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Volume 31 Issue 6
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Rogue Wave Solutions for the Heisenberg Ferromagnet Equations
ZHANG Yan, NIE Xian-Jia, ZHA Qi-Lao
Chin. Phys. Lett. 2014, 31 (06): 060201 .   DOI: 10.1088/0256-307X/31/6/060201
Abstract   PDF(pc) (888KB) ( 737 )
Darboux transformation of the Heisenberg ferromagnet equation is constructed by the Darboux matrix method. In application, the rogue wave solutions of the Heisenberg ferromagnet equation are obtained. In particular, rogue waves are discussed and illustrated.
Characteristics of Entanglement Wave in Two Parallel Spin Chains
LI Xin, LI Zhong-Fang, SHI Zhi-Long, WANG Xiao-Qin
Chin. Phys. Lett. 2014, 31 (06): 060301 .   DOI: 10.1088/0256-307X/31/6/060301
Abstract   PDF(pc) (715KB) ( 281 )
Based on the solvable spin-1/2 Heisenberg chain we demonstrate how two many-body systems are entangled due to their partial entanglement. The entanglement wave in the two spin chains displays a damped oscillation if the spin number is N>3, and only propagates with a certain velocity depending on the coupling constant J. Moreover, the entanglement wave will be reflected on the other ends of the two spin chains. A simple scheme for transferring some special two-qubit states to other two distant qubits is also proposed.
Quantum Dissonance as an Indicator of Quantum Phase Transition in the XXZ Chain
ZHANG Ye-Qi, HE Qi-Liang, HU Zheng-Da, LIU Ji-Cai
Chin. Phys. Lett. 2014, 31 (06): 060302 .   DOI: 10.1088/0256-307X/31/6/060302
Abstract   PDF(pc) (493KB) ( 341 )
We investigate the behavior of quantum dissonance in the anti-ferromagnetic XXZ spin S=1/2 chain, which exhibits a quantum phase transition. Based on a unified view of quantum and classical correlations, quantum dissonance is analytically calculated and is compared with entanglement, discord, and classical correlations for the ground state of the system. It is found that the nearest-neighbor quantum dissonance achieves an extremum and exhibits the sharpest change at the critical point. Therefore, quantum dissonance may serve as a more efficient indicator of quantum phase transitions in the XXZ spin chain.
Hawking Radiation of Dirac Field in the Linear Dilaton Black Hole
LI Ran
Chin. Phys. Lett. 2014, 31 (06): 060401 .   DOI: 10.1088/0256-307X/31/6/060401
Abstract   PDF(pc) (381KB) ( 179 )
By studying the perturbation of massless Dirac field in the background of linear dilaton black hole we show that the covariant Dirac equation can be separated into radial and angular equations. The Damour–Ruffini method is applied to derive the spectrum of Hawking radiation for the Dirac field, from which the Hawking temperature can be read off. It is shown that the Hawking temperature is consistent with the result calculated from the surface gravity.
Chaotic Motion of a Charged Particle around a Weakly Magnetized Schwarzschild Black Hole Containing Cosmic String
HUANG Qi-Hong, CHEN Ju-Hua, WANG Yong-Jiu
Chin. Phys. Lett. 2014, 31 (06): 060402 .   DOI: 10.1088/0256-307X/31/6/060402
Abstract   PDF(pc) (895KB) ( 1012 )
We discuss the conditions where a charged particle that was originally revolving around a weakly magnetized black hole containing cosmic string in the innermost stable circular orbit will escape to infinity after it is kicked by another particle or photon. We find that the motion of the kicked particle is chaotic. The critical escape energy and velocity of the kicked charged particle with different initial radial velocities are obtained.
Error Analysis of the Density-Matrix Renormalization Group Algorithm for a Chain of Harmonic Oscillators
MA Yong-Jun, WANG Jia-Xiang, XU Xin-Ye, WEI Qi, Sabre Kais
Chin. Phys. Lett. 2014, 31 (06): 060501 .   DOI: 10.1088/0256-307X/31/6/060501
Abstract   PDF(pc) (594KB) ( 182 )
We investigate the application of the density-matrix renormalization group (DMRG) algorithm to a one-dimensional harmonic oscillator chain and compare the results with exact solutions, aiming at improving the algorithm's efficiency. It is demonstrated that the algorithm can show quite accurate results if the procedure is properly organized; for example, by using the optimized bases. The errors of calculated ground state energy and the energy gap between the ground state and the first excited state are analyzed, and they are found to be critically dependent upon the size of the system or the energy level structure of the studied system and the number of states targeted during the DMRG procedure.
Photodiode-Based Chua's Circuit with Light Controllability
NAM Sang Guk, NGUYEN Van Ha, SONG Hanjung
Chin. Phys. Lett. 2014, 31 (06): 060502 .   DOI: 10.1088/0256-307X/31/6/060502
Abstract   PDF(pc) (1498KB) ( 261 )
We present a photodiode-based Chua's chaotic circuit that is controllable by light. The proposed circuit consists of an inductor, two passive capacitors, a photodiode-based variable resistor, and a positive feedback trans-conductor with negative nonlinearity. The chaotic dynamics of the circuit were verified by using the simulation program with integrated circuit emphasis analysis using the 0.35 μm complementary metal-oxide-semiconductor process parameters. The gain results (such as the time waveform, frequency analysis, three-dimensional attractor, bifurcation and Lyapunov exponents diagrams) confirm that the chaotic behavior of the circuit could be controlled by light intensity via the photodiode-based variable resistor.
Analytical Approach to Exact Solutions for the Wick-Type Stochastic Space-Time Fractional KdV Equation
Hossam A. Ghany
Chin. Phys. Lett. 2014, 31 (06): 060503 .   DOI: 10.1088/0256-307X/31/6/060503
Abstract   PDF(pc) (435KB) ( 334 )
This study is devoted to giving an analytical approach to exact solutions for the Wick-type stochastic space-time fractional KdV equation. By means of Hermite transform, white noise theory, and the fractional Riccati equation method, we derive white noise functional solutions for the Wick-type stochastic space-time fractional KdV equations. Exact traveling wave solutions for the variable coefficients space-time fractional KdV equations are given by using the fractional Riccati equation method. The obtained results include soliton-like, periodic, and rational solutions.
Average Mean Escape Time for an Overdamped Spatially-Periodic System and Application to Josephson Junction
LI Jing-Hui
Chin. Phys. Lett. 2014, 31 (06): 060504 .   DOI: 10.1088/0256-307X/31/6/060504
Abstract   PDF(pc) (458KB) ( 197 )
We investigate the average mean escape time of particles over a potential barrier for an overdamped spatially periodic system driven by thermal fluctuations and subject to a dc constant bias force and an ac time-oscillatory drive. Some new anomalous behaviors of the average mean escape time are found, including: multiple resonant activation, multiple anti-Resonant activation, and thermally weakened stability. Some of the experimental verifications of these results are theoretically applied to the Josephson junction.
Response of a Superconducting Quantum Interference Device to Alternating Magnetic Field
LI Jing-Hui
Chin. Phys. Lett. 2014, 31 (06): 060505 .   DOI: 10.1088/0256-307X/31/6/060505
Abstract   PDF(pc) (486KB) ( 170 )
We study the response of a superconducting quantum interference device (SQUID) to an alternating magnetic field. It is found that, for some suitably selected parameters' values, we can obtain stochastic resonance for the amplitude of the steady average voltage of the SQUID versus the dichotomous noise strength, and frequency (stochastic) resonance for the amplitude of the stationary average voltage of the SQUID as a function of the frequency of the alternating magnetic field. Our results can be useful for electrical power generation using the alternating magnetic field energy of a SQUID.
Villain Transformation for Ferrimagnetic Spin Chain
Chin. Phys. Lett. 2014, 31 (06): 060506 .   DOI: 10.1088/0256-307X/31/6/060506
Abstract   PDF(pc) (528KB) ( 211 )

By using the Villain transformation, the Heisenberg ferrimagnetic spin chain is calculated. Two branches of the low-lying excitation in both the absence and presence of magnetic field are obtained. The thermodynamic quantities (such as free energy, magnetization, specific heat and static magnetic susceptibility) are also evaluated at finite temperature. This is the first time to calculate the Ferrimagnetic spin chain by using Villain's method, and we find that the results at a low temperature are quite similar to the previous calculation. The results of free energy and magnetization in zero temperature suggest that the Villain transformation has a good efficiency.

Dynamics in the Kuramoto Model with a Discontinuous Bimodal Distribution of Natural Frequencies
WU Xiao-Li, YANG Jun-Zhong
Chin. Phys. Lett. 2014, 31 (06): 060507 .   DOI: 10.1088/0256-307X/31/6/060507
Abstract   PDF(pc) (1440KB) ( 286 )
We consider a Kuramoto model in which the natural frequencies of oscillators follow a discontinuous bimodal distribution constructed from a Lorentzian one. Different synchronous dynamics (such as different types of travelling wave states, standing wave states, and stationary synchronous states) are identified and the transitions between them are investigated. We find that increasing the asymmetry in frequency distribution brings the critical coupling strength to a low value and that strong asymmetry is unfavorable to standing wave states.
Instanton Induced Charged Fermion and Neutrino Masses in a U(3)C×U(3)L×U(3)R Gauge Symmetry
S. Nassiri
Chin. Phys. Lett. 2014, 31 (06): 061101 .   DOI: 10.1088/0256-307X/31/6/061101
Abstract   PDF(pc) (452KB) ( 157 )
Using instanton effects, we consider a U(3)C×U(3)L×U(3)R gauge symmetry obtained from intersecting D6-branes. This is equivalent to the trinification model extended by the three U(1) factors that survive as global symmetries in the low energy effective model. In the corresponding three-stack, the fermion masses are induced by the possible stringy corrections to the corresponding superpotential by using E2-instantons. Using the known data with neutrino masses mvτ~1 eV, we show the magnitudes of the relevant scales.
Tuning and Validation of the Lundcharm Model with J/ψ Decays
YANG Rui-Ling, PING Rong-Gang, CHEN Hong
Chin. Phys. Lett. 2014, 31 (06): 061301 .   DOI: 10.1088/0256-307X/31/6/061301
Abstract   PDF(pc) (459KB) ( 165 )
Using decays collected with the BES III detector, Lundcharm model parameters are optimized with J/ψ light hadron decays. The dependence of the response function on model parameters is approximated up to the quadratic term, and the model parameters are optimized by simultaneously fitting J/ψ inclusive charged track distributions and event shapes. The Monte Carlo simulations show that optimal parameters yield satisfactory MC distributions as compared to both the J/ψ and ψ(2S) data distributions. These optimal values are suggested for the Lundcharm model to produce J/ψ and ψ(2S) decays to light hadrons.
Electromagnetic Transition Strengths and New Insight into the Chirality in 106Ag
ZHENG Yun, ZHU Li-Hua, WU Xiao-Guang, HE Chuang-Ye, LI Guang-Sheng, HAO Xin, YU Bei-Bei, YAO Shun-He, ZHANG Biao, XU Chuan, WANG Jian-Guo, GU Long
Chin. Phys. Lett. 2014, 31 (06): 062101 .   DOI: 10.1088/0256-307X/31/6/062101
Abstract   PDF(pc) (655KB) ( 234 )

Excited states in 106Ag are populated through the heavy-ion fusion evaporation reaction 100Mo(11B,5n)106Ag at a beam energy of 60 MeV. Lifetimes are measured for transitions of the two negative-parity rotational bands in the nucleus 106Ag. The reduced transition probabilities show a great difference between the two bands. The staggering of the B(M1) and B(M1)/B(E2) values with spin are not observed. The bands are identified to be built on two distinct quasiparticle configurations. These results are contrary to an earlier suggestion that the pair of bands in 106Ag are chiral doublet bands.

Magnetic Effects in Color-Flavor Locked Superconducting Phase with the Additional Chiral Condensates
REN Chun-Fu, ZHANG Xiao-Bing, ZHANG Yi
Chin. Phys. Lett. 2014, 31 (06): 062501 .   DOI: 10.1088/0256-307X/31/6/062501
Abstract   PDF(pc) (579KB) ( 188 )

In the color-flavor locked quark superconducting phase with the additional chiral condensates, the magnetic effects are investigated within the three-flavor Nambu–Jona–Lasinio framework. Based on the rotated electromagnetic mechanism, we incorporate the effective quark masses into the coexistence phase self-consistently. The numerical calculation shows that the magnetic catalysis of effective masses is different from the known phenomenon that occurs in the unpaired quark matter. Moreover, the interplay between magnetic catalysis and gap splitting is studied for the first time.

Low-Energy Direct Capture in the 12C(α,γ)16O Reaction
H. Sadeghi, R. Ghasemi
Chin. Phys. Lett. 2014, 31 (06): 062502 .   DOI: 10.1088/0256-307X/31/6/062502
Abstract   PDF(pc) (628KB) ( 280 )
The spectra of light nuclei provide the first test of nuclear interaction models. The reaction amount determines the relative abundance of most elements in red giant stars, neutron stars, and black holes. Due to the fact that this reaction occurs at low energies, the experimental measurement is very difficult and perhaps impossible. In this work, the radiative capture of the 12C(α,γ)16O reaction at very low-energies is taken as a case study. Using the M3Y potential we calculate the astrophysical factor for transition E1 and E2. In comparison with other theoretical methods and available recent experimental data, excellent agreement is achieved for the astrophysical S-factor of this process.
First-Principle Study of H2 Adsorption on Mg3N2(110) Surface
CHEN Yu-Hong, ZHANG Bing-Wen, ZHANG Cai-Rong, ZHANG Mei-Ling, KANG Long, LUO Yong-Chun
Chin. Phys. Lett. 2014, 31 (06): 063101 .   DOI: 10.1088/0256-307X/31/6/063101
Abstract   PDF(pc) (651KB) ( 1040 )
The adsorption of H2 on two kinds of Mg3N2(110) crystal surface is studied by first principles. Adsorption sites, adsorption energy, and the electronic structure of the Mg3N2(110)/H2 systems are calculated separately. It is found that H2 is mainly adsorbed as chemical adsorption, on these sites the H2 molecules are dissociated and the H atoms tend to the top of two N, respectively, forming two NH, or the H atoms tend to the same N forming one NH2. There are also some physical adsorption sites. One of the bridge sites of Mg3N2(110) surface is more favorable than the other sites. On this site, H atoms tend to the top of two N, forming two NH. This process belongs to strong chemical adsorption. The interaction between H2 molecule and Mg3N2(110) surface is mainly due to the overlap-hybridization among H 1s, N 2s, and N 2p states, covalent bonds are formed between the N and H atoms.
Calculation of Higher-Order Foldy-Wouthuysen Transformation Hamiltonian
MEI Xue-Song, ZHAO Shu-Min, QIAO Hao-Xue
Chin. Phys. Lett. 2014, 31 (06): 063102 .   DOI: 10.1088/0256-307X/31/6/063102
Abstract   PDF(pc) (420KB) ( 203 )

The Foldy–Wouthuysen Hamiltonian of a light atomic system that has an 8 contribution to energy levels is calculated. The case of a Dirac–Coulomb field is discussed. The results can be used for relativistic and radiative corrections to energy levels in the low-energy part. A divergent operator δ2(r) emerges. This is probably due to the nature of the point-like charge source. The effective method of radiation calculation may be re-checked.

Microwave-Optical Double-Resonance Spectroscopy Experiment of 199Hg+ Ground State Hyperfine Splitting in a Linear Ion Trap
LIU Hao, YANG Yu-Na, HE Yue-Hong, LI Hai-Xia, CHEN Yi-He, SHE Lei, LI Jiao-Mei
Chin. Phys. Lett. 2014, 31 (06): 063201 .   DOI: 10.1088/0256-307X/31/6/063201
Abstract   PDF(pc) (563KB) ( 230 )
We report a spectroscopy experiment of the 199Hg+ ground state hyperfine splitting in a linear ion trap. The ions are optically pumped by a discharge lamp and cooled by helium buffer gas. The ground state hyperfine splitting is measured to be 40507347996.8(0.1) Hz by the microwave-optical double-resonance method. A narrow line width as 30 mHz is also observed. This progress builds the foundation for the realization of trapped 199Hg+ ion frequency standards.
Above-Threshold Ionization of Xenon by Chirped Intense Laser Pulses
WANG Chuan-Liang, SUN Ren-Ping, CHEN Yong-Ju, GONG Cheng, LAI Xuan-Yang, KANG Hui-Peng, QUAN Wei, LIU Xiao-Jun
Chin. Phys. Lett. 2014, 31 (06): 063202 .   DOI: 10.1088/0256-307X/31/6/063202
Abstract   PDF(pc) (596KB) ( 220 )
We experimentally investigate above-threshold ionization of xenon subject to chirped intense laser pulses. While for few-cycle laser pulses free of chirp, the Freeman resonance narrow peaks in the photoelectron spectra become strongly suppressed, they will re-emerge for laser pulses with a certain chirp. Moreover, the position of the resonant peaks exhibits a strong dependence on the direction of the chirp. The experimental features can be understood by a two-step ionization process; that is, a multi-photon excitation plus subsequent ionization process.
Ultra-High Efficiency Magnetic Transport of 87Rb Atoms in a Single Chamber Bose–Einstein Condensation Apparatus
GAO Kui-Yi, LUO Xin-Yu, JIA Feng-Dong, YU Cheng-Hui, ZHANG Feng, YIN Ji-Ping, XU Lin, YOU Li, WANG Ru-Quan
Chin. Phys. Lett. 2014, 31 (06): 063701 .   DOI: 10.1088/0256-307X/31/6/063701
Abstract   PDF(pc) (748KB) ( 266 )
We report the ultra-high efficiency transport of cold 87Rb atoms using a moving magnetic quadrupole potential generated by three overlapping pairs of fixed coils. The transfer efficiency is better than 97%, which is the highest ever reported to our knowledge. The temperature increase due to heating is less than 10 μK when the initial cloud temperature is 110 μK. Our setup is similar to the magnetic transferring belt design [Phys. Rev. A 63 (2001) 031401(R)], although it is simpler because the push coil is not required. We use it to transport atoms away from a magneto-optical trap to very close to the wall of the glass cell, facilitating future experiments employing three-dimensional optical lattices, high resolution in-situ imaging, and magnetic Feshbach resonances.
Design of a Simple Integrated Coupler for SPP Excitation in a Dielectric Coated Ag Thin Film
Rakibul Hasan Sagor, Md. Ruhul Amin, Md. Ghulam Saber
Chin. Phys. Lett. 2014, 31 (06): 064201 .   DOI: 10.1088/0256-307X/31/6/064201
Abstract   PDF(pc) (605KB) ( 204 )
A simple integrated coupler is proposed for the efficient excitation of surface plasmon polariton (SPP) mode in a thin metal film. The SPP mode is generated in a single Ag-dielectric interface by the incident field and coupled with an Ag thin film. The coupling efficiency at different wavelengths using two different dielectrics, gallium lanthanum sulfide (GLS) and aluminum gallium arsenide (AlGaAs) is calculated by analyzing the SPP propagation dynamics with the finite difference time domain method. A maximum coupling efficiency of 70% is obtained at a wavelength of 460 nm when GLS is used, whereas the corresponding value obtained for AlGaAs is 60% at 560 nm. The proposed structure can be used to excite SPPs in a nano-thin film from an external bulky source and is easier to fabricate since a single interface metal-dielectric configuration is used to excite the metal-thin film.
A MOCVD-Growth Multi-Wavelength Laser Monolithically Integrated on InP
ZHANG Xi-Lin, LU Dan, ZHANG Rui-Kang, WANG Wei, JI Chen
Chin. Phys. Lett. 2014, 31 (06): 064202 .   DOI: 10.1088/0256-307X/31/6/064202
Abstract   PDF(pc) (631KB) ( 223 )
We present an arrayed waveguide grating multi-wavelength laser (MWL). The device is operated with five wavelength channels of 194 GHz spacing around a central wavelength of 1.57 μm. A side mode suppression ratio of better than 35 dB for all channels is demonstrated. A very attractive feature of the MWL is that it has been realized by a novel one step regrowth approach to achieve a high quality active and passive interface.
Facile Synthesis of Au Nanocube-CdS Core-Shell Nanocomposites with Enhanced Photocatalytic Activity
LIU Xiao-Li, LIANG Shan, LI Min, YU Xue-Feng, ZHOU Li, WANG Qu-Quan
Chin. Phys. Lett. 2014, 31 (06): 064203 .   DOI: 10.1088/0256-307X/31/6/064203
Abstract   PDF(pc) (2144KB) ( 231 )

Au nanocube-CdS core-shell nanocomposites are prepared by using a one-pot method in aqueous phase with cetyltrimethylammonium bromide as the surfactant. The extinction properties and photocatalytic activity of Au-CdS nanocomposites are investigated. Compared with the pure Au nanocubes, the Au-CdS nanocomposites exhibit enhanced extinction intensity. Compared with CdS nanoparticles, the Au-CdS nanocomposites exhibit improved photocatalytic activity. Furthermore, the photocatalytic efficiency is even better with the increase in the core size of the Au-CdS nanocomposites. Typically, the photocatalytic efficiency of the Au-CdS with 62 nm sized Au nanocubes is about two times higher than that of the pure CdS. It is believed that the Au-CdS nanocomposites may find potential applications in environmental fields, and this synthesis method can be extended to prepare a wide variety of functional composites with Au cores.

Optimization of Single or Range of Harmonics by Using Two Gas Jets
LI Xiao-Yong, WANG Guo-Li, ZHOU Xiao-Xin
Chin. Phys. Lett. 2014, 31 (06): 064204 .   DOI: 10.1088/0256-307X/31/6/064204
Abstract   PDF(pc) (744KB) ( 255 )
The interference of high-order harmonics generated by two successive gas jets within a single laser pulse is discussed by a modeling with the inclusion of macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. Based on the interference, we show that one can extract the laser Rayleigh range from the interference of harmonics and the accuracy of retrieve is independent of carrier-envelope phase while dependent on the pulse duration. Moreover, we demonstrate that it is possible to optimize the single or range of harmonics with a high ratio relative to the adjacent orders by changing the separation of two gas jets, which is unavailable by using a single gas jet and linear polarized laser pulse.
Modeling of Fano Resonance in High-Contrast Resonant Grating Structures
HU Jin-Hua, HUANG Yong-Qing, REN Xiao-Min, DUAN Xiao-Feng, LI Ye-Hong, WANG Qi, ZHANG Xia, WANG Jun
Chin. Phys. Lett. 2014, 31 (06): 064205 .   DOI: 10.1088/0256-307X/31/6/064205
Abstract   PDF(pc) (520KB) ( 377 )
A new model is presented for Fano resonance in resonant grating structure based on the temporal coupled mode theory. By using this model, the reflection spectrum can be reproduced with the information of eigenmode of the structure, which can be numerically calculated by the finite element method. Therefore, the eigenmode plays a key role in determining the profile of the line shape of the Fano resonance in the resonant grating structure. When the space of two grating modulations is decreased, the line shape experiences a significant change. Such a drastic change can be attributed to the increase of quality factor of the eigenmodes. Thus, our model not only provides a simple and intuitive understanding on the mechanism of Fano resonance, but it also offers a convenient way to engineer the line shape of the Fano resonance. The proposed model can be used in many applications, such as biosensors, optical filters, and optical switchers.
Numerical Investigation on Scattering of an Arbitrarily Incident Bessel Beam by Fractal Soot Aggregates
CUI Zhi-Wei, HAN Yi-Ping, YU Mei-Ping
Chin. Phys. Lett. 2014, 31 (06): 064206 .   DOI: 10.1088/0256-307X/31/6/064206
Abstract   PDF(pc) (1386KB) ( 231 )
Scattering of an arbitrarily incident Bessel beam by fractal soot aggregates is numerically investigated. The incident beam is described by the vector expressions of the zero-order Bessel beam in combination with rotation Euler angles. The scattering problems involving fractal soot aggregates are formulated with a hybrid vector finite element-boundary integral-domain decomposition method. Some numerical results are included to show the scattering behaviors of fractal soot aggregates when they are illuminated by Bessel beams.
Measuring Carrier-Envelope Phase of Few-Cycle Laser Pulses Using High-Order Above-Threshold Ionization Photoelectrons
DENG Yong-Kai, LI Min, YU Ji-Zhou, LIU Yuan-Xing, LIU Yun-Quan, GONG Qi-Huang
Chin. Phys. Lett. 2014, 31 (06): 064207 .   DOI: 10.1088/0256-307X/31/6/064207
Abstract   PDF(pc) (561KB) ( 373 )
We experimentally demonstrate the measurement of carrier-envelope phase of few-cycle laser pulses. We have built a stereo above-threshold ionization setup. The photoelectron energy spectra of high-order above-threshold ionization are measured in both the left and right directions in the linearly polarized laser fields. It is shown that the left-right asymmetry of the spectra is dependent on carrier-envelope phase of few-cycle laser pulses. Two asymmetry parameters from the low-energy and high-energy regions at the above-threshold ionization plateau map a phase ellipse, in which the points indicate the absolute value of carrier-envelope phase. We have calibrated the phase ellipse by comparison with the semiclassical calculation. This setup allows us to determine the value of the absolute phase of few-cycle laser pulses.
Non-Classical Correlated Photon Pairs Generation via Cascade Transition of 5S1/2–5P3/2–5D5/2 in a Hot 85Rb Atomic Vapor
ZHANG Wei, DING Dong-Sheng, PAN Jian-Song, SHI Bao-Sen
Chin. Phys. Lett. 2014, 31 (06): 064208 .   DOI: 10.1088/0256-307X/31/6/064208
Abstract   PDF(pc) (1968KB) ( 274 )
We experimentally prepare the non-classical correlated photon pairs at the wavelengths of 780 and 776 nm via the cascade transition of 5S1/2–5P3/2–5D5/2 in a hot 85Rb atomic ensemble. By measuring the function of cross-correlation and auto-correlation of photons, a violation of Cauchy–Schwarz inequality by a factor of 283 is obtained, which clearly indicates a strong non-classical correlation between the generated photons. We also find that noise photons scattered from pump lasers have a strong effect on the Cauchy–Schwarz inequality factor by changing the intensity of the pump laser, the experimental results are consistent with the theoretical predictions.
Passively Q-Switched Tm,Ho:YVO4 Laser with Cr:ZnS Saturable Absorber at 2 µm
DU Yan-Qiu, YAO Bao-Quan, CUI Zheng, DUAN Xiao-Ming, DAI Tong-Yu, JU You-Lun, PAN Yu-Bai, CHEN Min, SHEN Zuo-Chun
Chin. Phys. Lett. 2014, 31 (06): 064209 .   DOI: 10.1088/0256-307X/31/6/064209
Abstract   PDF(pc) (787KB) ( 181 )
A stable diode-pumped passively Q-switched Tm,Ho:YVO4 laser with Cr:ZnS saturable absorber is reported. The shortest pulse duration of ~500 ns with the central wavelength of 2041 nm is obtained at the pump power of 7.4 W, corresponding to the pulse energy of 3.5 μJ at repetition rate of 65 kHz.
Experimental and Numerical Investigation of Single Frequency Amplifier with Photonic Bandgap Fiber at 1178 nm
WANG Jian-Hua, CUI Shu-Zhen, HU Jin-Meng, CAO Fen, FANG Yong, LU Hui-Ling
Chin. Phys. Lett. 2014, 31 (06): 064210 .   DOI: 10.1088/0256-307X/31/6/064210
Abstract   PDF(pc) (673KB) ( 203 )
A single frequency photonic bandgap fiber amplifier at 1178 nm is investigated experimentally and numerically. With a pump power of 81 W, a single frequency 1178 nm fiber laser of 10.3 W is obtained with a 3 W seed laser and a 20 m gain fiber. Numerical simulation is conducted with a rate equation model taking amplified spontaneous emission and stimulated Brillouin scattering (SBS) into consideration. Temperature distribution along the fiber is applied for SBS suppression, more than 50 W single frequency fiber laser at 1178 nm is predicted theoretically with a 5 W seed laser and a 40 m long gain fiber with five temperature steps.
Confined and Interface Phonons in Chirped GaAs-AlGaAs Superlattices
HU Yong-Zheng, LIU Feng-Qi, WANG Li-Jun, LIU Jun-Qi, WANG Zhan-Guo
Chin. Phys. Lett. 2014, 31 (06): 064211 .   DOI: 10.1088/0256-307X/31/6/064211
Abstract   PDF(pc) (623KB) ( 228 )
The confined longitudinal optical, transverse optical and interface phonon modes in chirped GaAs-AlGaAs superlattices grown on the (001)-oriented GaAs substrate are studied by the micro-Raman spectroscopy. The phonon modes are probed at the (001) and (110) faces. The temperature dependence of the longitudinal optical, transverse optical and interface phonon modes are achieved. The temperature dependence of the longitudinal optical phonon frequencies demonstrates that a tensile strain exists in the GaAs layers of the chirped superlattices, which is significant for analyzing the device failure of a terahertz quantum cascade laser.
A Novel Algorithm for the Sound Field of Elliptically Shaped Transducers
DING De-Sheng, LÜ Hua, SHEN Chang-Sheng
Chin. Phys. Lett. 2014, 31 (06): 064301 .   DOI: 10.1088/0256-307X/31/6/064301
Abstract   PDF(pc) (858KB) ( 191 )
An alternative extension to the Gaussian-beam expansion technique is presented for efficient computation of the Fresnel field integral for elliptically symmetric sources. With a known result that the circ function is approximately decomposed into a sum of Gaussian functions, the cosine function is similarly expanded by the Bessel–Fourier transform. Two expansions are together inserted into this integral, it is then expressible in terms of the simple algebraic functions. The numerical examples for the elliptical and uniform piston transducers are presented, in good agreement with the results given by other methods. The approach is applicable to treat the field radiation problem for a large and important group of piston sources in acoustics.
Structural and Physical Properties of AsxSe100−x Glasses
FANG Ming-Lei, XU Feng, WEI Wen-Hou, YANG Zhi-Yong
Chin. Phys. Lett. 2014, 31 (06): 066101 .   DOI: 10.1088/0256-307X/31/6/066101
Abstract   PDF(pc) (526KB) ( 250 )
We prepare the samples of AsxSe100?x glasses with x=20, 31, 40 and 50, and measure the glass-transition temperatures Tg, the density and elastic, and optical properties of the glasses. The density, elastic constants and third optical nonlinearity coefficient are found to exhibit the maximal values for the As40Se60 composition. Analysis of x-ray photoelectron spectra of these AsxSe100?x glasses indicate that the chemically stoichiometric As40Se60 consists of perfect corner-sharing pyramidal AsSe3/2 units, while the others contain defect bonds such as As–As and Se–Se. The optical nonlinearity does not correlate with the concentration of Se, contrary to the report by Quemard et al for Ge–Se glasses.
Correlation between Atomic Size Ratio and Poisson's Ratio in Metallic Glasses
WANG Ai-Kun, WANG Shi-Guang, XUE Rong-Jie, LIU Guo-Cai, ZHAO Kun
Chin. Phys. Lett. 2014, 31 (06): 066102 .   DOI: 10.1088/0256-307X/31/6/066102
Abstract   PDF(pc) (423KB) ( 211 )
We report the correlation between atomic size ratio and Poisson's ratio in various metallic glasses. It is found that atomic size ratio has an influence on the atomic packing density of metallic glasses, which would significantly impact the shear modulus rather than bulk modulus. The findings may be helpful for understanding the structural origin of Poisson's ratio in metallic glasses, and are instructive for designing tough metallic glasses with large Poisson's ratio.
First-principles Prediction for Mechanical and Optical Properties of Al3BC3
QIU Ping-Yi
Chin. Phys. Lett. 2014, 31 (06): 066201 .   DOI: 10.1088/0256-307X/31/6/066201
Abstract   PDF(pc) (745KB) ( 243 )
Using the first-principles technique, we systematically investigate the elastic, electronic, mechanical and optical properties of Al3BC3. The calculated structural parameters of Al3BC3 are in agreement with the experimental results. Electronic structure calculations indicate that Al3BC3 has a larger indirect band gap. Based on the first-principles model of intrinsic hardness, the theoretical hardness of Al3BC3 is calculated to be 14.7 GPa, indicating a potential hard material. The analyses of electronic structure, charge density distribution and Mulliken overlap population provide further understanding of the hardness and C–B bonding properties of Al3BC3.
Transport Properties and the Entropy-Scaling Law for Liquid Tantalum and Molybdenum under High Pressure
CAO Qi-Long, HUANG Duo-Hui, YANG Jun-Sheng, WAN Ming-Jie, WANG Fan-Hou
Chin. Phys. Lett. 2014, 31 (06): 066202 .   DOI: 10.1088/0256-307X/31/6/066202
Abstract   PDF(pc) (721KB) ( 324 )
Molecular dynamics simulations are applied to study the transport properties, including the self-diffusion coefficient and viscosity, of liquid tantalum and molybdenum under high pressure conditions. The temperature dependence of self-diffusion coefficient, viscosity and the pair correlation entropy under high pressure conditions are investigated. Our results show that the Arrhenius law well describes the temperature dependence of self-diffusion coefficients and viscosity under high pressure, and the diffusion activation energy decreases with increasing pressure, while the viscosity activation energy increases with increasing pressure. The temperature dependence of the pair correlation entropy is well described by 1/T scaling. Furthermore, we find that the entropy-scaling laws, proposed by Rosenfeld for self-diffusion coefficients and viscosity in simple liquids under ambient pressure, still hold well for liquid tantalum and molybdenum under high pressure conditions.
Exothermic Supercooled Liquid–Liquid Transition in Amorphous Sulfur
ZHANG Dou-Dou, LIU Xiu-Ru, HONG Shi-Ming, LI Liang-Bin, CUI Kun-Peng, SHAO Chun-Guang, HE Zhu, XU Ji-An
Chin. Phys. Lett. 2014, 31 (06): 066401 .   DOI: 10.1088/0256-307X/31/6/066401
Abstract   PDF(pc) (838KB) ( 233 )
Amorphous sulfur (a-S) is prepared by rapidly compressing molten sulfur to high pressure. From differential scanning calorimeter measurements, a large exothermic peak has been observed around 396 K. Online wide-angled x-ray scattering spectra indicate that no crystallization occurs in the temperature range 295–453 K, suggesting that the exothermal process corresponds to an amorphous-to-amorphous transition. The transition from amorphous sulfur to liquid sulfur is further verified by the direct observation of sulfur melt at the temperature of the associated transition. This is the first time of reporting that a-S transforms to liquid sulfur directly, which has avoided a crystallization process. What is more, the transition is an exothermic and a volume expansion process.
A Novel Sandwich Needlelike Structure in Annealed P3HT:PCBM Blend Films
ZENG Xue-Song, SHI Tong-Fei, LI Ning, LI Xin-Hua, ZHAO Yu-Feng, WANG Wen-Bo, ZHOU Bu-Kang, DUAN Hua-Hua, WANG Yu-Qi
Chin. Phys. Lett. 2014, 31 (06): 067201 .   DOI: 10.1088/0256-307X/31/6/067201
Abstract   PDF(pc) (2044KB) ( 456 )
A unique needlelike sandwich structure is observed in the P3HT:PCBM blend films after annealing at 220°C. The real-time observation of a growing needle indicates that the needle exhibits 7 μm/min longitudinal growth rate and no lateral growth. Both confocal fluorescence and Raman microscopic mapping measurements reveal that these needles have a PCBM core sandwiched between P3HT edges. According to the eutectic nature of P3HT:PCBM nature, when annealing at high temperature (~220°C), the aggregation of PCBM results in recrystallization of P3HT in the PCBM-depleted regions. These results will give clearer understanding of the melting, diffusion, and recrystallization behavior of the organic eutectic system.
Synthesis of Homogenous Bilayer Graphene on Industrial Cu Foil
LUO Wen-Gang, WANG Hua-Feng, CAI Kai-Ming, HAN Wen-Peng, TAN Ping-Heng, HU Ping-An, WANG Kai-You
Chin. Phys. Lett. 2014, 31 (06): 067202 .   DOI: 10.1088/0256-307X/31/6/067202
Abstract   PDF(pc) (1723KB) ( 188 )
We synthesize the homogenous graphene films on cheap industrial Cu foils using low pressure chemical vapor deposition. The quality and the number of layers of graphene are characterized by Raman spectra. Through carefully tuning the growth parameters, we find that the growth temperature, hydrocarbon concentration and the growth time can substantially affect the growth of high-quality graphene. Both single and bilayer large size homogenous graphenes have been synthesized in optimized growth conditions. The growth of graphene on Cu surface is found to be self ceasing in the bilayer graphene process with the low solubility of carbon in Cu. Furthermore, we have optimized the transfer process, and clear graphene films almost free from impurity are successfully transferred onto Si/SiO2 substrates. The field effect transistors of bilayer graphene are fabricated, which demonstrates a maximum hole (electron) mobility of 4300 cm2V?1s?1 (1920 cm2V?1s?1) at room temperature.
Transport Properties of Surface-Modulated Gold Atomic-Chains and Nanofilms: Ab initio Calculations
ZHAO Shang-Qian, LÜ Yan, LÜ Wen-Gang, LIANG Wen-Jie, WANG En-Ge
Chin. Phys. Lett. 2014, 31 (06): 067301 .   DOI: 10.1088/0256-307X/31/6/067301
Abstract   PDF(pc) (815KB) ( 199 )
Transport properties of gold atomic-chains and nanofilms under surface modulation are studied by performing self-consistent first-principle calculations. Quantum conducting channels of gold atomic-chains with absorbing atoms can be partly transparent or even blocked for certain injecting energies. Conductances of gold nanofilms with ridges show great dependence on their structures. We demonstrate that the transport properties of gold atomic-chains and nanofilms can be engineered through surface modulation, which may be helpful for designing low-dimensional nanodevices.
A First-principles Study of Spin-polarized Transport Properties of a Co-coordination Complex
WU Qiu-Hua, ZHAO Peng, LIU De-Sheng
Chin. Phys. Lett. 2014, 31 (06): 067302 .   DOI: 10.1088/0256-307X/31/6/067302
Abstract   PDF(pc) (786KB) ( 252 )
Based on non-equilibrium Green's function formalism and density functional theory calculations, we investigate the spin-polarized transport properties of a Co-coordination complex between two gold electrodes, in which a Co ion is trapped between two 4-mercaptopyridine molecules. Our results demonstrate that the transmission spectra of the system show distinctive features in the spin-up and spin-down channels. Moreover, the current-voltage curves confirm that the system can exhibit robust spin-filtering effect at finite bias voltage, giving the system potential in molecular spintronics applications.
Single-ZnO-Nanobelt-Based Single-Electron Transistors
JI Xiao-Fan, XU Zheng, CAO Shuo, QIU Kang-Sheng, TANG Jing, ZHANG Xi-Tian, XU Xiu-Lai
Chin. Phys. Lett. 2014, 31 (06): 067303 .   DOI: 10.1088/0256-307X/31/6/067303
Abstract   PDF(pc) (616KB) ( 265 )
We fabricate single electron transistors based on a single ZnO nanobelt using standard micro-fabrication techniques. The transport properties of the devices are characterized at room temperature and at low temperature (4.2 K). At room temperature, the source-drain current increases linearly as the bias voltage increases, indicating a good ohmic contact in the transistors. At 4.2 K, a Coulomb blockade regime is observed up to a bias voltage of a few millivolts. With scanning the back gate voltage, Coulomb oscillations can be clearly resolved with a period around 1 V. From the oscillations, the charging energy for the single electron transistor is calculated to be about 10 meV, which suggests that confined quantum dots exist with sizes around 35 nm in diameter. The irregular Coulomb diamonds are observed due to the multi-tunneling junctions between dots in the nanobelt.
Surface States of Bi2Se3 Nanowires in the Presence of Perpendicular Magnetic Fields
SHI Li-Kun, LOU Wen-Kai
Chin. Phys. Lett. 2014, 31 (06): 067304 .   DOI: 10.1088/0256-307X/31/6/067304
Abstract   PDF(pc) (690KB) ( 267 )
We study the surface states of Bi2Se3 nanowires (NWs) in the presence of perpendicular magnetic fields. It is found that the minigap of Bi2Se3, arising from the quantized surface states around the circumference of NWs can be closed by perpendicular magnetic fields. With increasing magnetic fields, the Landau levels and edge states appear and localize at the center and edge of NWs, respectively. More interestingly, magnetic fields split the electron surface subbands with opposite tangential momenta, leading to specific edge states with low group velocity.
Weak Electron-Phonon Coupling and Unusual Electron Scattering of Topological Surface States in Sb(111) by Laser-Based Angle-Resolved Photoemission Spectroscopy
XIE Zhuo-Jin, HE Shao-Long, CHEN Chao-Yu, FENG Ya, YI He-Mian, LIANG Ai-Ji, ZHAO Lin, MOU Dai-Xiang, HE Jun-Feng, PENG Ying-Ying, LIU Xu, LIU Yan, LIU Guo-Dong, DONG Xiao-Li, YU Li, ZHANG Jun, ZHANG Shen-Jin, WANG Zhi-Min, ZHANG Feng-Feng, YANG Feng, PENG Qin-Jun, WANG Xiao-Yang, CHEN Chuang-Tian, XU Zu-Yan, ZHOU Xing-Jiang
Chin. Phys. Lett. 2014, 31 (06): 067305 .   DOI: 10.1088/0256-307X/31/6/067305
Abstract   PDF(pc) (1523KB) ( 294 )
High-resolution laser-based angle-resolved photoemission (ARPES) measurements are carried out on Sb(111) single crystal. Two kinds of Fermi surface sheets are observed, which are derived from the topological surface states: one small hexagonal electron-like Fermi pocket around Γ point and the other six elongated lobes of hole-like Fermi pockets around the electron pocket. Clear Rashba-type band splitting due to the strong spin-orbit coupling is observed to be anisotropic in the momentum space. Our super-high-resolution ARPES measurements reveal no obvious kink in the surface band dispersions, indicating a weak electron-phonon interaction in the surface states. In particular, the electron scattering rate for these topological surface states is nearly a constant over a large energy window near the Fermi level that is unusual in terms of the conventional picture.
Electronic and Optic Properties of Cubic Spinel CdX2O4 (X=In, Ga, Al) through Modified Becke–Johnson Potential
A. Manzar, G. Murtaza, R. Khenata, Masood Yousaf, S. Muhammad, Hayatullah
Chin. Phys. Lett. 2014, 31 (06): 067401 .   DOI: 10.1088/0256-307X/31/6/067401
Abstract   PDF(pc) (878KB) ( 402 )
A new potential approximation known as modified Becke–Johnson based on density functional theory is applied to compute the electronic band profile and optical response of CdIn2O4, CdGa2O4 and CdAl2O4 compounds. The direct band gap with common LDA, GGA and EV-GGA is drastically underestimated compared with modified Becke–Johnson approximation, whose results are significantly closer to the experimental findings. The optical properties like dielectric constant, refractive index, reflectivity, optical conductivity and absorption coefficient are also computed. A unique characteristic associated with cation replacement is studied; the replacement of cation In by Ga and Ga by Al significantly reduces the direct energy band gap in these compounds. This variation is of crucial importance for band gap dependent optical properties of these compounds, which is also proof for applications of these compounds in optoelectronic devices.
Anomalous Temperature Dependence of the Quality Factor in a Superconducting Coplanar Waveguide Resonator
ZHOU Pin-Jia, WANG Yi-Wen, WEI Lian-Fu
Chin. Phys. Lett. 2014, 31 (06): 067402 .   DOI: 10.1088/0256-307X/31/6/067402
Abstract   PDF(pc) (813KB) ( 13200 )
We present the measurements of the temperature dependence of the internal quality factor (Qi) of a microwave resonator, well below the superconducting transition temperature. The device is a quarter-wavelength niobium (Tc=9.2 K) coplanar waveguide resonator. The measured |S21| parameter shows typically the skewed Lorentzian distributions, from which the fitted quality factor monotonically decreases with the temperature increasing from 30 mK to 900 mK. It is observed that for the lower temperature range (i.e., at T<700 mK) the temperature dependence of the fitted Qi deviates significantly from the predictions of the usual Mattis–Bardeen theory. The measured 3 dB internal quality factor Q'i also verifies such an anomalous temperature dependence. Physically, this phenomenon could be attributed dominantly to the effects of the two-level systems in the device, rather than the usual temperature-dependent complex conductance.
Observation of Strong-Coupling Pairing with Weakened Fermi-Surface Nesting at Optimal Hole Doping in Ca0.33Na0.67Fe2As2
SHI Ying-Bo, HUANG Yao-Bo, WANG Xiao-Ping, SHI Xun, ROEKEGHEM A-Van, ZHANG Wei-Lu, XU Na, RICHARD Pierre, QIAN Tian, RIENKS Emile, THIRUPATHAIAH S, ZHAO Kan, JIN Chang-Qing, SHI Ming, DING Hong
Chin. Phys. Lett. 2014, 31 (06): 067403 .   DOI: 10.1088/0256-307X/31/6/067403
Abstract   PDF(pc) (938KB) ( 192 )
We report an angle-resolved photoemission investigation of optimally doped Ca0.33Na0.67Fe2As2. The Fermi surface topology of this compound is similar to that of the well-studied Ba0.6K0.4Fe2As2 material, except for larger hole pockets resulting from a higher hole concentration per Fe atoms. We find that the quasi-nesting conditions are weakened in this compound compared to Ba0.6K0.4Fe2As2. Similar to Ba0.6K0.4Fe2As2, we observe nearly isotropic superconducting gaps with Fermi surface-dependent magnitudes for Ca0.33Na0.67Fe2As2. A small variation in the gap size along the momentum direction perpendicular to the surface is found for one of the Fermi surfaces. Our superconducting gap results on all Fermi surface sheets fit simultaneously very well to a global gap function derived from a strong coupling approach, which contains only 2 global parameters.
Consistency between Itinerant and Local-Moment Pictures for Superconductivity in Alkaline Iron Selenide Superconductors
LI Hai-Chao, XIANG Yuan-Yuan, WANG Qiang-Hua
Chin. Phys. Lett. 2014, 31 (06): 067404 .   DOI: 10.1088/0256-307X/31/6/067404
Abstract   PDF(pc) (649KB) ( 202 )
We study the superconducting pairing in an effective one-orbital model for alkaline iron-selenide superconductors. In both itinerant and local-moment pictures, we find that the nearest-neighbor hopping t1 plays a crucial role. The pairing symmetry changes from s-wave to d-wave as t1 is enhanced. For a reasonable t1 relevant to the experiment, the pairing symmetry is s-wave in both pictures, in agreement with the angle-resolved photo-emission. The results resolve the previous theoretical inconsistency in the two pictures.
Structure Dependence of Magnetic Properties for Annealed GaMnN Films Grown by MOCVD
JIANG Xian-Zhe, YANG Xue-Lin , JI Cheng, XING Hai-Ying, YANG Zhi-Jian, WANG Cun-Da, YU Tong-Jun, ZHANG Guo-Yi
Chin. Phys. Lett. 2014, 31 (06): 067501 .   DOI: 10.1088/0256-307X/31/6/067501
Abstract   PDF(pc) (664KB) ( 193 )
GaMnN/GaN multilayers and conventional GaMnN single layers are grown by metal-organic chemical vapor deposition. Both kinds of samples show room-temperature ferromagnetism. After thermal annealing, the sample with GaMnN/GaN multilayer structure displays a larger coercivity and better thermal stability compared to the GaMnN single layer. The annealing effects on VGa related defects are observed from photoluminescence measurements. Moreover, a different magnetic behavior is also found in the annealed GaMnN films grown on different (n-type GaN and p-type GaN) templates. These kinds of structure-dependent magnetic behaviors indicate that defects or carriers transformation introduced during annealing may have important effects on the electronic structure of Mn ions and on the ferromagnetism. Our work may be helpful for further understanding the origin of ferromagnetism in GaN-based diluted magnetic semiconductors.
Charge Loss Characteristics of Different Al Contents in a HfAlO Trapping Layer Investigated by Variable Temperature Kelvin Probe Force Microscopy
ZHANG Dong, HUO Zong-Liang, JIN Lei, HAN Yu-Long, CHU Yu-Qiong, CHEN Guo-Xing, LIU Ming, YANG Bao-He
Chin. Phys. Lett. 2014, 31 (06): 067701 .   DOI: 10.1088/0256-307X/31/6/067701
Abstract   PDF(pc) (1249KB) ( 231 )
Kelvin probe force microscopy (KFM) technology is applied to investigate the charge storage and loss characteristics of the HfAlO charge trapping layer with various Al contents. The experimental results demonstrate that with the increase of Al contents in the HfAlO trapping layer, trap density significantly increases. Improvement of data retention characteristic is also observed. Comparing the vertical charge loss and lateral charge spreading of the HfAlO trapping layers, the former plays a major role in the charge loss mechanism. Variable temperature KFM measurement results show that the extracted effective electron trap energy level increases with increasing Al contents in HfAlO trapping layer, which is in accordance with the charge loss characteristics.
Low Frequency Ultra-Thin Compact Metamaterial Absorber Comprising Split-Ring Resonators
LIN Bao-Qin, DA Xin-Yu, ZHAO Shang-Hong, MENG Wen, LI Fan, ZHENG Qiu-Rong, WANG Bu-Hong
Chin. Phys. Lett. 2014, 31 (06): 067801 .   DOI: 10.1088/0256-307X/31/6/067801
Abstract   PDF(pc) (823KB) ( 380 )
We present a design of a low frequency ultra-thin compact and polarization-insensitive metamaterial absorber (MA). The designed MA is a two-layer structure, a periodic array of novel split-ring resonators (SRRs), which are constructed in an FR4 dielectric layer, and another ultra-thin grounded sheet is attached to the bottom. Numerical simulated results show that the proposed MA can realize effective absorption at the frequency 281.9 MHz, and its overall thickness is just only 0.29% of the resonant wavelength, the unit space is only 2.57%, and the absorbance is kept well for a wide range of incident angles for different polarizations. In addition, the proposed MA is changed into a more compact one when the inter-digital structures are introduced in the SRRs. One convenient experiment is carried out in a rectangular waveguide simulator.
A Model on the Mn Luminescence Band Redshift with Mn(II) Doping and Aggregation within CdS:Mn Microwires
MUHAMMAD Arshad Kamran, ZHANG Yong-You, LIU Rui-Bin, SHI Li-Jie, ZOU Bing-Suo
Chin. Phys. Lett. 2014, 31 (06): 067802 .   DOI: 10.1088/0256-307X/31/6/067802
Abstract   PDF(pc) (1520KB) ( 287 )

We report the microphoto-luminescence band redshifts with individual and multi-Mn(II) ion emissions within CdS microwires. The localized exciton magnetic polarons (LEMPs) corresponding to the – optical transitions of Mn(II) account for this shift. This LEMP emission from the double-, three- and four-Mn(II) ions with ferromagnetic coupling after photoexcitation can happen in diluted magnetic semiconductors, except for the individual Mn(II) doping. In addition, a simple spin-exchange polaronic model is established to account for these emission peaks well. Through this model, we can verify the local geometry of the Mn(II) ions in CdS microwires.

Near-Infrared Properties of Hybridized Plasmonic Rectangular Split Nanorings
LIAO Zhong-Wei, HUANG Ying-Zhou, WANG Xiao-Yong, CHAU Irene Yeung-Yeung, WANG Shu-Xia, WEN Wei-Jia
Chin. Phys. Lett. 2014, 31 (06): 067803 .   DOI: 10.1088/0256-307X/31/6/067803
Abstract   PDF(pc) (2161KB) ( 283 )
The near-infrared properties of gold rectangular split nanorings (RSNs) are investigated by simulation using the finite element method. In the results, the distribution and enhancement of electromagnetic (EM) fields are confirmed by the distribution of charge and current density. The spectrum variation with split distance of RSNs in absorption is in accordance with the hybridization theory. The influence of split distance and light wavelength on the enhancement of EM field is also studied for devices that make use of surface plasmon resonance in near-infrared, such as in optical trapping, biomedicine, and solar energy. Additionally, the spectra in mediums with various refractive indices suggest the potential application of the hybridized plasmonic RSNs as an ultra-sensitive sensor in the near-infrared region.
Influence of Electric Field Distribution on High-Power Array Antenna Radiation Pattern with Rectangular Aperture
YANG Yi-Ming, YUAN Cheng-Wei, QIAN Bao-Liang
Chin. Phys. Lett. 2014, 31 (06): 068401 .   DOI: 10.1088/0256-307X/31/6/068401
Abstract   PDF(pc) (790KB) ( 198 )
The antenna element with rectangular aperture is one of the main forms of the array antenna. The electric field amplitude distribution of the rectangular aperture, as well as the phase distribution is the most important parameter that affects the radiation gain and beam direction of the array antenna. In this work, a theoretical study is carried out on array antennae for high-power microwave (HPM) applications. An electric integration method is applied to obtain the far-field radiation pattern with different kinds of electric field distributions. Moreover, the influence of the electric field amplitude and phase on the performance of the array antenna is analyzed. For one antenna element, uniform electric field distribution is not the best choice. However, the uniform distribution has specific advantages for an array antenna consisting of combined antenna elements. The phase deviation has more significant influence on the performance of the array antenna than the amplitude deviation. It indicates that a good working phase shifter with high-power capacity and time-adjusting capability is very important.
Developments of High-Efficiency Flexible Cu(In,Ga)Se2 Thin Film Solar Cells on a Polyimide Sheet by Sodium Incorporation
ZHANG Li, LIU Fang-Fang, LI Feng-Yan, HE Qing, LI Chang-Jian, LI Bao-Zhang, ZHU Hong-Bing
Chin. Phys. Lett. 2014, 31 (06): 068402 .   DOI: 10.1088/0256-307X/31/6/068402
Abstract   PDF(pc) (569KB) ( 362 )
We present the fabrication of flexible Cu(In,Ga)Se2 (CIGS) solar cells on a polyimide (PI) sheet with and without Na incorporation. A sodium element is incorporated into the CIGS absorber by using a NaF precursor after Mo back contact deposition. X-ray diffraction patterns show that the (112) preferred orientation of the as-grown CIGS films is decreased by Na incorporation. The secondary phase of (Inx,Ga1?x)2Se3 is observed for the CIGS films with Na. There is no significant difference in the grain size with and without Na incorporation from surface and cross-sectional SEM images. Additionally, the increase of carrier concentration and decrease of resistivity of CIGS absorber are induced by Na doping. Finally, the flexible CIGS solar cells on PI sheets with efficiency close to 11%, containing Na, are achieved. The improvement of cell efficiency can be attributed to the modified electrical properties of the CIGS film by Na incorporation.
Properties of Heat Generation in a Double Quantum Dot
ZHOU Li-Ling, LI Yong-Jun, HU Hua
Chin. Phys. Lett. 2014, 31 (06): 068501 .   DOI: 10.1088/0256-307X/31/6/068501
Abstract   PDF(pc) (697KB) ( 169 )
We investigate the electronic-current-induced heat generation in a double quantum dot connected by two normal leads. The dots are coupled in series with a coupling strength td. It is found that, at zero temperature and weak dot-lead coupling, td affects the heating and current heavily. In particular, the effects on the heat generation and on the current are quite different. For example, at a heating valley the current can exhibit a deep valley, a plateau, or a high peak depending on td. As a result, we can find an ideal working condition, large current while small heating, for the double dots system by tuning the interdot coupling strength.
High-Voltage AlGaN/GaN-Based Lateral Schottky Barrier Diodes
KANG He, WANG Quan, XIAO Hong-Ling, WANG Cui-Mei, JIANG Li-Juan, FENG Chun, CHEN Hong, YIN Hai-Bo, WANG Xiao-Liang, WANG Zhan-Guo, HOU Xun
Chin. Phys. Lett. 2014, 31 (06): 068502 .   DOI: 10.1088/0256-307X/31/6/068502
Abstract   PDF(pc) (600KB) ( 688 )
Lateral Schottky barrier diodes (SBDs) on AlGaN/GaN heterojunctions are fabricated and studied. The characteristics of the fabricated SBDs with different Schottky contact diameters and different Schottky-Ohmic contact spacings are investigated. The breakdown voltage can be increased by either increasing the Schottky-Ohmic contact spacing or increasing the Schottky contact diameter. However, the specific on-resistance is increased at the same time. A high breakdown voltage of 1400 V and low reverse leakage current below 20 nA are achieved by the device with a Schottky contact diameter of 100 μm and a contact spacing of 40 μm, yielding a high VBR2/RON,sp value of 194 MW?cm?2.
Ion Binding Energies Determining Functional Transport of ClC Proteins
YU Tao, GUO Xu, ZOU Xian-Wu, SANG Jian-Ping
Chin. Phys. Lett. 2014, 31 (06): 068701 .   DOI: 10.1088/0256-307X/31/6/068701
Abstract   PDF(pc) (724KB) ( 140 )
The ClC-type proteins, a large family of chloride transport proteins ubiquitously expressed in biological organisms, have been extensively studied for decades. Biological function of ClC proteins can be reflected by analyzing the binding situation of Cl? ions. We investigate ion binding properties of ClC-ec1 protein with the atomic molecular dynamics simulation approach. The calculated electrostatic binding energy results indicate that Cl? at the central binding site Scen has more binding stability than the internal binding site Sint. Quantitative comparison between the latest experimental heat release data isothermal titration calorimetry (ITC) and our calculated results demonstrates that chloride ions prefer to bind at Scen than Sint in the wild-type ClC-ec1 structure and prefer to bind at Sext and Scen than Sint in mutant E148A/E148Q structures. Even though the chloride ions make less contribution to heat release when binding to Sint and are relatively unstable in the Cl? pathway, they are still part contributors for the Cl? functional transport. This work provides a guide rule to estimate the importance of Cl? at the binding sites and how chloride ions have influences on the function of ClC proteins.
A Simple Interconnection Layer for Tandem Organic Solar Cells with Improved Efficiency and Fill Factor
ZHENG Ke-Ning, YANG Li-Ying, CAO Huan-Qi, QIN Wen-Jing, YIN Shou-Gen
Chin. Phys. Lett. 2014, 31 (06): 068801 .   DOI: 10.1088/0256-307X/31/6/068801
Abstract   PDF(pc) (566KB) ( 563 )

We demonstrate a simple interconnection layer (ICL) that can be employed in tandem organic solar cells. An ICL with an optimized structure of Ca/Au/MoO3 is used between two sub cells composed of identical regioregularpoly(3-hexylthiophen) (P3HT):[6,6]-phenyl C61-butyric acid methylester (PCBM) photoactive layers. Power conversion efficiency (PCE) of 3.24% and fill factor (FF) of 68.0% are achieved with such an ICL under simulated sunlight (100 mW⋅cm−2). Compared with the best values of devices with ICLs of Ca/Al/MoO3, PCE is improved by 68.9% and FF is improved by 15.5%. The improved performances are attributed to the optical and electrical balances in both sub cells. The presented ICL extracts free charges efficiently from both sub cells thereby suppressing the exaction recombination in each sub cell.

Effect of Mixing Assortativity on Extreme Events in Complex Networks
LING Xiang
Chin. Phys. Lett. 2014, 31 (06): 068901 .   DOI: 10.1088/0256-307X/31/6/068901
Abstract   PDF(pc) (678KB) ( 285 )
We investigate the effect of mixing assortativity on the occurrence of extreme events in complex networks. The bias random walk model is adopted with a preferential transition probability tuned by a parameter α. We derive exact expressions for the stationary distribution probability and for the occurrence probability of extreme events. They reveal that the occurrence of extreme events strongly depends on the mixing assortativity of the network. It is shown that, for non-assortative (rk=0), assortative (rk=0.15) and disassortative (rk=?0.15) scale-free networks, the minimal occurrence of extreme events will happen at α=?1.0, α=?0.6 andα=0.2, respectively.
62 articles