Current Issue

Volume 23 Issue 12
Online Date:
Previous Issue    Next Issue
Original Articles
Fisher Information of Wavefunctions: Classical and Quantum
LUO Shun-Long
Chin. Phys. Lett. 2006, 23 (12): 3127-3130 .  
Abstract   PDF(pc) (203KB) ( 1308 )
A parametric quantum mechanical wavefunction naturally induces parametric probability distributions by taking absolute square, and we can consider its classical Fisher information. On the other hand, it also induces parametric rank-one projections which may be viewed as density operators, and we can talk about its quantum Fisher information. Among many versions of quantum Fisher information, there are two prominent ones. The first, defined via a quantum score function, was introduced by Helstrom in 1967 and is well known. The second, defined via the square root of the density operator, has its origin in the skew information introduced by Wigner and Yanase in 1963 and remains relatively unnoticed. This study is devoted to investigating the relationships between the classical Fisher information and these two versions of quantum Fisher information for wavefunctions. It is shown that the two versions of quantum Fisher information differ by a factor 2 and that they dominate the classical Fisher information. The non-coincidence of these two versions of quantum Fisher information may be interpreted as a manifestation of quantum discord. We further calculate the difference between the Helstrom quantum Fisher information and the classical Fisher information, and show that it is precisely the instantaneous phase fluctuation of the wavefunctions.
Single Qubit and Its Universal Logic Gate Made of a Heisenberg Spin Cluster with Five Particles
TAO Jun, WANG Shun-Jin
Chin. Phys. Lett. 2006, 23 (12): 3131-3134 .  
Abstract   PDF(pc) (217KB) ( 581 )
We investigate an anisotropic Heisenberg spin cluster with five particles controlled by a time-dependent magnetic field. With the algebraic dynamical method, we obtain the exact analytical solution to the time dependent Schrödinger equation. Based on the analytical solution, it is shown that the system can be used as a universal single qubit logic gate controlled by the strength and frequency of the magnetic field, and the six special single qubit logic gates can be realized physically. We also discuss the anti-decoherence property of the qubit and its logic gates resulted from particle coupling effect and collectivity of the cluster.
Locality Violation with Spin-Type W States without Using Inequalities
SONG Ke-Hui, ZHANG Yong-Sheng, ZHOU Zheng-Wei&sup, GUO Guang-Can
Chin. Phys. Lett. 2006, 23 (12): 3135-3137 .  
Abstract   PDF(pc) (214KB) ( 476 )
Using even and odd coherent states, we define a new state, which is called the spin-type W state. With the spin-type W states, we provide a new scheme for testing fundamental aspects of quantum mechanics and refuting local hidden variable theory without using inequalities. Finally, a scheme for preparing the spin-type W states, and discussion of experimental possibility and the effect of the measurement on physical observables due to a close orthogonality of the two coherent states are given.
Quantum Entanglement in a System of Two Spatially Separated Atoms Coupled to the Thermal Reservoir
LIAO Xiang-Ping, , FANG Mao-Fa, ZHENG Xiao-Juan&sup, CAI Jian-Wu,
Chin. Phys. Lett. 2006, 23 (12): 3138-3142 .  
Abstract   PDF(pc) (251KB) ( 546 )
We study quantum entanglement between two spatially separated atoms coupled to the thermal reservoir. The influences of the initial state of the system, the atomic frequency difference and the mean number of the thermal field on the entanglement are examined. The results show that the maximum of the entanglement obtained with nonidentical atoms is greater than that obtained with identical atoms. The degree of entanglement is progressively decreased with the increase of the thermal noise. Interestingly, the two atoms can be easily entangled even when the two atoms are initially prepared in the most mixed states.

Teleportation of an Arbitrary Multipartite GHZ-Class State by One EPR Pair
WANG Ya-Hong, YU Chang-Shui&sup, SONG He-Shan
Chin. Phys. Lett. 2006, 23 (12): 3142-3144 .  
Abstract   PDF(pc) (201KB) ( 614 )
We present a scheme for perfectly teleporting an arbitrary and unknown N-particle GHZ-class state from a sender to a receiver. We just need one quantum channel composed of two or three particles in the maximally entangled state. The sender performs one Bell-state measurement on two of her particles and N-1 Hadamard operations and N-1 von Neumann measurements on the rest N-1 particles. The receiver adopts one corresponding unitary transformation on his particles shared with the sender. After that, the receiver can obtain the original N-particle GHZ-class state by introducing N-1 ancillary particles and carrying out N-1 controlled-NOT operations. We also generalize the scheme to the case of controlled teleportation.
Dynamics of Genuine Three-Qubit Entanglement in Ising Spin Systems
PANG Chao-Yang, LI Yu-Liang
Chin. Phys. Lett. 2006, 23 (12): 3145-3147 .  
Abstract   PDF(pc) (213KB) ( 548 )
We investigate the dynamics of genuine three-qubit entanglement in the Ising model of three spins. A scheme is presented for generating the genuine three-qubit entanglement by the nearest-neighbour couplings. The effect of magnetic fields on the dynamics of genuine three-qubit entanglement is also discussed.
Quantum Secret Sharing with Two-Particle Entangled States
LIU Wei-Tao, LIANG Lin-Mei, LI Cheng-Zu, YUAN Jian-Min
Chin. Phys. Lett. 2006, 23 (12): 3148-3151 .  
Abstract   PDF(pc) (226KB) ( 632 )
We present a new protocol for the quantum secret sharing (QSS) task among multiparties with two-particle entangled states. In our scheme, the secret is split among a number of participating partners and the reconstruction requires collaboration of all the authorized partners. Instead of multiparticle Greenberger--Horne--Zeilinger states, only two-particle entangled states are employed in this scheme. By local operations and individual measurements on either of the two entangled particles, each authorized partner obtains a sequence of secret bits shared with other authorized partners. This protocol can be experimentally realized using only linear optical elements and simple entanglement source. It is scalable in practice.
A Flexible Improvement for Ping-Pong Protocol
LIU Yu, HUA Sha&sup, WANG Xiao-Xin&sup, LI Yue&sup, YE Jun&sup, LI Jun
Chin. Phys. Lett. 2006, 23 (12): 3152-3154 .  
Abstract   PDF(pc) (217KB) ( 574 )
A deterministic quantum communication protocol, called the ping-pong protocol, has been represented by Boström and Felbinger [Phys. Rev. Lett. 89 (2002) 187902]. Based on an entangled pair of photons, it allows asymptotically secure key distribution and quasi-secure direct communication. However, it was concluded from our previous research that the experiment realization of this protocol requires two optic paths strictly equivalent for interferometry. Here we propose an improved protocol, which is more flexible and secure for conceivable applications. Its feasibility and security are also discussed.
Tunable Nongeometric Phase Gates for Two Hot Ions via Adiabatic Evolution of Dark States
ZHENG Shi-Biao
Chin. Phys. Lett. 2006, 23 (12): 3155-3157 .  
Abstract   PDF(pc) (184KB) ( 448 )
We propose a scheme for implementing nongeometric phase gates for two trapped ions via adiabatic passage of dark states. During the operation, the vibrational mode is only virtually excited, thus the scheme is insensitive to heating. Furthermore, the spontaneous emission is suppressed since the ions are always in the electronic ground states. The scheme is robust against small fluctuations of parameters, and the conditional phase is tunable.
Entangled States Used in Remote Information Concentration and Their Properties
CHEN Yin-Hua, YU Ya-Fei, ZHANG Zhi-Ming
Chin. Phys. Lett. 2006, 23 (12): 3158-3160 .  
Abstract   PDF(pc) (189KB) ( 460 )
We analyse a process of remote information concentration achieved by the W state. The result turns out to be neither as good as performed by the GHZ state nor as by the Smolin bound entangled state. Based on this particular phenomenon, the properties of the three entangled states are realized.
A Complete Foliation of Schwarzschild Spacetime by Free Falling Hypersurfaces
M. Ayub Faridi, Amjad Pervez&sup, Haris Rashid&sup, Fazal-e-Aleem&sup,
Chin. Phys. Lett. 2006, 23 (12): 3161-3164 .  
Abstract   PDF(pc) (246KB) ( 370 )
Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everywhere except at the singularity r=0 the mean extrinsic curvature becomes infinity.
How to Define the Equality of Durations in Measurement of Time
ZHAO Zheng&sup, TIAN Gui-Hua, LIU Liao&sup, GAO Si-Jie&sup,
Chin. Phys. Lett. 2006, 23 (12): 3165-3169 .  
Abstract   PDF(pc) (201KB) ( 490 )
We develop the research on measurement of time worked by Poincaré, Einstein, Landau and other researchers. Based on the convention that the velocity of light is isotropic and is a constant in empty spacetime, we not only answer the question about the definition of the synchronization of rate of clocks located at different places, but also find the solution to the issue of how to define the equality of two durations in measurement of time.
Quantum Radiation of a Non-stationary Kerr--Newman Black Hole in de Sitter Space--Time
JIANG Qing-Quan, YANG Shu-Zheng&sup,
Chin. Phys. Lett. 2006, 23 (12): 3169-3172 .  
Abstract   PDF(pc) (225KB) ( 403 )
Hawking radiation of Klein--Gordon and Dirac particles in a non-stationary Kerr--Newman--de-Sitter black hole is studied by introducing a new tortoise coordinate transformation. The result shows that the Fermi--Dirac radiant spectrum displays a new term that represents the interaction between the spin of spinor particles and the rotation of black holes, which is absent in the Bose--Einstein distribution of Klein--Gordon particles.
Photo-thermal Shot Noise in End Mirrors of LIGO due to Correlation of Power Fluctuation
WU Shi-Chen, WAN Zhen-Zhu, LI Huan&sup, LIU Zhong-Zhu
Chin. Phys. Lett. 2006, 23 (12): 3173-3175 .  
Abstract   PDF(pc) (244KB) ( 397 )
The effect of input power fluctuation on photo-thermal shot noise in the end mirrors of a laser interferometer gravitational-wave observatory (LIGO) is analysed according to the statistical optics, which is a supplement of Braginsky's research. The laser light folding in LIGO increases a correlation of input power fluctuation in the photo-thermal shot noise. This part of noise has spectral density proportional to ω-2 in low frequency bands, and ω-4 in high frequency bands. It is not a white noise and may affect the processing about data of interferometers. To obtain an advanced LIGO, photo-thermal shot noise in end mirrors due to correlation of input power fluctuation is up to Braginsky's photo-thermal noise in the frequency range 1--100 Hz.
Suppression of Chaos and Phase Locking in Two Coupled Nonidentical Neurons under Periodic Input
ZHENG Yan-Hong, LU Qi-Shao, WANG Qing-Yun
Chin. Phys. Lett. 2006, 23 (12): 3176-3179 .  
Abstract   PDF(pc) (319KB) ( 399 )
Dynamical behaviour of two coupled neurons with at least one of them being chaotic is presented. Bifurcation diagrams and Lyapunov exponents are calculated to diagnose the dynamical behaviour of the coupled neurons with the increasing coupling strength. It is found that when the coupling strength increases, a chaotic neuron can be controlled by the coupling between neurons. At the same time, phase locking is studied by the maxima of the differences of instantaneous phases and average frequencies between two coupled neurons, and the inherent connection of phase locking and the suppression of chaos is formulated. It is observed that the onset of phase locking is closely related to the suppression of chaos. Finally, a way for suppression of chaos in two coupled nonidentical neurons under periodic input is suggested.
Mean First-Passage Time in Optical Bistable Systems
NING Li-Juan, XU Wei
Chin. Phys. Lett. 2006, 23 (12): 3180-8182 .  
Abstract   PDF(pc) (206KB) ( 456 )
The transient properties of an optical bistable system driven by multiplicative and additive noises are investigated. The effects of multiplicative and additive noises intensities on the mean first-passage times (MFPTs) in two opposite directions are discussed. The results show that the intensities of multiplicative and additive noises affect the MFPTs on two directions in the same way.
Noises in Detecting Relic Gravitational Wave
LEE Zhi-Jun, WAN Zhen-Zhu,
Chin. Phys. Lett. 2006, 23 (12): 3183-8186 .  
Abstract   PDF(pc) (298KB) ( 369 )
We analyse the three basic kinds of noises in detecting the relic gravitational wave (GW), which are the noises caused by the thermal radiation in the detecting cavity and by the scattering of the Gaussian beam in the detecting cavity, and noise in the microwave radiometers. The analysis shows that a reasonable signal-to-noise ratio may be achieved for a detecting device with a suitable geometric structure only when the temperature of the environment is no more than T=0.6 K, and the power of the radiation of the Gaussian beam is no less than P=105 W.
Robust Blind Adaptive Channel Equalization in Chaotic Communication Systems
Chin. Phys. Lett. 2006, 23 (12): 3187-3189 .  
Abstract   PDF(pc) (219KB) ( 463 )
Based on the bounded property and statistics of chaotic signal and the idea of set-membership identification, we propose a set-membership generalized least mean square (SM-GLMS) algorithm with variable step size for blind adaptive channel equalization in chaotic communication systems. The steady state performance of the proposed SM-GLMS algorithm is analysed, and comparison with an extended Kalman filter (EKF)-based adaptive algorithm and variable gain least mean square (VG-LMS) algorithm is performed for blind adaptive channel equalization. Simulations show that the proposed SM-GLMS algorithm can provide more significant steady state performance improvement than the EKF-based adaptive algorithm and VG-LMS algorithm.
Bipartite Entanglement in the Two-Mode Quantum Kicked Top
SONG Li-Jun, WANG Xiao-Guang, LI Yong-Da, ZONG Zhan-Guo
Chin. Phys. Lett. 2006, 23 (12): 3190-3193 .  
Abstract   PDF(pc) (401KB) ( 443 )
We show that the bipartite entanglement in the two-mode quantum kicked top can reveal the underlying chaotic and regular structures in phase space: namely, the entanglement displays a rapid rise after a very short time for an initial spin coherent state centred in a chaotic region of the phase space, whereas the entanglement displays a periodic modulation for the coherent state centred at an elliptic fixed point. The quantum--classical correspondence is investigated by studying the mean and maximal linear entropy.
Quantum Thermal Transport through Extremely Cold Dielectric Chains
LIU Hui-Ping, YI Lin
Chin. Phys. Lett. 2006, 23 (12): 3194-3197 .  
Abstract   PDF(pc) (228KB) ( 400 )
In the framework of Green's function theory out of equilibrium, a Landauer--Buttiker (LB) formula for thermal conductance is derived. A simplified model for describing extremely cold dielectric chains is proposed for the first time. Further we apply the present LB formula for studying thermal conductance at low-lying modes, emerging in dielectric atom chains. We find that quantum thermal conductance undergoes an anomalous transition due to new quasiparticle excitations, resulting from nonlinear atom--atom interactions. This theoretical prediction is in excellent agreement with a high-accuracy measurement to thermal conductance quantum.
Application of Electron-Shelving Detection via 423 nm Transition in Calcium-Beam Optical Frequency Standard
HUANG Kai-Kai, ZHANG Jian-Wei, YU De-Shui, CHEN Zhen-Hui, ZHUAN Wei, CHEN Jing-Biao
Chin. Phys. Lett. 2006, 23 (12): 3198-3201 .  
Abstract   PDF(pc) (254KB) ( 710 )
A new scheme of small compact optical frequency standard based on thermal calcium beam with application of 423 nm shelving detection and sharp-angle velocity selection detection is proposed. Combining these presented techniques, we conclude that a small compact optical frequency standard based on thermal calcium beam will outperform the commercial caesium-beam microwave clock, like the 5071 Cs clock (from HP to Agilent, now Symmetricom company), both in accuracy and stability.
Temperature-Insensitive Chemical Sensor with Twin Bragg Gratings in an Optical Fibre
SANG Xin-Zhu, YU Chong-Xiu, YAN Bin-Bin, MA Jian-Xin, MENG Zhao-Fang, Mayteevarunyoo T.&sup, LU Nai-Guang
Chin. Phys. Lett. 2006, 23 (12): 3202-3204 .  
Abstract   PDF(pc) (211KB) ( 679 )
To reduce temperature sensitivity of the fibre Bragg grating (FBG) chemical sensor, a simple method is proposed by measuring the peak wavelength difference between an etched FBG and an un-etched one in an optical fibre. Thermal characteristics and chemical sensitivity of the sensor are experimentally investigated. The experimental results indicate that the etched FBG and the rest one have almost the same thermal response, and concentration changes of the surrounding chemical solutions can be detected by measuring the peak wavelength difference between them. The sensor has been used to measure the concentrations of propylene glycol solutions and sugar solutions, and it could detect 0.7% and 0.45% concentration changes for them with an optical spectrum analyser in resolution of 10 pm.
Colour-Charged Quark Matter in Astrophysics?
QIU Cong-Xin, XU Ren-Xin
Chin. Phys. Lett. 2006, 23 (12): 3205-3207 .  
Abstract   PDF(pc) (276KB) ( 408 )
Colour confinement is only a supposition, which has not yet been proven in QCD. Here we propose that macroscopic quark--gluon plasma in astrophysics could hardly maintain colourless because of causality. It is expected that the existence of chromatic strange quark stars as well as chromatic strangelets preserved from the QCD phase transition in the early Universe could be unavoidable if their colourless correspondents do exist.
Analysis of X(1576) as a Tetraquark State with the QCD Sum Rules
WANG Zhi-Gang, WAN Shao-Long&sup,
Chin. Phys. Lett. 2006, 23 (12): 3208-3210 .  
Abstract   PDF(pc) (220KB) ( 454 )
We take the viewpoint that X(1576) is the tetraquark state which consists of a scalar diquark and an anti-scalar-diquark in relative P-wave, and calculate its mass in the framework of the QCD sum rule approach. The numerical value of the mass mx=(1.66±0.14) GeV is consistent with the experimental data. There might be some tetraquark components in the vector meson X(1576).
Nuclear Effects in Structure Functions xF₃([x,Q²) from Charge Current Neutrino Deep Inelastic Scattering
DUAN Chun-Gui, , SHEN Peng-Nian, LI Guang-Lie,
Chin. Phys. Lett. 2006, 23 (12): 3211-3214 .  
Abstract   PDF(pc) (242KB) ( 532 )
By taking advantage of the model-independent nuclear parton distributions, the structure functions xF₃(x,Q²) are calculated, in comparison with the experimental data from CCFR neutrino--nuclei charge current deep inelastic scattering. It is shown that shadowing and anti-shadowing effects occur in valence quark distributions for small and medium x regions, respectively. It is suggested that the neutrino experimental data should be employed in the future for pinning down the nuclear parton distributions.
Structure of Di-Ω Dibaryon
DAI Lian-Rong, ZHANG Zong-Ye, YU You-Wen&sup,
Chin. Phys. Lett. 2006, 23 (12): 3215-3218 .  
Abstract   PDF(pc) (252KB) ( 465 )
Previously, we extended our chiral SU(3) quark model to include the coupling between the quark and vector chiral fields [Nucl. Phys. A 727 (2003) 321]. Here we further study the structure of (ΩΩ)ST=00 dibaryon in the extended chiral SU(3) quark model by solving a resonating group method equation. The vector meson exchanges effect, hidden colour channel and colour screening effect are investigated, respectively. The results show that the (ΩΩ)ST=00 system is still the deeply bound state in the extended chiral SU(3) quark model in which the vector meson exchanges control the short-range quark--quark interaction, which is similar to the results obtained from the chiral SU(3) quark model. When the model space is enlarged by including the hidden colour channel, it is found that the energy of the hidden colour state |CC>str=-6,ST=00 is much higher than that of the (ΩΩ)ST=00 state, thus the CC channel has little effect on the binding energy of (ΩΩ)ST=00 state. When the error function confinement potential is considered, the bound state property would not change largely. Further, scalar meson mixing is considered. No matter whether S=-18° or ideal mixing is taken, (ΩΩ)ST=00 state is still a bound state.

Astrophysical Rates for ¹²N(p,)¹³O Direct Capture Reaction
LI Zhi-Hong
Chin. Phys. Lett. 2006, 23 (12): 3219-3121 .  
Abstract   PDF(pc) (329KB) ( 670 )
The proton capture on the unstable nuclei plays a very important role in nucleonsynthesis. The ¹²N(p,)¹³O reaction rates at the energies of astrophysical interest are estimated with the spectroscopic factor and asymptotic normalization coefficient methods. The present results show that the ¹²N(p,)¹³O reaction may play an important role in x-ray bursts.
Search for Double γ-Vibrational Bands in Neutron-Rich 105Mo Nucleus
DING Huai-Bo&sup, ZHU Sheng-Jiang, J. H. Hamilton&sup, A. V. Ramayya&sup, J. K. Hwang&sup, Y. X. Luo, J. O. Rasmussen&sup, I. Y. Lee&sup, CHE Xing-Lai&sup, CHEN Yong-Jing&sup, LI Ming-Liang
Chin. Phys. Lett. 2006, 23 (12): 3222-3225 .  
Abstract   PDF(pc) (277KB) ( 550 )
Levels in the neutron-rich 105Mo nucleus have been investigated by observing prompt γ-rays following the spontaneous fission fragments of 252Cf with the Gammasphere detector array. The yrast band has been confirmed and updated. The other two collective bands with the band head levels at 870.5 and 1534.6 keV are newly observed, and they are suggested as the candidates for one-phonon K=9/2 and two-phonon K=13/2 double γ-vibrational bands, respectively. Systematic characteristics of these bands have been discussed.
A Separable Pairing Force in Nuclear Matter
TIAN Yuan, MA Zhong-Yu
Chin. Phys. Lett. 2006, 23 (12): 3226-3229 .  
Abstract   PDF(pc) (225KB) ( 653 )
The method introduced by Duguet is adopted to derive a separable form of the pairing interaction in the ¹S0; channel from a bare or an effective nucleon--nucleon (NN) interaction in nuclear matter. With this approach the separable pairing interaction reproduces the pairing properties provided by its corresponding NN interaction. In this work, separable forms of pairing interactions in the ¹S0; channel for the bare NN interaction, Bonn potential and the Gogny effective interaction are obtained. It is found that the separable force of the Gogny effective interaction in the ¹S0 channel has a clear link with the bare NN interaction. With such a simple separable form pairing properties provided by the Gogny force in nuclear matter can be reproduced.

Beam Energy Dependence of the π-+ Ratio
ZHANG Fang, ZUO Wei, YONG Gao-Chan,
Chin. Phys. Lett. 2006, 23 (12): 3230-3233 .  
Abstract   PDF(pc) (255KB) ( 461 )
Using the isospin- and momentum-dependent hadronic transport model IBUU04, the effects of symmetry energy on the π-+ ratio are studied. Our investigations are based on the calculations of the ¹³²Sn+¹²⁴Sn semi-central collisions at beam energies of 400/A MeV, 600/A MeV and 800/A MeV. It is found that both the transverse momentum and kinetic energy distributions of the π-+ ratio are rather sensitive to the symmetry energy, especially around the Coulomb peaks. The position of the Coulomb peak is shown to be nearly independent of beam energy. The sensitivity of the π-+ ratio to the symmetry energy decreases as the beam energy increases from 600/A MeV to 800/A MeV.
Chemical Potential Dependence of Two-Quark Condensates
SUN Wei-Min, ZONG Hong-Shi, , WANG Fan,
Chin. Phys. Lett. 2006, 23 (12): 3234-3237 .  
Abstract   PDF(pc) (208KB) ( 366 )
By adopting the background field method, the response of the dressed quark propagator to the presence of finite chemical potential is analysed up to the second order. From this, we obtain a model-independent formula for the chemical potential dependence (up to the second order) of the in-medium two-quark condensate and show by both Lorentz covariance arguments and explicit calculations that the O(μ) contribution to the in-medium two-quark condensate vanishes identically.
Effects of Substrate Temperature on Helium Content and Microstructure of Nanocrystalline Titanium Films
PANG Hong-Chao&sup, LUO Shun-Zhong&sup, LONG Xing-Gui&sup, AN Zhu&sup, LIU Ning&sup, DUAN Yan-Min&sup, WU Xing-Chun&sup, YANG Ben-Fu&sup, WANG Pei-Lu&sup, ZHENG Si-Xiao
Chin. Phys. Lett. 2006, 23 (12): 3238-3241 .  
Abstract   PDF(pc) (762KB) ( 481 )
Helium-charged nanocrystalline titanium films have been deposited by He--Ar magnetron co-sputtering. The effects of substrate temperature on the helium content and microstructure of the nanocrystalline titanium films have been studied. The results indicate that helium atoms with a high concentration are evenly incorporated in the deposited titanium films. When the substrate temperature increases from 60°C to 350°C while the other deposition parameters are fixed, the helium content decreases gradually from 38.6 at.% to 9.2 at.%, which proves that nanocrystalline Ti films have a great helium storage capacity. The 2θ angle of the Bragg peak of (002) crystal planes of the He-charged Ti film shifts to a lower angle and that of (100) crystal plane is unchanged as compared with that of the pure Ti film, which indicates that the lattice parameter c increases and a keeps at the primitive value. The grain refining and helium damage result in the diffraction peak broadening.

Exact Timing of Returned Molecular Wavepacket
ZHANG Zhe, WANG Ting-Ying, ZHANG Gui-Zhong, W.T. Hill III
Chin. Phys. Lett. 2006, 23 (12): 3242-3244 .  
Abstract   PDF(pc) (199KB) ( 382 )
An ionizing wavepacket of electron will re-visit its parent molecular ion during photoionization by strong laser field. This scenario is associated with physical concepts such as molecular re-scattering/collision, interference, diffraction, molecular clock, and generation of XUV light via high-order harmonic generation. On the workbench of a reduced dimensionality model of molecular hydrogen ions irradiated by laser pulse of 0.01--10.0 a.u. intensities, one-cycle pulsewidth, and 800 nm wavelength, by deploying a momentum operator on the time-dependent wavefunction of an ionizing wavepacket, we can determine, in a precise manner, the exact time instant for the re-visiting electron to come back to the cation position. The time value is 57.6% of an optical cycle of the exciting laser pulse. This result may be useful in attosecond pump--probe experiments or molecular clock applications.
Spectrum Simulation of Li-Like Aluminium Plasma
PENG Feng, JIANG Gang, ZHU Zheng-He
Chin. Phys. Lett. 2006, 23 (12): 3245-3248 .  
Abstract   PDF(pc) (253KB) ( 589 )
X-ray emission spectra for L-shell of Li-like aluminium ions are simulated by using the flexible atomic code based on the collisional radiative model. Atomic processes including radiative recombination, dielectronic recombination, collisional ionization and resonance excitation from the neighbouring ion (Al9+ and Al11+) charge states of the target ion (Al10+) are considered in the model. In addition, the contributions of different atomic processes to the x-ray spectrum are analysed. The results show that dielectronic recombination, radiative recombination, collisional ionization and resonance excitation, other than direct collisional excitation, are very important processes.
Duration-Dependent Asymmetry in Photoionization of H atoms in Few-Cycle Laser Pulses
ZHANG Xiao-Mingv, ZHANG Jing-Tao, BAI Li-Hua&sup, GONG Qi-Huang, XU Zhi-Zhan,
Chin. Phys. Lett. 2006, 23 (12): 3249-3252 .  
Abstract   PDF(pc) (259KB) ( 379 )
The photoionization of H atoms irradiated by few-cycle laser pulses is studied numerically. The variations of the total ionization, the partial ionizations in opposite directions, and the corresponding asymmetry with the carrier--envelope phase in several pulse durations are obtained. We find that besides a stronger modulation on the partial ionizations, the change of pulse duration leads to a shift along carrier--envelope (CE) phase in the calculated signals. The phase shift arises from the nonlinear property of ionization and relates closely to the Coulomb attraction of the parent ion to the ionized electron. Our calculations show good agreement with the experimental observation under similar conditions.
Cross Sections of Electron Detachment for Si- and Ge- in Collision with Ar
GAO Mei, YANG En-Bo, LIU Yong, ZHANG Xue-Mei, LU Fu-Quan
Chin. Phys. Lett. 2006, 23 (12): 3253-3255 .  
Abstract   PDF(pc) (191KB) ( 444 )
Single electron detachment cross section for 10--40 keV Si- and Ge- in collisions with Ar are measured and compared with other available experimental results. In our experimental energy region, the trend of cross sections is almost constant. The cross sections of Ge larger than Si can be understood by including electron affinity and size of negative ions.
Electron Impact Ionization Cross Section of Nitrogen Atoms
YU Rong-Mei, ZHOU Ya-Jun, WANG Yang, JIAO Li-Guang
Chin. Phys. Lett. 2006, 23 (12): 3256-3258 .  
Abstract   PDF(pc) (192KB) ( 395 )
The direct ionization cross sections for electron scattering by nitrogen are calculated by applying an equivalent-local optical model from 15 eV to 1100 eV. The present results are compared with the experimental data and other theoretical calculation results.
Instability of Solution of Phase Retrieval in Direct Diffraction Phase-Contrast Imaging with Partially Coherent X-Ray Source
GUO Hua, HAN Shen-Sheng
Chin. Phys. Lett. 2006, 23 (12): 3259-3262 .  
Abstract   PDF(pc) (227KB) ( 370 )
The theoretical model of direct diffraction phase-contrast imaging with partially coherent x-ray source is expressed by an operator of multiple integral. It is presented that the integral operator is linear. The problem of its phase retrieval is described by solving an operator equation of multiple integral. It is demonstrated that the solution of the phase retrieval is unstable. The numerical simulation is performed and the result validates that the solution of the phase retrieval is unstable.

Measurements of AIM for Visible Wavelength Based on Individual Eye Model
WANG Wei, WANG Zhao-Qi, WANG Yan, ZUO Tong, ZHAO Kan-Xing
Chin. Phys. Lett. 2006, 23 (12): 3263-3266 .  
Abstract   PDF(pc) (218KB) ( 990 )
We measure and calculate the aerial image modulation (AIM) of human retina for visible wavelengths based on the individual eye model. By employing the optical design software ZEMAX, we obtain the modulation transfer function (MTF) of human eye in visible wavelengths. Using CSV-1000 and VAF-1000, the contrast sensitivity function (CSF) and the visual acuity (VA) for the same eye are measured. Then the AIM of human retina could be acquired by the relations between MTF and CSF and between MTF and VA. The AIM of human retina is independent of MTF, and the values of AIM for normal eyes (without retina disease) are similar, so the assembly average for large numbers of normal eyes can be a standard AIM curve, which is helpful for the diagnosis of diseases in the retina system.
Realization of Greenberg--Horne--Zeilinger (GHZ) and W Entangled States with Multiple Superconducting Quantum-Interference Device Qubits in Cavity QED
ZHENG An-Shou, WAN Zhen-Zhu, BI Jie
Chin. Phys. Lett. 2006, 23 (12): 3267-3270 .  
Abstract   PDF(pc) (248KB) ( 434 )
An alternative scheme is proposed for generating the Greenberg--Horne--Zeilinger (GHZ) and W types of the entangled states with multiple superconducting quantum-interference device (SQUID) qubits in a single-mode microwave cavity field. In this scheme, there is no transfer of quantum information between the SQUIDs and the cavity, the cavity is always in the vacuum and thus the requirement on the quality of cavity is greatly loosened. In addition, during the process of the generation of the W entangled state, the present method does not involve a real excitation of intermediate levels. Thus, decoherence due to energy relaxation of intermediate levels is minimized.
Intensity Tuning in Single Mode Microchip Nd:YAG Laser with External Cavity
TAN Yi-Dong, ZHANG Shu-Lian
Chin. Phys. Lett. 2006, 23 (12): 3271-3274 .  
Abstract   PDF(pc) (285KB) ( 432 )
We investigate the characteristics of intensity tuning in a single mode microchip Nd:YAG laser with an external cavity. The undulation of laser intensity in a period of λ/2 change of the internal cavity length is observed. Two different optical feedback cases are performed. One is an external cavity reflector perfectly aligned and the other is an external cavity reflector tilted. However, the fluctuation frequency of laser intensity in a period of λ/2 change of the internal cavity length in these two cases is found to be determined by the ratio of external cavity length to internal cavity length. Meanwhile, for the tilted external cavity, the fluctuation frequency is also related to multiple feedbacks in the tilted external cavity.
Self-Mixing Fringes of Vertical-Cavity Surface-Emitting Lasers under Dual Reflector Feedback
CHENG Xiang, ZHANG Shu-Lian, ZHANG Lian-Qing, TAN Yi-Dong
Chin. Phys. Lett. 2006, 23 (12): 3275-3277 .  
Abstract   PDF(pc) (324KB) ( 513 )
The self-mixing fringes which shift due to every one-twentieth wavelength displacement of the target are observed. Taking advantage of the dual reflectors in the external cavity of lasers, the resolution of the sensors has been improved by 10 times. The role of the each reflector has been discussed in detail.
High-Power Extracavity Pulse Compression in Solid Materials
LI Xiao-Fang, CHEN Xiao-Wei, JIANG Yong-Liang, LIU Jun, ZENG Zhi-Nan, LI Ru-Xin, XU Zhi-Zhan
Chin. Phys. Lett. 2006, 23 (12): 3278-3280 .  
Abstract   PDF(pc) (360KB) ( 579 )
A novel technique for high-power extracavity pulse compression with a nonlinear solid material is demonstrated. Before spectral broadening by self-phase modulation in the solid material, a short filament generated in argon is used as a spatial filter, which works for a uniform spectrum broadening over the spatial profile. Compensated by chirped mirrors, a 15-fs pulse is generated from a 32-fs input laser pulse. A total transmission larger than 80% after the solid material is achieved.
Fabrication of Long-Period Fibre Gratings Using 800 nm Femtosecond Laser Pulses
ZHANG Nan, YANG Jian-Jun, WANG Ming-Wei, ZHU Xiao-Nong
Chin. Phys. Lett. 2006, 23 (12): 3281-3284 .  
Abstract   PDF(pc) (218KB) ( 581 )
Long-period fibre gratings inside standard single-mode optical communication fibres are successfully fabricated with infrared femtosecond laser pulses. The refractive index perturbations are well confined within the fibre core by choosing the proper laser focusing parameters and translation speed of the fibre during the direct laser writing process. With the self-focusing effect considered and at a constant average irradiation dose of 1.62×10³ J/(cm²m), the threshold intensity for fabricating long-period gratings with infrared femtosecond laser pulses is determined to be 5.13×10¹³ W/cm².
Low Driving Voltage and Analysis of Azobenzene Polymer Doped Liquid Crystal Grating
SONG Jing, LIU Yong-Gang, MA Ji, XUAN Li
Chin. Phys. Lett. 2006, 23 (12): 3285-3287 .  
Abstract   PDF(pc) (475KB) ( 551 )
We mix azobenzene polymer and liquid crystal in certain ratio. Then the mixture is injected into cells. Nonlinearly photoinduced birefringence takes place when linearly polarized ultraviolet is applied with the pattern photomask covering on the cells, which results in the formation of azobenzene polymer doped liquid crystal grating. The obtained grating is characterized by an optical microscope and a He--Ne laser. The results indicate that the samples have clear grating structure, and the diffraction efficiencies can be modulated by electric field. The sample driving voltage is 0.6 V/μm. It is lower than the driving voltage of holographic polymer dispersed liquid crystal transmission grating and could be matched with the driving integrated circuit.
Phase-Locked Fibre Array for Coherent Combination and Atmosphere Aberration Compensation
HOU Jing, XIAO Rui
Chin. Phys. Lett. 2006, 23 (12): 3288-3290 .  
Abstract   PDF(pc) (321KB) ( 632 )
We report a fibre amplifier array that not only achieves coherent beam combination by compensation of phase noises of fibre amplifier, but also accomplishes correction of atmosphere aberration. It is of master-oscillator--multiple-amplifier (MOPA) configuration, which can be phase-locked by the multidither principle or heterodyne detection principle. First laboratory experiments of atmosphere aberration compensation of a three-element fibre amplifier array are reported. The atmosphere aberration is created by a phase screen in the experiment. The phase changes of the beam, which are introduced by the fibre amplifier and the phase screen, are both detected by the heterodyne detection method. Phase modulators are controlled to compensate for the phase in the three paths. No matter whether there is a phase screen producing atmosphere aberration or not, the dim dynamic interference fringes in the far field turn to a clear and stable pattern, and the peak intensity is maximized. It is indicated that the fibre amplifier array is phase-locked, and coherent combination of the three beams is achieved. It can be used not only to obtain high power fibre laser array but also in laser space communication.
A Wide-Band Thulium-Doped Silica Fibre Amplifier
DU Ge-Guo, LI Da-Jun, LI Hong-Wei, MAI Bing-Liang, YOU Jie-Shun, RUAN Shuang-Chen
Chin. Phys. Lett. 2006, 23 (12): 3291-3293 .  
Abstract   PDF(pc) (219KB) ( 518 )
We investigate a silica-based thulium-doped fibre amplifier, which is a promising candidate for an amplifying device in the S band, in detail using a single wavelength upconversion pumping scheme centred at 1064 nm. Our experimental results show that in terms of gain and noise figure, the bi-directional pumping scheme is the best one in the three pumping schemes, named forward, backward and bi-directional pumping schemes. The amplifier has a gain not only in the S band, but also in the C band, even in the L band. The gain is above 3 dB from 1525 nm to 1580 nm with a peak of 7.5 dB.
Shear Wave Field Radiated by an Electromagnetic Acoustic Transducer
WU Di, LI Ming-Xuan, WANG Xiao-Min
Chin. Phys. Lett. 2006, 23 (12): 3294-3296 .  
Abstract   PDF(pc) (245KB) ( 487 )
The horizontally polarized ultrasonic shear wave field emitted by an electromagnetic acoustic transducer (EMAT) is studied by the surface force distribution on the EMAT approximately described as an inhomogeneous horizontal shear force. The shear wave directivity pattern is plotted by numerical calculations based on our strictly analytic solutions of the wave field we presented previously. An experimental system of EMAT generation and piezoelectric transducer reception is set up to check the predictions of the theoretical wave field by measuring the ultrasonic signals through aluminium block. The directivity pattern of the wave field obtained from the experimental results conforms the theoretical prediction, which lays a foundation for engineering applications of EMATs.
Radiation Acoustic Field of a Linear Phased Array on a Cylindrical Surface
DENG Fang-Qing, ZHANG Bi-Xing, WANG Dong, SONG Gong-Pu
Chin. Phys. Lett. 2006, 23 (12): 3297-3300 .  
Abstract   PDF(pc) (386KB) ( 485 )
A new linear ultrasonic phased array fixed on a cylindrical surface is designed. This kind of the cylindrical phased array can meet the specific requirements of the application in testing pipe quality inside pipes. Using the transducer, we can not only avoid mechanical rotating but also test the quality of any point in a pipe by ultrasonic phase array technology. The focused acoustic field distributions in the axial, radial and tangential directions of the transducer are investigated theoretically by numerical simulation. The energy flux density, the width of the main lobe, the imaging resolution, the grating lobe elimination and other characteristics are analysed. The effect of the focal distance, effective aperture, transducer radius, number of total element, and steering angle on the acoustic field distribution is also studied thoroughly. Many important results are obtained.
Heat Transfer for Power Law Non-Newtonian Fluids
ZHENG Lian-Cun, ZHANG Xin-Xin, LU Chun-Qing
Chin. Phys. Lett. 2006, 23 (12): 3301-3304 .  
Abstract   PDF(pc) (237KB) ( 1155 )
We present a theoretical analysis for heat transfer in power law non-Newtonian fluid by assuming that the thermal diffusivity is a function of temperature gradient. The laminar boundary layer energy equation is considered as an example to illustrate the application. It is shown that the boundary layer energy equation subject to the corresponding boundary conditions can be transformed to a boundary value problem of a nonlinear ordinary differential equation when similarity variables are introduced. Numerical solutions of the similarity energy equation are presented.
Flow Characteristics of Deionized Water in Microtubes
JIANG Ren-Jie, SONG Fu-Quan, LI Hua-Mei
Chin. Phys. Lett. 2006, 23 (12): 3305-3308 .  
Abstract   PDF(pc) (436KB) ( 1218 )
We investigate the deionized water flows in microtubes made of quartz at high pressure under steady flow condition in situations that (i) pure nitrogen is used as the pressure source, and the experimental pressure is 0.1--1 MPa; (ii) the inner diameters of the experimental microtubes are from 6μm to 50μm. The results indicate that (i) the flow characteristics of the microtubes with inner diameters of 50μm, 20μm, 15μm, 10μm agree well with the traditional macro flow mechanics, (ii) there are obvious warps as compared with theoretical values in 6μm microtubes.
Magnetic Properties of Hf0.8Ta0.2(Fe0.97A0.03)2 (A=Al, Co, Mn) Systems
HUANG Yan-Jun, JIANG Zhong-Ying, CHEN Nan, HAN Zhi-Da, LI Shu-Zhen, HSIA Yuan-Fu
Chin. Phys. Lett. 2006, 23 (12): 3309-3312 .  
Abstract   PDF(pc) (294KB) ( 471 )
Mössbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe₂ are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems.
Numerical Simulation of Dust Void Evolution in Complex Plasmas with Ionization Effect
LIU Yue, WANG Zheng-Xiong, WANG Xiao-Gang,
Chin. Phys. Lett. 2006, 23 (12): 3313-3315 .  
Abstract   PDF(pc) (247KB) ( 542 )
We develop the nonlinear theory of dust voids [Phys. Rev. Lett. 90 (2003) 075001], focusing particularly on effects of the ionization, to investigate numerically the void evolution under cylindrical coordinates [Phys. Plasmas 13 (2006) 064502]. The ion velocity profile is solved by a more accurate ion motion equation with the ion convection and ionization terms. It is shown that the differences between the previous result and the one obtained with ionizations are significant for the distributions of the ion and dust velocities, the dust density, and etc., in the void formation process. Furthermore, the ionization can slow down the void formation process effectively.
Experimental Study on Spiral Patterns in Dielectric Barrier Discharge System
LIU Shu-Hua, DONG Li-Fang, LIU Fu-Cheng, LI Shu-Feng, LI Xue-Chen, WANG Hong-Fang
Chin. Phys. Lett. 2006, 23 (12): 3316-3319 .  
Abstract   PDF(pc) (1965KB) ( 497 )
Spiral patterns are obtained in a dielectric barrier discharge system with water electrodes. The dynamics of spiral formation and transition is investigated. Wavelength characteristic of spiral patterns is also studied. Correlation measurements indicate that the wavelength of spiral pattern increases with the increasing gas gap width and oscillates with the increasing drive frequency.
Gaseous Hydrogenation and Its Effect on Thermal Stability of Mg63Ni22Pr15 Metallic Glass
DU Yu-Lei, DENG Yan-Hui, XU Feng, CHEN Guang, CHEN Guo-Liang, ZHANG Qing-An
Chin. Phys. Lett. 2006, 23 (12): 3320-3322 .  
Abstract   PDF(pc) (231KB) ( 562 )
Mg63Ni22Pr15 metallic glasses are produced by a single roller melt-spinning technique. The hydrogen absorption and desorption capacities are respectively 0.38 and 0.14 wt.% at 313 K obtained by pressure-composition isotherm. The amorphous structure is found to be retained after gaseous hydrogenation. The glass transition temperature, the onset crystallization temperature, and the crystallization temperature of the hydrogenated Mg63Ni22Pr15 metallic glass are 550, 570 and 577 K, respectively, much higher than the corresponding values of 440, 470 and 499 K of the as-quenched sample. This means that dramatic enhancement of thermal stability occurs in Mg63Ni22Pr15 metallic glass due to hydrogenation.
First-Principles Study on the Electronic Structures for Y3+:PbWO₄ Crystals
CHEN Teng, LIU Ting-Yu, ZHANG Qi-Ren, LI Fang-Fei, YI Zhi-Jun, TIAN Dong-Sheng, ZHANG Xiu-Yan
Chin. Phys. Lett. 2006, 23 (12): 3323-3326 .  
Abstract   PDF(pc) (270KB) ( 509 )
The possible defect models of Y3+:PbWO₄ crystals are discussed by defect chemistry and the most possible substituting positions of the impurity Y3+ ions are studied by using the general utility lattice program (GULP). The calculated results indicate that in the lightly doped Y3+:PWO crystal, the main compensating mechanism is [2YPb++VPb2-], and in the heavily doped Y3+:PWO crystal, it will bring interstitial oxygen ions to compensate the positive electricity caused by YPb+, forming defect clusters of [2YPb++Oi2-] in the crystal. The electronic structures of Y3+:PWO with different defect models are calculated using the DV-X method. It can be concluded from the electronic structures that, for lightly doped cases, the energy gap of the crystal would be broadened and the 420 nm absorption band will be restricted; for heavily doped cases, because of the existence of interstitial oxygen ions, it can bring a new absorption band and reduce the radiation hardness of the crystal.
Optical Waveguide Formed in RbTiOPO4 Crystal by 6.0 MeV O3+ Implantation
JIAO Yang, WANG Ke-Ming, WANG Xue-Lin, CHEN Feng, WANG Lei, WANG Liang-Ling, LU Qing-Ming, MA Hong-Ji, NIE Rie
Chin. Phys. Lett. 2006, 23 (12): 3328-3330 .  
Abstract   PDF(pc) (242KB) ( 559 )
A planar optical waveguide was formed in RbTiOPO4; crystal by 6.0-MeV oxygen ion implantation with the dose of 2×1015 ions/cm² at room temperature. Annealing at 200°C for 30 min in air is performed to improve the thermal stability of the waveguide. The dark modes of the waveguide are measured at wavelengths 633 and 1539 nm, respectively. The refractive index profiles in the guiding layer are reconstructed by using the reflectivity calculation method. TRIM'98 code was carried out to simulate the damage profiles caused by the implantation process to obtain a better understanding of the waveguide formation.

Microstructure and Corrosion Performance of Oxide Coatings on Aluminium by Plasma Electrolytic Oxidation in Silicate and Phosphate Electrolyte
LV Guo-Hua, GU Wei-Chao, CHEN Huan, LI Li, NIU Er-Wu, YANG Si-Ze
Chin. Phys. Lett. 2006, 23 (12): 3331-3333 .  
Abstract   PDF(pc) (429KB) ( 1037 )
Ceramic coatings are fabricated on pure aluminium by plasma electrolytic oxidation (PEO) in three kinds of electrolyte systems [E1: 0.05M NaOH+0.033M Na₂SiO₃, E2: 0.025M NaOH+0.008M (NaPO₃)6; and E3: 0.025M NaOH+0.066M Na₂SiO₃+0.008M (NaPO₃)6]. The voltage--time responses show that the PEO process of E2 has the highest discharging voltage, which results in the biggest pores and heaviest cracks on the surfaces. X-ray diffraction results show that coatings produced in E1 and E3 are mainly composed of γ-Al₂O₃ and mullite, while coatings produced in E2 are mainly composed of α-Al₂O₃. After PEO treatment the corrosion resistance of aluminium is improved significantly and the coatings produced in E3 perform the best corrosion resistance.

A Solvable Symbiosis-Driven Growth Model
KE Jian-Hong, LIN Zhen-Quan, CHEN Xiao-Shuang
Chin. Phys. Lett. 2006, 23 (12): 3334-3337 .  
Abstract   PDF(pc) (216KB) ( 380 )
We introduce a two-species symbiosis-driven growth model, in which two species can mutually benefit for their monomer birth and the self-death of each species simultaneously occurs. By means of the generalized rate equation, we investigate the dynamic evolution of the system under the monodisperse initial condition. It is found that the kinetic behaviour of the system depends crucially on the details of the rate kernels as well as the initial concentration distributions. The cluster size distribution of either species cannot be scaled in most cases; while in some special cases, they both consistently take the universal scaling form. Moreover, in some cases the system may undergo a gelation transition and the pre-gelation behaviour of the cluster size distributions satisfies the scaling form in the vicinity of the gelation point. On the other hand, the two species always live and die together.
Al-Induced Crystallization Growth of Si Films by Inductively Coupled Plasma Chemical Vapour Deposition
Department of Physics, Lanzhou University, Lanzhou 0000
Chin. Phys. Lett. 2006, 23 (12): 3338-3340 .  
Abstract   PDF(pc) (322KB) ( 679 )
Polycrystalline Si (poly-Si) films are in situ grown on Al-coated glass substrates by inductively coupled plasma chemical vapour deposition at a temperature as low as 350°C. Compared to the traditional annealing crystallization of amorphous Si/Al-layer structures, no layer exchange is observed and the resultant poly-Si film is much thicker than Al layer. By analysing the depth profiles of the elemental composition, no remains of Al atoms are detected in Si layer within the limit (<0.01 at.%) of the used evaluations. It is indicated that the poly-Si material obtained by Al-induced crystallization growth has more potential applications than that prepared by annealing the amorphous Si/Al-layer structures.
Micro-Photoluminescence Confocal Mapping of Single V-Grooved GaAs Quantum Wire
HUANG Shao-Hua, CHEN Zhang-Hai, BAI Li-Hui, SHEN Xue-Chu, H. H. Tan&sup, L. Fu&sup, M. Fraser&sup, C. Jagadish&sup,
Chin. Phys. Lett. 2006, 23 (12): 3341-3344 .  
Abstract   PDF(pc) (618KB) ( 512 )
We perform the micro-photoluminescence measurement at low temperatures and a scanning optical mapping with high spatial resolution of a single V-grooved GaAs quantum wire modified by the selective ion-implantation and rapid thermally annealing. While the mapping shows the luminescences respectively from the quantum wires and from quantum well areas between quantum wires in general, the micro-photoluminescence at liquid He temperatures reveals a plenty of spectral structures of the PL band for a single quantum wire. The spectral structures are attributed to the inhomogeneity and non-uniformity of both the space structure and compositions of real wires as well as the defects nearby the interface between quantum wire and surrounding quantum well structures. All these make the excitons farther localized in quasi-zero-dimensional quantum potential boxes related to these non-uniformity and/or defects. The results also demonstrate the ability of micro-photoluminescence measurement and mapping for the characterization of both opto-electronic and structural properties of real quantum wires.
Photovoltaic Devices from Multi-Armed CdS Nanorods and Conjugated Polymer Composites
LIU Yan-Shan, WANG Li, QIN Dong-Huan), CAO Yong
Chin. Phys. Lett. 2006, 23 (12): 3345-3348 .  
Abstract   PDF(pc) (456KB) ( 736 )
We demonstrate the preparation of composite photovoltaic devices by using the blends of multi-armed CdS nanorods with conjugated polymer, poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). Multi-armed CdS nanorods are prepared by thermolysing single precursor cadmium ethylxanthate [Cd(exan)₂] in pure hexadecylamine solution under ambient conditions. The photoluminescence of MEH-PPV can be effectively quenched in the composites at high CdS nanocrystal (nc-CdS)/MEH-PPV ratios. Post-treatment of the multi-armed CdS nanorods by refluxing in pyridine significantly increases the performance of the composite photovoltaic devices. Power conversion efficiency is obtained to be 0.17% under AM 1.5 illumination for this composite device.
Critical Scaling of Extended Power Law I - V Isotherms near Vortex Glass Transition
HU Xiang, HE Li, NING Zhen-Hua, CHEN Kai-Xuan, YIN Lan, LU Guo, XU Xiao-Lin, GUO Jian-Dong, WANG Fu-Ren, LI Chuan-Yi, YIN Dao-Le
Chin. Phys. Lett. 2006, 23 (12): 3349-3351 .  
Abstract   PDF(pc) (292KB) ( 511 )
In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg--Landau (GL) functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I-V data of Strachan et al. [Phys. Rev. Lett. 87 (2001) 067007]. The puzzling question of the derivative plot for the I-V curves and the controversy surrounding the values of critical exponents are discussed.
Rotational Brownian Motion on Sphere Surface and Rotational Relaxation
Ekrem Ayd�, ner
Chin. Phys. Lett. 2006, 23 (12): 3352-3355 .  
Abstract   PDF(pc) (191KB) ( 380 )
The spatial components of the autocorrelation function of noninteracting dipoles are analytically obtained in terms of rotational Brownian motion on the surface of a unit sphere using multi-level jumping formalism based on Debye's rotational relaxation model, and the rotational relaxation functions are evaluated.
Electrical and Optical Properties of Bulk ZnO Single Crystal Grown by Flux Bridgman Method
LI Xin-Hua, XU Jia-Yue, JIN Min, SHEN Hui, LI Xiao-Min
Chin. Phys. Lett. 2006, 23 (12): 3356-3358 .  
Abstract   PDF(pc) (310KB) ( 1233 )
Zinc oxide (ZnO) single crystals are grown by the modified vertical Bridgman method using a PbF₂ flux. The maximum size of the as-grown ZnO crystal is about Ф25 mm×5 mm. The transmittance of the as-grown ZnO crystal is more than 70% in the range of 600--800 nm and the optical band gap is estimated to be 3.21 eV. The photoluminescence spectrum indicates that the as-grown ZnO crystal has a very low concentration of native defects and is much closed to its stoichiometry. The electrical measurement exhibits that the ZnO crystal has low electrical resistivity of 0.02394Ωcm-1 and a high carrier concentration of 2.10×1018 cm-3.

Focusing Properties in Photonic Crystal Structure Formed by Air Holes in Dielectric Background with Concave Interface
JIAN Zhi-Jian, PENG Jing-Cui, ZHOU Ren-Long
Chin. Phys. Lett. 2006, 23 (12): 3359-3362 .  
Abstract   PDF(pc) (948KB) ( 647 )
We investigate the focusing properties of photonic crystal structures with a concavo-concave as the photonic crystal boundary. The photonic crystal is constituted by air holes parallelly distributed in a uniform dielectric. A good-quality focus of a plane wave can appear out of the photonic crystal structure, and a strong far field focus is also formed from the photonic crystal interface. A negative-refractive beam at the frequency 0.195 (2πc/a) for the excited Bloch wave mode near the Brillouin zone edges under all incident angles are obtained by simulation.
Numerical Analysis and Comparison of Three Metal-Oxide-Type Super-Resolution Near Field Structures
QU Qing-Ling, WANG Yang, GAN Fu-Xi
Chin. Phys. Lett. 2006, 23 (12): 3363-3365 .  
Abstract   PDF(pc) (290KB) ( 531 )
Based on the Fresnel--Kirchhoff diffraction theory, we build up a Gaussian diffraction model of metal-oxide-type super-resolution near field structure (super-RENS), which can describe far field optical properties. The spectral contrast induced by refractive index and the structural changes in AgOx, PtOx and PdOx thin films, which are the key functional layers in super-RENS, are studied by using this model. Comparison results indicate that the spectral contrast depends intensively on the laser-induced distribution and change of the refractive index in the metal-oxide films. The readout mechanism of the metal-oxide-type super-RENS optical disc is further clarified. This Gaussian diffraction model can be used as a simple and effective method for choosing proper active materials in super-RENS.
Calculations of Backscattering Mueller Matrices for Turbid Media with a Sphere Queue Model
WANG Qing-Hua, LI Zhen-Hua, LAI Jian-Cheng, ZHANG Ying-Ying, HE An-Zhi
Chin. Phys. Lett. 2006, 23 (12): 3366-3368 .  
Abstract   PDF(pc) (467KB) ( 555 )
A sphere queue model is introduced to calculate Mueller matrices of turbid media. Combined with the single scattering approximation, the backscattering Mueller matrices of turbid media can be computed rapidly by Mie theory. The numerical results agree with the azimuthal dependences of backscattering Mueller matrices' patterns from turbid media, which indicates that the major contribution to the Mueller matrices' patterns comes from the single scattering of the sphere queue, and the multiple scattering considered as a high-order correction does not change the patterns. The numerical analysis reveals that the contrast of Mueller matrices' patterns will decrease with increase of the concentration of media and the distance from the incident point.
Characteristics of High In-Content InGaN Alloys Grown by MOCVD
ZHU Xue-Liang, GUO Li-Wei, YU Nai-Sen, PENG Ming-Zeng, YAN Jian-Feng, GE Bing-Hui, JIA Hai-Qiang, CHEN Hong, ZHOU Jun-Ming
Chin. Phys. Lett. 2006, 23 (12): 3369-3372 .  
Abstract   PDF(pc) (619KB) ( 1243 )
InN and In0.46Ga0.54N films are grown on sapphire with a GaN buffer by metalorganic chemical vapour deposition (MOCVD). Both high resolution x-ray diffraction and high resolution transmission electron microscopy results reveal that these films have a hexagonal structure of single crystal. The thin InN film has a high mobility of 475 cm2V-1s-1 and that of In0.46Ga0.54 is 163 cm2V-1s-1;. Room-temperature photoluminescence measurement of the InN film shows a peak at 0.72 eV, confirming that a high quality InN film is fabricated for applications to full spectrum solar cells.
Numerical Study on a Lateral Double-Gate Tunnelling Field Effect Transistor
HE Jin, BIAN Wei, TAO Ya-Dong, LIU Feng, SONG Yan, ZHANG Xing,
Chin. Phys. Lett. 2006, 23 (12): 3373-3375 .  
Abstract   PDF(pc) (308KB) ( 573 )
A novel lateral double-gate tunnelling field effect transistor (DG-TFET) is studied and its performance is presented by a two-dimensional device simulation with code ISE. The result demonstrates that this new tunnelling transistor allows for the steeper sub-threshold swing below 60 mV/dec, the super low supply voltage (operable at VDD<0.3 V) and the rail-to-rail logic (significant on-state current at the drain-source voltage VDS=50 mV) for the aggressive technology assumptions of the availability of high-k/metal stack with equivalent gate oxide thickness EOT=0.24 nm and the work function difference 4.5 eV of materials.
Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells
YANG Xiao-Hong, HAN Qin, NI Hai-Qiao, HUANG She-Song, DU Yun, PENG Hong-Ling, XIONG Yong-Hua, NIU Zhi-Chuan, WU Rong-Han
Chin. Phys. Lett. 2006, 23 (12): 3376-3379 .  
Abstract   PDF(pc) (235KB) ( 635 )
A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation. The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias.
Frequency Selectivity Behaviour in the Auditory Midbrain: Implications of Model Study
KUANG Shen-Bing, WANG Jia-Fu, ZENG Ting
Chin. Phys. Lett. 2006, 23 (12): 3380-3383 .  
Abstract   PDF(pc) (257KB) ( 728 )
By numerical simulations on frequency dependence of the spiking threshold, i.e. on the critical amplitude of periodic stimulus, for a neuron to fire, we find that bushy cells in the cochlear nuclear exhibit frequency selectivity behaviour. However, the selective frequency band of a bushy cell is far away from that of the preferred spectral range in human and mammal auditory perception. The mechanism underlying this neural activity is also discussed. Further studies show that the ion channel densities have little impact on the selective frequency band of bushy cells. These findings suggest that the neuronal behaviour of frequency selectivity in bushy cells at both the single cell and population levels may be not functionally relevant to frequency discrimination. Our results may reveal a neural hint to the reconsideration on the bushy cell functional role in auditory information processing of sound frequency.
Topological Properties of Urban Public Traffic Networks in Chinese Top-Ten Biggest Cities
LI Ping, XIONG Xing, QIAO Zhong-Liang, YUAN Gang-Qiang, SUN Xing, WANG Bing-Hong
Chin. Phys. Lett. 2006, 23 (12): 3384-3386 .  
Abstract   PDF(pc) (260KB) ( 629 )
We investigate the topological characteristics of complex networks as exemplified by the urban public traffic network (UPTN) in Chinese top-ten biggest cities. It is found that the UPTNs have small world behaviour, by the examination of their topological parameters. The quantitative analysis of the transport efficiency of the UPTNs reveals their higher local efficiency El and lower global efficiency Eg, which coincide well with the status quo of those Chinese cities still at their developing stage. Furthermore, the topological properties of efficiency in the UPTNs are also examined, and the findings indicate that, on the one hand, the UPTNs show robustness to random attacks and frangibility to malicious attacks on a global scale; on the other hand, the interrelation between UPTN efficiency and network motifs deserves our attention. The motifs which interrelate the UPTN efficiency are always triangular-formed patterns, e.g. motifs ID 238, ID 174 and ID 102, etc.
Conjecture on Avoidance of Big Crunch
SUN Cheng-Yi, ZHANG De-Hai
Chin. Phys. Lett. 2006, 23 (12): 3388-3390 .  
Abstract   PDF(pc) (176KB) ( 621 )
By conjecturing the physics at the Planck scale, we modify the definition of the Hawking temperature and modify the Friedmann equation. It is found that we can avoid the singularity of the big crunch and obtain a bouncing cosmological model.
74 articles