattering (S) matrix techniques, widely used for quantum transport in low dimensional systems and for the computation of electromagnetic fields, is shown here to provide a powerful formal platform for the analysis, and, in principle, the synthesis, of GNR multiport circuits. Periodic modes, solutions of GNR waveguides, are demonstrated to obey charge conservation and reciprocity constraints corresponding to unitary and symmetry properties of the S-matrix, under proper normalization conditions. We propose a systematic use of this approach to deal with problems such as scattering by lattice defects, the presence of external applied fields, crossing GNRs and T-junctions.

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We use the Markov Chain Monte Carlo method to investigate a global constraints on the generalized Chaplygin gas (GCG) model as the unification of dark matter and dark energy from the latest observational data: the Constitution dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the cosmic microwave background (CMB) data. In a non-flat universe, the constraint results for GCG model are, Ω _b h ² = 0.0235 ^+0.0021 _−0.0018 (1σ) ^+0.0028 _−0.0022 (2σ), Ω _k = 0.0035 ^+0.0172 _−0.0182 (1σ) ^+0.0226 _−0.0204 (2σ), A _s = 0.753 ^+0.037 _−0.035 (1σ) ^+0.045 _−0.044 (2σ), α = 0.043 ^+0.102 _−0.106 (1σ) ^+0.134 _−0.117 (2σ), and H ₀ = 70.00 ^+3.25 _−2.92 (1σ) ^+3.77 _−3.67 (2σ), which is more stringent than the previous results for constraint on GCG model parameters. Furthermore, according to the information criterion, it seems that the current observations much support ΛCDM model relative to the GCG model.

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The propagation of acoustic waves in a layered medium results in the energy loss due to scattering effect. The intrinsic attenuation is an additional effect which plays a very important role in seismic data inversion and reservoir characterization. In this paper we provide the theoretical and numerical study to compare both effects for a periodically layered medium. We also investigate the complex frequency roots (the organ modes) of the reflection/transmission responses.

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The simplicial framework of Engle–Pereira–Rovelli–Livine spin-foam models is generalized to match the diffeomorphism invariant framework of loop quantum gravity. The simplicial spin-foams are generalized to arbitrary linear 2-cell spin-foams. The resulting framework admits all the spin-network states of loop quantum gravity, not only those defined by triangulations (or cubulations). In particular, the notion of embedded spin-foam we use allows us to consider knotting or linking spin-foam histories. Also the main tools, the vertex structure and the vertex amplitude, are naturally generalized to an arbitrary valency case. The correspondence between all the SU(2) intertwiners and the SU(2)× SU(2) EPRL intertwiners is proved to be 1–1 in the case of the Barbero–Immirzi parameter |γ| ≥ 1.

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Several conceptual aspects of quantum gravity (QG) are studied on the example of the homogeneous isotropic loop quantum cosmology (LQC) model. In particular: (i) the proper time of the comoving observers is shown to be a quantum operator and a quantum spacetime metric tensor operator is derived. (ii) Solutions of the quantum scalar constraint for two different choices of the lapse function are compared and contrasted. In particular it is shown that in the case of a model with massless scalar field and cosmological constant Λ, the physical Hilbert spaces constructed for two choices of lapse are the same for Λ < 0 while they are significantly different for Λ > 0. (iii) The mechanism of the singularity avoidance is analyzed via detailed studies of an energy density operator, whose essential spectrum was shown to be an interval , where . (iv) The relation between the kinematical and the physical quantum geometry is discussed on the level of relation between observables.

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The low consumption achievable with Diesel engines and the subsequent reduction of CO ₂ emissions, together with the new technologies allowing to meet present and future legislation for pollutant emission reduction, make them attractive from an environmental viewpoint. However, current and future Diesel concepts are intrinsically noisy, and thus in the past few years, combustion noise was considered as an additional factor in engine development alongside performance, emissions and driveability. Otherwise, due to this negative issue intrinsic to Diesel combustion, end-users could be reluctant to drive Diesel-powered vehicles and their potential for environment preservation could thus be lost or underused. Evaluation procedures are then required, both for noise level and sound quality, that may be integrated into the global engine development process, avoiding the need to resort to long and expensive acoustic tests. In this paper, such a procedure, based on the noise source diagnostic through the definition of suitable components extracted from in-cylinder pressure, is proposed and validated. An innovative decomposition of the in-cylinder pressure signal is used to obtain such components, so that features associated with the excitation inside the cylinder may be properly identified. These combustion components, significant of the rate of heat release in the cylinder and the resonance in the combustion chamber, may be correlated with the overall noise level. A prediction of the radiated engine noise level more accurate than that obtained from the classical 'block attenuation' approach is achieved, while combustion process features related to the resulting noise level can be identified and thus corrective actions may be proposed.

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Theoretical developments related to gravitational interaction have questioned the notion of particle in quantum field theory (QFT). For instance, uniquely defined particle states do not exist in general, in QFT on a curved spacetime. More generally, particle states are difficult to define in a background-independent quantum theory of gravity. These difficulties have led some to suggest that in general QFT should not be interpreted in terms of particle states, but rather in terms of eigenstates of local operators. Still, it is not obvious how to reconcile this view with the empirically-observed ubiquitous particle-like behavior of quantum fields, apparent for instance in experimental high-energy physics, or 'particle' physics. Here we offer an element of clarification by observing that already in flat space there exist—strictly speaking—two distinct notions of particles: globally defined n-particle Fock-states and local particle states. The last describes the physical objects detected by finite-size particle detectors and are eigenstates of local field operators. In the limit in which the particle detectors are appropriately large, global and local particle states converge in a weak topology (but not in norm). This observation has little relevance for flat-space theories—it amounts to a reminder that there are boundary effects in realistic detectors—but is relevant for gravity. It reconciles the two points of view mentioned above. More importantly, it provides a definition of the local particle state that remains well defined even when the conventional global particle states are not defined. This definition plays an important role in quantum gravity.

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'Global warming' is a phrase that refers to the effect on the climate of human activities, in particular the burning of fossil fuels (coal, oil and gas) and large-scale deforestation, which cause emissions to the atmosphere of large amounts of 'greenhouse gases', of which the most important is carbon dioxide. Such gases absorb infrared radiation emitted by the Earth's surface and act as blankets over the surface keeping it warmer than it would otherwise be. Associated with this warming are changes of climate. The basic science of the 'greenhouse effect' that leads to the warming is well understood. More detailed understanding relies on numerical models of the climate that integrate the basic dynamical and physical equations describing the complete climate system. Many of the likely characteristics of the resulting changes in climate (such as more frequent heat waves, increases in rainfall, increase in frequency and intensity of many extreme climate events) can be identified. Substantial uncertainties remain in knowledge of some of the feedbacks within the climate system (that affect the overall magnitude of change) and in much of the detail of likely regional change. Because of its negative impacts on human communities (including for instance substantial sea-level rise) and on ecosystems, global warming is the most important environmental problem the world faces. Adaptation to the inevitable impacts and mitigation to reduce their magnitude are both necessary. International action is being taken by the world's scientific and political communities. Because of the need for urgent action, the greatest challenge is to move rapidly to much increased energy efficiency and to non-fossil-fuel energy sources.

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Hybrid nanoscale patterning strategies combine the registration and addressability of conventional lithographic techniques with the chemical and physical functionality enabled by intermolecular, electrostatic and/or biological interactions. This review aims to highlight and to provide a comprehensive description of recent developments in hybrid nanoscale patterning strategies that enhance existing lithographic techniques or can be used to fabricate functional chemical patterns that interact with their environment. These functional structures create new capabilities, such as the fabrication of physicochemical surfaces that can recognize and capture analytes from complex liquid or gaseous mixtures. The nanolithographic techniques we describe can be classified into three general areas: traditional lithography, soft lithography and scanning-probe lithography. The strengths and limitations of each hybrid patterning technique will be discussed, along with the current and potential applications of the resulting patterned, functional surfaces.

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We study the propagation of light pulses through scattering media using the time-dependent radiative transfer equation. A standard discrete-ordinate method is used to solve this equation in the space-frequency domain. We present calculations of diffuse transmission through scattering slabs, in the presence of absorption and anisotropic scattering. We show that the diffusive regime is attained at long times only for thick slabs. Comparisons with diffusion theory show that the proper choice of the diffusion constant is an important issue for time-dependent transport.

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The heart is a nonlinear biological system that can exhibit complex electrical dynamics, complete with period-doubling bifurcations and spiral and scroll waves that can lead to fibrillatory states that compromise the heart's ability to contract and pump blood efficiently. Despite the importance of understanding the range of cardiac dynamics, studying how spiral and scroll waves can initiate, evolve, and be terminated is challenging because of the complicated electrophysiology and anatomy of the heart. Nevertheless, over the last two decades advances in experimental techniques have improved access to experimental data and have made it possible to visualize the electrical state of the heart in more detail than ever before. During the same time, progress in mathematical modeling and computational techniques has facilitated using simulations as a tool for investigating cardiac dynamics. In this paper, we present data from experimental and simulated cardiac tissue and discuss visualization techniques that facilitate understanding of the behavior of electrical spiral and scroll waves in the context of the heart. The paper contains many interactive media, including movies and interactive two- and three-dimensional Java applets.

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The current status of experimental research on the transport characteristics of carbon nanotubes (CNTs) has been reviewed. Methods for measuring transport coefficients of CNTs have been considered. The available experimental data on the temperature dependence of thermal conductivity and electroconductivity of single-walled and multi-walled CNTs have been analyzed in terms of the ballistic mechanism of charge and heat transport.

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ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 μm in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10 ⁵ charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.

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We investigate the effects of Sr/La cation ordering/disordering and atomic relaxation on the electronic and magnetic properties of La _2/3Sr _1/3MnO ₃ (LSMO) by means of ab initio pseudopotential calculations. We consider a cation-ordered layered structure and a more homogeneously Sr-bulk-doped structure. Cation disordering and atomic relaxation both tend to push the LSMO system towards half-metallicity, increasing the minority-spin and spin-flip gaps. Lattice relaxation has a significant effect on the electronic density of states (DOS) of the layered LSMO and drastically reduces the initial differences found comparing the electronic properties of the perovskite structures with different dopant configurations. The trend with structural relaxation is understood in terms of an effective screening, due to the displacement of the O anions and La cations, of the local electric field produced by the ordered Sr dopants.

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The Wilkinson Microwave Anisotropy Probe ( WMAP) 5-year data provide stringent limits on deviations from the minimal, six-parameter Λ cold dark matter model. We report these limits and use them to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature. We also constrain models of dark energy via its equation of state, parity-violating interaction, and neutrino properties, such as mass and the number of species. We detect no convincing deviations from the minimal model. The six parameters and the corresponding 68% uncertainties, derived from the WMAP data combined with the distance measurements from the Type Ia supernovae (SN) and the Baryon Acoustic Oscillations (BAO) in the distribution of galaxies, are: Ω _b h ² = 0.02267 ^+0.00058 _–0.00059, Ω _c h ² = 0.1131 ± 0.0034, Ω _Λ = 0.726 ± 0.015, n _s = 0.960 ± 0.013, τ = 0.084 ± 0.016, and at k = 0.002 Mpc ^-1. From these, we derive σ ₈ = 0.812 ± 0.026, H ₀ = 70.5 ± 1.3 km s ^-1 Mpc ^–1, Ω _b = 0.0456 ± 0.0015, Ω _c = 0.228 ± 0.013, Ω _m h ² = 0.1358 ^+0.0037 _–0.0036, z _reion = 10.9 ± 1.4, and t ₀ = 13.72 ± 0.12 Gyr. With the WMAP data combined with BAO and SN, we find the limit on the tensor-to-scalar ratio of r < 0.22(95%CL), and that n _s > 1 is disfavored even when gravitational waves are included, which constrains the models of inflation that can produce significant gravitational waves, such as chaotic or power-law inflation models, or a blue spectrum, such as hybrid inflation models. We obtain tight, simultaneous limits on the (constant) equation of state of dark energy and the spatial curvature of the universe: –0.14 < 1 + w < 0.12(95%CL) and –0.0179 < Ω _k < 0.0081(95%CL). We provide a set of " WMAP distance priors," to test a variety of dark energy models with spatial curvature. We test a time-dependent w with a present value constrained as –0.33 < 1 + w ₀ < 0.21 (95% CL). Temperature and dark matter fluctuations are found to obey the adiabatic relation to within 8.9% and 2.1% for the axion-type and curvaton-type dark matter, respectively. The power spectra of TB and EB correlations constrain a parity-violating interaction, which rotates the polarization angle and converts E to B. The polarization angle could not be rotated more than –5 9 < Δα < 2 4 (95% CL) between the decoupling and the present epoch. We find the limit on the total mass of massive neutrinos of ∑ m _ν < 0.67 eV(95%CL), which is free from the uncertainty in the normalization of the large-scale structure data. The number of relativistic degrees of freedom (dof), expressed in units of the effective number of neutrino species, is constrained as N _eff = 4.4 ± 1.5 (68%), consistent with the standard value of 3.04. Finally, quantitative limits on physically-motivated primordial non-Gaussianity parameters are –9 < f ^local _NL < 111 (95% CL) and –151 < f ^equil _NL < 253 (95% CL) for the local and equilateral models, respectively.

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This paper focuses on cosmological constraints derived from analysis of WMAP data alone. A simple ΛCDM cosmological model fits the five-year WMAP temperature and polarization data. The basic parameters of the model are consistent with the three-year data and now better constrained: Ω _b h ² = 0.02273 ± 0.00062, Ω _c h ² = 0.1099 ± 0.0062, Ω _Λ = 0.742 ± 0.030, n _s = 0.963 ^+0.014 _–0.015, τ = 0.087 ± 0.017, and σ ₈ = 0.796 ± 0.036, with h = 0.719 ^+0.026 _–0.027. With five years of polarization data, we have measured the optical depth to reionization, τ>0, at 5σ significance. The redshift of an instantaneous reionization is constrained to be z _reion = 11.0 ± 1.4 with 68% confidence. The 2σ lower limit is z _reion > 8.2, and the 3σ limit is z _reion > 6.7. This excludes a sudden reionization of the universe at z = 6 at more than 3.5σ significance, suggesting that reionization was an extended process. Using two methods for polarized foreground cleaning we get consistent estimates for the optical depth, indicating an error due to the foreground treatment of τ ~ 0.01. This cosmological model also fits small-scale cosmic microwave background (CMB) data, and a range of astronomical data measuring the expansion rate and clustering of matter in the universe. We find evidence for the first time in the CMB power spectrum for a nonzero cosmic neutrino background, or a background of relativistic species, with the standard three light neutrino species preferred over the best-fit ΛCDM model with N _eff = 0 at >99.5% confidence, and N _eff > 2.3(95%confidence limit (CL)) when varied. The five-year WMAP data improve the upper limit on the tensor-to-scalar ratio, r < 0.43(95%CL), for power-law models, and halve the limit on r for models with a running index, r < 0.58(95%CL). With longer integration we find no evidence for a running spectral index, with dn _s / dln k = –0.037 ± 0.028, and find improved limits on isocurvature fluctuations. The current WMAP-only limit on the sum of the neutrino masses is ∑ m _ν < 1.3 eV(95%CL), which is robust, to within 10%, to a varying tensor amplitude, running spectral index, or dark energy equation of state.

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We report the superconductivity in iron-based oxyarsenide Sm[O _{1- x}F _x ]FeAs, with the onset resistivity transition temperature at 55.0K and Meissner transition at 54.6 K. This compound has the same crystal structure as LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the highest critical temperature among all materials besides copper oxides up to now.

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We construct three dimensional Chern-Simons-matter theories with gauge groups U( N) × U( N) and SU( N) × SU( N) which have explicit = 6 superconformal symmetry. Using brane constructions we argue that the U( N) × U( N) theory at level k describes the low energy limit of N M2-branes probing a C ⁴/ Z _k singularity. At large N the theory is then dual to M-theory on AdS ₄ × S ⁷/ Z _k . The theory also has a 't Hooft limit (of large N with a fixed ratio N/ k) which is dual to type IIA string theory on AdS ₄ × CP ³. For k = 1 the theory is conjectured to describe N M2-branes in flat space, although our construction realizes explicitly only six of the eight supersymmetries. We give some evidence for this conjecture, which is similar to the evidence for mirror symmetry in d = 3 gauge theories. When the gauge group is SU(2) × SU(2) our theory has extra symmetries and becomes identical to the Bagger-Lambert theory.

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We present new full-sky temperature and polarization maps in five frequency bands from 23 to 94 GHz, based on data from the first five years of the Wilkinson Microwave Anisotropy Probe ( WMAP) sky survey. The new maps are consistent with previous maps and are more sensitive. The five-year maps incorporate several improvements in data processing made possible by the additional years of data and by a more complete analysis of the instrument calibration and in-flight beam response. We present several new tests for systematic errors in the polarization data and conclude that W-band polarization data is not yet suitable for cosmological studies, but we suggest directions for further study. We do find that Ka-band data is suitable for use; in conjunction with the additional years of data, the addition of Ka band to the previously used Q- and V-band channels significantly reduces the uncertainty in the optical depth parameter, τ. Further scientific results from the five-year data analysis are presented in six companion papers and are summarized in Section 7 of this paper. With the five-year WMAP data, we detect no convincing deviations from the minimal six-parameter ΛCDM model: a flat universe dominated by a cosmological constant, with adiabatic and nearly scale-invariant Gaussian fluctuations. Using WMAP data combined with measurements of Type Ia supernovae and Baryon Acoustic Oscillations in the galaxy distribution, we find (68% CL uncertainties): Ω _b h ² = 0.02267 ^+0.00058 _–0.00059, Ω _c h ² = 0.1131 ± 0.0034, Ω _Λ = 0.726 ± 0.015, n _s = 0.960 ± 0.013, τ = 0.084 ± 0.016, and at k = 0.002 Mpc ^-1. From these we derive σ ₈ = 0.812 ± 0.026, H ₀ = 70.5 ± 1.3 km s ^-1 Mpc ^–1, Ω _b = 0.0456 ± 0.0015, Ω _c = 0.228 ± 0.013, Ω _m h ² = 0.1358 ^+0.0037 _–0.0036, z _reion = 10.9 ± 1.4, and t ₀ = 13.72 ± 0.12 Gyr. The new limit on the tensor-to-scalar ratio is r < 0.22(95%CL), while the evidence for a running spectral index is insignificant, dn _s / dln k = –0.028 ± 0.020 (68% CL). We obtain tight, simultaneous limits on the (constant) dark energy equation of state and the spatial curvature of the universe: –0.14 < 1 + w < 0.12(95%CL) and –0.0179 < Ω _k < 0.0081(95%CL). The number of relativistic degrees of freedom, expressed in units of the effective number of neutrino species, is found to be N _eff = 4.4 ± 1.5 (68% CL), consistent with the standard value of 3.04. Models with N _eff = 0 are disfavored at >99.5% confidence. Finally, new limits on physically motivated primordial non-Gaussianity parameters are –9 < f ^local _NL < 111 (95% CL) and –151 < f ^equil _NL < 253 (95% CL) for the local and equilateral models, respectively.

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Here we report a new quaternary iron-arsenide superconductor Nd[O _{1− x} F _x ]FeAs , with the onset resistivity transition at 51.9 K and Meissner transition at 51 K. This compound has the same crystal structure as LaOFeAs, and becomes the second superconductor after Pr[O _{1− x} F _x ]FeAs that superconducts above 50 K.

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The interplay between different ordered phases, such as superconducting, charge or spin ordered phases, is of central interest in condensed-matter physics. The very recent discovery of superconductivity with a remarkable T _c =26 K in Fe-based oxypnictide La(O _{1− x}F _x )FeAs (see Kamihara Y. et al., J. Am. Chem. Soc., 130 (2008) 3296) is a surprise to the scientific community and has generated tremendous interest. The pure LaOFeAs itself is not superconducting but shows an anomaly near 150 K in both resistivity and dc magnetic susceptibility. Here we provide combined experimental and theoretical evidences showing that a spin-density-wave (SDW) state develops at low temperature, in association with electron Nematic order. The electron-doping by F suppresses the SDW instability and induces the superconductivity. Therefore, the La(O _{1− x}F _x )FeAs offers an exciting new system showing competing orders in layered compounds.

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Here we report a new class of superconductors prepared by high-pressure synthesis in the quaternary family ReFeAsO _1−δ (Re=Sm, Nd, Pr, Ce, La) without fluorine doping. The onset superconducting critical temperature ( T _c ) in these compounds increases with the reduction of the Re atom size, and the highest T _c obtained so far is 55 K in SmFeAsO _1−δ. For the NdFeAsO _1−δ compound with different oxygen concentration a dome-shaped phase diagram was found.

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By partially substituting the tri-valence element La with di-valence element Sr in LaOFeAs, we introduced holes into the system. For the first time, we successfully synthesized the hole-doped new superconductors (La _{1- x}Sr _x )OFeAs. The maximum superconducting transition temperature at about 25 K was observed at a doping level of x=0.13. It is evidenced by Hall effect measurements that the conduction in this type of material is dominated by hole-like charge carriers, rather than electron-like ones. Together with the data of the electron-doped system La(O _{1- x}F _x )FeAs, a generic phase diagram is depicted and is revealed to be similar to that of the cuprate superconductors.

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We have performed a high-resolution angle-resolved photoelectron spectroscopy study on the newly discovered superconductor Ba _0.6K _0.4Fe ₂As ₂ ( T _c=37 K). We have observed two superconducting gaps with different values: a large gap (Δ~12 meV) on the two small hole-like and electron-like Fermi surface (FS) sheets, and a small gap (~6 meV) on the large hole-like FS. Both gaps, closing simultaneously at the bulk transition temperature ( T _c), are nodeless and nearly isotropic around their respective FS sheets. The isotropic pairing interactions are strongly orbital dependent, as the ratio 2Δ/ k _B T _c switches from weak to strong coupling on different bands. The same and surprisingly large superconducting gap due to strong pairing on the two small FSs, which are connected by the (π, 0) spin-density-wave vector in the parent compound, strongly suggests that the pairing mechanism originates from the inter-band interactions between these two nested FS sheets.