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Volume 27 Issue 4
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Prisoner's Dilemma on Co-Evolving Networks without Strategy Update
DAI Qiong-Lin, YANG Jun-Zhong
Chin. Phys. Lett. 2010, 27 (4): 040201 .   DOI: 10.1088/0256-307X/27/4/040201
Abstract   PDF(pc) (366KB) ( 597 )

We investigate the game theory in a structured population with the assumption that the evolution of network structure is far faster than that of strategy update. We find that the degree distribution for the final network consists of two distinct parts: the low degree part which is contributed to by defectors and a broadband in the regime with high degree which is formed by cooperators. The structure of the final network and the final strategy pattern have also been numerically proved to be independent of the game parameters.

Lie Algebra and Lie Super Algebra for Integrable Couplings of C-KdV Hierarchy
TAO Si-Xing, XIA Tie-Cheng
Chin. Phys. Lett. 2010, 27 (4): 040202 .   DOI: 10.1088/0256-307X/27/4/040202
Abstract   PDF(pc) (333KB) ( 445 )

Based on the constructed Lie algebra and Lie super algebra, the integrable couplings and super-integrable couplings of the C-KdV hierarchy are obtained respectively. Furthermore, its super-Hamiltonian structures are presented by using super-trace identity.

Solutions to the Modified Pöschl-Teller Potential in D-Dimensions
D. Agboola
Chin. Phys. Lett. 2010, 27 (4): 040301 .   DOI: 10.1088/0256-307X/27/4/040301
Abstract   PDF(pc) (332KB) ( 397 )

An approximate solution of the D-dimensional Schrödinger equation with the modified Pöschl-Teller potential is obtained with an approximation of the centrifugal term. Solution to the corresponding hyper-radial equation is given using the conventional Nikiforov-Uvarov method. The normalization constants for the Pöschl-Teller potential are also computed. The expectation values of -2> and are also obtained using the Feynman-Hellmann theorem.

Suppression of Chaos in a Bose-Einstein Condensate Loaded into a Moving Optical Superlattice Potential
LUO Xiao-Bing, XIA Xiu-Wen, ZHANG Xiao-Fei,
Chin. Phys. Lett. 2010, 27 (4): 040302 .   DOI: 10.1088/0256-307X/27/4/040302
Abstract   PDF(pc) (397KB) ( 554 )

We have shown that the application of modulating the secondary lattice is an efficient route to suppressing the generation of chaotic traveling waves of a Bose-Einstein Condensate with attractive interatomic interaction loaded into a moving optical superlattice consisting of two lattices. With the Melnikov method, we obtain the optimal value of the relative phase between the two lattice harmonics for the control of chaos. We also find that the regularization route as the potential depth of the secondary lattice is varied and fairly rich, including the period-doubling bifurcations.

Correlations Existing in Three-Qubit Product States
SUN Chun-Xiao, SHI Ming-Jun, DU Jiang-Feng
Chin. Phys. Lett. 2010, 27 (4): 040303 .   DOI: 10.1088/0256-307X/27/4/040303
Abstract   PDF(pc) (373KB) ( 399 )

Analytic results of the relationship between local noncommutativity and non-violations of Svetlichny inequalities for three-qubit separable states are obtained. It is shown that the converse trade-off relations presented by Seevinck and Uffinck [Phys. Rev. A 2007 76 042105] do not always hold for three-qubit states, and that there exists some correlation even though the state is the simple product state.

Unitarity Schrödinger Equation and Ground State Properties of the Finite Trapped Superfluid Fermi Gases in a BCS-BEC Crossover
ZHANG Wen-Yuan, WANG Cheng-Tao, MA Yong-Li
Chin. Phys. Lett. 2010, 27 (4): 040304 .   DOI: 10.1088/0256-307X/27/4/040304
Abstract   PDF(pc) (686KB) ( 363 )

On the basis of quantum hydrodynamical equations we derive a unitarity Schrödinger equation of a finite trapped superfluid Fermi gas valid in the whole interaction regime from BCS superfluid to BEC. This equation is just the Ginzburg-Laudau-type equation for the fermionic Cooper pairs in the BCS side, the Gross-Pitaevskii-type equation for the bosonic dimers in the BEC side, and a unitarity equation for a strongly interacting Fermi superfluid in the unitarity limit. By taking a modified Gauss-like trial wave function, we solve the unitarity Schrödinger equation, calculate the energy, chemical potential, sizes and profiles of the ground-state condensate, and discuss the properties of the ground state in the entire BCS-BEC crossover regimes.

Ground State Eigenfunction of Spheroidal Wave Functions
TIAN Gui-Hua, ZHONG Shu-Quan
Chin. Phys. Lett. 2010, 27 (4): 040305 .   DOI: 10.1088/0256-307X/27/4/040305
Abstract   PDF(pc) (292KB) ( 447 )

We study the spin-weighted spheroidal wave functions in the case of s=m=0. Their eigenvalue problem is investigated by the perturbation method in supersymmetric quantum mechanics. In the first three terms of parameter α=a2w2, the ground eigenvalue and eigenfunction are obtained. The obtained ground eigenfunction is elegantly in closed forms. These results are new and very useful for the application of the spheroidal wave functions.

Effective Mass Dirac--Morse Problem with any κ-value
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Chin. Phys. Lett. 2010, 27 (4): 040306 .   DOI: 10.1088/0256-307X/27/4/040306
Abstract   PDF(pc) (350KB) ( 381 )

The Dirac-Morse problem is investigated within the framework of an approximation to the term proportional to 1/r2 in the view of the position-dependent mass formalism. The energy eigenvalues and corresponding wave functions are obtained by using the parametric generalization of the Nikiforov-Uvarov method for any κ-value. We also study the approximate energy eigenvalues, and the corresponding wave functions in the case of the constant-mass for pseudospin, and spin cases, respectively.

Preparation of Arbitrary Four-Qubit W State with Atomic Ensembles via Rydberg Blockade
HAN Yang, WU Chun-Wang, GAO Ming, LIANG Lin-Mei, CHEN Ping-Xing, LI Cheng-Zu
Chin. Phys. Lett. 2010, 27 (4): 040307 .   DOI: 10.1088/0256-307X/27/4/040307
Abstract   PDF(pc) (421KB) ( 409 )

The generation of various entangled states is an essential task in quantum information processing. Recently, a scheme (PRA 79, 022304) has been suggested for generating Greenberger-Horne-Zeilinger state and cluster state with atomic ensembles based on the Rydberg blockade. Using similar resources as the earlier scheme, here we propose an experimentally feasible scheme of preparing arbitrary four-qubit W class of maximally and non-maximally entangled states with atomic ensembles in a single step. Moreover, we carefully analyze the realistic noises and predict that four-qubit W states can be produced with high fidelity (F~0.994) via our scheme.

Probabilistic Teleportation of Two-Particle State of General Formation in Ion Trap
LIAN Shi-Man, YAN Feng-Li
Chin. Phys. Lett. 2010, 27 (4): 040308 .   DOI: 10.1088/0256-307X/27/4/040308
Abstract   PDF(pc) (288KB) ( 480 )

We propose a scheme for the probabilistic teleportation of an unknown two-particle state of general formation in ion trap. It is shown that one can realize experimentally this teleportation protocol of two-particle state with presently available techniques.

Preparation of Cluster States of Atomic Qubits in Cavity QED
GUO Yu, DENG Hong-Liang
Chin. Phys. Lett. 2010, 27 (4): 040309 .   DOI: 10.1088/0256-307X/27/4/040309
Abstract   PDF(pc) (314KB) ( 410 )
We propose an optical scheme to generate cluster states of atomic qubits, with each trapped in separate optical cavity, via atom-cavity-laser interaction. The quantum information of each qubit is encoded on the degenerate ground states of the atom, hence the entanglement between them is relatively stable against spontaneous emission. A single-photon source and two classical fields are employed in the present scheme. By controlling the sequence and time of atom-cavity-laser interaction, we show that the atomic cluster states can be produced deterministically
Tripartite Entanglement via Microwave Driven Atomic Coherence
JIN Li-Xia, LüXin-You, SONG Pei-Jun, YANG Xiao-Xue
Chin. Phys. Lett. 2010, 27 (4): 040310 .   DOI: 10.1088/0256-307X/27/4/040310
Abstract   PDF(pc) (401KB) ( 406 )

We propose a new scheme to achieve the tripartite entanglement based on the standard criteria [Phys. Rev. A 67 (2003) 052315] in a inverse-tripod atomic system. In our scheme, the atomic coherence is introduced by two microwave fields which drive the upper three levels of atom. By numerically simulating the dynamics of system, we investigate the generation and evolution of entanglement in the presence of atom and cavity decay. As a result, the present research provides an efficient approach to achieve fully tripartite entanglement with different frequencies and initial states for each entangled mode, which may have impact on the progress of multicolored multi-notes quantum information networks.

Absorption Cross Section and Decay Rate of Stationary Axisymmetric Einstein-Maxwell Dilaton Axion Black Hole
LIU Chang-Qing
Chin. Phys. Lett. 2010, 27 (4): 040401 .   DOI: 10.1088/0256-307X/27/4/040401
Abstract   PDF(pc) (379KB) ( 425 )

The low energy absorption cross section and the decay rate of the stationary Axisymmetric Einstein-Maxwell Dilaton Axion black hole for massless scalar particles is calculated analytically. It is shown that the partial absorption cross section increases as the rotating parameter a and the absolute value of the dilaton D decreases. It is also shown that the partial absorption cross section is not always positive due to superradiance factor ω-mΩ. However, the decay rate of this black hole is always positive.

Bifurcation Analysis of the Full Velocity Difference Model
JIN Yan-Fei, XU Meng
Chin. Phys. Lett. 2010, 27 (4): 040501 .   DOI: 10.1088/0256-307X/27/4/040501
Abstract   PDF(pc) (326KB) ( 590 )

Bifurcation is investigated with the full velocity difference traffic model. Applying the Hopf theorem, an analytical Hopf bifurcation calculation is performed and the critical road length is determined for arbitrary numbers of vehicles. It is found that the Hopf bifurcation critical points locate on the boundary of the linear instability region. Crossing the boundary, the uniform traffic flow loses linear stability via Hopf bifurcation and the oscillations appear.

Statistical Interaction Term of One-Dimensional Anyon Models
ZHU Ren-Gui, WANG An-Min
Chin. Phys. Lett. 2010, 27 (4): 040502 .   DOI: 10.1088/0256-307X/27/4/040502
Abstract   PDF(pc) (275KB) ( 395 )

A form of statistical interaction term of one-dimensional anyons is introduced, based on which one-dimensional anyon models are theoretically realized, and the statistical transmutation between bosons (or fermions) and anyons is established in quantum mechanics formalism. Two kinds of anyon models which are being studied are recovered and reexplained naturally in our formalism.

Entropic Stochastic Resonance Driven by Colored Noise
ZHAO Liang, LUO Xiao-Qin, WU Dan, ZHU Shi-Qun, GU Ji-Hua
Chin. Phys. Lett. 2010, 27 (4): 040503 .   DOI: 10.1088/0256-307X/27/4/040503
Abstract   PDF(pc) (475KB) ( 561 )

The phenomenon of entropic stochastic resonance (ESR) in a two-dimensional confined system driven by a transverse periodic force is investigated when the colored fluctuation is included in the system. Applying the method of unified colored noise approximation, the approximate Fokker-Planck equation can be derived in the absence of the periodic force. Through the escaping rate of the Brownian particle from one well to the other, the power spectral amplification can be obtained. It is found that increasing the values of the noise correlation time and the signal frequency can suppress the ESR of the system.

CP Violation in Λb → Λł+ł-Decay in the Four–Generation Standard Model
V. Bashiry, N. Shirkhanghah, K. Zeynali,
Chin. Phys. Lett. 2010, 27 (4): 041201 .   DOI: 10.1088/0256-307X/27/4/041201
Abstract   PDF(pc) (413KB) ( 323 )

We present the first study of CP asymmetry in Λb →Λ decay when a new weak phase comes through the extension of three-generation standard model to the four-generation standard model. Taking =0.01,0.02,0.03 with phase {60°-120°}, which is consistent with therate and the Bs mixing parameter ΔmBs, we find out that CP asymmetry is quite sensitive to the existence of fourth generation. It can serve as a good tool to search for new physics effects, in particular, to search for the fourth generation quarks (t', b') via their indirect manifestations in loop diagrams.

Determination of J/φ Event Number via J/φ→μ+μ- and J/φ→ e+e- at BESIII
LI Jiang, LIAO Xiao-Tao, YANG Ming, YANG Hong-Xun, XU Min, ZHANG Bing-Xin, SHEN Xiao-Yan, YANG Yong-Xu
Chin. Phys. Lett. 2010, 27 (4): 041301 .   DOI: 10.1088/0256-307X/27/4/041301
Abstract   PDF(pc) (472KB) ( 357 )

The decays of J/φ→μ+μ- and J/φ→ e+e- are studied by Monte-Carlo simulation, based on the Beijing Spectrometer (BES)Ⅲ offline software system. The methods of determination of the J/φ event number via J/φ→μ+μ- and J/φ→ e+e- are presented, respectively. These methods can be used to determine the J/φevent number for the coming BESⅢ J/φ data sample.

K and K* Exchange Effects in Lambda Hypernuclei
Chin. Phys. Lett. 2010, 27 (4): 042101 .   DOI: 10.1088/0256-307X/27/4/042101
Abstract   PDF(pc) (440KB) ( 423 )

We study the effects of K and K*exchange between the Λ hyperon and the nucleon in a Λ hypernucleus, where the nuclear core is described by a successful relativistic mean-field (RMF) model. In general, K and K* are responsible for strangeness exchange in the one-boson-exchange potential model, which are absent in the RMF calculation. We investigate the contribution of Fock terms derived from K and K* exchange. We use a pseudovector coupling for K exchange, which is found to provide a repulsive potential for the Λ particle in hypernuclei. Both vector and tensor couplings for K* exchange are taken into account, whose combined effect on the Λ single-particle energy is found to be small.

Proton Ratio of HL-2A Bucket Ion Source
YU Li-Ming, LEI Guang-Jiu, CAO Jian-Yong, YANG Li-Mei, JIANG Shao-Feng, HAN Xiao-Yu, ZHANG Xian-Ming, SUN Ping, ZOU Gui-Qing, LU Da-Lun, LIU He, JIANG Tao, DUAN Xu-Ru
Chin. Phys. Lett. 2010, 27 (4): 042901 .   DOI: 10.1088/0256-307X/27/4/042901
Abstract   PDF(pc) (560KB) ( 383 )

For heating the tokamak plasma effectively, the ion source must be capable of producing ions with high proton ratio. The proton ratio, which is found to be more than 65.6% at the ion current of 19.6 A with the extraction voltage of 39.6 kV, is measured with an image spectrograph by Doppler shift effect of Balmer-α-radiation spectrum emitted from fast hydrogen particles. The tendency of proton ratio with the ion density in experiment is almost the same as the mode devised by Zhang et al. Okumura et al. only gave the affection of the plasma volume and ion loss area on the proton ratio, but the relationship between the ion density in chamber and the proton ratio was not presented. We give the relationship.

Relativistic Energies and Auger Widths of High-Lying Doubly-Excited States 1s23lnl'1De in Be-Like O4+ Ions
GOU Bing-Cong, ZHUO Lin, WU Xiao-Li
Chin. Phys. Lett. 2010, 27 (4): 043101 .   DOI: 10.1088/0256-307X/27/4/043101
Abstract   PDF(pc) (332KB) ( 467 )

The saddle-point variational method and restricted variational method are used to calculate energies of doubly-excited singlet states 1s23lnl' (n=3-5) 1De in Be-like O4+ ions, including the mass polarization and relativistic corrections. The saddle-point complex-rotation method is used to compute the Auger widths and Auger transition rates. These results are compared with other theoretical and experimental data in the literature.

Interaction between B-Doped C60 Fullerene and Glycine Amino Acid from First-Principles Simulation
M. D. Ganji, H. Yazdani
Chin. Phys. Lett. 2010, 27 (4): 043102 .   DOI: 10.1088/0256-307X/27/4/043102
Abstract   PDF(pc) (687KB) ( 982 )

The possibility of formation of complexes between glycine and boron doped C60 (C59B) fullerene is investigated and compared with that of C60 fullerene by using the density functional theory calculations. It has been found that the binding of glycine to C59B generated the most stable complexes via its carbonyl oxygen active site, with a binding energy of -37.89 kcal/mol, while the glycine molecule prefers to bind to the pure C60 cage via its amino nitrogen active site, consistent with the recent experimental and theoretical studies. We have also tested the stability of the most stable Gly-C59B complex with ab initio molecular dynamics simulation, carried out at room temperature. These indicate that the B-doped C60 fullerenes seem to be more suitable materials for bindings to proteins than pure C60 fullerenes.

Control of a Cloud of Laser-Cooled 40Ca+ in a Linear Ion Trap
ZHOU Fei, XIE Yi, XU You-Yang, LI Jiao-Mei, HUANG Xue-Ren, FENG Mang
Chin. Phys. Lett. 2010, 27 (4): 043201 .   DOI: 10.1088/0256-307X/27/4/043201
Abstract   PDF(pc) (704KB) ( 431 )

A cloud of laser-cooled 40Ca+ is successfully trapped and manipulated under well control in our home-built linear ion trap, which is designed and constructed solely for studying quantum information processing. By exploring the variation of the ion cloud with respect to the trap parameters, we have optimized the trapping condition and obtained very good fluorescence spectra. We observe the dynamics of the ion cloud, and estimate the temperature of the ion cloud to be of the order of milli-Kelvin.

Theory of Tunnel Ionization in Complex Systems
ZHANG Bin, ZHAO Zeng-Xiu
Chin. Phys. Lett. 2010, 27 (4): 043301 .   DOI: 10.1088/0256-307X/27/4/043301
Abstract   PDF(pc) (420KB) ( 678 )

We present a detailed derivation of the Ammosov-Delone-Krainov theory of tunnel ionization in complex systems (CS-ADK). A few mistakes in the previous works have been found and corrected. The theory is then applied to CO2, showing that CS-ADK yields better agreement with experiment than the molecular ADK theory.

Ionization and Charge Transfer of Atomic Hydrogen by Highly Charged Ions
DING Bao-Wei, HU Bi-Tao
Chin. Phys. Lett. 2010, 27 (4): 043401 .   DOI: 10.1088/0256-307X/27/4/043401
Abstract   PDF(pc) (477KB) ( 452 )

Cross sections for charge transfer and ionization of atomic hydrogen by highly charged ions Aq+ (q=6-9) are evaluated using a simple and classical method based on the previous works by Bohr and Lindhard [K. Dan. Vidensk. Selsk. Mat. Fys. Medd 28 (1954) No 7], Brandt [Nucl. Instrum. Methods Phys. Res. 214 (1983) 93] and Ben-Itzhak et al. [J. Phys. B: At. Mol. Opt. Phys. 26 (1993) 1711]. It is proved that the present calculations are feasible to some extent in comparison with available experimental data and quantum calculations.

Rotational and Vibrational State Distributions of CsH and Relative Reactivity in Reactions of Cs(62D,72D) with H2
WANG Da-Gui, WANG Xue-Yan, ZHOU Dong-Dong, MU Li-Sai, SHEN Yi-Fan, DAI Kang
Chin. Phys. Lett. 2010, 27 (4): 043402 .   DOI: 10.1088/0256-307X/27/4/043402
Abstract   PDF(pc) (516KB) ( 384 )

By using a pump-probe technique, the nascent rotational and vibrational state distributions of CsH are obtained in the Cs(62D,72D) plus H2 reaction. The nascent CsH molecules are found to populate the lowest two vibrational (v”=0 and 1) levels of the ground electronic state. By comparing the spectral intensities of the CsH action spectra with those of pertinent Cs atomic fluorescence excitation spectra, the relative reactivity with H2 is in an order of 62D3/2>62D5/2>72D3/2>72D5/2. The rotational temperatures are found to be slightly below the cell temperature. The relative fractions (< &#402;V>, <&#402;R>, <&#402;T>) of average energy disposal are derived as (0.2,0.12,0.68), (0.2,0.12,0.68), (0.07,0.04,0.89) and (0.07,0.04,0.89) for the 62D3/2, 62D5/2,72D3/2 and 72D5/2, respectively. The major available energy is released as translation. These results support that the reaction mechanism of Cs( 62D,72D) plus H2 is primarily a collinear abstraction and not an insertion.

An Experimental Observation of Axial Variation of Average Size of Methane Clusters in a Gas Jet
HAN Ji-Feng, YANG Chao-Wen, MIAO Jing-Wei, LU Jian-Feng, LIU Meng, LUO Xiao-Bing, SHI Mian-Gong
Chin. Phys. Lett. 2010, 27 (4): 043601 .   DOI: 10.1088/0256-307X/27/4/043601
Abstract   PDF(pc) (407KB) ( 502 )

Axial variation of average size of methane clusters in a gas jet produced by supersonic expansion of methane through a cylindrical nozzle of 0.8 mm in diameter is observed using a Rayleigh scattering method. The scattered light intensity exhibits a power scaling on the backing pressure ranging from 16 to 50 bar, and the power is strongly Z dependent varying from 8.4 (Z=3 mm) to 5.4 (Z=11 mm), which is much larger than that of the argon cluster. The scattered light intensity versus axial position shows that the position of 5 mm has the maximum signal intensity. The estimation of the average cluster size on axial position Z indicates that the cluster growth process goes forward until the maximum average cluster size is reached at $Z=9$ mm, and the average cluster size will decrease gradually for Z>9 mm.

High Power THz Undulator Radiation from Linear Accelerator
LIN Xu-Ling, ZHANG Jian-Bing, LU Yu, LUO Feng, LU Shan-Liang, YU Tie-Min, DAI Zhi-Min,
Chin. Phys. Lett. 2010, 27 (4): 044101 .   DOI: 10.1088/0256-307X/27/4/044101
Abstract   PDF(pc) (584KB) ( 822 )

A 30-MeV femto-second electron linac is built at the Shanghai Institute of Applied Physics, which can produce high power, coherent THz undulator radiation. We report the experimental facility and measurement of the power, frequency spectrum. First experiments show the averaged power at THz to be about 20 mW.

Anti-Reflective Fluoride Coatings for Widely Tunable Deep-Ultraviolet Diode-Pumped Solid-State Laser Applications
LI Bin-Cheng, LIN Da-Wei, HAN Yan-Ling, GUO Chun, ZHANG Yun-Dong, LIU Hong-Xiang
Chin. Phys. Lett. 2010, 27 (4): 044201 .   DOI: 10.1088/0256-307X/27/4/044201
Abstract   PDF(pc) (512KB) ( 1238 )

An anti-reflective (AR) fluoride coating in the 170-230 nm spectral range is prepared by the thermal evaporation method for the applications of widely tunable deep-ultraviolet diode-pumped solid-state lasers. The transmittance of an AR coated calcium fluoride (CaF2) window in thickness 3 mm is measured to be in the range of 95.8% at 170 nm to 97.1% at 230 nm, with the maximum transmittance 99.2% and the minimum residual reflectance 0.04% appeared at 195 nm. The experimental results indicate that treating the AR coated window and the bare substrate with ultraviolet irradiation can significantly improve their optical performance.

Laser-Induced Silver Nanoparticles Deposited on Optical Fiber Core for Surface-Enhanced Raman Scattering
LI Ming-Shan, YANG Chang-Xi
Chin. Phys. Lett. 2010, 27 (4): 044202 .   DOI: 10.1088/0256-307X/27/4/044202
Abstract   PDF(pc) (711KB) ( 750 )

We report on surface-enhanced Raman scattering (SERS) probes based on silver nanoparticles which are deposited on the core of the distal end of standard single mode fibers, by means of the very simple, versatile, and low-cost laser-induced nanoparticle technique. The morphological features of the Ag nanoparticles vary according to the experimental conditions such as laser power, illumination time, and concentration of the reaction solution. The SERS activity of the probes is demonstrated with the detections of rhodamine 6G aqueous solutions. The detections are made from both ends of the probes, i.e., in direct detection mode from the end with nanoparticles and in remote detection mode from the distal end, respectively.

Dressed Four-Wave Mixing Spectroscopy Modified by Polarization Interference and Atom-Wall Collision in Micrometric Thin Cells
LI Yuan-Yuan, , LI-Li, BAI Jin-Tao, LI Chang-Biao, ZHANG Yan-Peng, HOU Xun,
Chin. Phys. Lett. 2010, 27 (4): 044203 .   DOI: 10.1088/0256-307X/27/4/044203
Abstract   PDF(pc) (461KB) ( 433 )

Dressed four-wave mixing (DFWM) spectroscopy is investigated theoretically in some micrometric thin cells. It is found that DFWM spectra can be modified by polarization interference of atoms and transient effects induced by atom-wall collision. This modification can lead to width-narrowing of DFWM lines and facilitates to implement experiment of high resolution DFWM spectroscopy in a confined atomic system.

Generation of Red Light Femtosecond Pulses from an Intra-Cavity Frequency-Doubled Cr4+ : Forsterite Laser
ZHONG Xin, ZHOU Bin-Bin, ZHAN Min-Jie, WEI Zhi-Yi
Chin. Phys. Lett. 2010, 27 (4): 044204 .   DOI: 10.1088/0256-307X/27/4/044204
Abstract   PDF(pc) (498KB) ( 443 )

We demonstrate the generation of red light femtosecond laser pulses from an intra-cavity frequency-doubled Cr4+:forsterite laser. An average output power of 75 mW is obtained at the central wavelength of 647 nm with a pulse width of 55 fs by inserting a 500-μm-thick BBO crystal in the laser cavity. The bandwidth of the spectrum of second harmonic pulses is 9 nm, corresponding to a time-bandwidth product of 0.355.

Theoretical Design of a Wedged Output Coupler Coated by Capacitive Strip-Grating for Optically Pumped Terahertz Lasers
QI Chun-Chao, ZUO Du-Luo, MENG Fan-Qi, CHENG Zu-Hai,
Chin. Phys. Lett. 2010, 27 (4): 044205 .   DOI: 10.1088/0256-307X/27/4/044205
Abstract   PDF(pc) (378KB) ( 576 )

An output coupler for optically pumped terahertz laser consisting of capacitive strip-grating and wedged high-resistivity silicon substrate is designed theoretically and its transmittance performance is also discussed. The etalon effects frequently occurring in previous experiments are effectively suppressed, and thus a flat and accurate transmittance spectrum is obtained in a narrow wavenumber interval of 2 cm-1 near a particular center wavenumber. Furthermore the transmittance sensitivity to the slight shift of substrate thickness is also completely eliminated. The wedged output coupler is easy to fabricate and its substrate may be used repeatedly to meet various transmittance requirements.

New Approach for Normalizing Photon-Added and Photon-Subtracted Squeezed States
FAN Hong-Yi, JIANG Nian-Quan
Chin. Phys. Lett. 2010, 27 (4): 044206 .   DOI: 10.1088/0256-307X/27/4/044206
Abstract   PDF(pc) (337KB) ( 433 )

We present a new concise approach for normalizing m-photon-added squeezed state -photon-subtracted squeezed state , i.e., we construct the generating function andrespectively, after calculating them and comparing the result with the standard form of generating function of Legendre polynomials Pm,we find m<r|r>m=m!cosh mrPm(cosh r), and , where r is the squeezing parameter.

Scheme for Generating a χ-Type Four-Atom Entangled State in Cavity QED
Chin. Phys. Lett. 2010, 27 (4): 044207 .   DOI: 10.1088/0256-307X/27/4/044207
Abstract   PDF(pc) (291KB) ( 476 )

We propose a scheme for generating a χ-type four-atom entangled state in cavity QED. In the present scheme, the atoms interact simultaneously with a highly detuned cavity mode with the assistance of a strong classical field. The scheme is insensitive to the cavity decay and the thermal field, which is of importance from the experimental point of view.

Optical Properties of Zinc-Blende InGaN/GaN Quantum Well Structures and Comparison with Experiment
PARK Seoung-Hwan, LEE Yong-Tak
Chin. Phys. Lett. 2010, 27 (4): 044208 .   DOI: 10.1088/0256-307X/27/4/044208
Abstract   PDF(pc) (486KB) ( 691 )

Optical properties of zinc-blende InGaN/GaN QW structures are investigated using the multiband effective-mass theory. The transition wavelength values at 300 K ranged from 440 to 570 nm in the investigated range of the In composition and the well width. The theoretical wavelengths show reasonable agreement with the experimental results. The optical gain decreases with the increasing well width. This is mainly due to the reduction in the quasi-Fermi-level separation because the optical matrix element increases with the well width.

Spatial Splitting and Intensity Suppression of Four-Wave Mixing in V-Type Three-Level Atomic System
LI Chuang-She, YIN Wei-Tao, YUAN Chen-Zhi, SHI Mei-Zhen, ZHAO Yan, ZHANG Yan-Peng
Chin. Phys. Lett. 2010, 27 (4): 044209 .   DOI: 10.1088/0256-307X/27/4/044209
Abstract   PDF(pc) (716KB) ( 426 )

We illustrate our experimental observation of coexisting the controllable spatial splitting and intensity suppression of four-wave mixing (FWM) beam in a V-type three-level atomic system. The peak number and separation distance of the FWM beam are controlled by the intensities and frequencies of the laser beams, as well as atomic density.

Enhancement of Continuous Variable Entanglement in Four-Wave Mixing due to Atomic Memory Effects
ZHU Yu-Zhu, HU Xiang-Ming, WANG Fei, LI Jing-Yan
Chin. Phys. Lett. 2010, 27 (4): 044210 .   DOI: 10.1088/0256-307X/27/4/044210
Abstract   PDF(pc) (488KB) ( 439 )

We explore the effects of atomic memory on quantum correlations of two-mode light fields from four-wave mixing. A three-level atomic system in Λ configuration is considered, in which the atomic relaxation times are comparable to or longer than the cavity relaxation times and thus there exists the atomic memory. The quantum correlation spectrum in the output is calculated without the adiabatic elimination of atomic variables. It is shown that the continuous variable entanglement is enhanced over a wide range of the normalized detuning in the intermediate and bad cavity cases compared with the good cavity case. In some situations more significant enhancement occurs at sidebands.

Coupled THz Waveguide Utilizing Surface Plasmon Polaritons on Thin Dielectric Slab Sandwiched between Two Corrugated Metallic Claddings
TIAN Dong-Bin, ZHANG Huai-Wu, WEN Qi-Ye, XIE Yun-Song, SONG Yuan-Qiang
Chin. Phys. Lett. 2010, 27 (4): 044211 .   DOI: 10.1088/0256-307X/27/4/044211
Abstract   PDF(pc) (656KB) ( 584 )

We present a comprehensive experimental study of terahertz (THz) wave propagation utilizing surface plasmon polaritons (SPPs) on the interfaces of a thin dielectric core layer sandwiched between two corrugated metallic claddings. THz wave impinges on the structured surfaces at normal incidence. Long-lasting oscillation propagation features are observed in the temporal waveform after traveling through the periodic arrays. The enhanced THz transmission can be achieved due to the coupling between incident waves to SPPs at the bottom and top interfaces. The finite element method is used to simulate the field distribution and the transmission mode in the waveguide. The hybrid waveguide with low absorption has great potential applications in THz integrated devices.

Supercontinuum Gneneration and Modes Analysis in Secondary Cores of a Hollow-Core Photonic Crystal Fiber
GUO Yuan, RUAN Shuang-Chen, YAN Pei-Guang, LI Irene-Ling, YU Yong-Qin
Chin. Phys. Lett. 2010, 27 (4): 044212 .   DOI: 10.1088/0256-307X/27/4/044212
Abstract   PDF(pc) (668KB) ( 540 )

We demonstrate the generation of supercontinuum spectra in three secondary cores of a hollow-core photonic crystal fiber pumped by femtosecond laser pulses, respectively. The supercontinuum spectra are mainly a result of the soliton self-frequency shift and an amplification of dispersive wave at visible wavelengths. Detailed mode simulations show that with the increasing core length, the modes transfer from "double-points" to "single-point" since the pump laser is more easily coupled into the two side cores of a secondary core when the core length is small. The simulation results also explain why the experimental observed far-field beam patterns of first two secondary cores are different.

Infrared Femtosecond Laser Direct-Writing Digital Volume Gratings in Fused Silica
WANG Ying, LI Yu-Hua, LU Pei-Xiang
Chin. Phys. Lett. 2010, 27 (4): 044213 .   DOI: 10.1088/0256-307X/27/4/044213
Abstract   PDF(pc) (625KB) ( 457 )

We demonstrate that digital volume gratings can be fabricated in fused silica glass conveniently by direct femtosecond laser writing. The diffraction efficiencies of volume gratings can be essentially modulated by simply stacking and offsetting the unit structure. A series of volume gratings, which have the pitches of 5 μm and the size of 1mm×1mm, have been fabricated with the writing speed of 500 μm/s, with which the processing period of each grating layer could be reduced to several minutes with a 1-kHz femtosecond laser system. Results show that the power spectrum of the diffracted waves of the volume gratings are dependent on the layer gap and layer offsetting.

Numerical Simulation for Coherent and Partially Coherent Beam Propagation through Atmospheric Turbulence
QIAN Xian-Mei, ZHU Wen-Yue, WANG An-Ting, GU Chun, RAO Rui-Zhong
Chin. Phys. Lett. 2010, 27 (4): 044214 .   DOI: 10.1088/0256-307X/27/4/044214
Abstract   PDF(pc) (523KB) ( 800 )

Propagation properties of coherent and partially coherent beams in atmospheric turbulence are investigated respectively by using numerical simulation. It is found that a partially coherent beam has a spreading larger than a coherent beam. However, from the point view of relative beam spreading and intensity scintillation, a partially coherent beam is less affected than the corresponding coherent beam, which may be the most important virtue of partially coherent beams that could be utilized to improve the performance of laser engineering. The beam wandering is almost independent of the degree of the source coherence. More aperture averaging occurs when the beam becomes more coherent.

A Fractal Model for Effective Thermal Conductivity of Isotropic Porous Silica Low-k Materials
DONG Xi-Jie, HU Yi-Fan, WU Yu-Ying, ZHAO Jun, WAN Zhen-Zhu
Chin. Phys. Lett. 2010, 27 (4): 044401 .   DOI: 10.1088/0256-307X/27/4/044401
Abstract   PDF(pc) (462KB) ( 568 )

We establish a new model based on fractal theory and cubic spline interpolation to study the effective thermal conductivity of isotropic porous silica low-k materials. A 3D fractal model is introduced to describe the structure of the silica xerogel and silica hybrid materials (such as methylsilsesquioxane, MSQ). Combined with fractal structure, a more suitable medium approximation is developed to study the isotropic porous silica xerogel and MSQ materials. Cubic spline interpolation for fitting discrete predictions from the fractal model is used to obtain the continuous function of the effective thermal conductivity versus porosity. Compared with other common models, the effective thermal conductivity predicted by our model presents better agreement with the experimental data for all porosity. These results indicate that the proposed model is valid.

Local Heating Effect of Flow Past a Circular Cylinder
XIN Xiao-Feng, CHEN Cheng, WANG Bo-Fu, MA Dong-Jun, SUN De-Jun
Chin. Phys. Lett. 2010, 27 (4): 044701 .   DOI: 10.1088/0256-307X/27/4/044701
Abstract   PDF(pc) (488KB) ( 595 )
Heating effects of air flows past a two-dimensional circular cylinder at low Reynolds numbers and low Mach numbers are investigated by numerical simulation. The cylinder wall is heated partially rather than heated on the whole surface as with previous researches. The heating effects are completely different for various heating locations on the cylinder surface. Heating either windward or leeward side stabilizes the flow and reduces or completely suppresses vortex shedding from the cylinder at supercritical Reynolds numbers, which is consistent with previous results of heating on the whole surface of the cylinder. However, as the lateral sides of the cylinder (perpendicular to the stream-wise direction) are heated, an adverse effect is found for the first time in that the flow is destabilized and vortex shedding can be excited at subcritical Reynolds numbers. As the lateral sides of the cylinder are cooled, the flow is stabilized.
Analysis of High Codimensional Bifurcation and Chaos for the Quad Bundle Conductor's Galloping
LIU Fu-Hao, ZHANG Qi-Chang, TAN Ying
Chin. Phys. Lett. 2010, 27 (4): 044702 .   DOI: 10.1088/0256-307X/27/4/044702
Abstract   PDF(pc) (518KB) ( 444 )

A two-degree-of-freedom model of iced, electrical quad bundle conductor is developed to comprehensively describe the different galloping behaviors observed. By applying centre manifold and invertible linear transformation, the co-dimension-2 bifurcation is analyzed. The relationships of parameters between this system and the original system are obtained to analyze and to control the galloping of the quad iced bundle conductor. The space trajectory, Lyapunov exponent and Lyapunov dimension are investigated via numerical simulation to present a rigorous proof of existence of chaos.

Role of Viscosity Stratification and Insoluble Surfactant in Instability of Two-Layer Channel Flow
PENG Jie, ZHU Ke-Qin
Chin. Phys. Lett. 2010, 27 (4): 044703 .   DOI: 10.1088/0256-307X/27/4/044703
Abstract   PDF(pc) (365KB) ( 461 )

We study, for the case of the two layer plane Poiseuille flow, the effect of viscosity stratification and interfacial surfactant on the flow instability. Considering a normal mode of the streamwise wave number α, both the linear and energy analyses are presented. The expressions of perturbation energy supplied at the interface are derived. The result demonstrates that the jumps of horizontal velocity and tangential stress of the perturbed flow across the interface could be induced by the presence of viscosity stratification and surfactant. This is expected to be responsible for the Yih and Marangoni instability.

Generation of Broadband High Harmonics through Linear Mode Conversion in Inhomogeneous Plasmas
XU Hui, SHENG Zheng-Ming, ZHENG Jun, XIA Yun-Jie
Chin. Phys. Lett. 2010, 27 (4): 045201 .   DOI: 10.1088/0256-307X/27/4/045201
Abstract   PDF(pc) (496KB) ( 421 )

The generation of high order harmonics from an inhomogeneous ovderdense plasma target irradiated by an ultrashort intense laser pulse is studied by numerical simulation. During such interaction, ultrafast electron bunches are generated and excite electron plasma oscillations as they pass through the overdense target. These plasma oscillations will emit high-frequency electromagnetic emission by linear mode conversion. Instead of the integer harmonics generation, the emission appears with a broadband and even continuous spectrum corresponding to the electron plasma frequency range of the inhomogeneous plasma density.

Cavity-Defect Plasma Bragg Gratings
ZHENG Jun, SHENG Zheng-Ming, YE Zhi-Cheng, ZHANG Jie, MIMA Kunioki
Chin. Phys. Lett. 2010, 27 (4): 045202 .   DOI: 10.1088/0256-307X/27/4/045202
Abstract   PDF(pc) (599KB) ( 354 )

Plasma Bragg grating (PBG) is composed of periodic variations of plasma and dielectric or vacuum. The defect mode characteristic of the PBG with a cavity-defect is studied by one-dimensional particle-in-cell (1D PIC) simulation. It is shown that the laser pulse with the defect frequency can be localized around the defect partly and at the same time leak out of both sides of the grating slowly because of the few number of the grating period. This results in local high laser field intensity and high plasma density produced at the defect area, from which the third harmonic is enhanced by one order of magnitude. With the enhancement of the light coupled to the defect and the decrease of the light leaking out of the defect, the conversion efficiency of the third harmonic from the incident laser can be increased.

Growth of Pure Zinc Blende GaAs Nanowires: Effect of Size and Density of Au Nanoparticles
YE Xian, HUANG Hui, REN Xiao-Min, YANG Yi-Su, GUO Jing-Wei, HUANG Yong-Qing, WANG Qi
Chin. Phys. Lett. 2010, 27 (4): 046101 .   DOI: 10.1088/0256-307X/27/4/046101
Abstract   PDF(pc) (913KB) ( 573 )

Pure zinc blende GaAs nanowires were grown by metal organic chemical vapor deposition on GaAs(111)B substrates via Au catalyzed vapor-liquid-solid mechanism. The diameter, size distribution, and density of Au particles can be changed by varying the Au film thickness. We find that the grown nanowires are of rod-like shapes and pure zinc blende structure; moreover, the growth rate depends on the density of Au particles and it is independent of its diameters. It can be concluded that the nanowire was grown with main contributions from the direct impingement of vapor species onto the Au-Ga droplets and contributions from adatom diffusion can be negligible. The results indicate that the droplet acts as a catalyst rather than an adatom collector.

Growth and Characterization of CIS Thin Films Prepared by Ion Beam Sputtering Deposition
FAN Ping, LIANG Guang-Xing, ZHENG Zhuang-Hao, CAI Xing-Min, ZHANG Dong-Ping
Chin. Phys. Lett. 2010, 27 (4): 046801 .   DOI: 10.1088/0256-307X/27/4/046801
Abstract   PDF(pc) (658KB) ( 633 )

Copper indium diselenide (CuInSe2) thin films were prepared by ion beam sputtering Cu, In and Se targets continuously on BK7 glass substrates and the three-layer film was then annealed in the same vacuum chamber. X-ray diffraction shows that the CuInSe2 thin films have a single chalcopyrite structure with preferential (112) orientation. Scanning electron microscopy reveals that the CIS thin films consist of uniform and densely packed grain clusters. Energy dispersive x-ray spectroscopy demonstrates that the elemental composition of CIS films approaches the stochiometric composition ratios of 1:1:2. Raman measurement shows that the main peak is at about 174 cm-1 and this peak is identified as the A1 vibrational mode from chalcopyrite ordered CuInSe2. Optical transmission and absorption spectroscopy measurement reveal an energy band gap of about 1.05 eV and an absorption coefficient of 105 cm-1. The film resistivity is about 0.01 Ωcm.

Surface Structure and Electronic Property of InP(001)-(2×1)S Surface: A First-Principles Study
LI Deng-Feng, XIAO Hai-Yan, XUE Shu-Wen, YANG Li, ZU Xiao-Tao
Chin. Phys. Lett. 2010, 27 (4): 046802 .   DOI: 10.1088/0256-307X/27/4/046802
Abstract   PDF(pc) (482KB) ( 465 )

The surface structure and electronic property of InP(001)-(2×1)S surface under S-rich condition are investigated based on first-principles simulations. The analyses of phase transition show that the 3B model is the most stable structure and the S-S dimer is difficult to form. The geometry of the 3B structure agrees well with the experiments. It is also found that the 3B structure has a good passivation with a band gap of about 1.24eV. The results indicate that the 3B structure is the best candidate for the sulfur-rich InP(001)(2×1)A phase.

Raman Spectrum of Epitaxial Graphene on SiC (0001) by Pulsed Electron Irradiation
HUANG Qing-Song, GUO Li-Wei, WANG Wen-Jun, WANG Gang, WANG Wan-Yan, JIA Yu-Ping, LIN Jing -Jing, LI Kang, CHEN Xiao-Long
Chin. Phys. Lett. 2010, 27 (4): 046803 .   DOI: 10.1088/0256-307X/27/4/046803
Abstract   PDF(pc) (540KB) ( 580 )

We report new Raman features of epitaxial graphene (EG) on Si-face 4H-SiC prepared by pulsed electron irradiation (PEI). With increasing graphene layers, frequencies of G and 2D peaks show blue-shifts and approach those of bulk highly-oriented pyrolytic graphite. It is indicated that the EG is slightly tension strained and tends to be strain-free. Meanwhile, single Lorentzian line shapes are well fitted to the 2D peaks of EG on SiC(0001) and their full widths at half maximum decrease with the increasing graphene layers, which indicates that the multilayer EG on Si-face can also contain turbostratic stacking by our PEI route instead of only AB Bernal stacking by a traditional thermal annealing method. It is worth noting that the stacking style plays an important role on the charge carrier mobility. Therefore our findings will be a candidate for growing quality graphene with high carrier mobility both on the Si- and C-terminated SiC substrate. Mechanisms behind the features are studied and discussed.

Kondo and Coulomb Interaction Effects in Spin-Polarized Transport through Double Quantum Dots
CHEN Jia-Feng, WU Shao-Quan, HOU Tao, ZHAO Guo-Ping
Chin. Phys. Lett. 2010, 27 (4): 047201 .   DOI: 10.1088/0256-307X/27/4/047201
Abstract   PDF(pc) (1059KB) ( 446 )

By means of the slave-boson mean-field approximation, we theoretically investigate the Kondo and Coulomb interaction effects in spin-polarized transport through two coupled quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. The density of states is calculated in the Kondo regime for the effect of the interdot Coulomb repulsion with both parallel and antiparallel lead-polarization alignments. Our results reveal that the interdot Coulomb interaction between quantum dots greatly influence the density of states of the dots. We then clarify relevant underlying physics of this problem.

Resonance Transport of Graphene Nanoribbon T-Shaped Junctions
KONG Xiao-Lan, XIONG Yong-Jian
Chin. Phys. Lett. 2010, 27 (4): 047202 .   DOI: 10.1088/0256-307X/27/4/047202
Abstract   PDF(pc) (467KB) ( 582 )

We investigate the transport properties of T-shaped junctions composed of armchair graphene nanoribbons of different widths. Three types of junction geometries are considered. The junction conductance strongly depends on the atomic features of the junction geometry. When the shoulders of the junction have zigzag type edges, sharp conductance resonances usually appear in the low energy region around the Dirac point, and a conductance gap emerges. When the shoulders of the junction have armchair type edges, the conductance resonance behavior is weakened significantly, and the metal-metal-metal junction structures show semimetallic behaviors. The contact resistance also changes notably due to the various interface geometries of the junction.

Long-Lasting Phosphorescence Properties of Pyrochlore La2Ti2O7:Pr3+ Phosphor
CHU Ming-Hui, JIANG Da-Peng, ZHAO Cheng-Jiu, LI Bin
Chin. Phys. Lett. 2010, 27 (4): 047203 .   DOI: 10.1088/0256-307X/27/4/047203
Abstract   PDF(pc) (761KB) ( 875 )

The La2Ti2O7:Pr3+, which emits red color luminescence upon UV light excitation, is prepared by the conventional high-temperature solid-state method and its luminescent properties are systematically investigated. X-ray diffraction, photoluminescence, afterglow emission spectra and long-lasting phosphorescence (LLP) decay curves are used to characterize this phosphor. After irradiation by a 290-nm UV light for 3 min, the Pr3+-doped La2Ti2O7 phosphor emits intense red emitting afterglow from the 1D2→3H4 transitions, and its afterglow can be seen with the naked eye in the dark clearly for more than 1 h after removal of the excitation source. The afterglow decay curve of the Pr3+-doped La2Ti2O7 phosphor contains a fast decay component and another slow decay one. The possible mechanism of this red light emitting LLP phosphor is also discussed based on the experimental results.

Fabrication and Properties of Double-Side Tl2Ba2CaCu2O8 Thin Film on CeO2 Buffered Sapphire Substrate
YOU Feng, WANG Zheng, XIE Qing-Lian, JI Lu, YUE Hong-Wei, ZHAO Xin-Jie, FANG Lan, YAN Shao-Lin
Chin. Phys. Lett. 2010, 27 (4): 047401 .   DOI: 10.1088/0256-307X/27/4/047401
Abstract   PDF(pc) (657KB) ( 457 )

The double-side Tl2Ba2CaCu2O8 (Tl-2212) superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Tl-2212 thin films on CeO2 buffered sapphire substrates were fabricated by a dc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the c-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106 K, the critical current density Jc is around 3.5 MA/cm2 at 77 K, and the microwave surface resistance Rs at 77 K and 10 GHz of the film is as low as 390 μΩ

Mechanical Reinforcement and Piezoelectric Properties of PZT Ceramics Embedded with Nano-Crystalline
WANG Da-Wei&#, , JIN Hai-Bo&#, , YUAN Jie, WEN Bao-Li ZHAO Quan-Liang, ZHANG De-Qing, CAO Mao-Sheng
Chin. Phys. Lett. 2010, 27 (4): 047701 .   DOI: 10.1088/0256-307X/27/4/047701
Abstract   PDF(pc) (593KB) ( 898 )

The double-scale lead zirconate titanate (PZT) piezoelectric ceramics were prepared by the solid state processing with PZT nano-crystalline and micro-powder. The microstructures, electrical and mechanical properties of the double-scale PZT are investigated. All the sintered ceramics exhibit a single perovskite structure and the grain size of the double-scale PZT reduces due to the incorporation of PZT nano-crystalline. Compared to normal PZT, the mechanical properties increase significantly and the piezoelectric properties decrease slightly. Mechanisms responsible for the reinforcement of the double-scale PZT are discussed.

A Photovoltaic InAs Quantum-Dot Infrared Photodetector
TANG Guang-Hua, XU Bo, JIANG Li-Wen, KONG Jin-Xia, KONG Ning, LIANG De-Chun, LIANG Ping, YE Xiao-Ling, JIN Peng, LIU Feng-Qi, CHEN Yong-Hai, WANG Zhan-Guo
Chin. Phys. Lett. 2010, 27 (4): 047801 .   DOI: 10.1088/0256-307X/27/4/047801
Abstract   PDF(pc) (499KB) ( 420 )

A photovoltaic quantum dot infrared photodetector with InAs/GaAs/AlGaAs structures is reported. The detector is sensitive to normal incident light. At zero bias and 78 K, a clear spectral response in the range of 2-7 μm has been obtained with peaks at 3.1, 4.8 and 5.7 μm. The bandgap energies of GaAs and Al0.2Ga0.8As at 78 K are calculated and the energy diagram of the transitions in the Quantum-Dot Infrared Photodetector (QDIP) is given out. The photocurrent signals can be detected up to 110 K, which is state-of-the-art for photovoltaic QDIP. The photovoltaic effect in our detector is a result of the enhanced band asymmetry as we design in the structure.

Growth and Characteristics of Freestanding Hemispherical Diamond Films by Microwave Plasma Chemical Vapor Deposition
WANG Qi-Liang, LÜ, Xian-Yi, LI Liu-An, CHENG Shao-Heng, LI Hong-Dong
Chin. Phys. Lett. 2010, 27 (4): 047802 .   DOI: 10.1088/0256-307X/27/4/047802
Abstract   PDF(pc) (708KB) ( 430 )

Freestanding hemispherical diamond films have been fabricated by microwave plasma chemical vapor deposition using graphite and molybdenum (Mo) as substrates. Characterized by Raman spectroscopy and scanning electron microscopy, the crystalline quality of the films deposited on Mo is higher than that on graphite, which is attributed to the difference in intrinsic properties of the two substrates. By decreasing the methane concentration, the diamond films grown on the Mo substrate vary from black to white, and the optical transparency is enhanced. After polishing the growth side, the diamond films show an infrared transmittance of 35-60% in the range 400-4000 cm-1.

Effects of Annealing Temperature on Structural and Optical Properties of ZnO Thin Films
XU Jian-Ping, SHI Shao-Bo, LI Lan, ZHANG Xiao-Song, WANG Ya-Xin, CHEN Xi-Ming
Chin. Phys. Lett. 2010, 27 (4): 047803 .   DOI: 10.1088/0256-307X/27/4/047803
Abstract   PDF(pc) (891KB) ( 1880 )

The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si (100) substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700 \circC. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial oxygen (Oi), interstitial zinc (Zni) and zinc vacancy,which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.

Electroluminescence from Multilayered Diamond/CeF3/SiO2 Films
LEI Tong, WANG Xiao-Ping, WANG Li-Jun, LV Cheng-Rui, ZHANG Shi, ZHU Yu-Zhuan
Chin. Phys. Lett. 2010, 27 (4): 048101 .   DOI: 10.1088/0256-307X/27/4/048101
Abstract   PDF(pc) (607KB) ( 567 )

We report a thin film electroluminescent device with a three-layer structure (diamond/CeF3/SiO2 films), which has a luminance of 1.5 cd/m2 at dc voltage 215 V. The electroluminescence spectrum at room temperature shows that the main peaks locate at 527 and 593 nm, which are attributed to isolated emission centers of Ce3+ ions.

Electrical Studies on Pentacene Thin Film Transistors with Different Channel Widths
Jaya Lohani, Manoj Gaur, Upendra Kumar, V. R. Balakrishnan, Harsh, S. V. Eswaran
Chin. Phys. Lett. 2010, 27 (4): 048102 .   DOI: 10.1088/0256-307X/27/4/048102
Abstract   PDF(pc) (610KB) ( 757 )

In order to conduct electrical studies on organic thin film transistors, top-contact devices are fabricated by growing polycrystalline films of freshly synthesized pentacene over Si/SiO2 substrates with two different channel widths under identical conditions. Reasonable field effect mobilities in order of 10-2-10-3 cm2V-1s-1 are obtained in these devices. An elaborative electrical characterization of all the devices is undertaken to study the variance in output saturation current, field effect mobility, and leakage current with aging under ambient conditions. As compared to the devices with longer channel width, the devices with shorter channel width exhibit better electrical performance initially. However, the former devices sustain the moderate performance much longer than the latter ones.

Numerical Simulations of Calcium Ions Spiral Wave in Single Cardiac Myocyte
BAI Yong-Qiang, ZHU Xing,
Chin. Phys. Lett. 2010, 27 (4): 048201 .   DOI: 10.1088/0256-307X/27/4/048201
Abstract   PDF(pc) (779KB) ( 388 )

The calcium ions (Ca2+) spark is an elementary Ca2+ release event in cardiac myocytes. It is believed to buildup cell-wide Ca2+ signals, such as Ca2+ transient and Ca2+ wave, through a Ca2+-induced Ca2+ release (CICR) mechanism. Here the excitability of the Ca2+ wave in a single cardiac myocyte is simulated by employing the fire-diffuse-fire model. By modulating the dynamic parameters of Ca2+ release and re-uptake channels, we find three Ca2+ signaling states in a single cardiac myocyte: no wave, plane wave, and spiral wave. The period of a spiral wave is variable in the different regimes. This study indicates that the spiral wave or the excitability of the system can be controlled through micro-modulation in a living excitable medium.

A Low-Voltage Silicon Light Emitting Device in Standard Salicide CMOS Technology
WANG Wei, HUANG Bei-Ju, DONG Zan, LIU Hai-Jun, ZHANG Xu, GUAN Ning, CHEN Jin, GUO Wei-Lian, NIU Ping-Juan, CHEN Hong-Da
Chin. Phys. Lett. 2010, 27 (4): 048501 .   DOI: 10.1088/0256-307X/27/4/048501
Abstract   PDF(pc) (908KB) ( 593 )

A silicon-based field emission light emitting diode for low-voltage operation is fabricated in the standard 0.35 μm 2P4M salicide complementary metal-oxide-semiconductor (CMOS) technology. Partially overlapping p+ and n+ regions with a salicide block layer are employed in this device to constitute a heavily doped p+-n+ junction which has soft "knee" Zener breakdown characteristics, thus its working voltage can be reduced preferably below 5 V, and at the same time the power efficiency is improved. The spectra of this device are spread over 500 nm to 1000 nm with the main peak at about 722 nm and an obvious red shift of the spectra peak is observed with the increasing current through the device. During the emission process, field emission rather than avalanche process plays a major role. Differences between low-voltage Zener breakdown emission and high-voltage avalanche breakdown emission performance are observed and compared.

Weak Gate Effect in 1,3-Benzenedithiol Molecular Device
SU Wen-Yong, LUO Yi
Chin. Phys. Lett. 2010, 27 (4): 048502 .   DOI: 10.1088/0256-307X/27/4/048502
Abstract   PDF(pc) (516KB) ( 420 )

We introduce a full interaction Hamiltonian method to the generalized quantum chemical approach and apply it to investigate the electron tunneling properties of 1,3-benzenedithiol molecular device. The weak gate effect we calculate is consistent with the experiment. The asymmetric current character mainly comes from the asymmetry of the molecule and the nonlinear responding to the gate electric field.

Interest-Driven Model for Human Dynamics
SHANG Ming-Sheng, CHEN Guan-Xiong, DAI Shuang-Xing, WANG Bing-Hong, ZHOU Tao,
Chin. Phys. Lett. 2010, 27 (4): 048701 .   DOI: 10.1088/0256-307X/27/4/048701
Abstract   PDF(pc) (482KB) ( 556 )

Empirical observations indicate that the interevent time distribution of human actions exhibits heavy-tailed features. The queuing model based on task priorities is to some extent successful in explaining the origin of such heavy tails, however, it cannot explain all the temporal statistics of human behavior especially for the daily entertainments. We propose an interest-driven model, which can reproduce the power-law distribution of interevent time. The exponent can be analytically obtained and is in good accordance with the simulations. This model well explains the observed relationship between activities and power-law exponents, as reported recently for web-based behavior and the instant message communications.

Heterogeneity of Some Cooperation/Competition Properties
XU Xiu-Lian, FU Chun-Hua, LIU Ai-Fen, HE Da-Ren
Chin. Phys. Lett. 2010, 27 (4): 048901 .   DOI: 10.1088/0256-307X/27/4/048901
Abstract   PDF(pc) (399KB) ( 392 )

We show that the heterogeneity index, which was proposed by Hu and Wang [Physica A 387 (2008) 3769], can be used to describe the disparity of the cooperation sharing or competition gain distributions, which is very important for understanding the dynamics of a cooperation/competition system. An analytical relation between the distribution parameters and the heterogeneity index is derived, which is in good agreement with the empirical results. Our theoretical and empirical analyses also show that the relation between the distribution parameters can be analytically derived from the so-called Zhang-Chang model [Physica A 360 (2006) 599; 383 (2007) 687). This strongly recommends a possibility to create a general dynamic cooperation/competition model.

Comment on ``Mechanism for Alternating Electric Fields Induced-Effects on Cytosolic Calcium''
Dimitris J. Panagopoulos, Andreas Karabarbounis, Lukas H. Margaritis
Chin. Phys. Lett. 2010, 27 (4): 049901 .   DOI: 10.1088/0256-307X/27/4/049901
Abstract   PDF(pc) (212KB) ( 456 )

Comment on "Mechanism for Alternating Electric Fields Induced-Effects on Cytosolic Calcium"

Reply to Comment on ``Mechanism for Alternating Electric Fields Induced-Effects on Cytosolic Calcium''
LUO Ming-Yan, SONG Kun, ZHANG Xu, LEE Imshik
Chin. Phys. Lett. 2010, 27 (4): 049902 .   DOI: 10.1088/0256-307X/27/4/049902
Abstract   PDF(pc) (207KB) ( 373 )
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