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Volume 32 Issue 09
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Quantum Illumination with Noiseless Linear Amplifier
ZHANG Sheng-Li, WANG-Kun, GUO Jian-Sheng, SHI Jian-Hong
Chin. Phys. Lett. 2015, 32 (09): 090301 .   DOI: 10.1088/0256-307X/32/9/090301
Abstract   PDF(pc) (602KB) ( 22740 )
Quantum illumination, that is, quantum target detection, is to detect the potential target with two-mode quantum entangled state. For a given transmitted energy, the quantum illumination can achieve a target-detection probability of error much lower than the illumination scheme without entanglement. We investigate the usefulness of noiseless linear amplification (NLA) for quantum illumination. Our result shows that NLA can help to substantially reduce the number of quantum entangled states collected for joint measurement of multi-copy quantum state. Our analysis on the NLA-assisted scheme could help to develop more efficient schemes for quantum illumination.
On Delay of the Delayed Choice Experiment
SUN Jun, SUN Yong-Nan, LI Chuan-Feng, GUO Guang-Can
Chin. Phys. Lett. 2015, 32 (09): 090302 .   DOI: 10.1088/0256-307X/32/9/090302
Abstract   PDF(pc) (529KB) ( 609 )
Following a suggestion by Wheeler, several delayed choice experiments have been performed. However, in those experiments one fact has always been ignored: that due to the fact that the single photon is nonlocal in time, the outcome will change if one changes the time to switch the experimental configuration within the photon's wavepacket. This study obtains some insights into this aspect by proposing an experimental scheme based on the delayed choice experiment and giving some related analysis. The result shows a transitional behavior from a particle to a wave, leading to a conclusion that the measuring operator could be time dependent and be changed in a single measurement.
Seismic Noise Suppression for Ground-Based Investigation of an Inertial Sensor by Suspending the Electrode Cage
TAN Ding-Yin, YIN Hang, ZHOU Ze-Bing
Chin. Phys. Lett. 2015, 32 (09): 090401 .   DOI: 10.1088/0256-307X/32/9/090401
Abstract   PDF(pc) (417KB) ( 432 )
Performance test of a high precise accelerometer or an inertial sensor on the ground is inevitably limited by the seismic noise. A torsion pendulum has been used to investigate the performances of an electrostatic accelerometer, where the test mass is suspended by a fiber to compensate for its weight, and this scheme demonstrates an advantage, compared with the high-voltage levitation scheme, in which the effect of the seismic noise can be suppressed for a few orders of magnitude in low frequencies. In this work, the capacitive electrode cage is proposed to be suspended by another pendulum, and theoretical analysis shows that the effects of the seismic noise can be further suppressed for more than one order by suspending the electrode cage.
A Multifractal Detrended Fluctuation Analysis of the Ising Financial Markets Model with Small World Topology
ZHANG Ang-Hui, LI Xiao-Wen, SU Gui-Feng, ZHANG Yi
Chin. Phys. Lett. 2015, 32 (09): 090501 .   DOI: 10.1088/0256-307X/32/9/090501
Abstract   PDF(pc) (929KB) ( 12666 )

We present a multifractal detrended fluctuation analysis (MFDFA) of the time series of return generated by our recently-proposed Ising financial market model with underlying small world topology. The result of the MFDFA shows that there exists obvious multifractal scaling behavior in produced time series. We compare the MFDFA results for original time series with those for shuffled series, and find that its multifractal nature is due to two factors: broadness of probability density function of the series and different correlations in small- and large-scale fluctuations. This may provide new insight to the problem of the origin of multifractality in financial time series.

First Evaluation and Frequency Measurement of the Strontium Optical Lattice Clock at NIM
LIN Yi-Ge, WANG Qiang, LI Ye, MENG Fei, LIN Bai-Ke, ZANG Er-Jun, SUN Zhen, FANG Fang, LI Tian-Chu, FANG Zhan-Jun
Chin. Phys. Lett. 2015, 32 (09): 090601 .   DOI: 10.1088/0256-307X/32/9/090601
Abstract   PDF(pc) (546KB) ( 949 )

An optical lattice clock based on 87Sr is built at National Institute of Metrology (NIM) of China. The systematic frequency shifts of the clock are evaluated with a total uncertainty of 2.3×10−16. To measure its absolute frequency with respect to NIM's cesium fountain clock NIM5, the frequency of a flywheel H-maser of NIM5 is transferred to the Sr laboratory through a 50-km-long fiber. A fiber optical frequency comb, phase-locked to the reference frequency of this H-maser, is used for the optical frequency measurement. The absolute frequency of this Sr clock is measured to be 429228004229873.7(1.4) Hz.

Measurement of Refractive Index Ranging from 1.42847 to 2.48272 at 1064 nm Using a Quasi-Common-Path Laser Feedback System
XU Ling, TAN Yi-Dong, ZHANG Shu-Lian, SUN Li-Qun
Chin. Phys. Lett. 2015, 32 (09): 090701 .   DOI: 10.1088/0256-307X/32/9/090701
Abstract   PDF(pc) (569KB) ( 424 )
Wavelength 1064 nm is one of the most widely used laser wavelengths in industries and science. The high-precision measurement of the refractive index of optical materials at 1064 nm is significant for improving the optical design. We study the direct measurement of refractive index at 1064 nm of lasers, including calcium fluoride (CaF2), fused silica and zinc selenide (ZnSe), whose refractive indices cover a large range from 1.42847 to 2.48272. The measurement system is built based on the quasi-common-path Nd:YAG laser feedback interferometry. The thickness can be measured simultaneously with the refractive index. The results demonstrate that the system has absolute uncertainties of ~10?5 and ~10?4 mm in refractive index and thickness measurement, respectively.
Consistency of Perfect Fluidity and Jet Quenching in Semi-Quark-Gluon Monopole Plasmas
Jiechen Xu, Jinfeng Liao, Miklos Gyulassy
Chin. Phys. Lett. 2015, 32 (09): 092501 .   DOI: 10.1088/0256-307X/32/9/092501
Abstract   PDF(pc) (654KB) ( 604 )

We utilize a new framework, CUJET3.0, to deduce the energy and temperature dependence of the jet transport parameter, q^ (E<10 GeV, T), from a combined analysis of available data on nuclear modification factor and azimuthal asymmetries from high energy nuclear collisions at RHIC/BNL and LHC/CERN. Extending a previous perturbative-QCD based jet energy loss model (known as CUJET2.0) with (2+1)D viscous hydrodynamic bulk evolution, this new framework includes three novel features of nonperturbative physics origin: (i) the Polyakov loop suppression of color-electric scattering (aka 'semi-QGP' of Pisarski et al.), (ii) the enhancement of jet scattering due to emergent magnetic monopoles near Tc (aka 'magnetic scenario' of Liao and Shuryak), and (iii) thermodynamic properties constrained by lattice QCD data. CUJET3.0 reduces to v2.0 at high temperatures T>400 MeV, while greatly enhances q^ near the QCD deconfinement transition temperature range. This enhancement accounts well for the observed elliptic harmonics of jets with pT>10 GeV. Extrapolating our data-constrained q^ down to thermal energy scales, E∼2 GeV, we find for the first time a remarkable consistency between high energy jet quenching and bulk perfect fluidity with η/s T3q^∼0.1 near Tc.

Dual-Wavelength Bad Cavity Laser as Potential Active Optical Frequency Standard
XU Zhi-Chao, PAN Duo, ZHUANG Wei, CHEN Jing-Biao
Chin. Phys. Lett. 2015, 32 (09): 093201 .   DOI: 10.1088/0256-307X/32/9/093201
Abstract   PDF(pc) (758KB) ( 460 )
We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118°C and 144°C, both the 1359 nm and 1470 nm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127°C Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a≈40 for 1359 nm and 1470 nm lasers. The 1470 nm laser linewidth is measured to be 407.3 Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.
Nucleus–Nucleus Effects in Fully Differential Cross Sections for Energetic C6++He Collisions with Small Momentum Transfer
LU Chen-Wen, AN Wen-Fang, SUN Shi-Yan, JIA Xiang-Fu
Chin. Phys. Lett. 2015, 32 (09): 093401 .   DOI: 10.1088/0256-307X/32/9/093401
Abstract   PDF(pc) (653KB) ( 312 )
The modified Coulomb–Born approximation with and without the internuclear interaction (MCB-NN and MCB) is used to calculate the fully differential cross sections (FDCS) for the single ionization of helium by 100 MeV/amu C6+ impact. The effects of the internuclear interaction on the FDCS are examined in geometries. The results are compared with experimental data and theoretical predictions from a three-body distorted-wave (3DW) model and a time-dependent close-coupling model. It is shown that the present MCB-NN results are in good agreement with the experiments in the scattering plane and the MCB results qualitatively reproduce the experimental structure outside the scattering plane. In particular, the MCB theory predicts the 'double-peak' structure in the perpendicular plane.
Giant Asymmetric Transmission and Optical Rotation of a Three-Dimensional Metamaterial
HUANG Lei, FAN Yun-Hui, WU Shan, YU Li-Zhi
Chin. Phys. Lett. 2015, 32 (09): 094101 .   DOI: 10.1088/0256-307X/32/9/094101
Abstract   PDF(pc) (681KB) ( 459 )
We show that giant asymmetric transmission and optical rotation for linear polarizations can be achieved by a chiral three-dimensional metamaterial composed of L-shaped and C-shaped metallic particles. Numerical calculations on the electric field distributions indicate that the coupling between the electric dipolar and quadrupolar resonances in the L- and C-shaped metallic particles contributes to these effects.
High-Power Continuous-Wave Nd:GdVO4 Solid-State Laser Dual-End-Pumped at 880 nm
MAO Ye-Fei, ZHANG Heng-Li, SANG Si-Han, ZHANG Xin, YU Xi-Long, XING Ji-Chuan, XIN Jian-Guo, JIANG Yi
Chin. Phys. Lett. 2015, 32 (09): 094201 .   DOI: 10.1088/0256-307X/32/9/094201
Abstract   PDF(pc) (682KB) ( 416 )
A high-power cw all-solid-state Nd:GdVO4 laser operating at 880 nm is reported. The laser consists of a low doped level Nd:GdVO4 crystal dual-end-pumped by two high-power diode lasers and a compact negative confocal unstable–stable hybrid resonator. At an incident pump power of 820 W, a maximum cw output of 240 W at 1064 nm is obtained. The optical-to-optical efficiency and slope efficiency are 40.7% and 53.2%, respectively. The M2 factors in the unstable direction and in the stable direction are 4.38 and 5.44, respectively.
Theoretical Study of Local Surface Plasmon Resonances on a Dielectric-Ag Core-Shell Nanosphere Using the Discrete-Dipole Approximation Method
MA Ye-Wan, WU Zhao-Wang, ZHANG Li-Hua, LIU Wan-Fang, ZHANG Jie
Chin. Phys. Lett. 2015, 32 (09): 094202 .   DOI: 10.1088/0256-307X/32/9/094202
Abstract   PDF(pc) (495KB) ( 427 )
The local surface plasmon resonances (LSPRs) of dielectric-Ag core-shell nanospheres are studied by the discrete-dipole approximation method. The result shows that LSPRs are sensitive to the surrounding medium refractive index, which shows a clear red-shift with the increasing surrounding medium refractive index. A dielectric-Ag core-shell nanosphere exhibits a strong coupling between the core and shell plasmon resonance modes. LSPRs depend on the shell thickness and the composition of dielectric-core and metal-shell. LSPRs can be tuned over a longer wavelength range by changing the ratio of core to shell value. The lower energy mode ω? shows a red-shift with the increasing dielectric-core value and the inner core radius, while blue-shifted with the increasing outer shell thickness. The underlying mechanisms are analyzed with the plasmon hybridization theory and the phase retardation effect.
Electromagnetically Induced Self-Imaging in Four-Level Doppler Broadening Medium
WANG Chun-Fang, WANG Feng, YANG Li-Ru
Chin. Phys. Lett. 2015, 32 (09): 094203 .   DOI: 10.1088/0256-307X/32/9/094203
Abstract   PDF(pc) (622KB) ( 359 )
We show the influences of temperature on the self-imaging in the coherent atomic system which consists of four-level 87Rb atoms. The different-direction self-imaging, the corresponding imaging quality, and the imaging contrast ratio in this Doppler broadening medium are studied. As a result, the imaging-position linearly increases with the temperature, while the quality of the self-imaging does not show clear connection with the temperature. Due to the weaker mutual interference in the higher temperature, the contrast ratios in the two directions increase. The interesting results are important and may have potential applications in imaging storage and processing.
A Polarization-Insensitive Broadband Metamaterial Absorber at the Optical Regime
SHI Jun-Xian, ZHANG Wen-Chao, XU Wan, ZHU Qing, JIANG Xia, LI Dong-Dong, YAN Chang-Chun, ZHANG Dao-Hua
Chin. Phys. Lett. 2015, 32 (09): 094204 .   DOI: 10.1088/0256-307X/32/9/094204
Abstract   PDF(pc) (807KB) ( 402 )
We present a polarization-insensitive broadband absorber which has a feature of metal-insulator-metal structures. The top metal layer consists of four-fan-rings-shaped gold. Simulations show that the absorber exhibits an absorption of nearly unity at the wavelength of 386.1 nm and a relative absorption bandwidth of 0.548, which refers to the ratio of the full absorption bandwidth over an absorption of 0.9 to the central wavelength. Meanwhile, the absorption is nearly independent of the polarized direction of the incident wave. This absorption bandwidth with insensitive polarization is widely reported to date for such metal-insulator-metal structures. Such a structure offers a way of realization of a polarization-insensitive broadband absorber ranging in ultraviolet-to-visible wavelengths.
Electromagnetic Scattering of a High-Order Bessel Trigonometric Beam by Typical Particles
CUI Zhi-Wei, HAN Yi-Ping, CHEN An-Tao
Chin. Phys. Lett. 2015, 32 (09): 094205 .   DOI: 10.1088/0256-307X/32/9/094205
Abstract   PDF(pc) (2126KB) ( 374 )
The scattering of an electromagnetic high-order Bessel trigonometric beam by several typical homogeneous dielectric particles is investigated. The incident beam is represented by the vector expressions in Cartesian coordinates. The scattering problems involving homogeneous dielectric particles are formulated with the surface integral equation method. As an example, the effects of the beam's parameters on the differential scattering cross section for a sphere are analyzed in detail. Then the numerical results for the scattering of a high-order Bessel trigonometric beam by three typical nonspherical particles, including a spheroid, a cylinder, and a cube, are presented.
A Single-Frequency Linearly Polarized Fiber Laser Using a Newly Developed Heavily Tm3+-Doped Germanate Glass Fiber at 1.95 µm
YANG Qi, XU Shan-Hui, LI Can, YANG Chang-Sheng, FENG Zhou-Ming, XIAO Yu, HUANG Xiang, YANG Zhong-Min
Chin. Phys. Lett. 2015, 32 (09): 094206 .   DOI: 10.1088/0256-307X/32/9/094206
Abstract   PDF(pc) (666KB) ( 504 )
A compact linearly polarized, low?noise, narrow-linewidth, single-frequency fiber laser at 1950 nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm3+-doped germanate glass fiber. Over 100-mW stable continuous-wave single transverse and longitudinal mode lasing at 1950 nm are achieved. The measured relative intensity noise is less than -135 dB/Hz at frequencies over 5 MHz. The signal-to-noise ratio of the laser is larger than 72 dB, and the laser linewidth is less than 6 kHz, while the obtained linear polarization extinction ratio is higher than 22 dB.
A 60 W Tm:YLF Laser with Triple Tm:YLF Rods
ZHU Guo-Li
Chin. Phys. Lett. 2015, 32 (09): 094207 .   DOI: 10.1088/0256-307X/32/9/094207
Abstract   PDF(pc) (572KB) ( 545 )
A narrow linewidth stable high-power continuous-wave 3.5% Tm3+ doped LiYF4 (Tm:YLF) laser is reported. By using dual F–P etalons and three Tm:YLF rods in a cavity, laser output of ~60 W at 1907.7 nm is obtained with a slope efficiency of 34.8%. The M2 factor is found to be ~2.0 under an output power of 30 W. In addition, the relaxation oscillation and efficiency of the Tm:YLF laser are also studied. The relaxation oscillation of the Tm:YLF laser is improved obviously by setting the ratio of pump beam to oscillating laser beam as ~1.5:1 and the efficiency is increased in comparison with the ratio of ~1.3:1.
Vector Based Reconstruction Method in Magneto-Acousto-Electrical Tomography with Magnetic Induction
GUO Liang, LIU Guang-Fu, YANG Yan-Ju, LIU Guo-Qiang
Chin. Phys. Lett. 2015, 32 (09): 094301 .   DOI: 10.1088/0256-307X/32/9/094301
Abstract   PDF(pc) (492KB) ( 435 )
Magneto-acousto-electrical tomography with magnetic induction (MAET-MI) is an imaging modality proposed for noninvasive conductivity imaging of high spatial resolution. A conductivity reconstruction algorithm based on the current vector is presented in the MAET-MI. Firstly, the fundamental mechanism of the MAET-MI is introduced in both the forward and the inverse problems. Then the orthogonal matching pursuit algorithm is implemented to reconstruct the current vector according to the reciprocal theorem. Furthermore, the two components of the current vector are employed to reconstruct the conductivity, which is based on the proposed logarithmic reconstruction algorithm. Lastly, a computer simulation is conducted to show the capability and the reliability of the proposed method in the conductivity reconstruction.
Analysis of Long-Range Transmission Loss in the West Pacific Ocean
WU Li-Li, PENG Zhao-Hui
Chin. Phys. Lett. 2015, 32 (09): 094302 .   DOI: 10.1088/0256-307X/32/9/094302
Abstract   PDF(pc) (672KB) ( 399 )
A long-range sound propagation experiment was conducted in the West Pacific Ocean in July 2013. Linear frequency-modulated signals with a frequency band of 260–360 Hz were transmitted by a transducer hung on a floating ship during the experiment and were received by a horizontal line array towed by another ship sailing away from the transducer. The maximum distance between the two ships was 1029 km. Signals were received at the distances 34–220 km, 612–635 km and 926–1029 km. Transmission loss versus distance between source and receiver was obtained and compared with the theoretical results predicted by the parabolic equation method program RAM. It is shown that RAM is adequate for estimating the transmission loss for distances up to 1029 km. When the water depth is larger than the surface conjugate depth, the ocean bottom rarely influences the transmission loss in the convergence zones. However, in the opposite situation, the ocean bottom contributes significantly to the transmission loss.
Self-Organized Criticality Theory Model of Thermal Sandpile
PENG Xiao-Dong, QU Hong-Peng, XU Jian-Qiang, HAN Zui-Jiao
Chin. Phys. Lett. 2015, 32 (09): 094501 .   DOI: 10.1088/0256-307X/32/9/094501
Abstract   PDF(pc) (731KB) ( 356 )
A self-organized criticality model of a thermal sandpile is formulated for the first time to simulate the dynamic process with interaction between avalanche events on the fast time scale and diffusive transports on the slow time scale. The main characteristics of the model are that both particle and energy avalanches of sand grains are considered simultaneously. Properties of intermittent transport and improved confinement are analyzed in detail. The results imply that the intermittent phenomenon such as blobs in the low confinement mode as well as edge localized modes in the high confinement mode observed in tokamak experiments are not only determined by the edge plasma physics, but also affected by the core plasma dynamics.
Characteristics of Resistance Triggering of a Pulsed Vacuum Arc Ion Source
LAN Chao-Hui, LONG Ji-Dong, ZHENG Le, DONG Pan, YANG Zhen, WANG Tao, LI Jie
Chin. Phys. Lett. 2015, 32 (09): 095201 .   DOI: 10.1088/0256-307X/32/9/095201
Abstract   PDF(pc) (996KB) ( 546 )
Triggering scheme is a significant factor that may influence the process of vacuum arc initiation. In this work, the characteristics of resistance triggering of a pulsed vacuum arc ion source are investigated and compared with the independent pulse generator triggering. The results show that although the resistance triggering method is capable of triggering a vacuum arc ion source by properly choosing the resistance and electric parameters, it inevitably increases the rise time of the arc current. A high speed multiframe camera is used to reveal the transition process of arc initiation during one shot. From the images it is conjectured that the lower voltage between the cathode and the anode may be the reason that leads to the lower transition speed of discharge at the moment of arc initiation.
How Does the Guide Field Affect the Asymmetry of Hall Magnetic and Electric Fields in Fast Magnetic Reconnection?
LAI Xiang-Sheng, ZHOU Meng, DENG Xiao-Hua, LI Tang-Mu, HUANG Shi-Yong
Chin. Phys. Lett. 2015, 32 (09): 095202 .   DOI: 10.1088/0256-307X/32/9/095202
Abstract   PDF(pc) (2164KB) ( 340 )
Recent studies show that the out-of-plane quadrupolar magnetic field in fast magnetic reconnection is distorted in the presence of a guide field. It is asymmetric with respect to the current sheet. In this work, we analyze the spatial and amplitude asymmetries of the Hall magnetic field By and the Hall electric field Ez in reconnection with different guide fields by a series of 2.5-D particle-in-cell simulations. We derive the relation between the asymmetry of By and Ez and the guide field strength. In addition, by analyzing the different terms in the generalized ohm's law, we find that the electric field Ez is mainly balanced by the Hall term, and the amplitude asymmetry is mainly caused by the Hall effect.
Fabrication of Amorphous Silver Nanowires by Helium Ion Beam Irradiation
Shehla H., Ali A. Zongo S. Javed I. Ishaq A. Khizar H. Naseem S. Maaza M.
Chin. Phys. Lett. 2015, 32 (09): 096101 .   DOI: 10.1088/0256-307X/32/9/096101
Abstract   PDF(pc) (752KB) ( 528 )
Amorphous silver nanowires (a-Ag NWs) are fabricated from crystalline Ag NWs by using 5 MeV helium (He+) ion beam irradiation. At low dose (5×1015 ion/cm2), few defects are created in Ag NWs. As dose increases, more damage to the crystalline structure of Ag NWs is observed. Finally at high dose (8×1016 ion/cm2), the face-centered cubic structure of Ag NWs is transformed into the amorphous structure with similar morphology as Ag NWs. Phase transformation of crystalline Ag NWs upon irradiation with 5 MeV He+ ions is observed through high resolution transmission electron microscopy. Synthesis of large scale amorphous metal nanowires and metal nanowire alloy systems are discussed.
Electronic and Optical Properties of TiS2 Determined from Generalized Gradient Approximation Study
Hamza El-Kouch, Larbi El Farh, Jamal Sayah, Allal Challioui
Chin. Phys. Lett. 2015, 32 (09): 096102 .   DOI: 10.1088/0256-307X/32/9/096102
Abstract   PDF(pc) (659KB) ( 1015 )
The electronic and optical properties of TiS2 are studied by using an ab-initio calculation within the frame of density functional theory. A linearized and augmented plane wave basis set with the generalized gradient approximation as proposed by Perdew et al. is used for the energy exchange-correlation determination. The results show a metallic character of TiS2, and the plots of total and partial densities of states of TiS2 show the metallic character of the bonds and a strong hybridization between the states d of Ti and p of S below the Fermi energy. The optical properties of the material such as real and imaginary parts of dielectric constant (ε(ω)=ε1 (ω)+iε2 (ω)), refractive index n(ω), optical reflectivity R(ω), for E//x and E//z are performed for the energy range of 0–14 eV.
Urtra-Hard Bonds in P-Carbon Stronger than Diamond
GUO Wen-Feng, WANG Ling-Sheng, LI Zhi-Ping, XIA Mei-Rong, GAO Fa-Ming
Chin. Phys. Lett. 2015, 32 (09): 096201 .   DOI: 10.1088/0256-307X/32/9/096201
Abstract   PDF(pc) (592KB) ( 424 )
The hardness and ideal strength of P-carbon, i.e., a new carbon phase for the cold-compressed carbon with an orthogonal structure recently proposed and named as P-carbon, are investigated by means of first-principles calculations. The strength calculations reveal that the failure mode in P-carbon is dominated by the tensile type. The ideal tensile strength of P-carbon is calculated to be 76.7 GPa in the [001] direction, which is higher than that of the previously known most stable Z-carbon, of 71.4 GPa. Meanwhile, the theoretical Vickers hardness of P-carbon is estimated as 89 GPa, which is comparable with that of diamond. Especially, two types of bonds in P-carbon with hardness values of 114 GPa and 105 GPa are significantly stronger than those of diamond. The results provide insight into exploration of the ultra-hard P-carbon for potentially technological applications.
Low Thermal Conductivity of Paperclip-Shaped Graphene Superlattice Nanoribbons
LU Xing, ZHONG Wei-Rong
Chin. Phys. Lett. 2015, 32 (09): 096501 .   DOI: 10.1088/0256-307X/32/9/096501
Abstract   PDF(pc) (823KB) ( 451 )
We design some graphene superlattice structures with ultra-low thermal conductivity 121 W/mK, which is only 6% of the straight graphene nanoribbons. The thermal conductivity of graphene superlattice nanoribbons (GSNRs) is investigated by using molecular dynamics simulations. It is reported that the thermal conductivity of graphene superlattice nanoribbons is significantly lower than that of the straight graphene nanoribbons (GNRs). Compared with the phonon spectra of straight GNRs, GSNRs have more forbidden bands. The overlap of phonon spectra between two supercells is shrinking.
Nanoindentation Models of Monolayer Graphene and Graphyne under Point Load Pattern Studied by Molecular Dynamics
XIANG Lang, WU Jian, MA Shuang-Ying, WANG Fang, ZHANG Kai-Wang
Chin. Phys. Lett. 2015, 32 (09): 096801 .   DOI: 10.1088/0256-307X/32/9/096801
Abstract   PDF(pc) (726KB) ( 486 )
Molecular dynamics simulations are performed to study the nanoindentation models of monolayer suspended graphene and graphyne. Fullerenes are selected as indenters. Our results show that Young's modulus of monolayer-thick graphyne is almost half of that of graphene, which is estimated to be 0.50 TPa. The mechanical properties of graphene and graphyne are different in the presence of strain. A pre-tension has an important effect on the mechanical properties of a membrane. Both the pre-tension and Young's modulus plots demonstrate index behavior. The toughness of graphyne is stronger than that of graphene due to Young's modulus magnitude. Young's moduli of graphene and graphyne are almost independent of the size ratio of indenter to membrane.
Effects of Si δ-Doping Condition and Growth Interruption on Electrical Properties of InP-Based High Electron Mobility Transistor Structures
ZHOU Shu-Xing, QI Ming, AI Li-Kun, XU An-Huai, WANG Li-Dan, DING Peng, JIN Zhi
Chin. Phys. Lett. 2015, 32 (09): 097101 .   DOI: 10.1088/0256-307X/32/9/097101
Abstract   PDF(pc) (1116KB) ( 502 )
The InGaAs/InAlAs/InP high electron mobility transistor (HEMT) structures with lattice-matched and pseudomorphic channels are grown by gas source molecular beam epitaxy. Effects of Si δ-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si δ-doping concentration (Nd) is about 5.0×1012 cm?2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission electron microscopy. An InGaAs/InAlAs/InP HEMT device with a gate length of 100 nm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT=249 GHz and fmax>400 GHz.
Structural and Transport Properties of the Weyl Semimetal NbAs at High Pressure
ZHANG Jun, LIU Feng-Liang, DONG Jin-Kui, XU Yang, LI Na-Na, YANG Wen-Ge, LI Shi-Yan
Chin. Phys. Lett. 2015, 32 (09): 097102 .   DOI: 10.1088/0256-307X/32/9/097102
Abstract   PDF(pc) (641KB) ( 650 )
We perform a series of high-pressure synchrotron x-ray diffraction (XRD) and resistance measurements on the Weyl semimetal NbAs. The crystal structure remains stable up to 26 GPa according to the powder XRD data. The resistance of NbAs single crystal increases monotonically with pressure at low temperature. Up to 20 GPa, no superconducting transition is observed down to 0.3 K. These results show that the Weyl semimetal phase is robust in NbAs, and applying pressure may not be a good way to obtain a topological superconductor from Weyl semimetal NbAs.
A New Quantity to Characterize Stochastic Resonance
WANG Yu-Xin, ZHAI Ji-Quan, XU Wei-Wei, SUN Guo-Zhu, WU Pei-Heng
Chin. Phys. Lett. 2015, 32 (09): 097401 .   DOI: 10.1088/0256-307X/32/9/097401
Abstract   PDF(pc) (1207KB) ( 438 )
In a double-well system, we investigate theoretically the population distribution of a particle perturbed by a weak sinusoidal signal with a Gaussian white noise accompanied. Our numerical simulation shows that the probability of the particle staying in the right potential well, PR, exhibits an extreme value at specific noise intensity D depending on the frequency of the sinusoidal signal, which is a key feature of stochastic resonance. This is confirmed by calculating the power spectrum of the output signal, in which the extreme value of the amplitude locates at the same noise intensity. These results provide us with a new way to quantify the stochastic resonance by measuring the population distribution of the particle.
The Model for Linear Magnetoresistance of Two-Dimensional Metal-Semiconductor Composites with Interfacial Shells
XU Jie, WANG Guo-Dong, LI Shan-Dong, LI Qiang, GAO Xiao-Yang
Chin. Phys. Lett. 2015, 32 (09): 097501 .   DOI: 10.1088/0256-307X/32/9/097501
Abstract   PDF(pc) (643KB) ( 297 )
A metal-semiconductor composite with the interfacial shells is investigated theoretically for the large linear magnetoresistance effect of high doping Ag2Se and Ag2Te materials. The magnetoresistance (MR) of composites is a function of the magnetic field, temperature, the conductivities of two phases without magnetic field, and the thickness and conductivity of the interfacial shells. The MR increases with the increase of the magnetic field and with the decrease of temperature, and no saturation is found even under the high magnetic field. Moreover, it is interestingly found that the interfacial shell is an important factor for the MR of the composites. The MR increases with the thickness and the conductivity of the interfacial shells. Lastly, the theoretical results on the MR are compared with the experimental data. It is found that the value of the MR of the composite with the interfacial shell is larger than that without the interfacial shell.
Three-Dimensional Phase Field Simulations of Hysteresis and Butterfly Loops by the Finite Volume Method
XI Li-Ying, CHEN Huan-Ming, ZHENG Fu, GAO Hua, TONG Yang, MA Zhi
Chin. Phys. Lett. 2015, 32 (09): 097701 .   DOI: 10.1088/0256-307X/32/9/097701
Abstract   PDF(pc) (1380KB) ( 388 )
Three-dimensional simulations of ferroelectric hysteresis and butterfly loops are carried out based on solving the time dependent Ginzburg–Landau equations using a finite volume method. The influence of externally mechanical loadings with a tensile strain and a compressive strain on the hysteresis and butterfly loops is studied numerically. Different from the traditional finite element and finite difference methods, the finite volume method is applicable to simulate the ferroelectric phase transitions and properties of ferroelectric materials even for more realistic and physical problems.
Top-Emitting White Organic Light-Emitting Diodes Based on Cu as Both Anode and Cathode
MU Ye, ZHANG Zhen-Song, WANG Hong-Bo, QU Da-Long, WU Yu-Kun, YAN Ping-Rui, LI Chuan-Nan, ZHAO Yi
Chin. Phys. Lett. 2015, 32 (09): 097801 .   DOI: 10.1088/0256-307X/32/9/097801
Abstract   PDF(pc) (646KB) ( 393 )
It is still challenging to obtain broadband emission covering visible light spectrum as much as possible with negligible angular dependence. In this work, we demonstrate a low driving voltage top-emitting white organic light-emitting diode (TEWOLED) based on complementary blue and yellow phosphor emitters with negligible angular dependence. The bottom copper anode with medium reflectance, which is compatible with the standard complementary metal oxide semiconductor (CMOS) technology below 0.13 μm, and the semitransparent multilayer Cs2CO3/Al/Cu cathode as a top electrode, are introduced to realize high-performance TEWOLED. Our TEWOLED achieves high efficiencies of 15.4 cd/A and 12.1 lm/W at a practical brightness of 1000 cd/m2 at low voltage of 4 V.
Time-Resolved Photoluminescence Study of Silicon Nanoporous Pillar Array
WANG Xiao-Bo, YAN Ling-Ling, LI Yong, LI Xin-Jian
Chin. Phys. Lett. 2015, 32 (09): 097802 .   DOI: 10.1088/0256-307X/32/9/097802
Abstract   PDF(pc) (709KB) ( 372 )
A silicon nanoporous pillar array (Si-NPA) is thought to be a promising functional substrate for constructing a variety of Si-based optoelectronic nanodevices, due to its unique hierarchical structure and enhanced physical properties. This makes the in-depth understanding of the photoluminescence (PL) of Si-NPA crucial for both scientific research and practical applications. In this work, the PL properties of Si-NPA are studied by measuring both the steady-state and time-resolved PL spectrum. Based on the experimental data, the three PL bands of Si-NPA, i.e., the ultraviolet band, the purple-blue plateau and the red band are assigned to the oxygen-excess defects in Si oxide or silanol groups at the surface of Si nanocrystallites (nc-Si), oxygen deficiency defects in Si oxide, and band-to-band transition of nc-Si under the frame of quantum confinement combining with the surface states like Si=O and Si–O–Si bonds at the surface of nc-Si, respectively. These results may provide some novel insight into the PL process of Si-NPA and may be helpful for clarifying the PL mechanism.
High-Efficiency Green Phosphorescent Organic Light-Emitting Diode Based on Simplified Device Structures
ZHANG Hong-Mei, WANG Dan-Bei, ZENG Wen-Jin, YAN Min-Nan
Chin. Phys. Lett. 2015, 32 (09): 097803 .   DOI: 10.1088/0256-307X/32/9/097803
Abstract   PDF(pc) (619KB) ( 506 )

A high-efficiency green phosphorescent organic light emitting diode with a simplified structure is achieved that is free of a hole transport layer. The design of this kind of device structure not only saves the consumption of organic materials but also greatly reduces the structural heterogeneities and effectively facilitates the charge injection into the emissive layer. The resulting green phosphorescent organic light-emitting diodes (PHOLEDs) exhibit higher electroluminescent efficiency. The maximum external quantum efficiency and current efficiency reach 23.7% and 88 cd/A, respectively. Moreover the device demonstrates satisfactory stability, keeping 23.7% and 88 cd/A, 22% and 82 cd/A, respectively, at a luminance of 100 and 1000 cd/m2. The working mechanism for achieving high efficiency based on such a simple device structure is discussed correspondingly. The improved charge carrier injection and transport balance are proved to prominently contribute to achieve the high efficiency and great stability at high luminance in the green PHOLEDs.

Effect of High-Temperature Annealing on Yellow and Blue Luminescence of Undoped GaN
CHAI Xu-Zhao, ZHOU Dong, LIU Bin, XIE Zi-Li, HAN Ping, XIU Xiang-Qian, CHEN Peng, LU Hai, ZHANG Rong, ZHENG You-Dou
Chin. Phys. Lett. 2015, 32 (09): 097804 .   DOI: 10.1088/0256-307X/32/9/097804
Abstract   PDF(pc) (698KB) ( 534 )
The effect of high-temperature annealing on the yellow and blue luminescence of the undoped GaN is investigated by photoluminescence (PL) and x-ray photoelectron spectroscopy (XPS). It is found that the band-edge emission in the GaN apparently increases, and the yellow luminescence (YL) and blue luminescence (BL) bands dramatically decrease after annealing at 700°C. At the annealing temperature higher than 900°C, the YL and BL intensities show an enhancement for the nitrogen annealed GaN. This fact should be attributed to the increment of the Ga and N vacancies in the GaN decomposition. However, the integrated PL intensity of the oxygen annealed GaN decreases at the temperature ranging from 900°C to 1000°C. This results from the capture of many photo-generated holes by high-density surface states. XPS characterization confirms that the high-density surface states mainly originate from the incorporation of oxygen atoms into GaN at the high annealing temperature, and even induces the 0.34 eV increment of the upward band bending for the oxygen annealed GaN at 1000°C.
A Facile Route to Cotton-Like BiOCl Nanomaterial with Enhanced Dye-Sensitized Visible Light Photocatalytic Efficiency
ZHAO Mei, DONG Li-Feng, LI Cheng-Dong, YU Li-Yan, LI Ping
Chin. Phys. Lett. 2015, 32 (09): 098101 .   DOI: 10.1088/0256-307X/32/9/098101
Abstract   PDF(pc) (8364KB) ( 118 )
A facile route is developed to fabricate BiOCl porous cotton-like nanostructure by using Bi2O3 and hydrochloric acid as raw materials. The BiOCl nanomaterial is actually hierarchically structured by numerous ultrathin nanosheets. The nanosheets are around 50–500 nm in lateral size and 2–12 nm in thickness. High-resolution transmission electron microscopy and selected-area electron diffraction analyses indicate that single-crystalline BiOCl nanosheets have the predominant growth direction along [110], the bottom and top surfaces are {001} facets, and four lateral surfaces are {110} facets. The BiOCl nanosheets are dominantly enclosed by {001} facets. From the diffuse reflectance spectroscopy spectrum, the light absorption edge and band gap energy (Eg) are estimated to be 416 nm and 2.98 eV, respectively. The BiOCl photocatalyst possesses superior activity for methyl orange (MO) degradation under visible light irradiation and the photodegradation efficiency is up to 91.5%/180 min. The correlation between morphology and microstructure with enhanced MO-sensitized photodegradation performance under visible light is investigated.
Morphological and Microstructural Evolution and Related Impurity Incorporation in Non-Polar a-Plane GaN Grown on r-Sapphire Substrates
JIANG Ren-Yuan, XU Sheng-Rui, ZHANG Jin-Cheng, JIANG Teng, JIANG Hai-Qing, WANG Zhi-Zhe, FAN Yong-Xiang, HAO Yue
Chin. Phys. Lett. 2015, 32 (09): 098102 .   DOI: 10.1088/0256-307X/32/9/098102
Abstract   PDF(pc) (1033KB) ( 405 )
Effects of the growth temperature on morphological and microstructural evolution of a-plane GaN films grown on r-plane sapphires by metal organic chemical vapor deposition are investigated by atomic force microscopy and secondary ion mass spectroscopy (SIMS). Surface morphology, structural quality and related impurity incorporation are very sensitive to the growth temperature. A significant difference of yellow luminescence is observed and attributed to the incorporation of carbon into GaN films, which is confirmed by SIMS analysis. Our results show that the sample with triangular-pit morphology has significantly higher concentrations of oxygen than the other sample with pentagon-like pit morphology, which is induced by the existence of an N-face in triangular pits.
Facile Synthesis of Rose-Like NiO Nanoparticles and Their Ethanol Gas-Sensing Property
ZHANG Yong, XIE Long-Zhen, LI Hai-Rong, WANG Peng, LIU Su, PENG Ying-Quan, ZHANG Miao
Chin. Phys. Lett. 2015, 32 (09): 098103 .   DOI: 10.1088/0256-307X/32/9/098103
Abstract   PDF(pc) (1927KB) ( 480 )
In this study, rose-like nickel oxide (NiO) nanoparticles with diameters of 400–500 nm are prepared on ITO glass substrates by simple electrodeposition in NiSO46H2O solution at room temperature followed by oxidation in air. Scanning electron microscopy, x-ray diffraction and a transmission electron microscope are used for analyses of the NiO nanoparticles. The ethanol gas sensitivity of these nanoparticles is studied. The results indicate that the rose-like NiO nanoparticles could be used for the fabrication of ethanol gas sensors to monitor the low concentration of ethanol gas in air. Furthermore, at 5 ppm, the NiO nanorose-based sensors show a high response to ethanol (Rg/Ra=8.4).
Quasiclassical-Trajectory Investigation on the Isotopic Effect of H(D)+LiF→H(D)F+Li (v=0–4, j=0) Reaction
XIE Ting-Xian, ZHANG Ying-Ying, SHI Ying, JIN Ming-Xing
Chin. Phys. Lett. 2015, 32 (09): 098201 .   DOI: 10.1088/0256-307X/32/9/098201
Abstract   PDF(pc) (795KB) ( 323 )
A quasi-classical trajectory (QCT) method is employed to investigate the scalar properties and vector correlations of H+LiF→HF+Li and D+LiF→DF+Li reactions. The collision energy (Ecol=4–25 kcal/mol) and vibrational excitation effects (v=0–4) are studied by using the Aguado–Paniagua2-potential energy surface (AP2-PES) [J. Chem. Phys. 107 (1997) 10085]. The reaction probability, cross section and rate constant are calculated, which demonstrate obvious energy and vibrational excitation dependences in the probability, cross section, and a high-temperature region of the rate constant. In addition, two product angular distributions P(θr) and P(φr) are calculated to facilitate a deeper insight into vector correlations. The H+LiF→HF+Li and D+LiF→DF+Li reactions reveal strong isotopic effects. Moreover, these scalar and vector results of both the reactions show sensitive behaviors to the changes of vibrational levels and the collision energy.
Solution-Processed High Mobility Top-Gate N-Channel Polymer Field-Effect Transistors
XIANG Lan-Yi, YING Jun, HAN Jin-Hua, WANG Wei, XIE Wen-Fa
Chin. Phys. Lett. 2015, 32 (09): 098501 .   DOI: 10.1088/0256-307X/32/9/098501
Abstract   PDF(pc) (595KB) ( 606 )
Polymer field-effect transistors operated in the n-channel model with a top-gate/bottom-contact are processed using a solution method. The transistor performance depends on the gate dielectric layer. A high performance polymer transistor is achieved, with the saturated electron mobility of about 0.46 cm2/Vs, threshold voltage nearly 0 V and subthreshold sway of about 0.9 V/decade, employing a polystyrene (PS) dielectric layer. The transistor performances are further improved with increasing current and lower operation voltages by utilizing a bi-layer gate dielectric, comprising a thin PS dielectric layer adjacent to the semiconductor to minimize the density of the interface traps for obtaining a small VT, a large μ and a poly(methyl methacrylate) (PMMA) dielectric layer with a relatively high-κ adjacent to the gate electrode for enlarging the capacitance, processed from the orthogonal solvents.
A Novel Interface-Gate Structure for SOI Power MOSFET to Reduce Specific On-Resistance
HU Sheng-Dong, JIN Jing-Jing, CHEN Yin-Hui, JIANG Yu-Yu, CHENG Kun, ZHOU Jian-Lin, LIU Jiang-Tao, HUANG Rui, YAO Sheng-Jie
Chin. Phys. Lett. 2015, 32 (09): 098502 .   DOI: 10.1088/0256-307X/32/9/098502
Abstract   PDF(pc) (886KB) ( 483 )
A novel silicon-on-insulator (SOI) power metal-oxide-semiconductor field effect transistor with an interface-gate (IG SOI) structure is proposed, in which the trench polysilicon gate extends into the buried oxide layer (BOX) at the source side and an IG is formed. Firstly, the IG offers an extra accumulation channel for the carriers. Secondly, the subsidiary depletion effect of the IG results in a higher impurity doping for the drift region. A low specific on-resistance is therefore obtained under the condition of a slightly enhanced breakdown voltage for the IG SOI. The influences of structure parameters on the device performances are investigated. Compared with the conventional trench gate SOI and lateral planar gate SOI, the specific on-resistances of the IG SOI are reduced by 36.66% and 25.32% with the breakdown voltages enhanced by 2.28% and 10.83% at the same SOI layer of 3 μm, BOX of 1 μm, and half-cell pitch of 5.5 μm, respectively.
Close-Loop Bell–Bloom Magnetometer with Amplitude Modulation
HUANG Hai-Chao, DONG Hai-Feng, HAO Hui-Jie, HU Xu-Yang
Chin. Phys. Lett. 2015, 32 (09): 098503 .   DOI: 10.1088/0256-307X/32/9/098503
Abstract   PDF(pc) (639KB) ( 953 )
A high sensitive optical amplitude modulation magnetometer is investigated and demonstrated experimentally. We build an experimental platform for the atomic magnetometer and configure it as a Bell–Bloom magnetometer with amplitude modulation of 50% duty cycle square waveform. The open-loop input-output model is deduced from the Bloch equation and is verified experimentally. Instead of locking the frequency by using a voltage control oscillator, we realize a closed loop using the coils to generate a feedback field which avoids the stringent requirement of a high resolution frequency meter and markedly expands the dynamic range as well as the bandwidth. We realize an open loop sensitivity of 0.8 pT/Hz1/2 at 20 Hz using a single light beam, which exceeds that of the state-of-the-art Bell–Bloom magnetometers, and the corresponding closed loop sensitivity is 1.2 pT/Hz1/2.
43 articles