Dec 2009, Volume 4 Issue 4
    

Cover illustration

  • Fermi surface of iron-based superconductor, Ba0.6K0.4 Fe2As2 (Tc=35 K), measured by high resolution angle-resolved photoemission spectroscopy (ARPES). Near the center Γ(0,0) point, two hole-like Fermi surface sheets are observed while near the corner M(β,β) point, two strong Fermi spots are observed. The two Fermi surface sheets near the Γ point show different superconducting gap: the inner one shows [Detail] ...


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  • Research articles
    Band structure, Fermi surface, and superconducting gap in FeAs-based superconductors revealed by angle-resolved photoemission spectroscopy
    Xing-jiang ZHOU (周兴江), Guo-dong LIU (刘国东), Hai-yun LIU (刘海云), Lin ZHAO (赵林), Wen-tao ZHANG (张文涛), Xiao-wen JIA (贾小文), Jian-qiao MENG (孟建桥),
    2009, 4(4): 427-432. https://doi.org/10.1007/s11467-009-0058-y
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    In this paper, we present a brief review on our angle-resolved photoemission measurements on the band structure, Fermi surface, and superconducting gap of the newly-discovered FeAs-based high temperature superconductors. (1) The Fermi surface of the FeAs-based compounds are characterized by the hole-like Fermi surface sheets near Γ (0, 0) and the existence of singular Fermi spots near M(π,
  • Research articles
    A unified description of cuprate and iron arsenide superconductors
    Mike GUIDRY, Yang SUN, Cheng-Li WU,
    2009, 4(4): 433-446. https://doi.org/10.1007/s11467-009-0068-9
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    We propose a unified description of cuprate and iron-based superconductivity. Consistency with magnetic structure inferred from neutron scattering implies significant constraints on the symmetry of the pairing gap for the iron-based superconductors. We find that this unification requires the orbital pairing formfactors for the iron arsenides to differ fundamentally from those for cuprates at the microscopic level.
  • Research articles
    Theory for superconductivity in iron pnictides at large coulomb U limit
    Wei-qiang CHEN（陈伟强）, Kai-yu YANG（杨开宇）, Yi ZHOU（周毅）, Fu-chun ZHANG（张富春）
    2009, 4(4): 447-454. https://doi.org/10.1007/s11467-009-0041-7
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    Superconductivity in iron pnictides is studied by using a two-orbital Hubbard model in the large U limit. The Coulomb repulsion induces an orbital-dependent pairing between charge carriers. The pairing is found mainly from the scattering within the same Fermi pocket where usually one single orbital dominates. The inter-pocket pair scatterings determine the symmetry of the singlet superconductivity, which is an extended s-wave at small Hund’s coupling, and d-wave at large Hund’s coupling and large U. The former is consistent with recent experiments of ARPES and Andreev reflection spectroscopy. Spin triplet states only become important at large exchange interaction J.
  • Research articles
    Magneto-thermopower of parent compound LaFeAsO
    Zeng-wei ZHU（朱增伟）, Qian TAO（陶前）, Yu-ke LI（李玉科）, Mi HE（何咪）, Guang-han CAO（曹光旱）, Zhu-an XU（许祝安）,
    2009, 4(4): 455-458. https://doi.org/10.1007/s11467-009-0015-9
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    We report the effect of magnetic field on the transport properties of polycrystalline parent compound LaFeAsO. The magnetic field has no significant influence on the structural phase transitions or spin density wave (SDW) ordering of small moments on iron, but causes large positive magento-resistance below 100K. Meanwhile, the absolute magnitude of thermopower, which is negative, increases remarkably with increasing magnetic field below 100K. Such a large positive magneto-thermopower was first reported in this iron arsenide. The result suggests that there could exist an enhancement of SDW gapping in holelike Fermi surface.
  • Research articles
    Optical properties of FeAs-based parent compound: A comparative study for polycrystalline EuFe 2 As 2 and LaFeAsO
    Wan-zheng HU (胡婉铮), Jing DONG (董靖), Gang LI (李岗), Zheng LI (李政), Ping ZHENG (郑萍), Gen-fu CHEN (陈根富), Jian-lin LUO (雒建林), Nan-lin WANG (王楠林)
    2009, 4(4): 459-463. https://doi.org/10.1007/s11467-009-0044-4
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    We report on a comparative optical investigation on EuFe2As2 and LaFeAsO polycrystalline samples. The spin-density wave (SDW) partial gap is observed for both compounds. The gap-like absorption peaks in the real part of conductivity for EuFe2As2 and LaFeAsO scale with their respective TSDW. Most remarkably, the study reveals a substantial difference in optical reflectance spectra for the two prototype compounds of 122 and 1111 systems: EuFe2As2 shows a much higher reflectivity with fewer phonon modes than that of LaFeAsO. This yields optical evidence for much stronger anisotropy between ab-plane and c-axis in 1111-type compounds.
  • Research articles
    Studies on the superconductivity for the “111” type iron arsenide superconductor
    Xian-cheng WANG (望贤成), Qing-qing LIU (刘清青), Liu-xiang YANG (杨留响), Zheng DENG (邓正), Yu-xi LÜ (吕玉玺), Wei-bo GAO (高伟波), Si-jia ZHANG (张思佳), Ri-cheng YU (禹日成), Chang-qing JIN (靳常青),
    2009, 4(4): 464-468. https://doi.org/10.1007/s11467-009-0042-6
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    The “111” type LixFeAs (x ranges from 0.8 to 1.2) with Cu2Sb type tetragonal structure was synthesized with Tc 18K. The isostructure NaFeAs was further studied, which shows superconductivity with Tc up to 26K. The effect of pressure on superconductivity was investigated.
  • Research articles
    Advances in surface plasmon resonance-based high throughput biochips
    San-jun ZHANG（张三军）, Lotfi BERGUIGA, Nicolas HUGO, Thibault ROLAND, Francoise ARGOUL, Juan ELEZGARAY, Wen-xue LI（李文雪）, He-ping ZENG（曾和平）
    2009, 4(4): 469-480. https://doi.org/10.1007/s11467-009-0069-8
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    This article reviews our recent advances in surface plasmon resonance (SPR) based biochips. It includes four issues, which are the preparation and characterization of high quality gold film, the preparation and characterization of self-assembled monolayer (SAM), dynamics of DNA adsorption on SAMs, and SPRbased microscopies. Numerous topics related to SPR, such as, the modeling of SPR by transmission matrix, effective medium theory, applications of SPR in biology, and SPR-based novel microscopies, are discussed. A novel electrochemical technique, which is extremely useful for the preparation and characterization of high quality SAMs, is also discussed.
  • Research articles
    Coherent population transfer in four-level ladder systems by single frequency-chirped laser pulse
    Xiao-hong LI（李小红）, Rui-zhou ZHANG（张瑞州）, Xian-zhou ZHANG（张现周）,
    2009, 4(4): 481-486. https://doi.org/10.1007/s11467-009-0065-z
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    Adiabatic passage induced by a frequency-chirped laser pulse in four-level ladder systems is investigated. Two different strategies for efficient population transfer (intuitive and counterintuitive laser pulse) are analyzed. For the larger detuning, the four-level ladder system can be reduced to a two-level system with which we are familiar. For the smaller detuning, the main conditions for realization of population transfer are the following: the width of the transform-limited laser pulse envelope frequency spectrum (without chirp) must be smaller and the peak Rabi frequency of the pulse must be larger than the detuning ε21 and ε21∼ε32 in the case of the three-photon resonance. With this laser pulse, it is possible to achieve complete population via the intermediate levels by three successive adiabatic passages. Complete inversion is also obtained by a counterintuitive direction of the frequency sweep.
  • Research articles
    One-dimensional self-assembly of inorganic nanoparticles
    Tao HU(胡涛), Yan GAO（高燕）, Zhi-yong TANG(唐智勇), Zhen-long WANG(王振龙)
    2009, 4(4): 487-496. https://doi.org/10.1007/s11467-009-0066-y
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    This review is focused on the recent research progresses on one-dimensional (1-D) inorganic nanoparticle (NP) assemblies. First, we introduce some preparation methods of 1-D NP assemblies, which are the base of the investigation to 1-D NP assemblies. In the following part, we discuss the formation mechanism of 1-D NP assemblies, which is very important for us to understand the self-assembly process. We also summarize the novel properties of 1-D NP assemblies. Finally, we outlook the development of 1-D NP assemblies in the near future. We believe that the scientific and technical potentials of NP assemblies are immense, and their future is bright.
  • Research articles
    Discrete breathers in a two-dimensional Morse lattice with an on-site harmonic potential
    Bin-bin LÜ(吕彬彬), Qiang TIAN(田强),
    2009, 4(4): 497-504. https://doi.org/10.1007/s11467-009-0062-2
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    Two-dimensional discrete breathers in a two-dimensional Morse lattice with on-site harmonic potentials are investigated. Under the harmonic approximation, the linear dispersion relations for the triangular and the square lattices are discussed. The existence of discrete breathers in a two-dimensional Morse lattice with on-site harmonic potentials is proved by using local inharmonic approximation and the numerical method. The localization and amplitude of two-dimensional discrete breathers correlate closely to the Morse parameter a and the on-site parameter κ.
  • Research articles
    Preparation of carbon fiber/ZnO core-shell structure by a simple method
    Kai DU（杜凯）, Rong-hui WEI（魏荣慧）, Qing-dong CHEN（陈庆东）, Jing-han YOU（尤景汉）, Hai-bin YANG（杨海滨）,
    2009, 4(4): 505-508. https://doi.org/10.1007/s11467-009-0072-0
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    Carbon fiber/ZnO was prepared by surface modification precipitation in aqueous solution. Corresponding nucleation and crystal growth model was proposed for this structure. The effects of annealing temperature on the structure and absorptive properties of the composites were investigated. Results showed that obtained ZnO shell was ca. 200nm on the surface of carbon fiber. The ZnO coating can protect the CFs from oxidation at a relatively high temperature. Energy bandgap calculated from the absorptive spectra was about 3.30eV.
  • Research articles
    A general derivation of differential cross section in quark–quark and quark–gluon scatterings at fixed impact parameter
    Shou-wan CHEN (陈寿万), Jian DENG (邓建), Qun WANG (王群), Jian-hua GAO (高建华),
    2009, 4(4): 509-516. https://doi.org/10.1007/s11467-009-0064-0
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    We propose a general derivation of differential cross section in quark–quark and quark–gluon scatterings at fixed impact parameters. The derivation is well defined and free of ambiguity in the conventional one. The approach can be applied to a variety of partonic and hadronic scatterings in low- or high-energy particle collisions.
  • Research articles
    Selfdual spin 2 theory in a 2+1 dimensional (A)dS space–time
    Pío J. ARIAS1, Rolando GAITAN D.,
    2009, 4(4): 517-524. https://doi.org/10.1007/s11467-009-0073-z
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    The lagrangian constraint analysis of the selfdual massive spin 2 theory in a 2+1 dimensional flat space–time and its extension to a curved one were performed. Demanding consistency of the degrees of freedom and causality in the model with gravitational interaction, gives rise to physical restrictions on non minimal coupling terms and background. Finally, a constant curvature scenario was explored, showing the existence of classes of forbidden mass values. Notorious aspects related with the construction of the reduced action and the one-particle exchange amplitude were mentioned.
  • Research articles
    On torsion-free vacuum solutions of the model of de Sitter gauge theory of gravity (II)
    Chao-guang HUANG（黄超光）, Meng-sen MA（马孟森）,
    2009, 4(4): 525-529. https://doi.org/10.1007/s11467-009-0063-1
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    It is shown that all torsion-free vacuum solutions of the model of de Sitter (dS) gauge theory of gravity are the vacuum solutions of Einstein field equations with the same positive cosmological constant. Furthermore, for the gravitational theories with more general quadratic gravitational Lagrangian (F2+T2), the torsion-free vacuum solutions are also the vacuum solutions of Einstein field equations.
  • Research articles
    Fluctuation around horizon on a Schwarzschild black hole using the null geodesic method
    Ji-li HUANG（黄基利）, Wen-biao LIU（刘文彪）,
    2009, 4(4): 530-533. https://doi.org/10.1007/s11467-009-0070-2
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    Using the null geodesic method, Hawking radiation from the horizon of a Schwarzschild black hole is calculated. The thermodynamics can be built successfully on the horizon where the apparent horizon and event horizon are coincident with each other. When a relativistic perturbation is given to the horizon, the first law of thermodynamics can also be constructed at a new supersurface near the horizon successfully. The expressions of the characteristic position and temperature are consistent with the previous result while the thermodynamics was built on the event horizon in a Vaidya black hole. Therefore, the thermodynamics of a dynamical black hole should be constructed on the apparent horizon exactly, and the event horizon thermodynamics is just one of the perturbations near the apparent horizon.
  • Research articles
    Diffractive upsilon photo-production off the proton in the QCD inspired model
    Ji-huan PAN (潘继环), Li-juan ZHOU (周丽娟), Wei-xing MA (马维兴),
    2009, 4(4): 534-548. https://doi.org/10.1007/s11467-009-0061-3
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    Based on the generalized vector meson dominance model in QCD, we study the photoproduction of vector meson Υ off the proton by use of the QCD-inspired model in which the contributions from quark–quark, gluon–gluon and quark–gluon interference term to observable are taken into consideration. Calculations are performed for total cross section σtot, differential cross section dσ/dt, ratio of the real part to imaginary part of forward scattering amplitude ρ and nuclear slop parameter function β. We analyze the individual contributions from quark gluon degrees of freedom and the QCD Odderon to the total cross section σtot (s), differential cross section dσ/dt, ratio of the real part to imaginary part of the forward scattering amplitude ρ, and nuclear slop parameter function β. The mediators of interactions between projectiles (the quark and antiquark pair fluctuated from the real photon) and the proton target (three quark system) are the tensor Glueball and Odderon instead of using the usual Pomeron exchange. The theoretical predictions for σtot(s) are consistent with the experimental data within error bars of the data. The data for dσ/dt, β and ρ are urgently needed. The gluon–gluon interaction makes a significant contribution to the observables while the Odderon contribution is negligibly small. Therefore, we may conclude that it is impossible to find the QCD Odderon in the γ+p→Υ+p process as suggested before.
  • Research articles
    Some explicit formulas of Lyapunov exponents for three-dimensional quadratic mappings
    Zeraoulia ELHADJ, J. C. SPROTT,
    2009, 4(4): 549-555. https://doi.org/10.1007/s11467-009-0060-4
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    This paper shows that there exist six different cases where it is possible to find rigorously a Lyapunov exponent for three-dimensional quadratic mappings. Some elementary examples are also given and discussed.
  • Research articles
    Modeling mobile ad hoc communication networks on two-dimensional square lattice
    Li WANG (王黎), Zhi-ming GU (古志鸣), Chen-ping ZHU (朱陈平), Xi-tao LI (李曦涛),
    2009, 4(4): 556-560. https://doi.org/10.1007/s11467-009-0074-y
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    In this paper, we model the mobile ad hoc communication network on a two-dimensional square lattice. Both structure and function of it depend on transmission range and site-occupancy of nodes. Critical occupancies σc for different transmission ranges r to maintain global connection are found. Universal scaling function behaves as η~f(Rβσ), where R=(r−r0)/r0, and the scaling exponent β=−0.61, which distinguishes itself from percolation in previous lattice or network models. When the occupancy σ is near the threshold σc, individual nodes self-organize into a dynamic small world network relative to geometric distance. The network has a cut-off degree below which clustering coefficient keeps constant, which distinguish itself from other systems and has its potential application in technical designs.