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  • High-order harmonics generation by few-cycle and multi-cycle femtosecond laser pulses

    Yun Chen-Xia, Teng Hao, Zhang Wei, Zhan Min-Jie, Han Hai-Nian, Zhong Xin, Wei Zhi-Yi, Wang Bing-Bing, Hou Xun
    Chin. Phys. B 2010, 19 (12): 124210
    This paper investigates experimentally high-order harmonic generation (HHG) of neon gas with 5-fs and 25-fs driving laser pulses. It has been demonstrated that the cutoff energy of the harmonic extreme ultraviolet photons is extended to 131 eV and the HHG spectrum near the cutoff region becomes cont...

  • Monolithic integration of electroabsorption modulators and tunnel injection distributed feedback lasers using quantum well intermixing

    Wang Yang, Pan Jiao-Qing, Zhao Ling-Juan, Zhu Hong-Liang, Wang Wei
    Chin. Phys. B 2010, 19 (12): 124215
    Electroabsorption modulators combining Franz–Keldysh effect and quantum confined Stark effect have been monolithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature ...

  • Investigation of fast pitch angle scattering of runaway electrons in the EAST tokamak

    Lu Hong-Wei, Hu Li-Qun, Li Ya-Dong, Zhong Guo-Qiang, Lin Shi-Yao, Xu Ping, EAST-Team
    Chin. Phys. B 2010, 19 (12): 125201
    This paper reports that an experimental investigation of fast pitch angle scattering (FPAS) of runaway electrons in the EAST tokamak has been performed. From the newly developed infrared detector (HgCdTe) diagnostic system, the infrared synchrotron radiation emitted by relativistic electrons can be ...

Chin. Phys. B  
  Chin. Phys. B--2010, Vol.19, No.12
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Completeness of the system of eigenvectors of off-diagonal operator matrices and its applications in elasticity theory

Huang Jun-Jie, Alatancang, Wang Hua
Chin. Phys. B, 2010, 19 (12): 120201 doi: 10.1088/1674-1056/19/12/120201
Full Text: [PDF 190 KB] (Downloads:847)
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This paper deals with off-diagonal operator matrices and their applications in elasticity theory. Two kinds of completeness of the system of eigenvectors are proven, in terms of those of the compositions of two block operators in the off-diagonal operator matrices. Using these results, the double eigenfunction expansion method for solving upper triangular matrix differential systems is proposed. Moreover, we apply the method to the two-dimensional elasticity problem and the problem of bending of rectangular thin plates on elastic foundation.

A moving Kriging interpolation-based boundary node method for two-dimensional potential problems

Li Xing-Guo, Dai Bao-Dong, Wang Ling-Hui
Chin. Phys. B, 2010, 19 (12): 120202 doi: 10.1088/1674-1056/19/12/120202
Full Text: [PDF 1029 KB] (Downloads:1462)
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In this paper, a meshfree boundary integral equation (BIE) method, called the moving Kriging interpolation-based boundary node method (MKIBNM), is developed for solving two-dimensional potential problems. This study combines the BIE method with the moving Kriging interpolation to present a boundary-type meshfree method, and the corresponding formulae of the MKIBNM are derived. In the present method, the moving Kriging interpolation is applied instead of the traditional moving least-square approximation to overcome Kronecker's delta property, then the boundary conditions can be imposed directly and easily. To verify the accuracy and stability of the present formulation, three selected numerical examples are presented to demonstrate the efficiency of MKIBNM numerically.

Lagrange equations of nonholonomic systems with fractional derivatives

Zhou Sha, Fu Jing-Li, Liu Yong-Song
Chin. Phys. B, 2010, 19 (12): 120301 doi: 10.1088/1674-1056/19/12/120301
Full Text: [PDF 139 KB] (Downloads:2645)
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This paper obtains Lagrange equations of nonholonomic systems with fractional derivatives. First, the exchanging relationships between the isochronous variation and the fractional derivatives are derived. Secondly, based on these exchanging relationships, the Hamilton's principle is presented for non-conservative systems with fractional derivatives. Thirdly, Lagrange equations of the systems are obtained. Furthermore, the d'Alembert–Lagrange principle with fractional derivatives is presented, and the Lagrange equations of nonholonomic systems with fractional derivatives are studied. An example is designed to illustrate these results.

Analytical solutions of transient pulsed eddy current problem due to elliptical electromagnetic concentrative coils

Xiao Chun-Yan, Zhang Jun
Chin. Phys. B, 2010, 19 (12): 120302 doi: 10.1088/1674-1056/19/12/120302
Full Text: [PDF 1350 KB] (Downloads:1094)
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The electromagnetic concentrative coils are indispensable in the functional magnetic stimulation and have potential applications in nondestructive testing. In this paper, we propose a figure-8-shaped coil being composed of two arbitrary oblique elliptical coils, which can change the electromagnetic concentrative region and the magnitude of eddy current density by changing the elliptical shape and/or spread angle between two elliptical coils. Pulsed current is usually the excitation source in the functional magnetic stimulation, so in this paper we derive the analytical solutions of transient pulsed eddy current field in the time domain due to the elliptical concentrative coil placed in an arbitrary position over a half-infinite plane conductor by making use of the scale-transformation, the Laplace transform and the Fourier transform are used in our derivation. Calculation results of field distributions produced by the figure-8-shaped elliptical coil show some behaviours as follows: 1) the eddy currents are focused on the conductor under the geometric symmetric centre of figure-8-shaped coil; 2) the greater the scale factor of ellipse is, the higher the eddy current density is and the wider the concentrative area of eddy current along y axis is; 3) the maximum magnitude of eddy current density increases with the increase of spread angle. When spread angle is 180o, there are two additional reverse concentrative areas on both sides of x axis.

Two mutually conjugated tripartite entangled states and their fractional Fourier transformation kernel

Lü Cui-Hong, Fan Hong-Yi, Jiang Nian-Quan
Chin. Phys. B, 2010, 19 (12): 120303 doi: 10.1088/1674-1056/19/12/120303
Full Text: [PDF 178 KB] (Downloads:714)
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We newly construct two mutually-conjugate tripartite entangled state representations, based on which we propose the formulation of three-mode entangled fractional Fourier transformation (EFFT) and derive the transformation kernel. The EFFT's additivity property is proved and the eigenmode of EFFT is derived. As an application, we calculate the EFFT of the three-mode squeezed vacuum state.

Continuum modeling for two-lane traffic flow with consideration of the traffic interruption probability

Tian Chuan, Sun Di-Hua
Chin. Phys. B, 2010, 19 (12): 120501 doi: 10.1088/1674-1056/19/12/120501
Full Text: [PDF 431 KB] (Downloads:1069)
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Considering the effects that the probability of traffic interruption and the friction between two lanes have on the car-following behaviour, this paper establishes a new two-lane microscopic car-following model. Based on this microscopic model, a new macroscopic model was deduced by the relevance relation of microscopic and macroscopic scale parameters for the two-lane traffic flow. Terms related to lane change are added into the continuity equations and velocity dynamic equations to investigate the lane change rate. Numerical results verify that the proposed model can be efficiently used to reflect the effect of the probability of traffic interruption on the shock, rarefaction wave and lane change behaviour on two-lane freeways. The model has also been applied in reproducing some complex traffic phenomena caused by traffic accident interruption.

Chaotic matter shock wave of an open system

Deng Yan, Hai Wen-Hua, Rong Shi-Guang, Zhong Hong-Hua
Chin. Phys. B, 2010, 19 (12): 120502 doi: 10.1088/1674-1056/19/12/120502
Full Text: [PDF 541 KB] (Downloads:752)
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We investigate a one-dimensional open Bose–Einstein condensate with attractive interaction, by considering the effect of feeding from nonequilibrium thermal cloud and applying the time-periodic inverted-harmonic potential. Using the direct perturbation method and the exact shock wave solution of the stationary Gross–Pitaevskii equation, we obtain the chaotic perturbed solution and the Melnikov chaotic regions. Based on the analytical and the numerical methods, the influence of the feeding strength on the chaotic motion is revealed. It is shown that the chaotic regions could be enlarged by reducing the feeding strength and the increase of feeding strength plays a role in suppressing chaos. In the case of "nonpropagated" shock wave with fixed boundary, the number of condensed atoms increases faster as the feeding strength increases. However, for the free boundary the metastable shock wave with fixed front density oscillates its front position and atomic number aperiodically, and their amplitudes decay with the increase of the feeding strength.

S-curve networks and an approximate method for estimating degree distributions of complex networks

Guo Jin-Li
Chin. Phys. B, 2010, 19 (12): 120503 doi: 10.1088/1674-1056/19/12/120503
Full Text: [PDF 237 KB] (Downloads:694)
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In the study of complex networks almost all theoretical models have the property of infinite growth, but the size of actual networks is finite. According to statistics from the China Internet IPv4 (Internet Protocol version 4) addresses, this paper proposes a forecasting model by using S curve (logistic curve). The growing trend of IPv4 addresses in China is forecasted. There are some reference values for optimizing the distribution of IPv4 address resource and the development of IPv6. Based on the laws of IPv4 growth, that is, the bulk growth and the finitely growing limit, it proposes a finite network model with a bulk growth. The model is said to be an S-curve network. Analysis demonstrates that the analytic method based on uniform distributions (i.e., Barabási–Albert method) is not suitable for the network. It develops an approximate method to predict the growth dynamics of the individual nodes, and uses this to calculate analytically the degree distribution and the scaling exponents. The analytical result agrees with the simulation well, obeying an approximately power-law form. This method can overcome a shortcoming of Barabási–Albert method commonly used in current network research.

Adaptive synchronization of uncertain chaotic systems via switching mechanism

Feng Yi-Fu, Zhang Qing-Ling
Chin. Phys. B, 2010, 19 (12): 120504 doi: 10.1088/1674-1056/19/12/120504
Full Text: [PDF 261 KB] (Downloads:723)
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This paper deals with the problem of synchronization for a class of uncertain chaotic systems. The uncertainties under consideration are assumed to be Lipschitz-like nonlinearity in tracking error, with unknown growth rate. A logic-based switching mechanism is presented for tracking a smooth orbit that can be a limit cycle or a chaotic orbit of another system. Based on the Lyapunov approach, the adaptation law is determined to tune the controller gain vector online according to the possible nonlinearities. To demonstrate the efficiency of the proposed scheme, the well-known chaotic system namely Chua's circuit is considered as an illustrative example.

Generalized projective synchronization via the state observer and its application in secure communication

Wu Di, Li Juan-Juan
Chin. Phys. B, 2010, 19 (12): 120505 doi: 10.1088/1674-1056/19/12/120505
Full Text: [PDF 537 KB] (Downloads:768)
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Based on the improved state observer and the pole placement technique, by adding a constant which extends the scope of use of the original system, a new design method of generalized projective synchronization is proposed. With this method, by changing the projective synchronization scale factor, one can achieve not only complete synchronization, but also anti-synchronization, as well as arbitrary percentage of projective synchronization, so that the system may attain arbitrary synchronization in a relatively short period of time, which makes this study more meaningful. By numerical simulation, and choosing appropriate scale factor, the results of repeated experiments verify that this method is highly effective and satisfactory. Finally, based on this method and the relevant feedback concept, a novel secure communication project is designed. Numerical simulation verifies that this secure communication project is very valid, and moreover, the experimental result has been greatly improved in decryption time.

Cluster consensus of second-order multi-agent systems via pinning control

Lu Xiao-Qing, Francis Austin, Chen Shi-Hua
Chin. Phys. B, 2010, 19 (12): 120506 doi: 10.1088/1674-1056/19/12/120506
Full Text: [PDF 497 KB] (Downloads:1600)
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This paper investigates the cluster consensus problem for second-order multi-agent systems by applying the pinning control method to a small collection of the agents. Consensus is attained independently for different agent clusters according to the community structure generated by the group partition of the underlying graph and sufficient conditions for both cluster and general consensus are obtained by using results from algebraic graph theory and the LaSalle Invariance Principle. Finally, some simple simulations are presented to illustrate the technique.

Dynamic analysis of a new chaotic system with fractional order and its generalized projective synchronization

Niu Yu-Jun, Wang Xing-Yuan, Nian Fu-Zhong, Wang Ming-Jun
Chin. Phys. B, 2010, 19 (12): 120507 doi: 10.1088/1674-1056/19/12/120507
Full Text: [PDF 460 KB] (Downloads:1377)
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Based on the stability theory of the fractional order system, the dynamic behaviours of a new fractional order system are investigated theoretically. The lowest order we found to have chaos in the new three-dimensional system is 2.46, and the period routes to chaos in the new fractional order system are also found. The effectiveness of our analysis results is further verified by numerical simulations and positive largest Lyapunov exponent. Furthermore, a nonlinear feedback controller is designed to achieve the generalized projective synchronization of the fractional order chaotic system, and its validity is proved by Laplace transformation theory.

Topological horseshoe in nonlinear Bloch system

Fan Qing-Ju
Chin. Phys. B, 2010, 19 (12): 120508 doi: 10.1088/1674-1056/19/12/120508
Full Text: [PDF 576 KB] (Downloads:691)
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This paper demonstrates rigorous chaotic dynamics in nonlinear Bloch system by virtue of topological horseshoe and numerical method. It considers a properly chosen cross section and the corresponding Poincaré map, and shows the existence of horseshoe in the Poincaré map. In this way, a rigorous verification of chaos in the nonlinear Bloch system is presented.

Effect of power frequency excitation character on ferroresonance in neutral-grounded system

Hui Meng, Liu Chong-Xin
Chin. Phys. B, 2010, 19 (12): 120509 doi: 10.1088/1674-1056/19/12/120509
Full Text: [PDF 278 KB] (Downloads:897)
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In most earlier ferroresonance studies the traditional excitation characteristic of iron core, in which the traditional excitation characteristic contains harmonic voltages or currents, has been used as if it were made up of pure fundamental voltage or current. However, this is not always true. In comparison with traditional excitation characteristics, this paper introduces the power frequency excitation characteristic of the iron core, which contains no harmonics. The power frequency excitation characteristic of iron core has been obtained by Elector Magnetic Transient Program, resulting in discrete voltage and current pairs. Extensive simulations are carried out to analyse the effect of power frequency excitation characteristic on potential transformer ferroresonance. A detailed analysis of simulation results demonstrates that with power frequency excitation characteristic of iron core inclusion at certain excitation voltage the ferroresonance may happen, conversely it may not happen with traditional excitation characteristic inclusion.

A new four-dimensional chaotic system

Chen Yong, Yang Yun-Qing
Chin. Phys. B, 2010, 19 (12): 120510 doi: 10.1088/1674-1056/19/12/120510
Full Text: [PDF 339 KB] (Downloads:917)
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A new four-dimensional chaotic system with a linear term and a 3-term cross product is reported. Some interesting figures of the system corresponding different parameters show rich dynamical structures.

Function projective synchronization in partially linear drive–response chaotic systems

Zhang Rong, Xu Zhen-Yuan
Chin. Phys. B, 2010, 19 (12): 120511 doi: 10.1088/1674-1056/19/12/120511
Full Text: [PDF 268 KB] (Downloads:765)
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This paper gives the definition of function projective synchronization with less conservative demand for a scaling function, and investigates the function projective synchronization in partially linear drive–response chaotic systems. Based on the Lyapunov stability theory, it has been shown that the function projective synchronization with desired scaling function can be realized by simple control law. Moreover it does not need scaling function to be differentiable, bounded and non-vanished. The numerical simulations are provided to verify the theoretical result.

A novel extended Tsypkin criterion for discrete-time descriptor systems with ferromagnetic hysteresis nonlinear physical phenomenon

Zhang Hua-Guang, Song Zheng, Zhang Qing-Ling
Chin. Phys. B, 2010, 19 (12): 120512 doi: 10.1088/1674-1056/19/12/120512
Full Text: [PDF 654 KB] (Downloads:697)
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This paper concerns the absolute stability problem of discrete-time descriptor systems with feedback connected ferromagnetic hysteresis nonlinearities. The ferromagnetic hysteresis model satisfies the passivity conditions of hysteresis operator, that is the input–output relation of the transformed operator is passive. The bound condition of the solution of the ferromagnetic hysteresis model is given. Through the framework of loop transformation, an augmented discrete-time descriptor system model is established for the stability analysis. A new extended Tsypkin criterion for the absolute stability of discrete-time descriptor systems with hysteresis is presented based on the linear matrix inequalities technique. A numerical example is given to illustrate the effectiveness of the extended criterion.

Convergence speed of consensus problems over undirected scale-free networks

Sun Wei, Dou Li-Hua
Chin. Phys. B, 2010, 19 (12): 120513 doi: 10.1088/1674-1056/19/12/120513
Full Text: [PDF 441 KB] (Downloads:898)
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Scale-free networks and consensus behaviour among multiple agents have both attracted much attention. To investigate the consensus speed over scale-free networks is the major topic of the present work. A novel method is developed to construct scale-free networks due to their remarkable power-law degree distributions, while preserving the diversity of network topologies. The time cost or iterations for networks to reach a certain level of consensus is discussed, considering the influence from power-law parameters. They are both demonstrated to be reversed power-law functions of the algebraic connectivity, which is viewed as a measurement on convergence speed of the consensus behaviour. The attempts of tuning power-law parameters may speed up the consensus procedure, but it could also make the network less robust over time delay at the same time. Large scale of simulations are supportive to the conclusions.

Forward and inverse problem for cardiac magnetic field and electric potential using two boundary element methods

Tang Fa-Kuan, Wang Qian, Hua Ning, Tang Xue-Zheng, Lu Hong, Ma Ping
Chin. Phys. B, 2010, 19 (12): 120601 doi: 10.1088/1674-1056/19/12/120601
Full Text: [PDF 1402 KB] (Downloads:858)
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This paper discusses the forward and inverse problem for cardiac magnetic fields and electric potentials. A torso-heart model established by boundary element method (BEM) is used for studying the distributions of cardiac magnetic fields and electric potentials. Because node-to-node and triangle-to-triangle BEM can lead to discrepant field distributions, their properties and influences are compared. Then based on constructed torso-heart model and supposed current source functional model–current dipole array, the magnetic and electric imaging by optimal constrained linear inverse method are applied at the same time. Through figure and reconstructing parameter comparison, though the magnetic current dipole array imaging possesses better reconstructing effect, however node-to-node BEM and triangle-to-triangle BEM make little difference to magnetic and electric imaging.

Effects of polarons on static polarizabilities and second order hyperpolarizabilities of conjugated polymers

Wang Ya-Dong, Meng Yan, Di Bing, Wang Shu-Ling, An Zhong
Chin. Phys. B, 2010, 19 (12): 127105 doi: 10.1088/1674-1056/19/12/127105
Full Text: [PDF 306 KB] (Downloads:885)
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According to the one-dimensional tight-binding SuSchrieffer–Heeger model, we have investigated the effects of charged polarons on the static polarizability, αxx, and the second order hyperpolarizabilities, γxxxx, of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su–Schrieffer–Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron–electron interactions on αxx and γxxxx of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of αxx and γxxxx increase as the on-site Coulomb interaction U increases for Uc and decrease with U for U >Uc, where Uc is a critical value of U at which the static polarizability or the second order hyperpolarizability reaches a maximal value of αmax or γmax. It is found that the effect of the e–e interaction on the value of αxx is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γxxxx is sensitive both to the ratio of U to V and to the size of the molecule.

Polarization singularities in near-field of Gaussian vortex beam diffracted by a circular aperture

Li Jian-Long
Chin. Phys. B, 2010, 19 (12): 124001 doi: 10.1088/1674-1056/19/12/124001
Full Text: [PDF 627 KB] (Downloads:639)
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Polarization singularities in the near-field of Gaussian vortex beams diffracted by a circular aperture are studied by a rigorous electromagnetic theory. It is shown that there exist C-points and L-lines, which depend on off-axis displacement parameters along the x and y directions, waist width, wavelength, and topological charge of the diffracted Gaussian vortex beam, as well as on propagation distance. The results are illustrated by numerical calculations.

Wave growth rate in a cylindrical metal waveguide with ion-channel guiding of a relativistic electron beam

Li Hai-Rong, Tang Chang-Jian, Wang Shun-Jin
Chin. Phys. B, 2010, 19 (12): 124101 doi: 10.1088/1674-1056/19/12/124101
Full Text: [PDF 286 KB] (Downloads:669)
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This paper addresses the formulae and numerical issues related to the possibility that fast wave may be grown when a relativistic electron beam through an ion channel in a cylindrical metal waveguide. To derive the dispersion equations of the beam–wave interaction, it solves relativistic Lorentz equation and Maxwell's equations for appropriate boundary conditions. It has been found in this waveguide structure that the TM0m modes are the rational operating modes of coupling between the electromagnetic modes and the betatron modes. The interaction of the dispersion curves of the electromagnetic TM0m modes and the upper betatron modes is studied. The growth rates of the wave are obtained, and the effects of the beam radius, the beam energy, the plasma frequency, and the beam plasma frequency on the wave growth rate are numerically calculated and discussed.

Focusing performance of small f-number metallic lens with depth-modulated slits

Gao Yang, Zhang Xue-Ru, Wang Yu-Xiao, Song Ying-Lin, Liu Shu-Tian
Chin. Phys. B, 2010, 19 (12): 124201 doi: 10.1088/1674-1056/19/12/124201
Full Text: [PDF 681 KB] (Downloads:615)
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This paper studies a small f-number metallic lens with depth-modulated slits. Slits filled with dielectric between silver plates are designed to produce desired optical phase retardations based on the particular propagation properties of surface plasmon polaritons in nanostructures. Numerical simulation of this structure is performed through the finite-difference time-domain method. Different from the conventional dielectric lens, the metallic lens can be used as a pure phase element without energy loss brought by the light refraction at curved surfaces and total internal reflection. The focusing performance is consequently improved, with larger diffraction efficiency than that of the same shaped dielectric lens.

Correlation and fractal properties of speckles in the extremely deep Fresnel diffraction region

Song Hong-Sheng, Liu Man, Liu Gui-Yuan, Xu Zhi-Wei, Teng Shu-Yun, Cheng Chuan-Fu
Chin. Phys. B, 2010, 19 (12): 124202 doi: 10.1088/1674-1056/19/12/124202
Full Text: [PDF 350 KB] (Downloads:826)
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Based on the Kirchhoff approximation and the theoretical analysis of the random light fields, the speckle intensity distributions in the extremely deep Fresnel diffraction region are simulated. The fractal property of the speckles as well as the relation between the speckle intensity distribution and the corresponding random surface is investigated. We design a microscope system to detect experimentally the speckles in the extremely deep Fresnel diffraction region, and the experimental results prove the conclusions drawn from our simulations.

Scheme for direct measurement of Wigner function in two-mode cavity QED driven by classical fields

Wu Huai-Zhi, Yang Zhen-Biao, Zheng Shi-Biao
Chin. Phys. B, 2010, 19 (12): 124203 doi: 10.1088/1674-1056/19/12/124203
Full Text: [PDF 270 KB] (Downloads:663)
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We propose a scheme for the direct measurement of Wigner function in two-mode cavity QED. The atoms are sent to resonantly interact with two orthogonally polarized cavity modes in the presence of strong classical field. The probability of measuring the atom in the ground state directly gives the useful information of the cavity field. This method can be used for quantum non-demolition measurement of the photon number.

Nonlinear interactions and quantum entanglement for collective fields in near-resonantly driven systems

Zhang Xiu, Hu Xiang-Ming, Zhang Xue-Hua, Wang Fei
Chin. Phys. B, 2010, 19 (12): 124204 doi: 10.1088/1674-1056/19/12/124204
Full Text: [PDF 351 KB] (Downloads:618)
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This paper proposes a novel form of multimode nonlinear interactions by using a near-resonantly dressed atomic ensemble in an optical cavity. Due to quantum interference, a pair of collective fields come into the bilinear interactions, whose strengths are proportional to the population difference between dressed states which are coupled to the collective fields. By such an interaction, it is possible to obtain perfect multimode squeezing and collective Einstein–Podolsky–Rosen (EPR) entanglement in the cavity output.

Atomic coherent states as energy eigenstates of a Hamiltonian describing a two-dimensional anisotropic harmonic potential in a uniform magnetic field

Meng Xiang-Guo, Wang Ji-Suo, Liang Bao-Long
Chin. Phys. B, 2010, 19 (12): 124205 doi: 10.1088/1674-1056/19/12/124205
Full Text: [PDF 205 KB] (Downloads:665)
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In this paper we find that a set of energy eigenstates of a two-dimensional anisotropic harmonic potential in a uniform magnetic field is classified as the atomic coherent states |τ> in terms of the spin values of j in the Schwinger bosonic realization. The correctness of the above conclusions can be verified by virtue of the entangled state <η| representation of the state |τ>.

Two-qutrit maximally entangled states prepared via adiabatic passage in ion-trapped system

Huang Bin, Lin Xia, Lin Hui, Cai Zhen-Hua, Yang Rong-Can
Chin. Phys. B, 2010, 19 (12): 124206 doi: 10.1088/1674-1056/19/12/124206
Full Text: [PDF 162 KB] (Downloads:702)
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This paper considers a scheme for the preparation of two-qutrit entangled states via adiabatic passage in ion-trapped system. In the proposal, the two three-level V-type ions are initially cooled to the ground states and need not be separately addressed. Moreover, only the ionic states act as memory and the system evolves in the dark space during the whole procedure, which makes the system robust against the decoherence and the fluctuation of the laser pulse.

Preparation and control of atomic optimal entropy squeezing states for a moving two-level atom under control of the two-mode squeezing vacuum fields

Zhou Bing-Ju, Liu Yi-Man, Zhao Ming-Zhuo, Liu Xiao-Juan
Chin. Phys. B, 2010, 19 (12): 124207 doi: 10.1088/1674-1056/19/12/124207
Full Text: [PDF 1523 KB] (Downloads:610)
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From the viewpoint of quantum information, this paper studies preparation and control of atomic optimal entropy squeezing states (AOESS) for a moving two-level atom under control of the two-mode squeezing vacuum fields. Necessary conditions of preparation of the AOESS are analysed, and numerical verification of the AOESS is finished. It shows that the AOESS can be prepared by controlling the time of the atom interaction with the field, cutting the entanglement between the atom and field, and adjusting squeezing factor of the field. An atomic optimal entropy squeezing sudden generation in different components can alternately be realized by controlling the field-mode structure parameter.

Absorption and slow light effect of pulsed light in a triple semiconductor quantum well

Huang Zhong-Hua, Chen Ai-Xi, Chen Zhao-Chu, Deng Li
Chin. Phys. B, 2010, 19 (12): 124208 doi: 10.1088/1674-1056/19/12/124208
Full Text: [PDF 414 KB] (Downloads:1039)
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Under the condition of two different cases, the absorption of a pulsed probe field and its slow propagation in a triple semiconductor quantum well are investigated. The result shows that semiconductor medium becomes transparent due to the action of control field. Another result shows that by choosing appropriate physical parameters, the slow propagation of the input field can be achieved. The proposed scheme has some potential applications and may lead to the development of the controlled technique of optical buffers and optical delay lines.

Optical switching based on the manipulation of microparticles in a colloidal liquid using strong scattering force

Liu Jin, Liu Zheng-Qi, Feng Tian-Hua, Dai Qiao-Feng, Wu Li-Jun, Lan Sheng
Chin. Phys. B, 2010, 19 (12): 124209 doi: 10.1088/1674-1056/19/12/124209
Full Text: [PDF 385 KB] (Downloads:540)
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This paper demonstrates the realization of an optical switch by optically manipulating a large number of polystyrene spheres contained in a capillary. The strong scattering force exerted on polystyrene spheres with a large diameter of 4.3 μm is employed to realize the switching operation. A transparent window is opened for the signal light when the polystyrene spheres originally located at the beam centre are driven out of the beam region by the strong scattering force induced by the control light. The switching dynamics under different incident powers is investigated and compared with that observed in the optical switch based on the formation of optical matter. It is found that a large extinction ratio of ~30dB and fast switching-on and switching-off times can be achieved in this type of switch.

High-order harmonics generation by few-cycle and multi-cycle femtosecond laser pulses Hot!

Yun Chen-Xia, Teng Hao, Zhang Wei, Zhan Min-Jie, Han Hai-Nian, Zhong Xin, Wei Zhi-Yi, Wang Bing-Bing, Hou Xun
Chin. Phys. B, 2010, 19 (12): 124210 doi: 10.1088/1674-1056/19/12/124210
Full Text: [PDF 642 KB] (Downloads:864)
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This paper investigates experimentally high-order harmonic generation (HHG) of neon gas with 5-fs and 25-fs driving laser pulses. It has been demonstrated that the cutoff energy of the harmonic extreme ultraviolet photons is extended to 131 eV and the HHG spectrum near the cutoff region becomes continuum as the driving laser pulse duration is 5 fs; whereas much lower cutoff photon energy and discrete harmonic spectrum near the cutoff region are presented as the laser pulse duration is 25 fs. The results can be explained by the fact that neutral atoms can be exposed to more intense laser field before they are depleted by ionization because of the extremely short rising time of the few-cycle pulse. The 5-fs driving laser pulse paves the way of generation of coherent x-ray in the water window and single attosecond pulse.

Time delay in InGaN multiple quantum well laser diodes at room temperature

Ji Lian, Jiang De-Sheng, Zhang Shu-Ming, Liu Zong-Shun, Zeng Chang, Zhao De-Gang, Zhu Jian-Jun, Wang Hui, Duan Li-Hong, Yang Hui
Chin. Phys. B, 2010, 19 (12): 124211 doi: 10.1088/1674-1056/19/12/124211
Full Text: [PDF 273 KB] (Downloads:753)
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This paper reports that a long delay between the beginning of pumping current pulse and the onset of optical pulse is observed in InGaN laser diodes. The delay time decreases as the pumping current increases, and the speed of the delay time reduction becomes slower as the current amplitude increases further. Such delay phenomena are remarkably less serious in laser diodes grown on GaN substrate than those on sapphire. It attributes the delay to the traps which cause a large optical loss by saturable absorption and retard the laser action. The traps can be bleached by capturing injected carriers. The effect of GaAs laser irradiation on InGaN laser action demonstrates that the traps responsible for the delay are deep centres which can be filled by the photo-assisted processes.

Hollow Gaussian beams in strongly nonlocal nonlinear media

Yang Zhen-Jun, Lu Da-Quan, Hu Wei, Zheng Yi-Zhou, Gao Xing-Hui
Chin. Phys. B, 2010, 19 (12): 124212 doi: 10.1088/1674-1056/19/12/124212
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The propagation of hollow Gaussian beams in strongly nonlocal nonlinear media is studied in detail. Two analytical expressions are derived. For hollow Gaussian beams, the intensity distribution always evolves periodically. However the second-order moment beam width can keep invariant during propagation if the input power is equal to the critical power. The interaction of two hollow Gaussian beams and the vortical hollow Gaussian beams are also discussed. The vortical hollow Gaussian beams with an appropriate topological charge can keep their shapes invariant during propagation.

Study of narrow-band second harmonic generation from a broad-band fundamental pulse

Wen Jing, Jiang Hong-Bing, Deng Yong-Kai, Gong Qi-Huang
Chin. Phys. B, 2010, 19 (12): 124213 doi: 10.1088/1674-1056/19/12/124213
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This paper studies the type-I phase-matched second harmonic generation using 25-fs input laser pulses in a thick BBO crystal. The harmonic signal exhibits a narrow spectrum bandwidth, even though the input pulse has a broad bandwidth. The energy transfer efficiency and modulation of the fundamental spectrum are investigated.

A novel highly efficient grating coupler with large filling factor used for optoelectronic integration

Zhou Liang, Li Zhi-Yong, Zhu Yu, Li Yun-Tao, Fan Zhong-Cao, Han Wei-Hua, Yu Yu-De, Yu Jin-Zhong
Chin. Phys. B, 2010, 19 (12): 124214 doi: 10.1088/1674-1056/19/12/124214
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A novel highly efficient grating coupler with large filling factor and deep etching is proposed in silicon-on-insulator for near vertical coupling between the rib waveguide and optical fibre. The deep slots acting as high efficient scattering centres are analysed and optimized. As high as 60% coupling efficiency at telecom wavelength of 1550-nm and 3-dB bandwidth of 61 nm are predicted by simulation. A peak coupling efficiency of 42.1% at wavelength 1546-nm and 3-dB bandwidth of 37.6 nm are obtained experimentally.

Monolithic integration of electroabsorption modulators and tunnel injection distributed feedback lasers using quantum well intermixing Hot!

Wang Yang, Pan Jiao-Qing, Zhao Ling-Juan, Zhu Hong-Liang, Wang Wei
Chin. Phys. B, 2010, 19 (12): 124215 doi: 10.1088/1674-1056/19/12/124215
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Electroabsorption modulators combining Franz–Keldysh effect and quantum confined Stark effect have been monolithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.

Read channel for signal waveform modulation multi-level disc

Wang He-Qun, Xu Hai-Zheng, Pan Long-Fa, Liu Hai-Long
Chin. Phys. B, 2010, 19 (12): 124216 doi: 10.1088/1674-1056/19/12/124216
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A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previous read channel composed of level detection and run-length detection, the present read channel shows superiority in capacity increase and robust performance. Especially, relying on the partial response maximum likelihood detection, lower bit error rate can be obtained.

Influences of semiconductor laser on fibre-optic distributed disturbance sensor based on Mach–Zehnder interferometer

Liang Sheng, Zhang Chun-Xi, Lin Bo, Lin Wen-Tai, Li Qin, Zhong Xiang, Li Li-Jing
Chin. Phys. B, 2010, 19 (12): 124217 doi: 10.1088/1674-1056/19/12/124217
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This paper investigates the influences of a semiconductor laser with narrow linewidth on a fibre-optic distributed disturbance sensor based on Mach–Zehnder interferometer. It establishes an effective numerical model to describe the noises and linewidth of a semiconductor laser, taking into account their correlations. Simulation shows that frequency noise has great influences on location errors and their relationship is numerically investigated. Accordingly, there is need to determine the linewidth of the laser less than a threshold and obtain the least location errors. Furthermore, experiments are performed by a sensor prototype using three semiconductor lasers with different linewidths, respectively, with polarization maintaining optical fibres and couplers to eliminate the polarization induced noises and fading. The agreement of simulation with experimental results means that the proposed numerical model can make a comprehensive description of the noise behaviour of a semiconductor laser. The conclusion is useful for choosing a laser source for fibre-optic distributed disturbance sensor to achieve optimized location accuracy. What is more, the proposed numerical model can be widely used for analysing influences of semiconductor lasers on other sensing, communication and optical signal processing systems.

The focusing performance with a horizontal time- reversal array at different depths in shallow water

Zhang Tong-Wei, Yang Kun-De, Ma Yuan-Liang
Chin. Phys. B, 2010, 19 (12): 124301 doi: 10.1088/1674-1056/19/12/124301
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The performance of time-reversal focusing with a horizontal line array at different depths is investigated by normal mode modeling and computer simulation. It is observed that the focusing performance of a bottom-mounted horizontal time-reversal array is much better than that of a horizontal time-reversal array at other depths in shallow water. The normal mode modeling is used to explain this result. The absolute values of the modes at different depths are compared. It is shown that the number of modes whose absolute values close to zero is smaller at the bottom than that at other depths. It means that the horizontal time-reversal array deployed at the bottom can sample more modes,obtain more information of the probe source and achieve better focusing performance. The numerical simulations of time-reversal focusing performance under various conditions, such as different sound speed profiles, and different bottom parameters, lead to similar results.

Symmetry and conserved quantities of discrete generalized Birkhoffian system

Zhang Ke-Jun, Fang Jian-Hui, Li Yan
Chin. Phys. B, 2010, 19 (12): 124601 doi: 10.1088/1674-1056/19/12/124601
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The Noether symmetry, the Mei symmetry and the conserved quantities of discrete generalized Birkhoffian system are studied in this paper. Using the difference discrete variational approach, the difference discrete variational principle of discrete generalized Birkhoffian system is derived. The discrete equations of motion of the system are established. The criterion of Noether symmetry and Mei symmetry of the system is given. The discrete Noether and Mei conserved quantities and the conditions for their existence are obtained. Finally, an example is given to show the applications of the results.

Investigation of hydrogen bonding in neat dimethyl sulfoxide and binary mixture (dimethyl sulfoxide + water) by concentration-dependent Raman study and ab initio calculation

Ouyang Shun-Li, Wu Nan-Nan, Liu Jing-Yao, Sun Cheng-Lin, Li Zuo-Wei, Gao Shu-Qin
Chin. Phys. B, 2010, 19 (12): 123101 doi: 10.1088/1674-1056/19/12/123101
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In this study, our vibrational spectroscopic analysis is made on hydrogen-bonding between dimethyl sulfoxide and water comprises both experimental Raman spectra and ab initio calculations on structures of various dimethyl sulfoxide/water clusters with increasing water content. The Raman peak position of the v(S=O) stretching mode of dimethyl sulfoxide serves as a probe for monitoring the degree of hydrogen-bonding between dimethyl sulfoxide and water. In addition, the two vibrational modes, namely, the CH3 symmetric stretching mode and the CH3 asymmetric stretching mode have been analysed under different concentrations. We relate the computational results to the experimental vibrational wavenumber trends that are observed in our concentration-dependent Raman study. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the nature of the hydrogen bonding and the structures of the hydrogen-bonded complexes studied.

Theoretical study on the complexes of He, Ne and Ar

Tong Xiao-Fei, Yang Chuan-Lu, Xiao Jing, Wang Mei-Shan, Ma Xiao-Guang
Chin. Phys. B, 2010, 19 (12): 123102 doi: 10.1088/1674-1056/19/12/123102
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This paper investigates the effect of basis sets through the potential energy curves (PECs) of six rare gas complexes He2, Ne2, Ar2, He–Ne, He–Ar, and Ne–Ar. The coupled cluster singles and doubles method with perturbative treatment of triple excitations, doubly augmented basis sets of d-aug-cc-pVQZ, bond functions, and basis set superposition errors are employed. The diffuse function is more effective than the polarization function on describing the dissociation energy. The PECs are fitted into analytical potential energy functions (APEFs) using three expressions. It is found that all the expressions are suitable for describing the complexes of rare gases. Based on these APEFs, the spectroscopic parameters are calculated and the results are compared with the theoretical and experimental data available in the literature.

Broadening of Cr nanostructures in laser-focused atomic deposition

Lu Xiang-Dong, Li Tong-Bao, Ma Yan
Chin. Phys. B, 2010, 19 (12): 123201 doi: 10.1088/1674-1056/19/12/123201
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This paper presents the experimental progress of laser-focused Cr atomic deposition and the experimental condition. The result is an accurate array of lines with a periodicity of 212.8±0.2 nm and mean full-width at half maximum as approximately 95 nm. Surface growth in laser-focused Cr atomic deposition is modeled and studied by kinetic Monte Carlo simulation including two events: the one is that atom trajectories in laser standing wave are simulated with the semiclassical equations of motion to obtain the deposition position; the other is that adatom diffuses by considering two major diffusion processes, namely, terrace diffusion and step-edge descending. Comparing with experimental results (Anderson W R, Bradley C C, McClelland J J and Celotta R J 1999 Phys. Rev. A59 2476), it finds that the simulated trend of dependence on feature width is in agreement with the power of standing wave, the other two simulated trends are the same in the initial stage. These results demonstrate that some surface diffusion processes play important role in feature width broadening. Numerical result also shows that high incoming beam flux of atoms deposited redounds to decrease the distance between adatoms which can diffuse to minimize the feature width and enhance the contrast.

A novel method to measure the isotope shifts and hyperfine splittings of all ytterbium isotopes for a 399-nm transition

Wang Wen-Li, Xu Xin-Ye
Chin. Phys. B, 2010, 19 (12): 123202 doi: 10.1088/1674-1056/19/12/123202
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We report the experimental results on measuring the isotope shifts and hyperfine splittings of all ytterbium isotopes for a 399-nm transition by using a quite simple and novel method. It benefits from the advantages of the modulation transfer spectroscopy in an ytterbium hollow cathode lamp and the Doppler-free spectroscopy in a collimated ytterbium atomic beam. The key technique in this experiment is simultaneously measuring the frequency separations of the two spectra twice, and the separation difference between two measurements is solely determined by the well-defined frequency of an acousto-optics modulator. Compared with the most of previously reported experimental results, ours are more accurate and completed, which will provide the useful information for developing a more accurate theoretical model to describe the interaction inside an ytterbium atom.

Controllable optical multi-well trap and its optical lattices using compounded cosine patterns

Zhou Qi, Lu Jun-Fa, Yin Jian-Ping
Chin. Phys. B, 2010, 19 (12): 123203 doi: 10.1088/1674-1056/19/12/123203
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This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam. Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns. It also discusses how to expand this multi-well trap to two-dimensional lattices with single- or multi-well trap by using an orthogonally or non-orthogonally modulated grating, as well as using incoherent multi-beam illumination, and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.

Influence of laser fields on the vibrational population of molecules and its wave-packet dynamical investigation

Wang Jun, Liu Fang, Yue Da-Guang, Zhao Juan, Xu Yan, Meng Qing-Tian, Liu Wing-Ki
Chin. Phys. B, 2010, 19 (12): 123301 doi: 10.1088/1674-1056/19/12/123301
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The time-dependent wave packet method is used to investigate the influence of laser-fields on the vibrational population of molecules. For a two-state system in laser fields, the populations on different vibrational levels of the upper and lower electronic states are given by wavefunctions obtained by solving the Schrödinger equation with the split-operator method. The calculation shows that the field parameters, such as intensity, wavelength, duration, and delay time etc. can have different influences on the vibrational population. By varying the laser parameters appropriately one can control the evolution of wave packet and so the vibrational population in each state, which will benefit the light manipulation of atomic and molecular processes.

Spectroscopic parameters and molecular constants of HI(X1Σ+), DI(X1Σ+) and TI(X1Σ+) isotope molecules

Zhang Xiao-Niu, Shi De-Heng, Zhu Zun-Lue, Sun Jin-Feng
Chin. Phys. B, 2010, 19 (12): 123501 doi: 10.1088/1674-1056/19/12/123501
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The potential energy curve (PEC) of HI(X1Σ+) molecule is studied using the complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration interaction approach at the correlation-consistent basis sets, aug-cc-pV6Z for H and aug-cc-pV5Z-pp for I atom. Using the PEC of HI(X1Σ+), the spectroscopic parameters of three isotopes, HI(X1Σ+), DI(X1Σ+) and TI(X1Σ+), are determined in the present work. For the HI(X1Σ+), the values of D0, De, Re, ωe, ωeχe, αe and Be are 3.1551 eV, 3.2958 eV, 0.16183 nm, 2290.60 cm-1, 40.0703 cm-1, 0.1699 cm-1 and 6.4373 cm-1, respectively; for the DI (X1Σ+), the values of D0, De, Re, ωe, ωeχe, αe and Be are 3.1965 eV, 3.2967 eV, 0.16183 nm, 1626.8 cm-1, 20.8581 cm-1, 0.0611 cm-1 and 3.2468 cm-1, respectively; for the TI (X1Σ+), the values of D0, De, Re, ωe, ωeχe, αe and Be are of 3.2144 eV, 3.2967 eV, 0.16183 nm, 1334.43 cm-1, 14.0765 cm-1, 0.0338 cm-1 and 2.1850 cm-1, respectively. These results accord well with the available experimental results. With the PEC of HI(X1Σ+) molecule obtained at present, a total of 19 vibrational states are predicted for the HI, 26 for the DI, and 32 for the TI, when the rotational quantum number J is equal to zero (J = 0). For each vibrational state, vibrational level G(ν), inertial rotation constant Bν and centrifugal distortion constant Dν are determined when J = 0 for the first time, which are in excellent agreement with the experimental results.

Structures and electronic properties of Mo2nNn (n=1–5): a density functional study

Chen Hang, Lei Xue-Ling, Liu Li-Ren, Liu Zhi-Feng, Zhu Heng-Jiang
Chin. Phys. B, 2010, 19 (12): 123601 doi: 10.1088/1674-1056/19/12/123601
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The lowest-energy structures and the electronic properties of Mo2nNn (n=1–5) clusters have been studied by using the density functional theory (DFT) simulating package DMol3 in the generalized gradient approximation (GGA). The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mon (n=2, 4, 6, 8, 10) clusters and nitrogen atoms which surround these cores. The average binding energy, the adiabatic electron affinity (AEA), the vertical electron affinity (VEA), the adiabatic ionization potential (AIP) and the vertical ionization potential (VIP) of Mo2nNn (n=1–5) clusters have been estimated. The HOMO–LUMO gaps reveal that the clusters have strong chemical activities. An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.

Ultraviolet laser ionization studies of 1-fluoronaphthalene clusters and density functional theory calculations

Zhang Shu-Dong, Zhang Hai-Fang, Tzeng Wen-Bi
Chin. Phys. B, 2010, 19 (12): 123602 doi: 10.1088/1674-1056/19/12/123602
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This paper studies supersonic jet-cooled 1-fluoronaphthalene (1FN) clusters by ultraviolet (UV) laser ionization at 281 nm in a time-of-flight mass spectrometer. The (1FN)n+ (n=1–3) series cluster ions are observed where the signal intensity decreases with increasing cluster size. The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured. Using density functional theory calculations, it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds. The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first "shell" in geometric structure while the larger clusters are generated based on this fundamental unit.

Competing role of catalysis-coagulation and catalysis-fragmentation in kinetic aggregation behaviours

Li Xiao-Dong, Lin Zhen-Quan, Song Mei-Xia, Ke Jian-Hong
Chin. Phys. B, 2010, 19 (12): 128201 doi: 10.1088/1674-1056/19/12/128201
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We propose a kinetic aggregation model where species A aggregates evolve by the catalysis-coagulation and the catalysis-fragmentation, while the catalyst aggregates of the same species B or C perform self-coagulation processes. By means of the generalized Smoluchowski rate equation based on the mean-field assumption, we study the kinetic behaviours of the system with the catalysis-coagulation rate kernel K(i,j;l)∝lv and the catalysis-fragmentation rate kernel F(i,j;l)∝lμ, where l is the size of the catalyst aggregate, and v and μ are two parameters reflecting the dependence of the catalysis reaction on the size of the catalyst aggregate. The relation between the values of parameters v and μ reflects the competing roles between the two catalysis processes in the kinetic evolution of species A. It is found that the competing roles of the catalysis-coagulation and catalysis-fragmentation in the kinetic aggregation behaviours are not determined simply by the relation between the two parameters v and μ, but also depend on the values of these two parameters. When v>μ and v≥0, the kinetic evolution of species A is dominated by the catalysis-coagulation and its aggregate size distribution ak(t) obeys the conventional or generalized scaling law; when v<μ and v≥0 or v<0 but μ≥0, the catalysis-fragmentation process may play a dominating role and ak(t) approaches the scale-free form; and in other cases, a balance is established between the two competing processes at large times and ak(t) obeys a modified scaling law.

Relative energy dissipation-induced effective attraction in granular mixture

Jia Yan, Yang Xian-Qing, Deng Min, Guo Hai-Ping, Ye Jian-Lan
Chin. Phys. B, 2010, 19 (12): 128202 doi: 10.1088/1674-1056/19/12/128202
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This paper presents the investigation of the clustering of the intruders in a vertically vibrated granular bed by means of event-driven simulations. The results indicate that the position of intruders in the vertical direction is not a key factor for their aggregation. Energy dissipation of the intruders and host particles are calculated in the process of intruder-host and host–host collisions. The relative energy dissipation of the intruders to that of the host particles is obtained. We find that clustering of the intruders happens when the relative energy dissipation is negative. The conclusion is verified when the restitution coefficient, density and diameter of the intruders are varied.

Critical volume fraction and size for a colloidal cluster to nucleate

Zhao Dan-Dan, Long Lian-Feng, Xiao Chang-Ming
Chin. Phys. B, 2010, 19 (12): 128203 doi: 10.1088/1674-1056/19/12/128203
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With the aid of the critical size of colloidal cluster, the critical volume fraction of phase transition of colloidal system is determined by the principle of entropy maximum and Carnahan–Starling (CS) state equation in this paper. In our discussion, no parameter is introduced externally, and our results are in good agreement with the experimental results.

Thermal stability of HfO2/Si (001) films prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen

Xu Run, Gong Wei-Ming, Yan Zhi-Jun, Wang Lin-Jun, Xia Yi-Ben
Chin. Phys. B, 2010, 19 (12): 128204 doi: 10.1088/1674-1056/19/12/128204
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HfO2 films on silicon substrates have been prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen. Synchrotron radiation photon–electron spectroscopy was used to investigate the thermal stability of HfO2 films under an ultrahigh vacuum environment. At the temperature of 750 oC, HfO2 films begin to decompose. After being further annealed at 850 oC for 3 min, HfO2 films decomposes completely, partially to form Hf-silicide and partially to form gaseous HfO. Two chemical reactions are responsible for this decomposition process. A small amount of Hf-silicide, which is formed at the very beginning of growth, may result in the films grown subsequently to be loosened, and thereby leads to a relatively low decomposition temperature.

Multi-grid simulation of pedestrian counter flow with topological interaction

Ma Jian, Song Wei-Guo, Liao Guang-Xuan
Chin. Phys. B, 2010, 19 (12): 128901 doi: 10.1088/1674-1056/19/12/128901
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We investigate the dynamics of pedestrian counter flow by using a multi-grid topological pedestrian counter flow model. In the model, each pedestrian occupies multi- rather than only one grid, and interacts with others in the form of topological interaction, which means that a moving pedestrian interacts with a fixed number of those nearest neighbours coming from the opposite direction to determine his/her own moving direction. Thus the discretization of space and time are much finer, the decision making process of the pedestrian is more reliable, which all together makes the moving behaviour and boundary conditions much more realistic. When compared with field observations, it can be found that the modified model is able to reproduce well fitted pedestrian collective behaviour such as dynamical variation of lane formation, clustering of pedestrians in the same direction, etc. The fundamental diagram produced by the model fits also well with field data in the free flow region. Further analyses indicate that with the increase of the size of pedestrian counter flow system, it becomes harder for the system to transit into a jamming state, while the increase of interaction range does not change the transition point from free flow to jamming flow in the multi-grid topological counter flow model. It is also found that the asymmetry of the injection rate of pedestrians on the boundaries has direct influence on the process of transition from free flow to jamming flow, i.e., a symmetric injection makes it easier for the system to transit into jamming flow.

Investigation of fast pitch angle scattering of runaway electrons in the EAST tokamak Hot!

Lu Hong-Wei, Hu Li-Qun, Li Ya-Dong, Zhong Guo-Qiang, Lin Shi-Yao, Xu Ping, EAST-Team
Chin. Phys. B, 2010, 19 (12): 125201 doi: 10.1088/1674-1056/19/12/125201
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This paper reports that an experimental investigation of fast pitch angle scattering (FPAS) of runaway electrons in the EAST tokamak has been performed. From the newly developed infrared detector (HgCdTe) diagnostic system, the infrared synchrotron radiation emitted by relativistic electrons can be obtained as a function of time. The FPAS is analysed by means of the infrared detector diagnostic system and the other correlative diagnostic systems (including electron–cyclotron emission, hard x-ray, neutrons). It is found that the intensity of infrared synchrotron radiation and the electron–cyclotron emission signal increase rapidly at the time of FPAS because of the fast increase of pitch angle and the perpendicular velocity of the energetic runaway electrons. The Parail and Pogutse instability is a possible mechanism for the FPAS.

Generation and characterization of millimeter-scale plasmas for the research of laser plasma interactions on Shenguang-III prototype

Li Zhi-Chao, Zheng Jian, Ding Yong-Kun, Yin Qiang, Jiang Xiao-Hua, Li San-Wei, Guo Liang, Yang Dong, Wang Zhe-Bin, Zhang Huan, Liu Yong-Gang, Zhan Xia-Yu, Tang Qi
Chin. Phys. B, 2010, 19 (12): 125202 doi: 10.1088/1674-1056/19/12/125202
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In order to produce millimeter-scale plasmas for the research of laser-plasma interactions (LPIs), gasbag target is designed and tested on Shenguang-III prototype laser facility. The x-ray pinhole images show that millimeter-scale plasmas are produced with the gasbag. The electron temperature inferred from the stimulated Raman scattering (SRS) spectrum is about 1.6 keV. The SRS spectrum also indicates that the electron density has a flat region within the duration of 200 ps. The obvious differences between the results of the gasbag and that of the void half hohlraum show the feasibility of the gasbag target in creating millimeter-scale plasmas. The LPIs in these millimeter-scale plasmas may partially mimic those in the ignition condition because the duration of the existence of a flat plasma density is much larger than the growth time of the two main instabilities, i.e., SRS and stimulated Brillouin scattering (SBS). So we make the conclusion that the gasbag target can be used to research the large-scale LPIs.

Site preference and thermodynamic properties of R3Ni13-xCoxB2 (R=Y, Nd and Sm)

Qian Ping, Liu Jiu-Li, Shen Jiang, Bai Li-Jun, Ran Qiong, Wang Yun-Liang
Chin. Phys. B, 2010, 19 (12): 126001 doi: 10.1088/1674-1056/19/12/126001
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This paper investigates the structural stability of intermetallics R3Ni13-xCoxB2 (R=Y, Nd and Sm) with Nd3Ni13B2-type structure and the site preferences of the transition element Co by using a series of interatomic pair potentials. The space group remains unchanged upon substitution of Co for Ni in R3Ni13-xCoxB2 and the calculated lattice constants are found to agree with reports in literatures. The calculated cohesive energy curves show that Co atoms substitute for Ni with a strong preference for the 3g sites and the order of site preference is 3g, 4h and 6i. Moreover, the total and partial phonon densities of states are first evaluated for the R3Ni13B2 compounds with the hexagonal Nd3Ni13B2-type structure.

Preferred clusters in metallic glasses

Yang Liang, Guo Gu-Qing
Chin. Phys. B, 2010, 19 (12): 126101 doi: 10.1088/1674-1056/19/12/126101
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In this work, we present a feasible scheme based on framework of the sophisticated Voronoi tessellation method in order to evaluate what clusters should be preferred for building blocks in any given metallic glass, by analysing the fivefold-symmetry axes as well as the degree of structural regularity in various clusters. This scheme is well proved by a group of experiments and calculations, which may have broad implications for exploration of obtaining explicit and proper structural pictures, and understanding the structural origin of the unique properties and glass forming ability in these novel amorphous alloys.

Study on the impedance of aligned carbon microcoils embedded in silicone rubber matrix

Zhu Ya-Bo, Zhang Lin, Guo Li-Tong, Xiang Dong-Hu
Chin. Phys. B, 2010, 19 (12): 126102 doi: 10.1088/1674-1056/19/12/126102
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This paper reports that carbon microcoils are grown through a chemical vapour deposit process, they are then embedded in silicone rubber, and manipulated to parallel with each other along their axes in the resulting composite. The impedance |Z| as well as phase angle θ of both the original carbon microcoil sheets and the aligned carbon microcoil/silicone rubber composites are measured. The results illustrate that carbon microcoils in different forms show different alternating current electric properties. The aligned carbon microcoils in the composites show stable parameters for f<104 Hz but a sharp decrease in both |Z| and θ for frequencies >104 Hz, which will also change as the carbon microcoils are extended. But, the original sheets have a pure resistance with their parameters stable throughout the entire alternating current frequency range investigated.

Wettability and formation mechanism of ZnO micro-spheres composed film

Yang Zhou, Xu Xiao-Liang, Gong Mao-Gang, Liu Ling, Liu Yan-Song
Chin. Phys. B, 2010, 19 (12): 126103 doi: 10.1088/1674-1056/19/12/126103
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This paper reports that the film composed of flower-like ZnO micro-spheres, which consists of nano-sheets, is fabricated by chemical bath deposition. By adding hydrogen fluoride (HF) into the reaction solution, which contains zinc nitrate hexahydrate and hexamethylenetetramine, the ZnO crystal growth process is changed and the film composed by ZnO micro-spheres is obtained after keeping the reaction solution at 95 oC for 2 h. The morphology, crystal phase and wettability of the sample are characterized by scanning electron microscope, x-ray diffraction and contact angle meter, respectively. The results show that the film has the micro-nano compound structure. After modification with heptadecafluorodecyltrimethoxy-silane, the wettability of the film changed from superhydrophilicity to superhydrophobicity, on which water contact angle and the sliding angle are 154o and less than 5o for 8-μL water droplet, respectively. Additionally, the formation mechanism of the ZnO micro-sphere is also discussed.

Dendritic sidebranches of a binary system with enforced flow

Li Xiang-Ming, Wang Zi-Dong
Chin. Phys. B, 2010, 19 (12): 126401 doi: 10.1088/1674-1056/19/12/126401
Full Text: [PDF 291 KB] (Downloads:520)
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In the present paper, the problem of sidebranches in the binary dendritic growth with enforced flow is studied. The positions of the first sidebranch and spacing of dendritic sidebranches are presented. For the neutral stable mode of dendritic growth, effects of various parameters on sidebranches are analysed. Our result shows that sidebranches are produced behind a critical point ξ'C.

The effect of deposition temperature on the intermixing and microstructure of Fe/Ni thin film

Chen Shang-Da, Wang Tao, Zheng De-Li, Zhou Yi-Chun
Chin. Phys. B, 2010, 19 (12): 126801 doi: 10.1088/1674-1056/19/12/126801
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The physical vapour deposition of Ni atoms on α-Fe(001) surface under different deposition temperatures were simulated by molecular dynamics to study the intermixing and microstructure of the interfacial region. The results indicate that Ni atoms hardly penetrate into Fe substrate while Fe atoms easily diffuse into Ni deposition layers. The thickness of the intermixing region is temperature-dependent, with high temperatures yielding larger thicknesses. The deposited layers are mainly composed of amorphous phase due to the abnormal deposition behaviour of Ni and Fe. In the deposited Ni-rich phase, the relatively stable metallic compound B2 structured FeNi is found under high deposition temperature conditions.

Magnetic properties of nitrogen doped ZnO

Shi Li-Bin, Jin Jian-Wei, Zhang Tian-Qian
Chin. Phys. B, 2010, 19 (12): 127001 doi: 10.1088/1674-1056/19/12/127001
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Using the first principle method based on density functional theory, this paper studies the electronic structure and the ferromagnetic stability in N-doped ZnO. The calculated results based on local density approximation (LDA) and LDA+U method show that ferromagnetism coupling between N atoms is more energetically favourable for eight geometrically distinct configurations. The dominant ferromagnetic interaction is due to the hybridization between O 2p and N 2p. The origin of the ferromagnetic state in N doped ZnO is discussed by analysing coupling between N 2p levels. We also analyse N dopant concentration and lattice strain effect on ferromagnetism.

First-principles study of disordering tendencies in Gd2B2O7 (B= Ti, Sn, Zr) compounds

Chen Zhong-Jun, Tian Dong-Bin
Chin. Phys. B, 2010, 19 (12): 127101 doi: 10.1088/1674-1056/19/12/127101
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This paper performs the density functional theory calculations to obtain some factors influencing the response of pyrochlores Gd2B2O7 (B= Ti, Sn, Zr) to ion irradiation-induced amorphization. The 48f oxygen position parameter x, cohesive energy, bond type and defect-formation energy are discussed. The results show that parameter x can be used to indicate the disordering tendencies within a given pyrochlore family. Bond type, cohesive energy and defect-formation energies can be used to explain some experimental observations, but they are not determined exclusively by radiation ''resistance'' for a different pyrochlore family.

Electronic structures and magnetocrystalline anisotropy energies of ordered Co1-xNix alloys: a first principles study

Zhang Sha, Pang Hua, Fang Yang, Li Fa-Shen
Chin. Phys. B, 2010, 19 (12): 127102 doi: 10.1088/1674-1056/19/12/127102
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The electronic structures and magnetocrystalline anisotropy (MA) of ordered hexagonal close-packed (hcp) Co1-xNix alloys are studied using the full-potential linear-augmented-plane-wave (FLAPW) method with generalized gradient approximation (GGA). Great changes of magnetocrystalline anisotropy energy (MAE) are gained with different Ni compositions. Also, in-plane magnetocrystalline anisotropy is obtained for Co15Ni in which the Snoek's limit is exceeded. It is found that the changes of the symmetry of the crystal field on Ni induce small variations in band structures around the Fermi level under different compositions, which plays an important role in modulating the magnetization direction, where the hybridization between Co-3d and Ni-3d orbits is of special importance in deciding the magnetocrystalline anisotropy of itinerant states. The rigid-band model is inapplicable to explain the evolution of magnetocrystalline anisotropy energy with Ni composition, and it is also inadequate to predict the magnetocrystalline anisotropy energy through the anisotropy of the orbital magnetic moment.

First principle calculation of elastic and thermodynamic properties of stishovite

Liu Xun, Zhou Xian-Ming, Zeng Zhao-Yi
Chin. Phys. B, 2010, 19 (12): 127103 doi: 10.1088/1674-1056/19/12/127103
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Using ab initio plane-wave pseudo-potential density functional theory method, the elastic constants and band structures of stishovite were calculated. The calculated elastic constants under ambient conditions agree well with previous experimental and theoretical data. C13, C33, C44, and C66 increase nearly linearly with pressure while C11 and C12 show irregularly changes with pressure over 20 GPa. The shear modulus (C11-C12)/2 was observed to decrease drastically between 40 GPa and 50 GPa, indicating acoustic mode softening in consistency with the phase transition to CaCl2-type structure around 50 GPa. The calculated band structures show no obvious difference at 0 and 80 GPa, being consistent with the high incompressibility of stishovite. With a quasi-harmonic Debye model, thermodynamic properties of stishovite were also calculated and the results are in good agreement with available experimental data.

The calculation of energy gaps in small single-walled carbon nanotubes within a symmetry-adapted tight-binding model

Yang Jie, Dong Quan-Li, Jiang Zhao-Tan, Zhang Jie
Chin. Phys. B, 2010, 19 (12): 127104 doi: 10.1088/1674-1056/19/12/127104
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This paper studies in detail the electronic properties of the semimetallic single-walled carbon nanotubes by applying the symmetry-adapted tight-binding model. It is found that the hybridization of πσ states caused by the curvature produces an energy gap at the vicinity of the Fermi level. Such effects are obvious for the small zigzag and chiral single-walled carbon nanotubes. The energy gaps decrease as the diameters and the chiral angles of the tubes increase, while the top of the valence band and the bottom of the conduction band of armchair tubes cross at the Fermi level. The numeral results agree well with the experimental results.

A scattering matrix approach to quantum pumping: beyond the small-AC-driving-amplitude limit

Zhu Rui
Chin. Phys. B, 2010, 19 (12): 127201 doi: 10.1088/1674-1056/19/12/127201
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In the adiabatic and weak-modulation quantum pump, net electron flow is driven from one reservoir to another by absorbing or emitting an energy quantum from or to the reservoirs. This paper considers high-order dependence of the scattering matrix on the time. Non-sinusoidal behaviour of strong pumping is revealed. The relation between the pumped current and the ac driving amplitude varies from power of 2, 1 to 1/2 when stronger modulation is exerted. Open experimental observation can be interpreted by multi-energy-quantum-related processes.

Spin-polarization-dependent transport in a quantum dot array coupled with an Aharonov–Bohm ring

Wang Rui, Kong Ling-Min, Zhou Yun-Qing, Zhang Cun-Xi, Xing Zhi-Yong
Chin. Phys. B, 2010, 19 (12): 127202 doi: 10.1088/1674-1056/19/12/127202
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In this paper the quantum transport in a dot-array coupled with an Aharonov–Bohm (AB) ring is investigated via single-band tight-binding Hamiltonian. It is shown that the output spin current is a periodic function of the magnetic flux in the quantum unit Φ0. The resonance positions of the total transmission probability do not depend on the size of the AB ring but the electronic spectrum. Moreover, the persistent currents in the AB ring is also spin-polarization dependent and different from the isolated AB ring where the persistent current is independent of spin polarization.

Design and manufacture of planar GaAs Gunn diode for millimeter wave application

Huang Jie, Yang Hao, Tian Chao, Dong Jun-Rong, Zhang Hai-Ying, Guo Tian-Yi
Chin. Phys. B, 2010, 19 (12): 127203 doi: 10.1088/1674-1056/19/12/127203
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GaAs-based planar Gunn diodes with AlGaAs hot electron injector have been successfully developed to be used as a local oscillator of 76 GHz in monolithic millimeter-wave integrated circuits. We designed two kinds of structure diode, one has a fixed distance between the anode and cathode, but has variational cathode area, the other has a fixed cathode area, but has different distances between two electrodes. The fabrication of Gunn diode is performed in accordance with the order of operations: cathode defining, mesa etching, anode defining, isolation, passivation, via hole and electroplating. A peak current density of 29.5 kA/cm2 is obtained. And the characteristics of negative differential resistance and the asymmetry of the current–voltage curve due to the AlGaAs hot electron injector are discussed in detail. It is demonstrated that the smaller size of active area corresponds to the smaller current, and the shorter distance between anode and cathode also corresponds to the lower threshold voltage and higher peak current, and hot electron injector can effectively enhance the radio frequency conversion efficiency and output power.

The electrical, optical properties of AlSb polycrystalline thin films deposited by magnetron co-sputtering without annealing

Huang Zheng, Wu Li-Li, Li Bing, Hao Xia, He Jian-Xiong, Feng Liang-Huan, Li Wei, Zhang Jing-Quan, Cai Yap-Ping
Chin. Phys. B, 2010, 19 (12): 127204 doi: 10.1088/1674-1056/19/12/127204
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In order to fabricate AlSb polycrystalline thin films without post annealing, this paper studies a technology of magnetron co-sputtering onto intentionally heated substrate. It compares the structural characteristics and electrical properties of AlSb films which are deposited at different substrate temperatures. It finds that the films prepared at a substrate temperature of 450 oC exhibit an enhanced grain growth with an average grain size of 21 nm and the lattice constant is 0.61562 nm that goes well with unstained lattice constant (0.61355 nm). The ln(σdark) ~1/T curves show that the conductivity activation energy is about 0.38 eV when the film is deposited at 450 oC without an annealing. The transmittance and reflectance spectra show that the film deposited at 450 oC has an optical band gap of 1.6 eV. These results indicate that we have prepared AlSb polycrystalline films which do not need a post annealing.

Transmission properties of frequency selective structures with air gaps

Meng Zhi-Jun, Wang Li-Feng, Lü Ming-Yun, Wu Zhe
Chin. Phys. B, 2010, 19 (12): 127301 doi: 10.1088/1674-1056/19/12/127301
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The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

Effects of a one-dimensional surface defect on designer surface plasmon polaritons

Ding Lan, Liu Jin-Song, Wang Ke-Jia
Chin. Phys. B, 2010, 19 (12): 127302 doi: 10.1088/1674-1056/19/12/127302
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By using a finite difference time domain (FDTD) method, the effects of a one-dimensional (1D) surface defect on designer surface plasmon polaritons (designer SPPs) supported by a 1D metallic grating in THz domain are investigated. When the size of the defect is in a special range which is not too large, the designer SPPs reflected and scattered by the defect are weak enough to be neglected. The defect only induces a disturbance in the energy distribution of the designer SPP supported by the whole defect grating. If the defect size exceeds the said range, the reflecting and scattering are dominant in the influences of the defect on designer SPPs. Our analysis opens opportunities to control and direct designer SPPs by introducing a 1D defect, especially in low frequency domain.

Electrical characteristics of SiGe-on-insulator nMOSFET and SiGe-silicon-on-aluminum nitride nMOSFET

Liu Hong-Xia, Li Bin, Li Jin, Yuan Bo, Hao Yue
Chin. Phys. B, 2010, 19 (12): 127303 doi: 10.1088/1674-1056/19/12/127303
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This paper investigates the electrical characteristics and temperature distribution of strained Si/SiGe n-type metal oxide semiconductor field effect transistor (nMOSFET) fabricated on silicon-on-aluminum nitride (SOAN) substrate. This novel structure is named SGSOAN nMOSFET. A comparative study of self-heating effect of nMOSFET fabricated on SGOI and SGSOAN is presented. Numerical results show that this novel SGSOAN structure can greatly eliminate excessive self-heating in devices, which gives a more promising application for silicon on insulator to work at high temperatures.

Performance comparison of Pt/Au and Ni/Au Schottky contacts on AlxGa1-x N/GaN heterostructures at high temperatures

Lin Fang, Shen Bo, Lu Li-Wu, Ma Nan, Xu Fu-Jun, Miao Zhen-Lin, Song Jie, Liu Xin-Yu, Wei Ke, Huang Jun
Chin. Phys. B, 2010, 19 (12): 127304 doi: 10.1088/1674-1056/19/12/127304
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In contrast with Au/Ni/Al0.25Ga0.75N/GaN Schottky contacts, this paper systematically investigates the effect of thermal annealing of Au/Pt/Al0.25Ga0.75N/GaN structures on electrical properties of the two-dimensional electron gas in Al0.25Ga0.75N/GaN heterostructures by means of temperature-dependent Hall and temperature-dependent current–voltage measurements. The two-dimensional electron gas density of the samples with Pt cap layer increases after annealing in N2 ambience at 600 du while the annealing treatment has little effect on the two-dimensional electron gas mobility in comparison with the samples with Ni cap layer. The experimental results indicate that the Au/Pt/Al0.25Ga0.75N/GaN Schottky contacts reduce the reverse leakage current density at high annealing temperatures of 400–600 du. As a conclusion, the better thermal stability of the Au/Pt/Al0.25Ga0.75N/GaN Schottky contacts than the Au/Ni/Al0.25Ga0.75N/GaN Schottky contacts at high temperatures can be attributed to the inertness of the interface between Pt and AlxGa1-xN.

Filling dependence of correlation exponents and metal-Mott insulator transition in strongly correlated electron systems

Lin Ming-Xi, Qi Sheng-Wen
Chin. Phys. B, 2010, 19 (12): 127401 doi: 10.1088/1674-1056/19/12/127401
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Using a universal relation between electron filling factor and ground state energy, this paper studies the dependence of correlation exponents on the electron filling factor of one-dimensional extended Hubbard model in a strong coupling regime, and demonstrates that in contrast to the usual Hubbard model (gc=1/2), the dimensionless coupling strength parameter gc heavily depends on the electron filling, and it has a "particle–hole" symmetry about electron quarter filling point. As increasing the nearest neighbouring repulsive interaction, the single particle spectral weight is transferred from low energy to high energy regimes. Moreover, at electron quarter filling, there is a metal-Mott insulator transition at the strong coupling point gc=1/4, and this transition is a continuous phase transition.

Nonlocal Andreev reflection with Rashba spin–orbital interaction in a triple-quantum-dot ring

Peng Ju, Yu Hua-Ling, Zuo Fen
Chin. Phys. B, 2010, 19 (12): 127402 doi: 10.1088/1674-1056/19/12/127402
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We theoretically studied the nonlocal Andreev reflection with Rashba spin–orbital interaction in a triple-quantum-dot (QD) ring, which is introduced as Rashba spin–orbital interaction to act locally on one component quantum dot. It is found that the electronic current and spin current are sensitive to the systematic parameters. The interdot spin-flip term does not play a leading role in causing electronic and spin currents. Otherwise the spin precessing term leads to shift of the peaks of the the spin-up and spin-down electronic currents in different directions and results in the spin current. Moreover, the spin–orbital interaction suppresses the nonlocal Andreev reflection, so we cannot obtain the pure spin current.

Magnetic and transport properties of Dy substituted layered perovskite La1.3Sr1.7Mn2O7

Zheng Lin, Lu Yi, Zhao Jian-Jun, Zhang Xiang-Qun, Xing Ru, Wu Hong-Ye, Jin Xiang, Zhou Min, Cheng Zhao-Hua
Chin. Phys. B, 2010, 19 (12): 127501 doi: 10.1088/1674-1056/19/12/127501
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The effect of Dy substitution for La site in layered manganese oxides La1.3Sr1.7Mn2O7 on the magnetic and electrical properties has been investigated. With the La3+ substituting by Dy3+, the long range three-dimensional ferromagnetism transition and the insulator–metal transition disappear. These effects are attributed to the lattice distortion due to the substitution of the smaller Dy3+. Addtionally, the small Dy3+ is inclined to occupy the R site which is in the rock-salt layer, then the distribution of La, Sr, Dy ions in Dy-doped sample should be more orderly than that in La1.3Sr1.7Mn2O7, so there is only one insulator–metal transition in the ρT curve of the sample with x=0.05 and x=0.1.

Effects of anisotropy on quantum fluctuation of a three-layer system with mutisublattice

Jiang Wei, Zhang Fan, Guan Hong-Yu, Liang Ji-Yan
Chin. Phys. B, 2010, 19 (12): 127502 doi: 10.1088/1674-1056/19/12/127502
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The quantum fluctuations of a three-layer Heisenberg model with six sublattices are studied by the retarded Green's function method and the spin-wave theory. The effects of anisotropy on the quantum fluctuations at zero temperature are discussed. The results show that the interlayer anisotropy plays an important role in balancing the quantum competitions.

Epitaxy surface effect on the first-order phase transition properties in a ferroelectric thin film

Lu Zhao-Xin, Teng Bao-Hua, Yang Xin, Rong Yong-Hui, Zhang Huai-Wu
Chin. Phys. B, 2010, 19 (12): 127701 doi: 10.1088/1674-1056/19/12/127701
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By modifying the interchange interactions and the transverse fields on the epitaxy surface layer, this paper studies the phase transition properties of an n-layer ferroelectric thin film by the Fermi-type Green's function technique based on the transverse Ising model with a four-spin interaction. The special attention is given to the effect of the epitaxy surface layer on the first-order phase transition properties in the parameter space constructed by the ratios of the bulk transverse field and the bulk four-spin interaction to the bulk two-spin interaction with the framework of the higher-order decoupling approximation to the Fermi-type Green's function. The results show that the first-order phase transition properties will be changed significantly due to the modification of interchange interaction and transverse field parameters on the epitaxy surface layer. The dependence of the first-order phase transition properties on the thickness of ferroelectric thin films is also discussed.

Enhanced deep ultraviolet emission from Si-doped AlxGa1-xN/AlN MQWs

Li Da-Bing, Hu Wei-Guo, Miyake Hideto, Hiramatsu Kazumasa, Song Hang
Chin. Phys. B, 2010, 19 (12): 127801 doi: 10.1088/1674-1056/19/12/127801
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Undoped and Si-doped AlGaN/AlN multiple quantum wells (MQWs) were grown on AlN/Sapphire templates by metalorganic phase vapor epitaxy. High-resolution x-ray diffraction measurements showed the high interface quality of the MQWs little affected by Si-doping. Room-temperature (RT) cathodoluminescence measurements demonstrated a significant enhancement of the RT deep ultraviolet emission at about 240 nm from the AlGaN/AlN MQWs by Si doping. The mechanism of the improved emission efficiency was that the Si-doping partially screens the internal electric field and thus leads to the increase of the overlap between electron and hole wavefunctions. Further theoretical simulation also supports the above results.

Optical characteristic and gap states distribution of amorphous SnO2:(Zn,In) film

Zhang Zhi-Guo
Chin. Phys. B, 2010, 19 (12): 127802 doi: 10.1088/1674-1056/19/12/127802
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In this paper the fabrication technique of amorphous SnO2:(Zn,In) film is presented. The transmittance and gap-states distribution of the film are given. The experimental results of gap-states distribution are compared with the calculated results by using the facts of short range order and lattice vacancy defect of the gap states theory. The distribution of gap state has been proved to be discontinuous due to the short-range order of amorphous structure.

Optimization and design of pigments for heat-insulating coatings

Wang Guang-Hai, Zhang Yue
Chin. Phys. B, 2010, 19 (12): 127803 doi: 10.1088/1674-1056/19/12/127803
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This paper reports that heat insulating property of infrared reflective coatings is obtained through the use of pigments which diffuse near-infrared thermal radiation. Suitable structure and size distribution of pigments would attain maximum diffuse infrared radiation and reduce the pigment volume concentration required. The optimum structure and size range of pigments for reflective infrared coatings are studied by using Kubelka–Munk theory, Mie model and independent scattering approximation. Taking titania particle as the pigment embedded in an inorganic coating, the computational results show that core-shell particles present excellent scattering ability, more so than solid and hollow spherical particles. The optimum radius range of core-shell particles is around 0.3~1.6μm. Furthermore, the influence of shell thickness on optical parameters of the coating is also obvious and the optimal thickness of shell is 100–300 nm.

Optical temperature sensor based on up-conversion fluorescence emission in Yb3+:Er3+ co-doped ceramics glass

Xu Wei, Li Cheng-Ren, Cao Bao-Sheng, Dong Bin
Chin. Phys. B, 2010, 19 (12): 127804 doi: 10.1088/1674-1056/19/12/127804
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Yb3+:Er3+ co-doped oxy-fluoride ceramics glass has been prepared. The mechanism of up-conversion emissions about Er3+ was discussed, and the temperature properties of green up-conversion fluorescence between 303 and 823 K were investigated. The results show that the sensitivity of this sample reaches its maximum value, about 0.0047 K-1, when the temperature is 383 K, indicating that this kind of sample can be used as high temperature and high sensitivity optical temperature sensor.

A novel low-swing interconnect optimization model with delay and bandwidth constraints

Zhu Zhang-Ming, Hao Bao-Tian, Yang Yin-Tang, Li Yue-Jin
Chin. Phys. B, 2010, 19 (12): 127805 doi: 10.1088/1674-1056/19/12/127805
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Interconnect power and repeater area are important in the interconnect optimization of nanometer scale integrated circuits. Based on the RLC interconnect delay model, by wire sizing, wire spacing and adopting low-swing interconnect technology, this paper proposed a power-area optimization model considering delay and bandwidth constraints simultaneously. The optimized model is verified based on 65-nm and 90-nm complementary metal-oxide semiconductor (CMOS) interconnect parameters. The verified results show that averages of 36% of interconnect power and 26% of repeater area can be saved under 65-nm CMOS process. The proposed model is especially suitable for the computer-aided design of nanometer scale systems-on-chip.

Plasmonic interactions between a perforated gold film and a thin gold film

Zhou Xin, Li Hong-Jian, Xie Su-Xia, Fu Shao-Li, Xu Hai-Qing, Wu Jin-Jun
Chin. Phys. B, 2010, 19 (12): 127806 doi: 10.1088/1674-1056/19/12/127806
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Based on the finite difference time domain method, we investigated theoretically the optical properties and the plasmonic interactions between a gold film perforated with periodic sub-wavelength holes and a thin gold film. We showed that the plasmon resonant energies and intensities depend strongly on the thicknesses of the two films and the lattice constant. Based on the distributions of normal electric field component Ez, tangential electric field component Ey and total energy, we showed that the optical transmission is due to the collaboration of the localized waveguide resonance, the surface plasmon resonance and the coupling of the flat-surface plasmon of the two layers.

Luminescence of Ce3+ in lanthanum silicon oxynitride

Hu Long, Xu Xue-Wen, Lu Zun-Ming, Fan Ying, Li Yang-Xian, Tang Cheng-Chun
Chin. Phys. B, 2010, 19 (12): 127807 doi: 10.1088/1674-1056/19/12/127807
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The luminescence properties of lanthanum silicon oxynitride (La-Si-O-N) series doped by trivalent Ce ions have been investigated to seek for tunable wavelength-conversion phosphor for white light emitting diode applications. Four compound hosts of LaSiO2N, La4Si2O7N2, La5Si3O12N, and La2Si6O3N8 were synthesized and examined in this work. Crystallographic examination for the equal amount of Ce3+ substitution indicated that the covalency degree decreased in a sequence LaSiO2N > La2Si6O3N8 > La4Si2O7N2 > La5Si3O12N, not simply in correlation to the ratio of N3/O2. Excitation and emission spectrum measurements showed the main features of Ce3+ luminescence in the series: the centre of gravity of 5d bands depends on crystal-field splitting more strongly than that on covalency of Ce–N bonding; nephelauxetic effect could not be observed clearly for the investigated series; to some extent Stokes shift was dominated by crystal-field splitting rather than Ce–N covalency degree.

A red oxide phosphor, Sr2ScAlO5:Eu2+ with perovskite-type structure, for white light-emitting diodes

Zhou Tian-Liang, Song Zhen, Song Xi-Ping, Bian Liu, Liu Quan-Lin
Chin. Phys. B, 2010, 19 (12): 127808 doi: 10.1088/1674-1056/19/12/127808
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Sr2ScAlO5:Eu2+, a red oxide phosphor with a perovskite-type structure, has been synthesized through a solid-state reaction and its luminescence properties have been investigated. An absorption band centering at 450 nm is observed from the diffuse reflection spectra and the excitation spectra, indicating that the phosphor can match perfectly with the blue light of InGaN light-emitting diodes. A broad red emission band at 620 nm is found from the emission spectra, originating from the 4f65d–4f7 transition of the Eu2+ ions. The best doping content of Eu in this material is about 5%. Sr2ScAlO5:Eu2+ is a highly promising red phosphor for use in white light-emitting diodes.

Morphology and photoluminescence of BaAl12O19:Mn2+ green phosphor prepared by flux method

Zhou Jun, Wang Yu-Hua, Liu Bi-Tao, Liu Ji-Di
Chin. Phys. B, 2010, 19 (12): 127809 doi: 10.1088/1674-1056/19/12/127809
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This paper reports that the green phosphor BaAl11.9O19:0.1Mn2+ is prepared by a flux assisted solid state reaction method. The effect of flux systems on the crystal structure, morphology and luminescent properties of the phosphor are studied in detail. The samples are characterized by the application of x-ray diffraction patterns, scanning electron microscopy patterns, luminescent spectra and decay curves. The results show that a pure phase BaAl12O19 can be achieved at the firing temperature above 1300 du by adding the proper flux system, the firing temperature is reduced at least 200 du in comparison with the conventional solid state reaction method. Maximum photoluminescence emission intensity is observed at 517 nm for (AlF3+Li2CO3) flux system under vacuum ultraviolet region (147 nm) excitation. The photoluminescence emission intensity and the decay time of these phosphor is found to be more superior to that of the corresponding sample prepared by the conventional solid state reaction method implying the suitability of this route for the preparation of display device worthy phosphor materials.
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