Table of contents

15 September 2010, Volume 19 Issue 9 Previous issue    Next issue

GENERAL

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Evolving laws of human cooperative behaviour Li Ke-Ping(李克平) and Fan Hong-Qiang(范红强) Chin. Phys. B, 2010, 19 (9):  090101.  DOI: 10.1088/1674-1056/19/9/090101 Abstract ( 1396 )   PDF (307KB) ( 606 )   In this study, we improve Lévy walk model, and make it suitable for simulating the collective behaviours of humans. Here we show how rescuers find missing persons by collective cooperative search in a natural background. In the search process, the search strategy represents an optimal algorithm which is used to maximize the success rates for finding missing persons. We simulate the rescuer's movement pattern, and find some basic laws governing the rescuer's cooperative search. For example, the probability that each rescuer finds missing persons shows a power law distribution.

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Meshless analysis of three-dimensional steady-state heat conduction problems Cheng Rong-Jun(程荣军) and Ge Hong-Xia(葛红霞) Chin. Phys. B, 2010, 19 (9):  090201.  DOI: 10.1088/1674-1056/19/9/090201 Abstract ( 1572 )   PDF (140KB) ( 2033 )   Steady-state heat conduction problems arisen in connection with various physical and engineering problems where the functions satisfy a given partial differential equation and particular boundary conditions, have attracted much attention and research recently. These problems are independent of time and involve only space coordinates, as in Poisson's equation or the Laplace equation with Dirichlet, Neuman, or mixed conditions. When the problems are too complex, it is difficult to find an analytical solution, the only choice left is an approximate numerical solution. This paper deals with the numerical solution of three-dimensional steady-state heat conduction problems using the meshless reproducing kernel particle method (RKPM). A variational method is used to obtain the discrete equations. The essential boundary conditions are enforced by the penalty method. The effectiveness of RKPM for three-dimensional steady-state heat conduction problems is investigated by two numerical examples.

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Effect of unequal injection rates and different hopping rates on asymmetric exclusion processes with junction Xiao Song(肖松), Cai Jiu-Ju(蔡九菊), Liu Fei(刘飞), and Liu Ming-Zhe(刘明哲) Chin. Phys. B, 2010, 19 (9):  090202.  DOI: 10.1088/1674-1056/19/9/090202 Abstract ( 1682 )   PDF (2721KB) ( 668 )   In this paper, the effects of unequal injection rates and different hopping rates on the asymmetric simple exclusion process (ASEP) with a 2-input 1-output junction are studied by using a simple mean-field approach and extensive computer simulations. The steady-state particle currents, the density profiles, and the phase diagrams are obtained. It is shown that with unequal injection rates and different hopping rates, the phase diagram structure is qualitatively changed. The theoretical calculations are in good agreement with Monte Carlo simulations.

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Payoff-based accumulative effect promotes cooperation in spatial prisoner's dilemma Liu Yong-Kui(刘永奎), Li Zhi(李~~智), Chen Xiao-Jie(陈小杰), and Wang Long(王~~龙) Chin. Phys. B, 2010, 19 (9):  090203.  DOI: 10.1088/1674-1056/19/9/090203 Abstract ( 1580 )   PDF (2506KB) ( 1144 )   We study the effect of accumulative payoff on the evolution of cooperation in the evolutionary prisoner's dilemma on a square lattice. We introduce a decaying factor for the accumulative payoff, which characterizes the extent that the historical payoff is accumulated. It is shown that for fixed values of the temptation to defect, the density of cooperators increases with the value of the decaying factor. This indicates that the more the historical payoff is involved, the more favourable cooperators become. In the critical region where the cooperator density converges to zero, cooperators vanish according to a power-law-like behaviour. The associated exponents agree approximately with the two-dimensional directed percolation and depend weakly on the value of the decaying factor.

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The complex variable reproducing kernel particle method for two-dimensional elastodynamics Chen Li(陈丽) and Cheng Yu-Min(程玉民) Chin. Phys. B, 2010, 19 (9):  090204.  DOI: 10.1088/1674-1056/19/9/090204 Abstract ( 1547 )   PDF (237KB) ( 822 )   On the basis of the reproducing kernel particle method (RKPM), a new meshless method, which is called the complex variable reproducing kernel particle method (CVRKPM), for two-dimensional elastodynamics is presented in this paper. The advantages of the CVRKPM are that the correction function of a two-dimensional problem is formed with one-dimensional basis function when the shape function is obtained. The Galerkin weak form is employed to obtain the discretised system equations, and implicit time integration method, which is the Newmark method, is used for time history analysis. And the penalty method is employed to apply the essential boundary conditions. Then the corresponding formulae of the CVRKPM for two-dimensional elastodynamics are obtained. Three numerical examples of two-dimensional elastodynamics are presented, and the CVRKPM results are compared with the ones of the RKPM and analytical solutions. It is evident that the numerical results of the CVRKPM are in excellent agreement with the analytical solution, and that the CVRKPM has greater precision than the RKPM.

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Symmetry reduction and exact solutions of the (3+1)-dimensional Zakharovben–Kuznetsov equation Dong Zhong-Zhou(董仲周), Chen Yong(陈勇), and Lang Yan-Huai(郎艳怀) Chin. Phys. B, 2010, 19 (9):  090205.  DOI: 10.1088/1674-1056/19/9/090205 Abstract ( 1516 )   PDF (951KB) ( 896 )   By means of the classical method, we investigate the (3+1)-dimensional Zakharov–Kuznetsov equation. The symmetry group of the (3+1)-dimensional Zakharov–Kuznetsov equation is studied first and the theorem of group invariant solutions is constructed. Then using the associated vector fields of the obtained symmetry, we give the one-, two-, and three-parameter optimal systems of group-invariant solutions. Based on the optimal system, we derive the reductions and some new solutions of the (3+1)-dimensional Zakharov–Kuznetsov equation.

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Spatial pattern formation of a ratio-dependent predator–prey model Lin Wang(林望) Chin. Phys. B, 2010, 19 (9):  090206.  DOI: 10.1088/1674-1056/19/9/090206 Abstract ( 1499 )   PDF (9707KB) ( 592 )   This paper presents a theoretical analysis of evolutionary process that involves organisms distribution and their interaction of spatially distributed population with diffusion in a Holling-III ratio-dependent predator–prey model, the sufficient conditions for diffusion-driven instability with Neumann boundary conditions are obtained. Furthermore, it presents novel numerical evidence of time evolution of patterns controlled by diffusion in the model, and finds that the model dynamics exhibits complex pattern replication, and the pattern formation depends on the choice of the initial conditions. The ideas in this paper may provide a better understanding of the pattern formation in ecosystems.

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Energy average formula of photon gas rederived by using the generalised Hermann–Feynman theorem Fan Hong-Yi(范洪义) and Jiang Nian-Quan(姜年权) Chin. Phys. B, 2010, 19 (9):  090301.  DOI: 10.1088/1674-1056/19/9/090301 Abstract ( 1493 )   PDF (81KB) ( 619 )   By virtue of the generalised Hermann–Feynmam theorem we re-derive the energy average formula of photon gas. This is another useful application of the theorem.

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Weak Noether symmetry for a nonholonomic controllable mechanical system Xia Li-Li(夏丽莉) and Shan Ling-Fang(山灵芳) Chin. Phys. B, 2010, 19 (9):  090302.  DOI: 10.1088/1674-1056/19/9/090302 Abstract ( 1495 )   PDF (85KB) ( 552 )   This paper discusses the weak Noether symmetry for a nonholonomic controllable mechanical system of Chetaev type, and presents expressions of three kinds of conserved quantities obtained by using weak Noether symmetry. Finally, the application of these new results is illustrated by an example.

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Conformal invariance and Hojman conserved quantities for holonomic systems with quasi-coordinates Luo Yi-Ping(罗一平) and Fu Jing-Li(傅景礼) Chin. Phys. B, 2010, 19 (9):  090303.  DOI: 10.1088/1674-1056/19/9/090303 Abstract ( 1563 )   PDF (97KB) ( 591 )   We propose a new concept of the conformal invariance and the conserved quantities for holonomic systems with quasi-coordinates. A one-parameter infinitesimal transformation group and its infinitesimal transformation vector of generators for holonomic systems with quasi-coordinates are described in detail. The conformal factor in the determining equations of the Lie symmetry is found. The necessary and sufficient conditions of conformal invariance, which are simultaneously of Lie symmetry, are given. The conformal invariance may lead to corresponding Hojman conserved quantities when the conformal invariance satisfies some conditions. Finally, an illustration example is introduced to demonstrate the application of the result.

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Conformal invariance and conserved quantities of Appell systems under second-class Mei symmetry Luo Yi-Ping(罗一平) and Fu Jing-Li(傅景礼) Chin. Phys. B, 2010, 19 (9):  090304.  DOI: 10.1088/1674-1056/19/9/090304 Abstract ( 1505 )   PDF (96KB) ( 812 )   In this paper we introduce the new concept of the conformal invariance and the conserved quantities for Appell systems under second-class Mei symmetry. The one-parameter infinitesimal transformation group and infinitesimal transformation vector of generator are described in detail. The conformal factor in the determining equations under second-class Mei symmetry is found. The relationship between Appell system's conformal invariance and Mei symmetry are discussed. And Appell system's conformal invariance under second-class Mei symmetry may lead to corresponding Hojman conserved quantities when the conformal invariance satisfies some conditions. Lastly, an example is provided to illustrate the application of the result.

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Fusion and fission solitons for the (2+1)-dimensional generalized Breor–Kaup system Qiang Ji-Ye(强继业), Ma Song-Hua(马松华), and Fang Jian-Ping(方建平) Chin. Phys. B, 2010, 19 (9):  090305.  DOI: 10.1088/1674-1056/19/9/090305 Abstract ( 1563 )   PDF (4181KB) ( 838 )   With a projective equation and a linear variable separation method, this paper derives new families of variable separation solutions (including solitory wave solutions, periodic wave solutions, and rational function solutions) with arbitrary functions for (2+1)-dimensional generalized Breor–Kaup (GBK) system. Based on the derived solitary wave excitation, it obtains fusion and fission solitons.

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Chaos and chaotic control in a relative rotation nonlinear dynamical system under parametric excitation Shi Pei-Ming(时培明), Han Dong-Ying(韩东颖), and Liu Bin(刘彬) Chin. Phys. B, 2010, 19 (9):  090306.  DOI: 10.1088/1674-1056/19/9/090306 Abstract ( 1546 )   PDF (167KB) ( 695 )   This paper studies the chaotic behaviours of a relative rotation nonlinear dynamical system under parametric excitation and its control. The dynamical equation of relative rotation nonlinear dynamical system under parametric excitation is deduced by using the dissipation Lagrange equation. The criterion of existence of chaos under parametric excitation is given by using the Melnikov theory. The chaotic behaviours are detected by numerical simulations including bifurcation diagrams, Poincaré map and maximal Lyapunov exponent. Furthermore, it implements chaotic control using non-feedback method. It obtains the parameter condition of chaotic control by the Melnikov theory. Numerical simulation results show the consistence with the theoretical analysis. The chaotic motions can be controlled to period-motions by adding an excitation term.

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Nonlinear two-mode squeezing obtained by analysing two-mode exponential quadrature operators in entangled state representation Liu Tang-Kun(刘堂昆), Shan Chuan-Jia(单传家), Liu Ji-Bing(刘继兵), and Fan Hong-Yi(范洪义) Chin. Phys. B, 2010, 19 (9):  090307.  DOI: 10.1088/1674-1056/19/9/090307 Abstract ( 1539 )   PDF (90KB) ( 781 )   By analysing the properties of two-mode quadratures in an entangled state representation (ESR) we derive from ESR some complicated exponential quadrature operators for nonlinear two-mode squeezing, which directly leads to wave function of the nonlinear squeezed state in ESR.

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Continuum states of modified Morse potential Wei Gao-Feng(卫高峰) and Chen Wen-Li(陈文利) Chin. Phys. B, 2010, 19 (9):  090308.  DOI: 10.1088/1674-1056/19/9/090308 Abstract ( 1481 )   PDF (99KB) ( 1509 )   Using a proper approximation scheme to the centrifugal term, we study any l-wave continuum states of the Schrõdinger equation for the modified Morse potential. The normalised analytical radial wave functions are presented, and a corresponding calculation formula of phase shifts is derived. It is shown that the energy levels of the continuum states reduce to those of the bound states at the poles of the scattering amplitude. Some numerical results are calculated to show the accuracy of our results.

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Exact solution of entanglement of the double Jaynes–Cummings model without rotating wave approximation Ren Xue-Zao(任学藻), Jiang Dao-Lai(姜道来), Cong Hong-Lu(丛红璐), and Li Lei(黎雷) Chin. Phys. B, 2010, 19 (9):  090309.  DOI: 10.1088/1674-1056/19/9/090309 Abstract ( 1787 )   PDF (671KB) ( 600 )   This paper investigates the influences of atom–field coupling and dipole–dipole coupling for atoms on the entanglement between two atoms by means of concurrence. The results show that the sudden death occurs when the atom–field coupling is strong enough, and the collapse and the revival appear when the dipole–dipole interaction is strong enough.

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Nondestructive and complete Bell-state analysis for atomic qubit systems He Yong(何勇) and Jiang Nian-Quan(姜年权) Chin. Phys. B, 2010, 19 (9):  090310.  DOI: 10.1088/1674-1056/19/9/090310 Abstract ( 1593 )   PDF (151KB) ( 632 )   This paper realizes a nondestructive and complete Bell-state analysis for atomic qubit systems by a designed nondestructive and complete Bell-state analyser. In the scheme, Bell states are completely discriminated by two bits of classical informations which comes from the locality single atom detection on two auxiliary atoms, during which the Bell states are not affected. The needed devices are well within the bounds of current technology, and then the scheme is experimentally feasible.

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Implementation of positive-operator-value measurements for single spin qubit via Heisenberg model Cheng Liu-Yong(程留永), Shao Xiao-Qiang(邵晓强), Zhang Shou(张寿), and Yeon Kyu-Hwang Chin. Phys. B, 2010, 19 (9):  090311.  DOI: 10.1088/1674-1056/19/9/090311 Abstract ( 1448 )   PDF (118KB) ( 647 )   This paper shows that a proposal for implementing all possible two-operator positive-operator-value measurements of single spin qubit can be obtained via introducing another spin qubit as ancilla. The realization process is accomplished from the free evolution of the Heisenberg XX model by considering nearest-neighbour spin interaction. A controlled-NOT gate, which is a significant operator for this scheme is also constructed and the generalisation to multiple-operator is considered finally.

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Applying invariant eigen-operator method to deriving normal coordinates of general classical Hamiltonian Fan Hong-Yi(范洪义), Chen Jun-Hua(陈俊华), and Yuan Hong-Chun (袁洪春) Chin. Phys. B, 2010, 19 (9):  090312.  DOI: 10.1088/1674-1056/19/9/090312 Abstract ( 1380 )   PDF (100KB) ( 528 )   For classical Hamiltonian with general form we find a new convenient way to obtain its normal coordinates, namely, let H be quantised and then employ the invariant eigen-operator (IEO) method (Fan et al. 2004 Phys. Lett. A 321 75) to derive them. The general matrix equation, which relies on M and L, for obtaining the normal coordinates of H is derived.

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Teleportation and thermal entanglement in two-qubit Heisenberg XYZ spin chain with the Dzyaloshinski–Moriya interaction and the inhomogeneous magnetic field Gao Dan(高丹), Zhao Zhen-Shuang(赵振双), Zhu Ai-Dong(朱爱东), Wang Hong-Fu(王洪福), Shao Xiao-Qiang(邵晓强), and Zhang Shou(张寿) Chin. Phys. B, 2010, 19 (9):  090313.  DOI: 10.1088/1674-1056/19/9/090313 Abstract ( 1699 )   PDF (125KB) ( 783 )   This paper studies the average fidelity of teleportation and thermal entanglement for a two-qubit Heisenberg XYZ chain in the presence of both an inhomogeneous magnetic field and a Dzyaloshinski–Moriya interaction. It shows that for a fixed Dz, the increase of bz will broaden the critical temperature at the cost of decreasing the thermal entanglement. And it can modulate the inhomogeneous magnetic field and the Dzyaloshinski–Moriya interaction for the average fidelity of teleportation to be optimal.

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Approximate solutions of Schrödinger equation for Eckart potential with centrifugal term F. Tacskin and G. Koccak Chin. Phys. B, 2010, 19 (9):  090314.  DOI: 10.1088/1674-1056/19/9/090314 Abstract ( 1640 )   PDF (228KB) ( 2660 )   The approximate analytical solutions of the Schr?dinger equation for the Eckart potential are presented for the arbitrary angular momentum by using a new approximation of the centrifugal term. The energy eigenvalues and the corresponding wavefunctions are obtained for different values of screening parameter. The numerical examples are presented and the results are in good agreement with the values in the literature. Three special cases, i.e., s-wave, $\xi=\lambda=1$, and $\beta=0$, are investigated.

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Concurrence, tangle and fully entangled fraction Li Ming(李明), Fei Shao-Ming(费少明), and Li-Jost Xianqing(李先清) Chin. Phys. B, 2010, 19 (9):  090315.  DOI: 10.1088/1674-1056/19/9/090315 Abstract ( 1973 )   PDF (189KB) ( 994 )   We show that although we cannot distil a singlet from many pairs of bound entangled states, the concurrence and the tangle of two entangled quantum states are always strictly larger than those of one of them, even both entangled quantum states are bound entangled. We present a relation between the concurrence and the fidelity of optimal teleportation. We also give new upper and lower bounds for concurrence and tangle.

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Generation of GHZ state and cluster state with atomic ensembles via the dipole–blockade mechanism Ni Bin-Bin(倪彬彬), Gu Yong-Jian(顾永建), Chen Xiao-Dong(陈晓东), Liang Hong-Hui(梁鸿辉), Lin Xiu(林秀), and Lin Xiu-Min(林秀敏) Chin. Phys. B, 2010, 19 (9):  090316.  DOI: 10.1088/1674-1056/19/9/090316 Abstract ( 1713 )   PDF (123KB) ( 607 )   This paper proposes scalable schemes to generate the Greenberger–Horne–Zeilinger (GHZ) state and the cluster state with atomic ensembles via the dipole blockade mechanism on an atom chip, where the qubit is not carried by a single atom but an atomic ensemble. In the protocols, multiqubit entangled states are determinately prepared. Needlessness for single-photon source further decreases the complexity of the experiment. Based on the present laboratory technique, the schemes may be realized. The achieved results reveal a prospect for large-scale quantum communication and quantum computation.

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Fast generation of cluster states in a linear ion trap Xu You-Yang(徐酉阳), Zhou Fei(周飞), Zhang Xiao-Long(张小龙), and Feng Mang(冯芒) Chin. Phys. B, 2010, 19 (9):  090317.  DOI: 10.1088/1674-1056/19/9/090317 Abstract ( 1549 )   PDF (230KB) ( 633 )   We propose a practical scheme to generate cluster states by simultaneously accomplishing two-qubit conditional gating on an array of equidistant ions by using transverse modes. Our operation is robust to heating and insensitive to Lamb–Dicke parameter. Meanwhile, as it is carried out in a geometric quantum computing fashion, our scheme enables the fast and high-fidelity generation of cluster states. The experimental feasibility is discussed with sophisticated ion trap techniques.

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Protecting entanglement by detuning: in Markovian environments vs in non-Markovian environments Huang Li-Yuan(黄利元) and Fang Mao-Fa(方卯发) Chin. Phys. B, 2010, 19 (9):  090318.  DOI: 10.1088/1674-1056/19/9/090318 Abstract ( 1567 )   PDF (405KB) ( 728 )   The models of two qubits separately trapped in two independent Markovian or non-Markovian environments have been investigated. The distinction of the two-qubit entanglement dynamics in different environments has also been discussed in detail. The results show that, in non-Markovian environments, the possible usage time of entanglement can be extended due to its memory effect. On the other hand, we note that, compared to Markovian environments, the two-qubit entanglement could be protected better in non-Markovian environments by modulating the detuning between qubits and cavities. Finally, an intuitive physical interpretation for these results is given.

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Thermal entanglement in two-qutrit spin-1 anisotropic Heisenberg model with inhomogeneous magnetic field Erhan Albayrak Chin. Phys. B, 2010, 19 (9):  090319.  DOI: 10.1088/1674-1056/19/9/090319 Abstract ( 1692 )   PDF (5463KB) ( 962 )   The thermal entanglement of a two-qutrit spin-1 anisotropic Heisenberg XXZ chain in an inhomogeneous magnetic field is studied in detail. The effects of the external magnetic field (B), a parameter b which controls the inhomogeneity of B, and the bilinear interaction parameters Jx=Jy≠Jz on the thermal variation of the negativity are studied in detail. It is found that negativity N decreases when the values of magnetic field, inhomogeneity b and temperature are increasing. In addition, N remains at higher temperatures for higher values of Jz and lower values of B and b.

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Thermodynamic geometry of the Garfinkle–Horowitz–Strominger dilaton black hole Lan Ming-Jian(兰明建), Chen Gang(陈刚), and Han Yi-Wen(韩亦文) Chin. Phys. B, 2010, 19 (9):  090401.  DOI: 10.1088/1674-1056/19/9/090401 Abstract ( 1567 )   PDF (95KB) ( 730 )   This paper studies the thermodynamic properties of the Garfinkle–Horowitz–Strominger dilaton black hole from the viewpoint of geometry. It calculates the heat capacity and the temperature of the black hole, Weinhold metric and Ruppeiner metric are also obtained respectively. It finds that they are both curved and the scalar curvature of the Weinhold geometry consists with the first-order transition point reproduced from the capacity, while the Ruppeiner one is both in accordance with the first-order and the second-order phase transition points reproduced from the capacity.

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Radiation energy flux of Dirac field of static spherically symmetric black holes Meng Qing-Miao(孟庆苗), Jiang Ji-Jian(蒋继建), Li Zhong-Rang(李中让), and Wang Shuai(王帅) Chin. Phys. B, 2010, 19 (9):  090402.  DOI: 10.1088/1674-1056/19/9/090402 Abstract ( 1321 )   PDF (91KB) ( 671 )   By the statistical entropy of the Dirac field of the static spherically symmetric black hole, the result is obtained that the radiation energy flux of the black hole is proportional to the quartic of the temperature of its event horizon. That is, the thermal radiation of the black hole always satisfies the generalised Stenfan–Boltzmann law. The derived generalised Stenfan–Boltzmann coefficient is no longer a constant. When the cut-off distance and the thin film thickness are both fixed, it is a proportional coefficient related to the space–time metric near the event horizon and the average radial effusion velocity of the radiation particles from the thin film. Finally, the radiation energy fluxes and the radiation powers of the Schwarzschild black hole and the Reissner–Nordström black hole are derived, separately.

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New finite-gap solutions for the coupled Burgers equations engendered by the Neumann systems Chen Jin-Bing(陈金兵), Geng Xian-Guo(耿献国), and Qiao Zhi-Jun(乔志军) Chin. Phys. B, 2010, 19 (9):  090403.  DOI: 10.1088/1674-1056/19/9/090403 Abstract ( 1416 )   PDF (141KB) ( 575 )   On the tangent bundle TSN-1 of the unit sphere SN-1, this paper reduces the coupled Burgers equations to two Neumann systems by using the nonlinearization of the Lax pair, whose Liouville integrability is displayed in the scheme of the r-matrix technique. Based on the Lax matrix of the Neumann systems, the Abel–Jacobi coordinates are appropriately chosen to straighten out the restricted Neumann flows on the complex torus, from which the new finite-gap solutions expressed by Riemann theta functions for the coupled Burgers equations are given in view of the Jacobi inversion.

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Energy and first law of thermodynamics for Born–Infeld–anti-de-Sitter black hole Wei Yi-Huan(魏益焕) Chin. Phys. B, 2010, 19 (9):  090404.  DOI: 10.1088/1674-1056/19/9/090404 Abstract ( 1653 )   PDF (94KB) ( 763 )   We calculate the local energy and the energy density of the Reisner–Norström–anti-de-Sitter black hole, study the first law of thermodynamics and show the Smarr formula for the Born–Infeld–anti-de-Sitter black hole. Applying the first law of thermodynamics to the black hole region, we analyse the three energy exchange processes between the black hole region and the outer and the inner regions.

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Tangent response in coupled dynamical systems Yan Hua(闫华), Wei Ping(魏平), and Xiao Xian-Ci(肖先赐) Chin. Phys. B, 2010, 19 (9):  090501.  DOI: 10.1088/1674-1056/19/9/090501 Abstract ( 1436 )   PDF (3354KB) ( 479 )   We construct new unidirectional coupling schemes for autonomous and nonautonomous drive systems, respectively. Each of these schemes makes the state of the response system asymptotically approach the first-order derivative of the state of the driver. From the point of view of geometry, the first-order derivative of the state of the driver can be viewed as a tangent vector of the trajectory of the driver, so the proposed schemes are named tangent response schemes. Numerical simulations of the Lorenz system and the forced Duffing oscillator verify the validity of the tangent response schemes. We further point out that the tangent response can be interpreted as a special kind of generalised synchronisation, thereby explaining why the response system can exhibit rich geometrical structures in its state space.

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An improved impulsive control approach to robust lag synchronization between two different chaotic systems Ma Tie-Dong(马铁东), Fu Jie(浮洁), and Sun Yue(孙跃) Chin. Phys. B, 2010, 19 (9):  090502.  DOI: 10.1088/1674-1056/19/9/090502 Abstract ( 1893 )   PDF (2955KB) ( 2188 )   In this paper, a novel robust impulsive lag synchronization scheme for different chaotic systems with parametric uncertainties is proposed. Based on the theory of impulsive functional differential equations and a new differential inequality, some new and less conservative sufficient conditions are established to guarantee that the error dynamics can converge to a predetermined region. Finally, some numerical simulations for the Lorenz system and Chen system are given to demonstrate the effectiveness and feasibility of the proposed method. Compared with the existing results based on so-called dual-stage impulsive control, the derived results reduce the complexity of impulsive controller, moreover, a larger stable region can be obtained under the same parameters, which can be shown in the numerical simulations finally.

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Synchronization between fractional-order chaotic systems and integer orders chaotic systems (fractional-order chaotic systems) Zhou Ping(周平), Cheng Yuan-Ming(程元明), and Kuang Fei(邝菲) Chin. Phys. B, 2010, 19 (9):  090503.  DOI: 10.1088/1674-1056/19/9/090503 Abstract ( 1771 )   PDF (143KB) ( 2137 )   Based on the idea of tracking control and stability theory of fractional-order systems, a controller is designed to synchronize the fractional-order chaotic system with chaotic systems of integer orders, and synchronize the different fractional-order chaotic systems. The proposed synchronization approach in this paper shows that the synchronization between fractional-order chaotic systems and chaotic systems of integer orders can be achieved, and the synchronization between different fractional-order chaotic systems can also be realized. Numerical experiments show that the present method works very well.

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Generalised synchronisation of spatiotemporal chaos using feedback control method and phase compression Wang Xing-Yuan(王兴元) and Zhang Na(张娜) Chin. Phys. B, 2010, 19 (9):  090504.  DOI: 10.1088/1674-1056/19/9/090504 Abstract ( 1545 )   PDF (3101KB) ( 673 )   Coupled map lattices are taken as examples to study the synchronisation of spatiotemporal chaotic systems. First, a generalised synchronisation of two coupled map lattices is realised through selecting an appropriate feedback function and appropriate range of feedback parameter. Based on this method we use the phase compression method to extend the range of the parameter. So, we integrate the feedback control method with the phase compression method to implement the generalised synchronisation and obtain an exact range of feedback parameter. This technique is simple to implement in practice. Numerical simulations show the effectiveness and the feasibility of the proposed program.

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A universal algorithm to generate pseudo-random numbers based on uniform mapping as homeomorphism Wang Fu-Lai(王福来) Chin. Phys. B, 2010, 19 (9):  090505.  DOI: 10.1088/1674-1056/19/9/090505 Abstract ( 1540 )   PDF (170KB) ( 1044 )   A specific uniform map is constructed as a homeomorphism mapping chaotic time series into [0,1] to obtain sequences of standard uniform distribution. With the uniform map, a chaotic orbit and a sequence orbit obtained are topologically equivalent to each other so the map can preserve the most dynamic properties of chaotic systems such as permutation entropy. Based on the uniform map, a universal algorithm to generate pseudo random numbers is proposed and the pseudo random series is tested to follow the standard 0-1 random distribution both theoretically and experimentally. The algorithm is not complex, which does not impose high requirement on computer hard ware and thus computation speed is fast. The method not only extends the parameter spaces but also avoids the drawback of small function space caused by constraints on chaotic maps used to generate pseudo random numbers. The algorithm can be applied to any chaotic system and can produce pseudo random sequence of high quality, thus can be a good universal pseudo random number generator.

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Novel pinning control strategies for synchronisation of complex networks with nonlinear coupling dynamics Liu Zhao-Bing(刘兆冰), Zhang Hua-Guang(张化光), and Sun Qiu-Ye(孙秋野) Chin. Phys. B, 2010, 19 (9):  090506.  DOI: 10.1088/1674-1056/19/9/090506 Abstract ( 1525 )   PDF (610KB) ( 567 )   This paper considers the global stability of controlling an uncertain complex network to a homogeneous trajectory of the uncoupled system by a local pinning control strategy. Several sufficient conditions are derived to guarantee the network synchronisation by investigating the relationship among pinning synchronisation, network topology, and coupling strength. Also, some fundamental and yet challenging problems in the pinning control of complex networks are discussed: (1) what nodes should be selected as pinned candidates? (2) How many nodes are needed to be pinned for a fixed coupling strength? Furthermore, an adaptive pinning control scheme is developed. In order to achieve synchronisation of an uncertain complex network, the adaptive tuning strategy of either the coupling strength or the control gain is utilised. As an illustrative example, a network with the Lorenz system as node self-dynamics is simulated to verify the efficacy of theoretical results.

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Theoretical and experimental study of Chen chaotic system with notch filter feedback control Zhang Xiao-Ming(张晓明), Chen Ju-Fang(陈菊芳), and Peng Jian-Hua(彭建华) Chin. Phys. B, 2010, 19 (9):  090507.  DOI: 10.1088/1674-1056/19/9/090507 Abstract ( 1754 )   PDF (1816KB) ( 952 )   Since the past two decades, the time delay feedback control method has attracted more and more attention in chaos control studies because of its simplicity and efficiency compared with other chaos control schemes. Recently, it has been proposed to suppress low-dimensional chaos with the notch filter feedback control method, which can be implemented in a laser system. In this work, we have analytically determined the controllable conditions for notch filter feedback controlling of Chen chaotic system in terms of the Hopf bifurcation theory. The conditions for notch filter feedback controlled Chen chaoitc system having a stable limit cycle solution are given. Meanwhile, we also analysed the Hopf bifurcation direction, which is very important for parameter settings in notch filter feedback control applications. Finally, we apply the notch filter feedback control methods to the electronic circuit experiments and numerical simulations based on the theoretical analysis. The controlling results of notch filter feedback control method well prove the feasibility and reliability of the theoretical analysis.

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Low dimensional chaos in the AT and GC skew profiles of DNA sequences Zhou Qian(周茜) and Chen Zeng-Qiang(陈增强) Chin. Phys. B, 2010, 19 (9):  090508.  DOI: 10.1088/1674-1056/19/9/090508 Abstract ( 1737 )   PDF (369KB) ( 700 )   This paper investigates the existence of low-dimensional deterministic chaos in the AT and GC skew profiles of DNA sequences. It has taken DNA sequences from eight organisms as samples. The skew profiles are analysed using continuous wavelet transform and then nonlinear time series methods. The invariant measures of correlation dimension and the largest Lyapunov exponent are calculated. It is demonstrated that the AT and GC skew profiles of these DNA sequences all exhibit low dimensional chaotic behaviour. It suggests that chaotic properties may be ubiquitous in the DNA sequences of all organisms.

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A new fractal algorithm to model discrete sequences Zhai Ming-Yue(翟明岳), Heidi Kuzuma, and James W. Rector Chin. Phys. B, 2010, 19 (9):  090509.  DOI: 10.1088/1674-1056/19/9/090509 Abstract ( 1308 )   PDF (1574KB) ( 1146 )   Employing the properties of the affine mappings, a very novel fractal model scheme based on the iterative function system is proposed. We obtain the vertical scaling factors by a set of the middle points in each affine transform, solving the difficulty in determining the vertical scaling factors, one of the most difficult challenges faced by the fractal interpolation. The proposed method is carried out by interpolating the known attractor and the real discrete sequences from seismic data. The results show that a great accuracy in reconstruction of the known attractor and seismic profile is found, leading to a significant improvement over other fractal interpolation schemes.

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Hierarchy property of traffic networks Li Xia-Miao(李夏苗),Zeng Ming-Hua(曾明华), Zhou Jin(周进), and Li Ke-Zan(李科赞) Chin. Phys. B, 2010, 19 (9):  090510.  DOI: 10.1088/1674-1056/19/9/090510 Abstract ( 1483 )   PDF (558KB) ( 929 )   The flourishing complex network theory has aroused increasing interest in studying the properties of real-world networks. Based on the traffic network of Chang–Zhu–Tan urban agglomeration in central China, some basic network topological characteristics were computed with data collected from local traffic maps, which showed that the traffic networks were small-world networks with strong resilience against failure; more importantly, the investigations of assortativity coefficient and average nearest-neighbour degree implied the disassortativity of the traffic networks. Since traffic network hierarchy as an important basic property has been neither studied intensively nor proved quantitatively, the authors are inspired to analyse traffic network hierarchy with disassortativity and to finely characterize hierarchy in the traffic networks by using the n-degree–n-clustering coefficient relationship. Through numerical results and analyses an exciting conclusion is drawn that the traffic networks exhibit a significant hierarchy, that is, the traffic networks are proved to be hierarchically organized. The result provides important information and theoretical groundwork for optimal transport planning.

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A super-high resolution frequency standard measuring approach based on phase coincidence characteristics between signals Li Zhi-Qi(李智奇), Zhou Wei(周渭), Chen Fa-Xi(陈发喜), and Liu Chen-Guang(刘晨光) Chin. Phys. B, 2010, 19 (9):  090601.  DOI: 10.1088/1674-1056/19/9/090601 Abstract ( 1583 )   PDF (91KB) ( 1966 )   A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10-13/s at 5 MHz, and the self-calibration resolution can achieve 10-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.

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Spectroscopic ellipsometric study of the optical properties of Ag2O film prepared by direct-current magnetron reactive sputtering Gao Xiao-Yong(郜小勇), Feng Hong-Liang(冯红亮), Ma Jiao-Min(马姣民), and Zhang Zeng-Yuan(张增院) Chin. Phys. B, 2010, 19 (9):  090701.  DOI: 10.1088/1674-1056/19/9/090701 Abstract ( 1700 )   PDF (176KB) ( 2264 )   The Ag2O film, as-deposited by direct-current magnetron reactive sputtering at a substrate temperature of 150 ℃, clearly shows a preferential orientation (111), and is capable of lowering the threshold value of the thermal decomposition temperature to about 200 ℃, which is helpful to its application in optical and magneto-optical storage. This paper fits its optical constants in terms of a general oscillator model by using measured ellipsometric parameters. The fitted oscillator energy 2.487 eV is close to the optical direct interband transition energy value of the Ag2O film determined by Tauc equation; whereas, the fitted oscillator energy 4.249 eV is far from the fitted plasma oscillator energy 4.756 eV by single-oscillator energy. The photoluminescence spectrum centred at about 2.31 eV indicates a direct-energy gap photoluminescence mechanism of the Ag2O film.

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Wavelength dependence four-wave mixing spectroscopy in a micrometric atomic vapour Li Yuan-Yuan(李院院), Li Li(李莉), Zhang Yan-Peng(张彦鹏), and Bi Si-Wen(毕思文) Chin. Phys. B, 2010, 19 (9):  090702.  DOI: 10.1088/1674-1056/19/9/090702 Abstract ( 1566 )   PDF (350KB) ( 582 )   This paper presents a theoretical study of wavelength dependence four-wave-mixing (FWM) spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke-narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.

ATOMIC AND MOLECULAR PHYSICS

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Electron impact excitation rate coefficients of N II ion Yang Ning-Xuan(杨宁选),Dong Chen-Zhong(董晨钟), Jiang Jun(蒋军), and Xie Lu-You(颉录有) Chin. Phys. B, 2010, 19 (9):  093101.  DOI: 10.1088/1674-1056/19/9/093101 Abstract ( 1466 )   PDF (598KB) ( 915 )   This paper calculates the electron impact excitation rate coefficients from the ground term 2s22p2 3P to the excited terms of the 2s22p2, 2s2p3, 2s22p3s, 2s22p3p, and 2s22p3d configurations of N II. In the calculations, multiconfiguration Dirac–Fork wave functions have been applied to describe the target-ion states and relativistic distorted-wave calculation has been performed to generate fine-structure collision strengths. The collision strengths are then averaged over a Maxwellian distribution of electron velocities in order to generate the effective collision strengths. The calculated rate coefficients are compared with available experimental and theoretical data, and some good agreements are found for the outer shell electron excitations. But for the inner shell electron excitations there are still some differences between the present calculations and available experiments.

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The theoretical study on the potential energy curve for X 3Δ state of TiO molecule Xu Guo-Liang(徐国亮), Xia Yao-Zheng(夏要争), Jia Guang-Rui(贾光瑞), Liu Yu-Fang(刘玉芳), and Zhang Xian-Zhou(张现周) Chin. Phys. B, 2010, 19 (9):  093102.  DOI: 10.1088/1674-1056/19/9/093102 Abstract ( 1391 )   PDF (138KB) ( 562 )   This paper applies the density functional theory method to optimise the structure for X 3Δ state of TiO molecule with the basis sets 6-31G, 6-31++G and 6-311G**. Comparing the attained results with the experiments, it obtains the conclusion that the basis set 6-31++G is most suitable for the optimal structure calculations of X 3Δ state of TiO molecule. The whole potential energy curve for the electronic state is further scanned by using B3P86/6-31++G method for the ground state, then it uses a least square fitted to Murrell–Sorbie functions, at last it calculates the spectroscopic constants and force constants, which are in better agreement with the experimental data.

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Investigation of inter-molecular hydrogen bonding in the binary mixture (acetone + water) by concentration dependent Raman study and ab initio calculations Ouyang Shun-Li(欧阳顺利), Wu Nan-Nan(吴楠楠), Sun Cheng-Lin(孙成林),Liu Jing-Yao(刘靖尧), Li Zuo-Wei(里佐威), and Gao Shu-Qin(高淑琴) Chin. Phys. B, 2010, 19 (9):  093103.  DOI: 10.1088/1674-1056/19/9/093103 Abstract ( 1505 )   PDF (1557KB) ( 1922 )   This paper reports that vibrational spectroscopic analysis on hydrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6-311+G(d,p) basis set. Changes in wavenumber position and linewidth (fullwidth at half maximum) have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.

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Extension of high-order harmonics and generation of an isolated attosecond pulse in the chirped laser field Wu Jie(伍杰),Zhai Zhen(翟振), and Liu Xue-Shen(刘学深) Chin. Phys. B, 2010, 19 (9):  093201.  DOI: 10.1088/1674-1056/19/9/093201 Abstract ( 1707 )   PDF (1015KB) ( 818 )   This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse.

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Matter-wave interference in an axial triple-well optical dipole trap Zhou Qi(周琦), Lu Jun-Fa(陆俊发), and Yin Jian-Ping(印建平) Chin. Phys. B, 2010, 19 (9):  093202.  DOI: 10.1088/1674-1056/19/9/093202 Abstract ( 1514 )   PDF (1906KB) ( 806 )   This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by ～37 μm were created when illuminating by a YAG laser with power 1 mW. These wells with average trapping depth ～0.5 μK and volume ～74 μm3 are suitable to trap and manipulate an atomic Bose–Einstein condensation (BEC). Due to a controllable grating implemented by a spatial light modulator, an evolution between a triple-well trap and a single-well one is achievable by adjusting the height of potential barrier between adjacent wells. Based on this novel triple-well potentials, the loading and splitting of BEC, as well as the interference between three freely expanding BECs, are also numerically stimulated within the framework of mean-field treatment. By fitting three cosine functions with three Gaussian envelopes to interference fringe, the information of relative phases among three condensates is extracted.

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Active manipulation of the selective alignment by two laser pulses Yang Zeng-Qiang(杨增强), Guo Zhi-Rong(郭志荣), and Ge Gui-Xian(葛桂贤) Chin. Phys. B, 2010, 19 (9):  093301.  DOI: 10.1088/1674-1056/19/9/093301 Abstract ( 1643 )   PDF (739KB) ( 746 )   This paper solves numerically the full time-dependent Schrõdinger equation based on the rigid rotor model, and proposes a novel strategy to determine the optimal time delay of the two laser pulses to manipulate the molecular selective alignment. The results illustrate that the molecular alignment generated by the first pulse can be suppressed or enhanced selectively, the relative populations of even and odd rotational states in the final rotational wave packet can be manipulated selectively by precisely inserting the peak of the second laser pulse at the time when the slope for the alignment parameter by the first laser locates a local maximum for the even rotational states and a local minimum for the odds, and vice versa. The selective alignment can be further optimised by selecting the intensity ratio of the two laser pulses on the condition that the total laser intensity and pulse duration are kept constant.

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Rotational analysis and line intensities of the HCO $\tilde{B}{}^2A'-\tilde{X}{}^2A'3^1_1$ band at 296 K Liu Yan-Hong(刘艳红), Du Xiao-Feng(杜晓峰), and Cheng Xin-Lu(程新路) Chin. Phys. B, 2010, 19 (9):  093302.  DOI: 10.1088/1674-1056/19/9/093302 Abstract ( 1562 )   PDF (169KB) ( 506 )   This paper computes the rotational energy levels of the HCO $\tilde{B}^2A'-\tilde{X}^2A'$ transition, especially, the higher values of the rotational quantum numbers NKaKc and Ka, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration–rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.

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Single electron loss in the collisions of C3 + and atomic hydrogen Liu Hui-Ping(刘会平), Ouyang Xiao-Ping(欧阳晓平), Hu Hua-Si(胡华四), and Su Guang-Hui(苏光辉) Chin. Phys. B, 2010, 19 (9):  093401.  DOI: 10.1088/1674-1056/19/9/093401 Abstract ( 1388 )   PDF (111KB) ( 514 )   This paper studies the projectile electron loss cross sections of C3 + colliding with atomic hydrogen in the frame work of extended over-barrier model at intermediate velocities (25 keV/u–600 keV/u). The electron loss is calculated in terms of the interaction between the screened target nucleus and the active projectile electron and of the interaction between projectile electron and target electron. Compared with the convergent close-coupling calculations, screening and anti-screening calculations, this model satisfactorily reproduces the experimentally obtained energy dependence of the electron-impact ionisation cross sections and the single electron loss cross sections over the energy range investigated here.

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Quantum reflection as the reflection of subwaves Yuan Wen(袁文), Yin Cheng(殷澄), Wang Xian-Ping(王贤平), and Cao Zhuang-Qi(曹庄琪) Chin. Phys. B, 2010, 19 (9):  093402.  DOI: 10.1088/1674-1056/19/9/093402 Abstract ( 1427 )   PDF (411KB) ( 769 )   This paper studies quantum reflection with recent research on reflection coefficient. Based on the analytical transfer matrix method, a novel explanation for this phenomenon is proposed that quantum reflection is the reflection of subwaves, which originate inherently from the inhomogeneity of the fields and is always neglected in the semiclassical regime. Comparison with exact formula and the numerical calculations for different potentials has confirmed the reliability and the validity of the proposed theory.

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Elastic scattering of electrons from water molecule Liu Jun-Bo(刘俊伯) and Zhou Ya-Jun(周雅君) Chin. Phys. B, 2010, 19 (9):  093403.  DOI: 10.1088/1674-1056/19/9/093403 Abstract ( 1415 )   PDF (130KB) ( 738 )   This paper uses the momentum–space optical potential method to calculate the e–H2O scattering elastic cross sections at the energy range from 6 eV to 50 eV, and the differential cross sections in the angle from 0° to 180° at 40 eV and 50 eV. The polarisation is taken into account via an ab initio equivalent-local potential. The cross sections are compared with experimental measurements and other theoretical calculations.

CLASSICAL AREAS OF PHENOMENOLOGY

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Interface phonon–polaritons in quantum well systems of polar ternary mixed crystals Bao Jin(包锦) and Liang Xi-Xia(梁希侠) Chin. Phys. B, 2010, 19 (9):  094101.  DOI: 10.1088/1674-1056/19/9/094101 Abstract ( 1586 )   PDF (1167KB) ( 659 )   The interface phonon–polaritons in quantum well systems consisting of polar ternary mixed crystals are investigated. The numerical results of the interface phonon–polariton frequencies in the GaAs/AlxGa1-xAs, ZnSxSe1-x/ZnS, and ZnxCd1-xSe/ ZnSe quantum well systems are obtained and discussed. It is shown that there are six branches of interface phonon–polariton modes distributed in three bulk phonon–polariton forbidden bands in the systems. The electric fields of interface phonon–polaritons are also presented and show the interface locality of the modes. The effects of the 'two-mode' and 'one-mode' behaviours of the ternary mixed crystals on the interface phonon–polariton modes are shown in the dispersion curves.

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Comparison between relay propagation and direct propagation of Gaussian–Schell-model beam in turbulent atmosphere along a slant path Chu Xiu-Xiang(储修祥), Liu Ze-Jin(刘泽金), and Wu Yi(吴毅) Chin. Phys. B, 2010, 19 (9):  094201.  DOI: 10.1088/1674-1056/19/9/094201 Abstract ( 1596 )   PDF (622KB) ( 637 )   The relay propagation of Gaussian–Schell-model in turbulent atmosphere along a slant path is studied in this paper. Based on the extended Huygens–Fresnel principle and a quadratic approximation, an analytical formula of average intensity for Gaussian–Schell-model beams in turbulent atmosphere along a slant path is derived, and some special cases are discussed. From the study and the comparison with the direct propagation, we can see that the relay propagation has an advantage over the direct propagation. When the altitude of the target is low, the peak intensity of relay propagation is much larger than that of direct propagation. However, because of the limitation of the relay system aperture for relay propagation and the variation of coherence length for direct propagation, the difference in peak intensity between the two propagations decreases with the increase of the target altitude.

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Coherent beam combining of hybrid phase control in master oscillator-power amplifier configuration Wang Xiao-Lin(王小林), Zhou Pu(周朴), Ma Yan-Xing(马阎星), Ma Hao-Tong(马浩统), Xu Xiao-Jun(许晓军), Liu Ze-Jin(刘泽金), and Zhao Yi-Jun(赵伊君) Chin. Phys. B, 2010, 19 (9):  094202.  DOI: 10.1088/1674-1056/19/9/094202 Abstract ( 1388 )   PDF (791KB) ( 831 )   A novel scalable architecture for coherent beam combining with hybrid phase control involving passive phasing and active phasing in master oscillator-power amplifier configuration is presented. Wide-linewidth mutually injected passive phasing fibre laser arrays serve as master oscillators for the power amplifiers, and the active phasing using stochastic parallel gradient descent algorithm is induced. Wide-linewidth seed laser can suppress the stimulated Brillouin scattering effectively and improve the output power of the fibre laser amplifier, while hybrid phase control provides a robust way for in-phase mode coherent beam combining simultaneously. Experiment is performed by active phasing fibre laser amplifiers with passive phasing fibre ring laser array seed lasers. Power encircled in the main-lobe increases1.57 times and long-exposure fringe contrast is obtained to be 78% when the system evolves from passive phasing to hybrid phasing.

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Sudden death and revival of entanglement of two qubits coupled collectively to a thermal reservoir Liao Xiang-Ping(廖湘萍), Fang Jian-Shu(方见树), and Fang Mao-Fa(方卯发) Chin. Phys. B, 2010, 19 (9):  094203.  DOI: 10.1088/1674-1056/19/9/094203 Abstract ( 1041 )   PDF (555KB) ( 550 )   In this paper, we investigate the entanglement of two qubits coupled collectively to a common thermal environment and find that the the collective decay can lead to a revival of the entanglement that has already been destroyed. We also show that the ability of the system to revival entanglement relies on the mean photon number of the thermal environment and the degree of entanglement of the initial state.

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Concurrence evolution of two qubits coupled with one-mode cavity separately Liu Wei-Ci(刘伟慈), Wang Fa-Qiang(王发强), and Liang Rui-Sheng(梁瑞生) Chin. Phys. B, 2010, 19 (9):  094204.  DOI: 10.1088/1674-1056/19/9/094204 Abstract ( 1724 )   PDF (3311KB) ( 643 )   The concurrence evolution of two qubits coupled with one-mode cavity separately is investigated exactly without adopting the rotating-wave approximation. The results show that for the resonant case, the concurrence evolution behaviour of the system is similar to that of the Markovian case when the coupling strength is weak, while the concurrence vanishes in a finite time and might revive fractional initial entanglement before it permanently vanishes when the coupling strength is strong. And for the detuning case, the entanglement could periodically recover after complete disentanglement. These results are quite different from those of system subjected to Jaynes–Cummings model.

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Robust generation of qutrit entanglement via adiabatic passage of dark states Yang Zhen-Biao(杨贞标), Wu Huai-Zhi(吴怀志), and Zheng Shi-Biao(郑仕标) Chin. Phys. B, 2010, 19 (9):  094205.  DOI: 10.1088/1674-1056/19/9/094205 Abstract ( 2396 )   PDF (203KB) ( 927 )   We propose a scheme for the deterministic generation of qutrit entanglement for two atoms trapped in an optical cavity. Taking advantage of the adiabatic passage, the operation is immune to atomic spontaneous emission as the atomic excited states are never populated; under certain conditions, the probability that the cavity is excited is negligible. We also study the influences of the dissipation due to the atomic spontaneous emission and cavity decay.

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Entanglement transfer via the Raman atom–cavity-field interaction Liang Mai-Lin(梁麦林) and Yuan Bing(袁兵) Chin. Phys. B, 2010, 19 (9):  094206.  DOI: 10.1088/1674-1056/19/9/094206 Abstract ( 1443 )   PDF (135KB) ( 623 )   For the Raman interaction between an atom and a two-mode cavity field prepared in the state |01$\rangle$ or |10$\rangle$, the atom and the field can be disentangled periodically. Such a property of Raman atom–field interaction allows the full entanglement transfer among many atoms and bimodal cavities. In the calculations, each atom is assumed to interact with its own cavity at a different time and so non-identical atoms can be treated conveniently. Entanglement sudden death is discussed too. Though atom–field interaction greatly changes the values of the concurrence for two atoms, configuration of the concurrence is almost not affected. When there is entanglement sudden death, atoms and cavities can still be entangled with one another. However, full entanglement transfer cannot be achieved for such systems with Raman atom–field interaction.

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Generation of a four-particle entangled state via cross-Kerr nonlinearity Zhao Li-Fang(赵丽芳), Lai Bo-Hui(赖柏辉), Mei Feng(梅锋), Yu Ya-Fei(於亚飞), Feng Xun-Li(冯勋立), and Zhang Zhi-Ming(张智明) Chin. Phys. B, 2010, 19 (9):  094207.  DOI: 10.1088/1674-1056/19/9/094207 Abstract ( 1566 )   PDF (105KB) ( 753 )   We propose a scheme for generating a genuine four-particle polarisation entangled state |χ00$\rangle$ that has many interesting entanglement properties and potential applications in quantum information processing. In our scheme, we use the weak cross-Kerr nonlinear interaction between field-modes and the non-demolition measurement method based on highly efficient homodyne detection, which is feasible under the current experiment conditions.

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In-situ growth of Ca/P salt on Ti surface induced by femtosecond lasers in hydroxyapatite suspension Liang Chun-Yong(梁春永), Wang Hong-Shui(王洪水), Yang Yang(杨阳), Yang Jian-Jun(杨建军), Chen Gui-Feng(陈贵锋), and Li Chang-Yi(李长义) Chin. Phys. B, 2010, 19 (9):  094208.  DOI: 10.1088/1674-1056/19/9/094208 Abstract ( 1373 )   PDF (2499KB) ( 692 )   Pure Ti plate surfaces are micro-ablated by femtosecond lasers in the ambience of hydroxyapatite suspension. It is found that three-stage hierarchical surface structures are produced with various laser energies. When the laser energy is 150 μJ, a lava-like structure with a distribution of nanoholes is dispersed evenly on the laser ablated surface. While in the case of 300 μJ, the grooves-and-islands micro-patterns covered with nanoparticles are generated on the surface. Remarkably, Ca/P based substances are revealed to firmly deposit on the micro-structured surfaces. More phosphate growth is seen for the higher laser energy. Discussions suggest that the additional elements deposition could be attributed to the chemical reaction of plasma related ions in the suspension and their subsequent crystallisation on the fresh surfaces of Ti plate due to the femtosecond laser ablation.

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Improvement of photorefractive properties in Hf:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios Sun Xiu-Dong(孙秀冬), Shi Hong-Xin(石宏新), Luo Su-Hua(骆素华), Meng Qing-Xin(孟庆鑫), and Jiang Yong-Yuan(姜永远) Chin. Phys. B, 2010, 19 (9):  094209.  DOI: 10.1088/1674-1056/19/9/094209 Abstract ( 1555 )   PDF (109KB) ( 744 )   Photorefractive properties of Hf:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf:Fe:LiNbO3 crystal grown from the melt with the [Li]/[Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf:Fe:LiNbO3 crystal with the [Li]/[Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the [Li]/[Nb] ratio in crystal is an effective method for Hf:Fe:LiNbO3 crystal to improve its photorefractive properties.

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Investigation on performance of all optical buffer with large dynamical delay time based on cascaded double loop optical buffers Wang Yong-Jun(王拥军), Wu Chong-Qing(吴重庆), Xin Xiang-Jun(忻向军), Yu Kuang-Lu(余贶琭), and Zhang Xiao-Lei(张晓磊) Chin. Phys. B, 2010, 19 (9):  094210.  DOI: 10.1088/1674-1056/19/9/094210 Abstract ( 1393 )   PDF (1093KB) ( 736 )   Optical buffers are critical for optical signal processing in future optical packet-switched networks. In this paper, a theoretical study as well as an experimental demonstration on a new optical buffer with large dynamical delay time is carried out based on cascaded double loop optical buffers (DLOBs). It is found that pulse distortion can be restrained by a negative optical control mode when the optical packet is in the loop. Noise analysis indicates that it is feasible to realise a large variable delay range by cascaded DLOBs. These conclusions are validated by the experiment system with 4-stage cascaded DLOBs. Both the theoretical simulations and the experimental results indicate that a large delay range of 1--9999 times the basic delay unit and a fine granularity of 25 ns can be achieved by the cascaded DLOBs. The performance of the cascaded DLOBs is suitable for the all optical networks.

RAPID COMMUNICATION

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High-order ghost imaging with N-colour thermal light Liu Qian(刘骞), Luo Kai-Hong(罗开红), Chen Xi-Hao(陈希浩), and Wu Ling-An(吴令安) Chin. Phys. B, 2010, 19 (9):  094211.  DOI: 10.1088/1674-1056/19/9/094211 Abstract ( 1994 )   PDF (355KB) ( 778 )   High-order ghost imaging with thermal light consisting of N different frequencies is investigated. The high-order intensity correlation and intrinsic correlation functions are derived for such N-colour light. It is found that they are similar in form to those for the monochromatic case, thus most of the conclusions we obtained previously for monochromatic Nth-order ghost imaging are still applicable. However, we find that the visibility of the N-colour ghost image depends strongly on the wavelength used to illuminate the object, and increases as this wavelength increases when the test arm is fixed. On the contrary, changes of wavelength in the reference arms do not lead to any change of the visibility.

CLASSICAL AREAS OF PHENOMENOLOGY

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Localisation and phase transition of acoustic waves in a soft medium containing air bubbles Liang Bin(梁彬), Zou Xin-Ye(邹欣晔), and Cheng Jian-Chun(程建春) Chin. Phys. B, 2010, 19 (9):  094301.  DOI: 10.1088/1674-1056/19/9/094301 Abstract ( 1395 )   PDF (178KB) ( 595 )   We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are particularly investigated in various cases for distinguishing efficiently the acoustic localisation from the effects of acoustic absorption caused by the viscosity of medium. The numerical results reveal the phenomenon of 'phase transition' characterized by an unusual collective oscillation of bubbles, which is an effective criterion to unambiguously identify the acoustic localisation in the presence of viscosity. Within the localisation region, the phenomenon of phase transition persists, and a remarkable decrease in the fluctuation of the oscillation phases of bubbles is observed. The localisation phenomenon will be impaired by the enhancement of the viscosity factors, and the extent to which the acoustic wave is localised may be determined by appropriately analyzing the values of the oscillation phases or the amount of reduction of the phase fluctuation. The results are particularly significant for the practical experiments in an attempt to observe the acoustic localisation in such a medium, which is in general subjected to the interference of the great ambiguity resulting from the effect of acoustic absorption.

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Difference-frequency ultrasound generation from microbubbles under dual-frequency excitation Ma Qing-Yu(马青玉), Qiu Yuan-Yuan(邱媛媛), Huang Bei(黄蓓), Zhang Dong(章东), and Gong Xiu-Fen(龚秀芬) Chin. Phys. B, 2010, 19 (9):  094302.  DOI: 10.1088/1674-1056/19/9/094302 Abstract ( 1425 )   PDF (338KB) ( 680 )   The difference-frequency (DF) ultrasound generated by using parametric effect promises to improve detection depth owing to its low attenuation, which is beneficial for deep tissue imaging. With ultrasound contrast agents infusion, the harmonic components scattered from the microbubbles, including DF, can be generated due to the nonlinear vibration. A theoretical study on the DF generation from microbubbles under the dual-frequency excitation is proposed in formula based on the solution of the RPNNP equation. The optimisation of the DF generation is discussed associated with the applied acoustic pressure, frequency, and the microbubble size. Experiments are performed to validate the theoretical predictions by using a dual-frequency signal to excite microbubbles. Both the numerical and experimental results demonstrate that the optimised DF ultrasound can be achieved as the difference frequency is close to the resonance frequency of the microbubble and improve the contrast-to-tissue ratio in imaging.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Tokamak residual zonal flow level in near-separatrix region Shi Bing-Ren(石秉仁) Chin. Phys. B, 2010, 19 (9):  095201.  DOI: 10.1088/1674-1056/19/9/095201 Abstract ( 1315 )   PDF (187KB) ( 530 )   Residual zonal flow level is calculated for tokamak plasmas in the near-separatrix region of a diverted tokamak. A recently developed method is used to construct an analytic divertor tokamak configuration. It is shown that the residual zonal flow level becomes smaller but still keeps finite near the separatrix because the neoclassical polarisation mostly due to the trapped particles goes larger in this region.

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Discrete Alfvén eigenmodes in international thermonuclear experimental reactor operations with negative magnetic shear Wang Jun(王军), Hu Shuang-Hui(胡双辉), Dai Qing-Ping(代清平), and Yao Long-Bao(姚龙宝) Chin. Phys. B, 2010, 19 (9):  095202.  DOI: 10.1088/1674-1056/19/9/095202 Abstract ( 1511 )   PDF (179KB) ( 666 )   Discrete Alfvén eigenmodes in steady-state operation scenarios with negative magnetic shear in the international thermonuclear experimental reactor are investigated in this paper. These magnetohydrodynamic eigenmodes are trapped by the $\alpha$ -induced potential wells along the magnetic field line. Here $\alpha=-q^2R{\rm d}\beta/{\rm d}r$ with q being the safety factor, $\beta$ the ratio between plasma and magnetic pressures, and R the major radius, and r the minor radius. Due to negligible continuum damping via wave energy tunneling, these Alfvén eigenmodes could be readily destabilized by energetic particles.

RAPID COMMUNICATION

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Combining SAD/SIR iteration and MR iteration in partial-model extension of proteins Hot! Zhang Tao(张涛), Wu Li-Jie(武丽杰), Gu Yuan-Xin(古元新), Zheng Chao-De(郑朝德), and Fan Hai-Fu(范海福) Chin. Phys. B, 2010, 19 (9):  096101.  DOI: 10.1088/1674-1056/19/9/096101 Abstract ( 1702 )   PDF (3630KB) ( 854 )   There are two kinds of dual-space partial-model extensions which involve the direct-method program OASIS. The first kind, named SAD/SIR iteration, uses SAD/SIR information, while the second kind, named molecular replacement (MR) iteration, does not use that information. In general, the SAD/SIR iteration is more powerful since more experimental information is used. However, in most cases when protein structures are solved with the molecular replacement method, SAD/SIR information is not available. Thus the MR iteration is particularly useful for the completion of models from molecular replacement. The SAD/SIR iteration will be automatically used in OASIS for data sets containing SAD/SIR signals, while the MR iteration will be dedicated to data sets without SAD/SIR signals. The present paper shows that for data containing SAD/SIR signals, a combination of SAD/SIR iteration and MR iteration could lead to significantly better results than that obtained from the SAD/SIR iteration alone.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Elastic properties of spherically anisotropic piezoelectric composites Wei En-Bo(魏恩泊), Gu Guo-Qing(顾国庆), and Poon Ying-Ming(潘英明) Chin. Phys. B, 2010, 19 (9):  096201.  DOI: 10.1088/1674-1056/19/9/096201 Abstract ( 1469 )   PDF (181KB) ( 805 )   Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed.

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Influence of pressure on the solid state phase transformation of Cu–Al–Bi alloy Li Gong(李工), Liu Jian-Hua(刘建华), Wang Wen-Kui(王文魁), and Liu Ri-Ping(刘日平) Chin. Phys. B, 2010, 19 (9):  096202.  DOI: 10.1088/1674-1056/19/9/096202 Abstract ( 1513 )   PDF (5116KB) ( 855 )   The solid state phase transformation of Cu–Al–Bi alloy under high pressure was investigated by x-ray diffraction, energy dispersive spectroscopy and transmission electron microscopy. Experimental results show that the initial crystalline phase in the Cu–Al–Bi alloy annealed at 750℃ under the pressures in the range of 0–6 GPa is $\alpha$-Cu solid solution (named as $\alpha$-Cu phase below), and high pressure has a great influence on the crystallisation process of the Cu–Al–Bi alloy. The grain size of the $\alpha$-Cu phase decreases with increasing pressure as the pressure is below about 3 GPa, and then increases (P >3 GPa). The mechanism for the effects of high pressure on the crystallisation process of the alloy has been discussed.

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Effects of high-pressure heat treatment on the solid-state phase transformation and microstructures of Cu61.13Zn33.94Al4.93 alloys Wang Hai-Yan(王海燕), Liu Jian-Hua(刘建华), Peng Gui-Rong(彭桂荣), and Wang Wen-Kui(王文魁) Chin. Phys. B, 2010, 19 (9):  096203.  DOI: 10.1088/1674-1056/19/9/096203 Abstract ( 1571 )   PDF (6339KB) ( 816 )   The phase transformation activation energy of the Cu61.13Zn33.94Al4.93 alloys, which were treated at 4 GPa and 700 ℃ for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu61.13Zn33.94Al4.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from (111) to (200) of α phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower β' → β and β → β ' transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like α phase in the range of 5–20 °C/min.

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Localized self-trapping in two-dimensional molecular lattice with interaction between Wannier–Mott excitons and phonon lattice Xu Quan(徐权) and Tian Qiang(田强) Chin. Phys. B, 2010, 19 (9):  096301.  DOI: 10.1088/1674-1056/19/9/096301 Abstract ( 1469 )   PDF (616KB) ( 524 )   We investigate the interactions of lattice phonons with Wannier–Mott exciton, the exciton that has a large radius in two-dimensional molecular lattice, by the method of continuum limit approximation, and obtain that the self-trapping can also appear in two-dimensional molecular lattice with a harmonic and nonlinear potential. The exciton effect on molecular lattice does not distort the molecular lattice but only makes it localized and the localization can also react, again through phonon coupling, to trap the energy and prevents its dispersion.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Structural, electronic and optical properties of orthorhombic distorted perovskite TbMnO3 Cai Lu-Gang(蔡鲁刚), Liu Fa-Min(刘发民), and Zhong Wen-Wu(钟文武) Chin. Phys. B, 2010, 19 (9):  097101.  DOI: 10.1088/1674-1056/19/9/097101 Abstract ( 1721 )   PDF (649KB) ( 2087 )   This paper calculates the structural parameters, electronic and optical properties of orthorhombic distorted perovskite-type TbMnO3 by first principles using density functional theory within the generalised gradient approximation. The calculated equilibrium lattice constants are in a reasonable agreement with theoretical and experimental data. The energy band structure, density of states and partial density of states of elements are obtained. Band structures show that TbMnO3 is an indirect band gap between the O 2p states and Mn 3d states, and the band gap is of 0.48 eV agreeing with experimental result. Furthermore, the optical properties, including the dielectric function, absorption coefficient, optical reflectivity, refractive index and energy loss spectrum are calculated and analysed, showing that the TbMnO3 is a promising dielectric material.

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Effect of local atomic disorder on the half-metallicity of full-Heusler Co2FeSi alloy: a first-principles study Li Guan-Nan(李冠男), Jin Ying-Jiu(金迎九), and Lee Jae Il(李在一) Chin. Phys. B, 2010, 19 (9):  097102.  DOI: 10.1088/1674-1056/19/9/097102 Abstract ( 1813 )   PDF (1507KB) ( 1036 )   This paper investigates the effect of atomic disorder on the electronic structure, magnetism, and half-metallicity of full-Heusler Co2FeSi alloy by using the full-potential linearized augmented plane wave method within the generalized gradient approximation (GGA) and GGA+U schemes. It considers three types of atomic disorders in Co2FeSi alloy: the Co–Fe, Co–Si, and Fe–Si disorders. Total energy calculations show that of the three types of disorders, the Fe–Si disorder is more likely to occur. It finds that for the Co–Si disorder, additional states appear in the minority band-gap at the EF and the half-metallcity is substantially destroyed, regardless of the disorder level. On the other hand, the Co–Fe and Fe–Si disorders have little effect on the half-metallicity at a low disorder level. When increasing the disorder levels, the half-metallcity is destroyed at about 9% of the Co–Fe disorder level, while that stays at 25% of the Fe–Si disorder level.

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First-principles study of Ga7As7 ionic cluster and influence of multi-charge on its structure Yang Jian-Song(杨建宋) and Li Bao-Xing(李宝兴) Chin. Phys. B, 2010, 19 (9):  097103.  DOI: 10.1088/1674-1056/19/9/097103 Abstract ( 1523 )   PDF (3287KB) ( 672 )   This paper investigates the structures and stabilities of neutral Ga7As7 cluster and its ions in detail by using first-principles density functional theory. Many low energy structures of Ga7As7 cluster are found. It confirms that the ground state structure of neutral Ga7As7 cluster is a pentagonal prism with four face atoms like a basket structure, as reported by previous works. The ground state structures of positive Ga7As7 cluster ions are different from that of the neutral cluster. These investigations suggest that Ga atoms occupy the capping positions more easily than As atoms. Mulliken population analyses also show that Ga atoms can lose or obtain charge more easily than As atoms. It finds that the neutral Ga7As7 cluster can become more stable by gaining one or two additional electrons but further more electrons would cause the decrease of binding energy. The ionisation energy increases with the increase of the number of the removed electrons. These calculated results indicate that the net magnetic moment of the neutral Ga7As7 cluster is zero because all electrons are paired together in their respective molecular orbits. But for the ionic Ga7As7 cluster with odd number of electrons, the net magnetic moment is 1.0 μB due to an unpaired electron.

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Structural, curvature and electronic properties of Rh adsorption on armchair single-walled carbon nanotube Yang Pei-Fang(杨培芳), Wu Feng-Min(吴锋民), Teng Bo-Tao(滕波涛), Liu Sha(刘莎), and Jiang Jian-Zhong(蒋健中) Chin. Phys. B, 2010, 19 (9):  097104.  DOI: 10.1088/1674-1056/19/9/097104 Abstract ( 1590 )   PDF (4145KB) ( 1020 )   This paper systematically studies the rolling effects of the (n, n) single-wall carbon nanotubes (SWCNT) with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs.

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Spin glass dynamics in RKKY interacting disordered magnetic system Zhang Kai-Cheng(张开成) and Song Peng-Yun(宋朋云) Chin. Phys. B, 2010, 19 (9):  097105.  DOI: 10.1088/1674-1056/19/9/097105 Abstract ( 1613 )   PDF (148KB) ( 672 )   Using the dynamical Monte Carlo method we investigate the nonequilibrium effects in RKKY-coupling disordered spin glass. By the simulation we reproduce the well-known aging and memory phenomena and find the energy relaxation at a certain temperature happens only to the corresponding spins, which directly causes the nonequilibrium effects. Combining the master equation and the energy relaxation we analyse these phenomena and explain them from the dynamical perspective.

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Parameter analysis for gate metal–oxide–semiconductor structures of ion-implanted 4H silicon carbide metal–semiconductor field-effect transistors Wang Shou-Guo(王守国), Zhang Yi-Men(张义门), and Zhang Yu-Ming(张玉明) Chin. Phys. B, 2010, 19 (9):  097106.  DOI: 10.1088/1674-1056/19/9/097106 Abstract ( 1733 )   PDF (486KB) ( 635 )   From the theoretical analysis of the thermionic emission model of current–voltage characteristics, this paper extracts the parameters for the gate Schottky contact of two ion-implanted 4H-SiC metal–semiconductor field-effect transistors (sample A and sample B for three and four times multiple ion-implantation channel region respectively) fabricated in the experiment, including the ideality factor, the series resistance, the zero-field barrier height, the interface oxide capacitance, the interface state density distribution, the neutral level of interface states and the fixed space charge density. The methods to improve the interface of the ion-implanted Schottky contact are given at last.

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Study of 4H-SiC junction barrier Schottky diode using field guard ring termination Chen Feng-Ping(陈丰平), Zhang Yu-Ming(张玉明), Lü Hong-Liang(吕红亮), Zhang Yi-Men(张义门), and Huang Jian-Hua(黄建华) Chin. Phys. B, 2010, 19 (9):  097107.  DOI: 10.1088/1674-1056/19/9/097107 Abstract ( 1728 )   PDF (2572KB) ( 2400 )   This paper reports that the 4H-SiC Schottky barrier diode, PiN diode and junction barrier Schottky diode terminated by field guard rings are designed, fabricated and characterised. The measurements for forward and reverse characteristics have been done, and by comparison with each other, it shows that junction barrier Schottky diode has a lower reverse current density than that of the Schottky barrier diode and a higher forward drop than that of the PiN diode. High-temperature annealing is presented in this paper as well to figure out an optimised processing. The barrier height of 0.79 eV is formed with Ti in this work, the forward drop for the Schottky diode is 2.1 V, with an ideality factor of 3.2, and junction barrier Schottky diode with blocking voltage higher than 400 V was achieved by using field guard ring termination.

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Thermal annealing induced photocarrier radiometry enhancement for ion implanted silicon wafers Liu Xian-Ming(刘显明), Li Bin-Cheng(李斌成), and Huang Qiu-Ping(黄秋萍) Chin. Phys. B, 2010, 19 (9):  097201.  DOI: 10.1088/1674-1056/19/9/097201 Abstract ( 1566 )   PDF (336KB) ( 878 )   An experimental study on the photocarrier radiometry signals of As+ ion implanted silicon wafers before and after rapid thermal annealing is performed. The dependences of photocarrier radiometry amplitude on ion implantation dose (1×1011–1×1016/cm2), implantation energy (20–140 keV) and subsequent isochronical annealing temperature (500–1100 $^\circ$C are investigated. The results show that photocarrier radiometry signals are greatly enhanced for implanted samples annealed at high temperature, especially for those with a high implantation dose. The reduced surface recombination rate resulting from a high built-in electric field generated by annealing-activated impurities in the pn junction is believed to be responsible for the photocarrier radiometry signal enhancement. Photocarrier radiometry is contactless and can therefore be used as an effective in-line tool for the thermal annealing process monitoring of the ion-implanted wafers in semiconductor industries.

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A new model for electromigration grain boundary noise based on free volume He Liang(何亮), Du Lei(杜磊), Zhuang Yi-Qi(庄奕琪), Chen Hua(陈华), Chen Wen-Hao(陈文豪), Li Wei-Hua(李伟华), and Sun Peng(孙鹏) Chin. Phys. B, 2010, 19 (9):  097202.  DOI: 10.1088/1674-1056/19/9/097202 Abstract ( 1496 )   PDF (199KB) ( 594 )   Grain boundary plays a key role in electromigration process of polycrystal interconnection. We take a free volume to represent a 'vacancy–ion complex' as a function of grain boundary specific resistivity, and develop a new characterisation model for grain boundary noise. This model reveals the internal relation between the boundary scattering section and electromigration noise. Comparing the simulation result with our experimental result, we find the source as well as the form of noise change in the electromigration process. In order to describe the noise enhancement at grain boundary quantitatively, we propose a new parameter——grain boundary noise enhancement factor, which reflects that the grain boundary noise can characterise the electromigration damage sensitively.

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Negative differential resistance behaviour in N-doped crossed graphene nanoribbons Chen Ling-Na(陈灵娜), Ma Song-Shan(马松山), Ouyang Fang-Ping(欧阳方平), Wu Xiao-Zan(伍小赞), Xiao Jin(肖金), and Xu Hui(徐慧) Chin. Phys. B, 2010, 19 (9):  097301.  DOI: 10.1088/1674-1056/19/9/097301 Abstract ( 1673 )   PDF (1991KB) ( 1292 )   By using first-principles calculations and nonequilibrium Green's function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.

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The physical process analysis of the capacitance–voltage characteristics of AlGaN/AlN/GaN high electron mobility transistors Wang Xin-Hua(王鑫华), Zhao Miao(赵妙), Liu Xin-Yu(刘新宇), Pu Yan(蒲颜), Zheng Ying-Kui(郑英奎), and Wei Ke(魏珂) Chin. Phys. B, 2010, 19 (9):  097302.  DOI: 10.1088/1674-1056/19/9/097302 Abstract ( 1933 )   PDF (193KB) ( 3724 )   This paper deduces the expression of the Schottky contact capacitance of AlGaN/AlN/GaN high electron mobility transistors (HEMTs), which will help to understand the electron depleting process. Some material parameters related with capacitance–voltage profiling are given in the expression. Detailed analysis of the forward-biased capacitance has been carried on. The gate capacitance of undoped AlGaN/AlN/GaN HEMT will fall under forward bias. If a rising profile is obviously observed, the donor-like impurity or trap is possibly introduced in the barrier.

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The dispersion relations for surface plasmon in a nonlinear–metal–nonlinear dielectric structure Liu Bing-Can(刘炳灿), Yu Li(于丽), Lu Zhi-Xin(逯志欣), and Zhang Kai(张恺) Chin. Phys. B, 2010, 19 (9):  097303.  DOI: 10.1088/1674-1056/19/9/097303 Abstract ( 1558 )   PDF (100KB) ( 954 )   In the asymmetric and symmetric nonlinear–metal–nonlinear dielectric structures, this paper studies the analytic dispersion relation for surface plasmon in a system consisting of a thin metallic film covered on two sides media of intensity-dependent refractive indexes by applying a generalised first integral approach. Especially in the symmetric waveguide structure, two possible modes can exist: the odd mode and the even mode. The dispersion relations of the two modes are obtained. Due to the nonlinear dielectric, the squared magnitude of the electric field at the interface appears and alters the dispersion relations. Numerical results are compared to those from a certain approximate treatment.

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Thermal activation of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height Ru Guo-Ping(茹国平), Yu Rong(俞融), Jiang Yu-Long(蒋玉龙), and Ruan Gang(阮刚) Chin. Phys. B, 2010, 19 (9):  097304.  DOI: 10.1088/1674-1056/19/9/097304 Abstract ( 1535 )   PDF (331KB) ( 828 )   This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I–V–T curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage Vj, excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, Vj needs to be smaller than the barrier height $\phi$. With proper scheme of series resistance connection where the condition of Vj > $\phi$ is guaranteed, I–V–T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I–V–T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I–V–T curves only for small barrier height inhomogeneity.

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Improving performances of ITO/GaP contact on AlGaInP light-emitting diodes Li Chun-Wei(李春伟), Zhu Yan-Xu(朱彦旭), Shen Guang-Di(沈光地), Zhang Yong-Hui(张勇辉), Qin Yuan(秦园), Gao Wei(高伟), Jiang Wen-Jing(蒋文静), and Zhou De-Shu(邹德恕) Chin. Phys. B, 2010, 19 (9):  097305.  DOI: 10.1088/1674-1056/19/9/097305 Abstract ( 1704 )   PDF (1691KB) ( 2074 )   In this paper AlGaInP light emitting diodes with different types of electrodes: Au/Zn/Au-ITO Au/Ti-ITO Au/Ge/Ni-ITO and Au-ITO are fabricated. The photoelectricity properties of those LEDs are studied. The results show that the Au/Zn/Au electrode greatly improves the performance of LEDs compared with the other electrodes. Because the Au/Zn/Au electrode not only forms a good Ohmic contact with indium tin oxide (ITO), but also reduces the specific contact resistances between ITO and GaP, which are 1.273×10-6 Ω · cm2 and 1.743×10-3 Ω ·cm2 between Au/Zn/Au-ITO and ITO-GaP respectively. Furthermore, the textured Zn/Au-ITO/Zn electrode is designed to improve the performances of LEDs, reduce the forward-voltage of the LED from 1.93 to 1.88 V, and increase the luminous intensity of the LEDs from 126 to 134 mcd when driven at 20 mA.

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The study on mechanism and model of negative bias temperature instability degradation in P-channel metal–oxide–semiconductor field-effect transistors Cao Yan-Rong(曹艳荣), Ma Xiao-Hua(马晓华), Hao Yue(郝跃), and Tian Wen-Chao(田文超) Chin. Phys. B, 2010, 19 (9):  097306.  DOI: 10.1088/1674-1056/19/9/097306 Abstract ( 1680 )   PDF (785KB) ( 783 )   Negative Bias Temperature Instability (NBTI) has become one of the most serious reliability problems of metal–oxide–semiconductor field-effect transistors (MOSFETs). The degradation mechanism and model of NBTI are studied in this paper. From the experimental results, the exponential value 0.25–0.5 which represents the relation of NBTI degradation and stress time is obtained. Based on the experimental results and existing model, the reaction–diffusion model with H + related species generated is deduced, and the exponent 0.5 is obtained. The results suggest that there should be H + generated in the NBTI degradation. With the real time method, the degradation with an exponent 0.5 appears clearly in drain current shift during the first seconds of stress and then verifies that H+ generated during NBTI stress.

RAPID COMMUNICATION

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Fabrication of suspended graphene devices and their electronic properties Li Qiang(李强), Cheng Zeng-Guang(程增光), Li Zhong-Jun(李忠军), Wang Zhi-Hua(王志华), and Fang Ying(方英) Chin. Phys. B, 2010, 19 (9):  097307.  DOI: 10.1088/1674-1056/19/9/097307 Abstract ( 1882 )   PDF (1469KB) ( 1953 )   Suspended graphene devices are successfully fabricated by using a novel PMMA/MMA/PMMA tri-layer resist technique. The gap between graphene and dielectric substrate can be easily controlled by the thickness of the bottom PMMA layer, and no wet-etching with hazardous hydrofluoric acid is involved in our fabrication process. Electrical characterizations on suspended graphene devices are performed in vacuum when in-situ current annealing directly leads to a significant improvement on transport properties of graphene, i.e., the increase of carrier mobility with the reduction of width of Dirac peak. Our results make a new opportunity to study intrinsic properties of graphene.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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High frequency behaviours and Mössbauer study of field annealed FeCuNbSiB alloy ribbons Ma Xiao-Ming(马小明), Li Zhi-Wei(李志伟), Wei Jian-Qiang(位建强), Wang Tao(王涛), and Li Fa-Shen(李发伸) Chin. Phys. B, 2010, 19 (9):  097401.  DOI: 10.1088/1674-1056/19/9/097401 Abstract ( 1402 )   PDF (170KB) ( 946 )   This paper investigates the high frequency behaviours and magnetic anisotropy of rapidly solidified FINEMET (Fe73.5Si13.5B9Nb3Cu1) alloy ribbons annealed in an applied magnetic field. It finds that the ribbons annealed with the applied magnetic field show much higher resonance frequencies and have even higher permeability at higher frequencies than the samples annealed without the magnetic field and the non-annealed ribbons. Mössbauer spectroscopy had been employed to study the spatial distribution of the magnetic moments of five selected FINEMET alloy ribbons in different heat-treated conditions. The results show that an easy plane has been established after annealling in the magnetic field, while for the other ribbons this effect is not significant. Hence, the relationship between magnetic field annealing and high frequency property has been bridged by the bianisotropic theory.

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Magnetic hysteresis and refrigeration capacity of Ni–Mn–Ga alloys near Martensitic transformation Fu Bin(傅斌), Long Yi(龙毅), Duan Jing-Fang(段静芳), Wang Chao-Lun(王超伦), Chang Yong-Qin(常永勤), Ye Rong-Chang(叶荣昌), and Wu Guang-Heng(吴光恒) Chin. Phys. B, 2010, 19 (9):  097501.  DOI: 10.1088/1674-1056/19/9/097501 Abstract ( 1562 )   PDF (640KB) ( 937 )   This paper studies the magnetic hysteresis and refrigeration capacity of Ni–Mn–Ga alloys in detail during heating and cooling isothermal magnetisation processes. The Ni–Mn–Ga alloys show larger magnetic hysteresis when they transform from austenite to martensite, but smaller magnetic hysteresis when they transform from martensite to austenite. This behaviour is independent of either the pure Ni–Mn–Ga alloys or the alloys doped with other elements. Because of the existence of the magnetic hysteresis, the relation between the magnetic entropy change and refrigeration capacity is not simply linear. For practical consideration, magnetocaloric effect of Ni–Mn–Ga alloys should be investigated both on cooling and heating processes.

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Ferromagnetism in Eu-doped ZnO films deposited by radio-frequency magnetic sputtering Tan Yong-Sheng(谭永胜), Fang Ze-Bo(方泽波), Chen Wei(陈伟), and He Pi-Mo(何丕模) Chin. Phys. B, 2010, 19 (9):  097502.  DOI: 10.1088/1674-1056/19/9/097502 Abstract ( 1482 )   PDF (112KB) ( 1069 )   This paper reports that Eu-doped ZnO films were successfully deposited on silicon (100) by radio-frequency magnetic sputtering. The x-ray diffraction patterns indicate that Eu substitutes for Zn in the lattice. Ferromagnetic loops were obtained by using superconducting quantum interference device at 10 K and room temperature. No discontinuous change was found in both of the zero-field-cooled and field-cooled curves. The observed ferromagnetism in Eu-doped ZnO can be attributed to a single magnetic phase. The saturation magnetisation decreased remarkably for the Eu-doped ZnO prepared by introducing 5% of oxygen in the sputtering gas or by the post annealing in O2, suggesting that the defects play key roles in the development of ferromagnetism in Eu-doped ZnO films.

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Properties study of LiNbO3 lateral field excited device working on thickness extension mode Zhang Zhi-Tian(张志甜), Zhang Chao(张超), Wang Wen-Yan(王文炎), Ma Ting-Feng(马廷锋), Liu Yan(刘岩), and Feng Guan-Ping(冯冠平) Chin. Phys. B, 2010, 19 (9):  097701.  DOI: 10.1088/1674-1056/19/9/097701 Abstract ( 1581 )   PDF (1436KB) ( 1135 )   This paper investigates the properties of thickness extension mode excited by lateral electric field on LiNbO3 by using the extended Christoffel–Bechmann method. It finds that the lateral field excitation coupling factor for a-mode (quasi-extensional mode) reaches its maximum value of 28% on X-cut LiNbO3. The characteristics of a lateral field excitation device made of X-cut LiNbO3 have been investigated and the lateral field excitation device is used for the design of a high frequency ultrasonic transducer. The time and frequency domain pulse/echo response of the LiNbO3 lateral field excitation ultrasonic transducer is analysed with the modified Krimholtz–Leedom–Matthae model and tested using traditional pulse/echo method. A LiNbO3 lateral field excitation ultrasonic transducer with the centre frequency of 33.44 MHz and the –6 dB bandwidth of 33.8% is acquired, which is in good agreement with the results of the Krimholtz–Leedom–Matthae model. Further analysis suggests that the LiNbO3 lateral field excitation device has great potential in the design of broadband high frequency ultrasonic transducers.

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Monte Carlo simulation on dielectric relaxation and dipole cluster state in relaxor ferroelectrics Hot! Zhu Chen(朱琛) and Liu Jun-Ming(刘俊明) Chin. Phys. B, 2010, 19 (9):  097702.  DOI: 10.1088/1674-1056/19/9/097702 Abstract ( 1560 )   PDF (251KB) ( 1046 )   The Ginzburg–Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of relaxor ferroelectrics. With the increase of random field, the dipole configuration evolves from the long-range ferroelectric order into the coexistence of short-range dipole-clusters and less polarized matrix. The dipole-cluster phase above the transition temperature and superparaelectric fluctuations far below this temperature are identified for the relaxor ferroelectrics. We investigate the frequency dispersion and the time-domain spectrum of the dielectric relaxation, demonstrating the Vogel–Fulcher relationship and the multi-peaked time-domain distribution of the dielectric relaxation.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Role of nitrogen and oxygen in emission of Si quantum dots formed by pulse laser Huang Wei-Qi(黄伟其), Liu Jia-Xing(刘家兴), Cai Cheng-Lan(蔡成兰), Lü Quan(吕泉), Liu Shi-Rong(刘世荣), and Qin Chao-Jian(秦朝建) Chin. Phys. B, 2010, 19 (9):  097801.  DOI: 10.1088/1674-1056/19/9/097801 Abstract ( 1483 )   PDF (3129KB) ( 922 )   Silicon quantum dots fabricated by nanosecond pulsed laser in nitrogen, oxygen or air atmosphere have enhanced photoluminescence (PL) emission with the stimulated emission observed at about 700 nm. It is difficult to distinguish between the photoluminescence peaks emitted from samples prepared in different atmospheres. The reason for the appearance of similar peaks may be the similar distribution of the localised states in the gap for different samples when silicon dangling bonds of quantum dots are passivated by nitrogen or oxygen. It is revealed that both the kind and the density of passivated bonds on quantum dot surface prepared in oxygen or nitrogen have a strong influence on the enhancement of PL emission.

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Relationship of annealing time and intrinsic defects of unintentionally doped 4H-SiC Cheng Ping(程萍), Zhang Yu-Ming(张玉明), Zhang Yi-Men(张义门), and Guo Hui(郭辉) Chin. Phys. B, 2010, 19 (9):  097802.  DOI: 10.1088/1674-1056/19/9/097802 Abstract ( 1585 )   PDF (1578KB) ( 947 )   With annealing temperature kept at 1573 K, the effects of annealing time on stability of the intrinsic defects in epitaxial unintentionally doped 4H-SiC prepared by low pressure chemical vapour deposition have been studied by electron spin resonance (ESR) and low temperature photoluminescence. This paper reports the results shown that annealing time has an important effect on the intrinsic defects in unintentionally doped 4H-SiC when annealing temperature kept at 1573 K. When the annealing time is less than 30 min, the intensity of ESR and photoluminescence is increasing with annealing time prolonged, and reaches the maximum when annealing time is 30 min. Then the intensity of ESR and photoluminescence is rapidly decreased with the longer annealing time, and much less than that of as-grown 4H-SiC when annealing time is 60 min, which should be related with the interaction among the intrinsic defects during the annealing process.

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An interconnect width and spacing optimization model considering scattering effect Zhu Zhang-Ming(朱樟明), Wan Da-Jing(万达经), and Yang Yin-Tang(杨银堂) Chin. Phys. B, 2010, 19 (9):  097803.  DOI: 10.1088/1674-1056/19/9/097803 Abstract ( 1383 )   PDF (277KB) ( 556 )   As the feature size of the CMOS integrated circuit continues to shrink, the more and more serious scattering effect has a serious impact on interconnection performance, such as delay and bandwidth. Based on the impact of the scattering effect on latency and bandwidth, this paper first presents the quality-factor model which optimises latency and bandwidth effectively with the consideration of the scattering effect. Then we obtain the analytical model of line width and spacing with application of curve-fitting method. The proposed model has been verified and compared based on the nano-scale CMOS technology. This optimisation model algorithm is simple and can be applied to the interconnection system optimal design of nano-scale integrated circuits.

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Improvement in the calculation of anti-Stokes energy transfer and experimental justification based on Er0.01YbxY1-0.01-xVO4 crystal Chen Xiao-Bo(陈晓波), Lu Jian(卢建), Zhang Yun-Zhi(张蕴芝), Xu Xiao-Ling(徐小灵), Feng Bao-Hua(冯宝华), Wang Ce(王策), Gregory J. Salamo, and Yang Guo-Jian(杨国建) Chin. Phys. B, 2010, 19 (9):  097804.  DOI: 10.1088/1674-1056/19/9/097804 Abstract ( 1402 )   PDF (549KB) ( 982 )   The improvement on the calculation of anti-Stokes energy transfer rate is studied in the present work. The additional proportion coefficient between Stokes and anti-Stokes light intensities of quantum Raman scattering theory as compared with the classical Raman theory is introduced to successfully describe the anti-Stokes energy transfer. The theoretical formula for the improvement on the calculation of anti-Stokes energy transfer rate is derived for the first time in this study. The correctness of introducing coefficient exp{ΔE / kT} from well-known Raman scatter theory is demonstrated also. Moreover, the experimental lifetime measurement in Er0.01YbxY1-0.01-xVO4 crystal is performed to justify the validity of our important improvement in the original phonon-assisted energy transfer theory for the first time.

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Electroluminescence of double-doped diamond thin films Zhang Shi(章诗), Wang Xiao-Ping(王小平), Wang Li-Jun(王丽军), Zhu Yu-Zhuan(朱玉传), Mei Cui-Yu(梅翠玉), Liu Xin-Xin(刘欣欣), Li Huai-Hui(李怀辉), and Gu Ying-Zhan(顾应展) Chin. Phys. B, 2010, 19 (9):  097805.  DOI: 10.1088/1674-1056/19/9/097805 Abstract ( 1580 )   PDF (2998KB) ( 862 )   A new electroluminescence device is fabricated by microwave plasma chemical vapour deposition system and electron beam vapour deposition system. It is comprised of highly doped silicon/diamond/boron/nitrogen-doped diamond/indium tin oxide thin films. Effects of process parameters on morphologies and structures of the thin films are detected and analysed by scanning electron microscopy, Raman spectrometer and x-ray photoelectron spectrometer. A direct-current (DC) power supply is used to drive the electroluminescence device. The blue light emission with a luminance of 1.2 cd·m- 2 is observed from this double-doped diamond thin film electroluminescence device at an applied voltage of 105 V.

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Mechanism and enhancement of photoluminescence from silicon nanocrystals implanted in SiO2 matrix Wu Zhi-Yong(吴志永), Liu Ke-Xin(刘克新), and Ren Xiao-Tang(任晓堂) Chin. Phys. B, 2010, 19 (9):  097806.  DOI: 10.1088/1674-1056/19/9/097806 Abstract ( 1480 )   PDF (1529KB) ( 551 )   Photoluminescence (PL) spectra of Si nanocrystals (NCs) prepared by 130 keV Si ions implantation onto SiO2 matrix were investigated as a function of annealing temperature and implanted ion dose. PL spectra consist of two PL peaks, originated from smaller Si NCs due to quantum confinement effect (QCE) and the interface states located at the surface of larger Si NCs. The evolution of number of dangling bonds (DBs) on Si NCs was also investigated. For hydrogen-passivated samples, a monotonic increase in PL peak intensity with the dose of implanted Si ions up to 3× 1017 ions /cm2 is observed. The number of DBs on individual Si NC, the interaction between DBs at the surface of neighbouring Si NCs and their effects on the efficiency of PL are discussed.

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Amorphous Er2O3 films for antireflection coatings Zhu Yan-Yan(朱燕艳), Fang Ze-Bo(方泽波), and Liu Yong-Sheng(刘永生) Chin. Phys. B, 2010, 19 (9):  097807.  DOI: 10.1088/1674-1056/19/9/097807 Abstract ( 1693 )   PDF (641KB) ( 948 )   This paper reports that stoichiometric, amorphous, and uniform Er2O3 films are deposited on Si(001) substrates by a radio frequency magnetron sputtering technique. Ellipsometry measurements show that the refractive index of the Er2O3 films is very close to that of a single layer antireflection coating for a solar cell with an air surrounding medium during its working wavelength. For the 90-nm-thick film, the reflectance has a minimum lower than 3% at the wavelength of 600 nm and the weighted average reflectances (400–1000 nm) is 11.6%. The obtained characteristics indicate that Er2O3 films could be a promising candidate for antireflection coatings in solar cells.

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Optical transmission through basic-structural-unit superlattices Zhang Guo-Gang(张国刚) and Yang Xiang-Bo(杨湘波) Chin. Phys. B, 2010, 19 (9):  097808.  DOI: 10.1088/1674-1056/19/9/097808 Abstract ( 1505 )   PDF (541KB) ( 555 )   In this paper, by the transparent-component-decimation (TCD) method we obtain three kinds of new basic-components (BCs) through simplifying and decomposing the BCs of three-component Thue--Morse (3CTM) sequence. Based on these new BCs we propose a type of basic-structural-units (BSUs) and investigate the optical transmission of the one-dimensional (1D) superlattices composed of these BSUs. It is found that if the substrates of the 1D BSU superlattices are certain, the optical transmission at the central wavelength (CW) will be determined completely by the number and the type of BSUs and has nothing to do with the marshalling sequence. In particular, if the substrates are identical, the numbers of different types of BSUs are all the same and the middle two elements of BSUs constitute a cycle, then no matter whether the system is periodic, or quasiperiodic, or aperiodic, or unordered, or even random, it will be transparent at the CW. The conclusion is confirmed by the numerical results. Similar to the even layers of neighbourhood identical elements in TCD method, such a kind of optical BSU subsystem can also be decimated from the chain in the process of transmission investigation. There would be a potential application in the designing of some interesting optical devices.

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Role of buffer layer in electronic structures of iron phthalocyanine molecules on Au(111) Hot! Sun Jia-Tao(孙家涛), Pan Li-Da(潘理达), Hu Hao(胡昊), Du Shi-Xuan(杜世萱), and Gao Hong-Jun(高鸿钧) Chin. Phys. B, 2010, 19 (9):  097809.  DOI: 10.1088/1674-1056/19/9/097809 Abstract ( 1579 )   PDF (1876KB) ( 654 )   We investigate the electronic structures of one and two monolayer iron phthalocyanine (FePc) molecules on Au(111) surfaces. The first monolayer FePc is lying flat on the Au(111) substrate, and the second monolayer FePc is tilted at ～15° relative to the substrate plane along the nearest neighbour [101-] direction with a lobe downward to the central hole of the unit cell in the first layer. The structural information obtained by first-principles calculations is in agreement with the experiment results. Furthermore, it is demonstrated that the electronic structures of FePc molecules in one-monolayer FePc/Au(111) system are perturbed significantly, while the electronic structures of FePc molecules in the second monolayer in two-monolayer FePc/Au(111) system remain almost unchanged due to the screening of the buffer layer on Au(111).

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Structures and magnetic behaviours of TiO2–Mn–TiO2 multilayers Liu Fa-Min(刘发民), Ding Peng(丁芃), and Li Jian-Qi(李建奇) Chin. Phys. B, 2010, 19 (9):  098101.  DOI: 10.1088/1674-1056/19/9/098101 Abstract ( 1218 )   PDF (6089KB) ( 838 )   The TiO2–Mn–TiO2 multilayers are successfully grown on glass and silicon substrates by alternately using radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and the magnetic behaviours of these films are characterised with x-ray diffraction, transmission electron microscope (TEM), vibrating sample magnetometer, and superconducting quantum interference device (SQUID). It is shown that the multi-film consists of a mixture of anatase and rutile TiO2 with an embedded Mn nano-film. It is found that there are two turning points from ferromagnetic phase to antiferromagnetic phase. One is at 42 K attributed to interface coupling between ferromagnetic Mn3O4 and antiferromagnetic Mn2O3, and the other is at 97 K owing to the interface coupling between ferromagnetic Mn and antiferromagnetic MnO. The samples are shown to have ferromagnetic behaviours at room temperature from hysteresis in the M–H loops, and their ferromagnetism is found to vary with the thickness of Mn nano-film. Moreover, the Mn nano-film has a critical thickness of about 18.5 nm, which makes the coercivity of the multi-film reach a maximum of about 3.965times 10 - 2 T.

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Reduction of the phosphorus contamination for plasma deposition of p–i–n microcrystalline silicon solar cells in a single chamber Wang Guang-Hong(王光红), Zhang Xiao-Dan(张晓丹), Xu Sheng-Zhi(许盛之), Zheng Xin-Xia(郑新霞), Wei Chang-Chun(魏长春), Sun Jian(孙建), Xiong Shao-Zhen(熊绍珍), Geng Xin-Hua(耿新华), and Zhao Ying(赵颖) Chin. Phys. B, 2010, 19 (9):  098102.  DOI: 10.1088/1674-1056/19/9/098102 Abstract ( 1455 )   PDF (184KB) ( 872 )   This paper investigates several pretreatment techniques used to reduce the phosphorus contamination between solar cells. They include hydrogen plasma pretreatment, deposition of a p-type doped layer, i-a-Si:H or μc-Si:H covering layer between solar cells. Their effectiveness for the pretreatment is evaluated by means of phosphorus concentration in films, the dark conductivity of p-layer properties and cell performance.

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Effect of slow-solvent-vapour treatment on performance of polymer photovoltaic devices Feng Zhi-Hui(冯志慧), Hou Yan-Bing(侯延冰), Shi Quan-Min(师全民), Liu Xiao-Jun(刘小君), and Teng Feng(滕枫) Chin. Phys. B, 2010, 19 (9):  098601.  DOI: 10.1088/1674-1056/19/9/098601 Abstract ( 1496 )   PDF (1834KB) ( 908 )   In this work, enhanced poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk-heterojunction photovoltaic devices are achieved via slow-solvent-vapour treatment. The correlations between the morphology of the active layer and the photovoltaic performance of polymer-based solar cell are investigated. The active layers are characterized by atomic force microscopy and optical absorption. The results show that slow-solvent-vapour treatment can induce P3HT self-organization into an ordered structure, leading to the enhanced absorption and efficient charge transport.

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

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Propagation of partially coherent beams carrying an edge dislocation through atmospheric turbulence along a slant path Li Jin-Hong(李晋红), Zhang Hong-Run(张洪润), and Lü Bai-Da(吕百达) Chin. Phys. B, 2010, 19 (9):  099201.  DOI: 10.1088/1674-1056/19/9/099201 Abstract ( 1464 )   PDF (1180KB) ( 748 )   This paper derives the explicit expressions for the average intensity, beam width and angular spread of Gaussian Schell-model (GSM) beams with edge dislocation propagating through atmospheric turbulence along a slant path. The propagation of GSM beams with edge dislocation through horizontal atmospheric turbulence can be treated as a special case through a slant one. The propagation properties of GSM beams with edge dislocation through slant atmospheric turbulence are studied, where the influence of edge dislocation parameters including the slope p and off-axis distance d on the spreading of GSM beams with edge dislocation in atmospheric turbulence is stressed. It shows that the spreading of the intensity profile of GSM beams with edge dislocation along a slant path is smaller than that along a horizontal path in the long-distance atmospheric propagation. The larger the slope |p| and the smaller the off-axis distance |d| are, the less the beam-width spreading and angular spread of GSM beams with edge dislocation are affected by turbulence. The GSM beams with edge dislocation is less affected by turbulence than that of GSM beams without edge dislocation. The results are illustrated numerically and their validity is interpreted physically.

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Effect of superstrong magnetic field on electron screening at the crusts of neutron stars Liu Jing-Jing(刘晶晶) Chin. Phys. B, 2010, 19 (9):  099601.  DOI: 10.1088/1674-1056/19/9/099601 Abstract ( 1541 )   PDF (161KB) ( 922 )   The influences of electron screening (ES) and electron energy correction (EEC) are investigated by superstrong magnetic field (SMF). We also discuss in detail the discrepant factor between our results and those of Fushiki, Gudmundsson and Pethick (FGP) in SMF. The results show that SMF has only a slight effect on ES when B < 109 T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B > 109 T . For instance, due to SMF the ES potential may be increased about 23.6% and the EEC may be increased about 4 orders of magnitude at ρ/μe = 1.0×106 mol/cm3 and T9 = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP's when B < 109 T . But the difference will be increased with increasing SMF.

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Effect of strong magnetic field on chemical potential and electron capture in magnetar Gao Jie(高杰), Luo Zhi-Quan(罗志全), Liu Wei-Wei(刘伟伟), and Li Gang(李港) Chin. Phys. B, 2010, 19 (9):  099701.  DOI: 10.1088/1674-1056/19/9/099701 Abstract ( 1611 )   PDF (117KB) ( 799 )   The chemical potential of electrons in a strong magnetic field is investigated. It is shown that the magnetic field has only a slight effect on electron chemical potential when B<1011 T, but electron chemical potential will decrease greatly when B>1011 T. The effects of a strong magnetic field on electron capture rates for 60Fe are discussed, and the result shows that the electron capture sharply decreases because of the strong magnetic field.

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Interference phase of mass neutrino in Reissner–Nordström–de Sitter space–time Huang He(黄河) and Wang Yong-Jiu(王永久) Chin. Phys. B, 2010, 19 (9):  099702.  DOI: 10.1088/1674-1056/19/9/099702 Abstract ( 1716 )   PDF (80KB) ( 611 )   In Reissner–Nordström–de Sitter space–time, we calculate the interference phase of mass neutrino along geodesic in the radial direction, and then investigate the effects of the cosmological constant La on the phase. Morever, the expression of the interference phase can be reduced to that in Reissner–Nordström space–time when Λ approaches to zero.