13,158 research outputs found

    Unforeseen high temperature and humidity stability of FeCl3_3 intercalated few layer graphene

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    We present the first systematic study of the stability of the structure and electrical properties of FeCl3_3 intercalated few-layer graphene to high levels of humidity and high temperature. Complementary experimental techniques such as electrical transport, high resolution transmission electron microscopy and Raman spectroscopy conclusively demonstrate the unforeseen stability of this transparent conductor to a relative humidity up to 100%100 \% at room temperature for 25 days, to a temperature up to 150\,^\circC in atmosphere and up to a temperature as high as 620\,^\circC in vacuum, that is more than twice higher than the temperature at which the intercalation is conducted. The stability of FeCl3_3 intercalated few-layer graphene together with its unique values of low square resistance and high optical transparency, makes this material an attractive transparent conductor in future flexible electronic applications.Comment: Scientific Reports, volume 5, article no. 760

    Observation of blue-shifted ultralong-range Cs2_{2} Rydberg molecules

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    We observe ultralong-range blue-shifted Cs2_{2} molecular states near ns1/2ns_{1/2} Rydberg states in an optical dipole trap, where 31≤n≤3431\leq n\leq34. The accidental near degeneracy of (n−4)l(n-4)l and nsns Rydberg states for l>2l>2 in Cs, due to the small fractional nsns quantum defect, leads to non-adiabatic coupling among these states, producing potential wells above the nsns thresholds. Two important consequences of admixing high angular momentum states with nsns states are the formation of large permanent dipole moments, ∼15−100 \sim 15-100\,Debye, and accessibility of these states via two-photon association. The observed states are in excellent agreement with theory. Both projections of the total angular momentum on the internuclear axis are visible in the experiment

    Monte Carlo Determination of Multiple Extremal Eigenpairs

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    We present a Monte Carlo algorithm that allows the simultaneous determination of a few extremal eigenpairs of a very large matrix without the need to compute the inner product of two vectors or store all the components of any one vector. The new algorithm, a Monte Carlo implementation of a deterministic one we recently benchmarked, is an extension of the power method. In the implementation presented, we used a basic Monte Carlo splitting and termination method called the comb, incorporated the weight cancellation method of Arnow {\it et al.}, and exploited a new sampling method, the sewing method, that does a large state space sampling as a succession of small state space samplings. We illustrate the effectiveness of the algorithm by its determination of the two largest eigenvalues of the transfer matrices for variously-sized two-dimensional, zero field Ising models. While very likely useful for other transfer matrix problems, the algorithm is however quite general and should find application to a larger variety of problems requiring a few dominant eigenvalues of a matrix.Comment: 22 pages, no figure

    Convergence of many-body wavefunction expansions using a plane wave basis: from the homogeneous electron gas to the solid state

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    Using the finite simulation-cell homogeneous electron gas (HEG) as a model, we investigate the convergence of the correlation energy to the complete basis set (CBS) limit in methods utilising plane-wave wavefunction expansions. Simple analytic and numerical results from second-order M{\o}ller-Plesset theory (MP2) suggest a 1/M decay of the basis-set incompleteness error where M is the number of plane waves used in the calculation, allowing for straightforward extrapolation to the CBS limit. As we shall show, the choice of basis set truncation when constructing many-electron wavefunctions is far from obvious, and here we propose several alternatives based on the momentum transfer vector, which greatly improve the rate of convergence. This is demonstrated for a variety of wavefunction methods, from MP2 to coupled-cluster doubles theory (CCD) and the random-phase approximation plus second-order screened exchange (RPA+SOSEX). Finite basis-set energies are presented for these methods and compared with exact benchmarks. A transformation can map the orbitals of a general solid state system onto the HEG plane wave basis and thereby allow application of these methods to more realistic physical problems.Comment: 15 pages, 9 figure

    The flux distribution of the three quark system in SU(3)

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    We study the abelian color-flux distribution of the three quark system in the maximally abelian gauge on SU(3) lattices. The distribution of the color electric field suggests YAnsatzY Ansatz, which might be interpreted through the dual superconductor picture as the result of the vacuum pressure in the confined phase. In order to clarify the flux structure, we investigate the color electric field in the three quark system also in the monopole part and in the photon part.Comment: 3pages, 5figures, Lattice2002(topology

    Fundamental properties and applications of quasi-local black hole horizons

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    The traditional description of black holes in terms of event horizons is inadequate for many physical applications, especially when studying black holes in non-stationary spacetimes. In these cases, it is often more useful to use the quasi-local notions of trapped and marginally trapped surfaces, which lead naturally to the framework of trapping, isolated, and dynamical horizons. This framework allows us to analyze diverse facets of black holes in a unified manner and to significantly generalize several results in black hole physics. It also leads to a number of applications in mathematical general relativity, numerical relativity, astrophysics, and quantum gravity. In this review, I will discuss the basic ideas and recent developments in this framework, and summarize some of its applications with an emphasis on numerical relativity.Comment: 14 pages, 2 figures. Based on a talk presented at the 18th International Conference on General Relativity and Gravitation, 8-13 July 2007, Sydney, Australi

    Flux Tubes of Two- and Three-Quark System in Full QCD

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    We study the abelian color flux of two- and three-quark systems in the maximally abelian gauge in lattice QCD with dynamical fermions. We find that the abelian flux tube formed between quark and antiquark is very much the same as in quenched QCD up to quark separations of RR∼\sim 2fm. The profile of the color electric field in three-quark system suggests YY ansatz, which might be interpreted as the result of the vacuum pressure in the confined phase. In order to clarify the flux structure, we investigate the color electric field of the three-quark system splittting the abelian gauge field into the monopole and photon parts.Comment: 4 pages, 4 figures, Talk given at XVI International Conference on Particles and Nuclei (PaNic02),Osaka, Japan, Sep.30 - Oct.4, 200
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