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Volume 33 Issue 04
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GENERAL
Security of the Decoy State Two-Way Quantum Key Distribution with Finite Resources
Ya-Bin Gu, Wan-Su Bao, Yang Wang, Chun Zhou
Chin. Phys. Lett. 2016, 33 (04): 040301 .   DOI: 10.1088/0256-307X/33/4/040301
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The quantum key distribution (QKD) allows two parties to share a secret key by typically making use of a one-way quantum channel. However, the two-way QKD has its own unique advantages, which means the two-way QKD has become a focus recently. To improve the practical performance of the two-way QKD, we present a security analysis of a two-way QKD protocol based on the decoy method with heralded single-photon sources (HSPSs). We make use of two approaches to calculate the yield and the quantum bit error rate of single-photon and two-photon pulses. Then we present the secret key generation rate based on the GLLP formula. The numerical simulation shows that the protocol with HSPSs has an advantage in the secure distance compared with weak coherent state sources. In addition, we present the final secret key generation rate of the LM05 protocol with finite resources by considering the statistical fluctuation of the yield and the error rate.

Coherence of Disordered Bosonic Gas with Two- and Three-Body Interactions
Xin Zhang, Zi-Fa Yu, Ju-Kui Xue
Chin. Phys. Lett. 2016, 33 (04): 040302 .   DOI: 10.1088/0256-307X/33/4/040302
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We theoretically and numerically investigate the coherence of disordered bosonic gas with effective two- and three-body interactions within a two-site Bose–Hubbard model. By properly adjusting the two- and three-body interactions and the disorder, the coherence of the system exhibits new and interesting phenomena, including the resonance character of coherence against the disorder in the purely two- or three-body interactions system. More interestingly, the disorder and three-body interactions together can suppress the coherence of the purely three-body interactions system, which is different from the case in which the disorder and two-body interactions together can enhance the coherence in certain values of two-body interaction. Furthermore, when two- or three-body interactions are attractive or repulsive, the phase coherence exhibits completely different phenomena. In particular, if two- or three-body interactions are attractive, the coherence of the system can be significantly enhanced in certain regions. Correspondingly, the phase coherence of the system is strongly related to the effective interaction energy. The results provide a possible way for studying the coherence of bosonic gas with multi-atoms' interactions in the presence of the disorder.
An Accurate Frequency Control Method and Atomic Clock Based on Coherent Population Beating Phenomenon
Yu-Xin Zhuang, Dai-Ting Shi, Da-Wei Li, Yi-Gen Wang, Xiao-Na Zhao, Jian-Ye Zhao, Zhong Wang
Chin. Phys. Lett. 2016, 33 (04): 040601 .   DOI: 10.1088/0256-307X/33/4/040601
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An accurate frequency control method and atomic clock based on the coherent population beating (CPB) phenomenon is implemented. In this scheme, the frequency difference of an rf and an atomic transition frequency can be digitally obtained by measuring the CPB oscillation frequency. The frequency measurement resolution of several milli-hertz can be achieved by using a 10 MHz oven controlled crystal oscillator as the reference. The expression of the Allan deviation of the CPB clock is theoretically deduced and it is revealed that the Allan deviation is inversely proportional to the signal-to-noise ratio and proportional to the line-width of coherent population trapping spectrum. We also approve that the CPB atomic clock has a large toleration of the drift of the local oscillator. In our CPB experimental system, a frequency instability of $3.0\times10^{-12}$ at 1000 s is observed. The important feature of high frequency measurement resolution of the CPB method may also be used in magnetometers, atomic spectroscopy, and other related research.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Influence of the Choice of $NN$ Potential Model on $\gamma d\to\pi^0d$ Observables near $\eta$-Threshold
E. M. Darwish
Chin. Phys. Lett. 2016, 33 (04): 041301 .   DOI: 10.1088/0256-307X/33/4/041301
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Influence of the choice of the $NN$ potential model governing the deuteron wave function on the observables for coherent $\pi^0$-photoproduction on the deuteron near $\eta$-threshold is investigated by using a three-body model for the intermediate $\eta NN$ system with separable two-body interactions. Results for unpolarized differential cross section and polarization observables are predicted. It is revealed that the choice of the $NN$ potential model has a visible effect on the differential cross section and most of the polarization observables, especially in the photon energy range of 600–800 MeV and extreme backward pion angles. We find that the deviation among results obtained by using different deuteron wave functions is quite large. The use of the CD-Bonn $NN$ potential for deuteron wave function doubles the differential cross section in this kinematic region. Compared with the experimental data from CLAS collaboration for differential cross section, sizeable discrepancies are found.
ATOMIC AND MOLECULAR PHYSICS
Interesting Features of Ionization Potentials for Elements ($Z\le 119$) along the Periodic Table
Chun Gu, Rui Jin, De-Ling Zeng, Xian-Fang Yue, Xiang Gao, Jia-Ming Li
Chin. Phys. Lett. 2016, 33 (04): 043201 .   DOI: 10.1088/0256-307X/33/4/043201
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The ionization potential (IP) is a basic property of an atom, which has many applications such as in element analysis. With the Dirac–Slater methods (i.e., mean field theory), IPs of all occupied orbitals for elements with atomic number ($Z\le 119$) are calculated conveniently and systematically. Compared with available experimental measurements, the theoretical accuracies of IPs for various occupied orbitals are ascertained. The map of the inner orbital IPs with good accuracies should be useful to select x-ray energies for element analysis. Based on systematic variations of the first IPs for the outermost orbitals in good agreement with experimental values as well as other IPs, mechanisms of electronic configurations of all atomic elements ($Z\le 119$) along the periodic table are elucidated. It is interesting to note that there exist some deficiencies of the intermediate orbital IPs, which are due to electron correlations and should be treated beyond the mean field theory.
Double Ionization Dynamics of Molecular Hydrogen in Ultrashort Intense Laser Fields
Yong-Ju Chen, Shao-Gang Yu, Ren-Ping Sun, Cheng Gong, Lin-Qiang Hua, Xuan-Yang Lai, Wei Quan, Xiao-Jun Liu
Chin. Phys. Lett. 2016, 33 (04): 043301 .   DOI: 10.1088/0256-307X/33/4/043301
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We experimentally investigate the double ionization of molecular hydrogen subjected to ultrashort intense laser pulses. The total kinetic energy release of the two coincident H$^{+}$ ions, which provides a diagnosis of different processes to double ionization of H$_{2}$, is measured for two different pulse durations, i.e., 25 and 5 fs, and various laser intensities. It is found that, for the long pulse duration (i.e., 25 fs), the double ionization occurs mainly via two processes, i.e., the charge resonance enhanced ionization and recollision-induced double ionization. Moreover, the contributions from these two processes can be significantly modulated by changing the laser intensity. In contrast, for a few-cycle pulse of 5 fs, only the recollsion-induced double ionization survives, and in particular, this process could be solely induced by the first-return recollision at appropriate laser intensities, providing an efficient way to probe the sub-laser-cycle molecular dynamics.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Design of a Novel Folded Waveguide for 60-GHz Traveling-Wave Tubes
Ming-Liang Liao, Yan-Yu Wei, Hai-Long Wang, Jin Xu, Yang Liu, Guo Guo, Xin-Jian Niu, Yu-Bin Gong, Gun-Sik Park
Chin. Phys. Lett. 2016, 33 (04): 044201 .   DOI: 10.1088/0256-307X/33/4/044201
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The 60-GHz traveling-wave tube (TWT) prevails nowadays as the amplifier for the satellite communication and electronic countermeasures. The folded waveguide (FW) is a promising all-metal slow-wave structure (SWS) for the 60-GHz TWT with advantages of robust performance, fine heat dissipation, considerable power and bandwidth. A novel FW periodically loaded with rectangular grooves is analyzed for the purpose of gaining higher power and gain. The rf characteristics are investigated by numerical simulation, and the nonlinear large-signal performance of such a TWT is analyzed by a 3D particle-in-cell code MAGIC. Compared with normal circuits, relatively higher continuous-wave power (40–56 W) and similar bandwidth (5 GHz) are predicted by simulation. Meanwhile, the designed operation voltage is 10.5 kV, which keeps the low-voltage advantage of the popular helix TWT competitor. The novel FW will favor the design of a broadband and high-power 60-GHz TWT.
Influence of Self-Diffraction Effect on Femtosecond Time-Resolved Single-Shot Optical Kerr Measurements
Meng-Meng Yue, Li-He Yan, Jin-Hai Si, Xun Hou
Chin. Phys. Lett. 2016, 33 (04): 044202 .   DOI: 10.1088/0256-307X/33/4/044202
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Femtosecond time-resolved single-shot optical Kerr gating (OKG) measurements are performed by focusing the probe pulse and using a cylindrical lens to introduce a spatially encoded time delay with respect to the pump pulse. By measuring the pump power and polarization dependence of the OKG signals in CS$_{2}$, the contribution of self-diffraction effect which is independent of the nonlinear response time of the material is directly observed on the rising edge of the time-resolved OKG signals. The influence of the self-diffraction effect on the optical Kerr signal could be controlled effectively by varying the polarization angle between pump and probe pulses.
Development of a Single-Longitudinal-Mode Ho:YAG Laser Based on Corner Cube
Jing Wu, You-Lun Ju, Tong-Yu Dai, Zhen-Guo Zhang, Bao-Quan Yao, Yue-Zhu Wang
Chin. Phys. Lett. 2016, 33 (04): 044203 .   DOI: 10.1088/0256-307X/33/4/044203
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We present a Tm-doped fiber laser pumped Fabry–Perot etalons Ho:YAG laser based on a corner cube. A maximum single-longitudinal-mode and fundamental transverse mode output power of 478 mW at the wavelength of 2091.06 nm is achieved with a pump power of 16.3 W, corresponding to an optical-to-optical efficiency of 2.9% and a slope efficiency of 7.9%. The single-longitudinal-mode and fundamental transverse mode are less sensitive to the rotating of the corner cube. The results indicate the potential impact of a single-longitudinal-mode Ho:YAG laser with corner cube geometry to improve the anti-maladjustment stability.
Simulation of Far-Field Properties of Coherent Vertical Cavity Surface Emitting Laser Array
Meng Xun, Chen Xu, Yi-Yang Xie, Jun Deng, Guo-Qing Jiang, Guan-Zhong Pan, Yi-Bo Dong, Hong-Da Chen
Chin. Phys. Lett. 2016, 33 (04): 044204 .   DOI: 10.1088/0256-307X/33/4/044204
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Far-field properties dependent on array scale, separation, element width and emitted wavelength are systematically analyzed theoretically and experimentally. An array model based on the finite-difference method is established to simulate the far-field profile of the coherent arrays. Some important conclusions are obtained. To achieve a higher quality beam, it is necessary to decrease separation between elements, or to increase the element width. Higher brightness can be achieved in the array with larger scale. Emitted wavelength also has an influence on the far-field profile. These analyses can be extended to the future design of coherent vertical cavity surface emitting laser arrays.
An Actively Mode-Locked Ho:YAG Solid-Laser Pumped by a Tm-Doped Fiber Laser
Bao-Quan Yao, He Li, Xiao-Lei Li, Yi Chen, Xiao-Ming Duan, Shuang Bai, Hong-Yu Yang, Zheng Cui, Ying-Jie Shen, Tong-Yu Dai
Chin. Phys. Lett. 2016, 33 (04): 044205 .   DOI: 10.1088/0256-307X/33/4/044205
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An actively mode-locked Ho:YAG laser pumped by a diode-pumped Tm-doped fiber laser is reported. For the cw operation, we obtain the maximum output power of 3.43 W with a central wavelength 2022.2 nm at the maximum incident pump power of 11.4 W, corresponding to a slope efficiency of 34.5%. The beam quality factor $M^{2}$ is 1.16, and the output beam is close to fundamental TEM$_{00}$. In the case of the CWML operation, a stable pulse train is generated with an average output power up to 3.41 W with a slope efficiency of 34.3% at the incident pump power of 11.4 W and a pulse duration of 294 ps at a repetition rate of 81.92 MHz. In addition, the maximum single pulse energy is 41.6 nJ.
Optical Transfer Function Reconstruction in Incoherent Fourier Ptychography
Zong-Liang Xie, Bo Qi, Hao-Tong Ma, Ge Ren, Yu-Feng Tan, Bi He, Heng-Liang Zeng, Chuan Jiang
Chin. Phys. Lett. 2016, 33 (04): 044206 .   DOI: 10.1088/0256-307X/33/4/044206
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An optical transfer function (OTF) reconstruction model is first embedded into incoherent Fourier ptychography (IFP). The leading result is a proposed algorithm that can recover both the super-resolution image and the OTF of an imaging system with unknown aberrations simultaneously. This model overcomes the difficult problem of OTF estimation that the previous IFP faces. The effectiveness of this algorithm is demonstrated by numerical simulations, and the superior reconstruction is presented. We believe that the reported algorithm can extend the original IFP for more complex conditions and may provide a solution by using structured light for characterization of optical systems' aberrations.
Temperature-Dependent Photoluminescence Characteristics of InAs/GaAs Quantum Dots Directly Grown on Si Substrates
Ting Wang, Hui-Yun Liu, Jian-Jun Zhang
Chin. Phys. Lett. 2016, 33 (04): 044207 .   DOI: 10.1088/0256-307X/33/4/044207
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The first operation of an electrically pumped 1.3-μm InAs/GaAs quantum-dot laser was previously reported epitaxially grown on Si (100) substrate. Here the direct epitaxial growth condition of 1.3-μm InAs/GaAs quantum on a Si substrate is further investigated using atomic force microscopy, etch pit density and temperature-dependent photoluminescence (PL) measurements. The PL for Si-based InAs/GaAs quantum dots appears to be very sensitive to the initial GaAs nucleation temperature and thickness with strongest room-temperature emission at 400$^\circ\!$C (170 nm nucleation layer thickness), due to the lower density of defects generated under this growth condition, and stronger carrier confinement within the quantum dots.
Raman Suppression in a Kilowatt Narrow-Band Fiber Amplifier
Man Hu, Yi-Feng Yang, Ye Zheng, Guang-Bo Liu, Jian-Hua Wang, Kai Liu, Xiao-Long Chen, Chun Zhao, Bing He, Jun Zhou
Chin. Phys. Lett. 2016, 33 (04): 044208 .   DOI: 10.1088/0256-307X/33/4/044208
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A novel technique to suppress stimulated Raman scattering in a high power narrow-band fiber amplifier is reported. By seeding with a combination of a broadband amplified spontaneous emission seed and a narrowband master oscillator seed, the Raman Stokes components can be reduced about 16 dB at a total output power of 1 kW. Raman suppression results are depicted in a different wavelengths seeding case and the same wavelength seeding case, respectively, with different seed power ratios.
Source-Space Compressive Matched Field Processing for Source Localization
Hao-Zhong Wang, Ning Wang, Da-Zhi Gao, Bo Gao
Chin. Phys. Lett. 2016, 33 (04): 044301 .   DOI: 10.1088/0256-307X/33/4/044301
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Source localization by matched-field processing (MFP) can be accelerated by building a database of Green's functions which however requires a bulk-storage memory. According to the sparsity of the source locations in the search grids of MFP, compressed sensing inspires an approach to reduce the database by introducing a sensing matrix to compress the database. Compressed sensing is further used to estimate the source locations with higher resolution by solving the $l_{1}-{\rm norm}$ optimization problem of the compressed Green's function and the data received by a vertical/horizontal line array. The method is validated by simulation and is verified with the experimental data.
Extraordinary Acoustic Transmission in a Helmholtz Resonance Cavity-Constructed Acoustic Grating
Si-Yuan Yu, Xu Ni, Ye-Long Xu, Cheng He, Priyanka Nayar, Ming-Hui Lu, Yan-Feng Chen
Chin. Phys. Lett. 2016, 33 (04): 044302 .   DOI: 10.1088/0256-307X/33/4/044302
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We investigate both experimentally and numerically a complex structure, where 'face-to-face' Helmholtz resonance cavities (HRCs) are introduced to construct a one-dimensional acoustic grating. In this system, pairs of HRCs can intensely couple with each other in two forms: a bonding state and an anti-bonding state, analogous to the character of hydrogen molecule with two atoms due to the interference of wave functions of sound among the acoustic local-resonating structures. The bonding state is a 'bright' state that interferes with the Fabry–Pèrot resonance mode, thereby causing this state to break up into two modes as the splitting of the extraordinary acoustic transmission peak. On the contrary, the anti-bonding state is a 'dark' state in which the resonance mode remains entirely localized within the HRCs, and has no contribution to the acoustic transmission.
Theoretical and Experimental Investigation of Flexural Vibration Transfer Properties of High-Pressure Periodic Pipe
Zhen-Dong Wei, Bao-Ren Li, Jing-Min Du, Gang Yang
Chin. Phys. Lett. 2016, 33 (04): 044303 .   DOI: 10.1088/0256-307X/33/4/044303
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According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We present theoretical and experimental investigations into the flexural vibration transfer properties of a high-pressure periodic pipe with the force on the inner pipe wall by oil pressure taken into consideration. The results show that the vibration attenuation of periodic pipe decreases along with the elevation of working pressure for the hydraulic system, and the band gaps in low frequency ranges move towards high frequency ranges. The periodic pipe has good vibration attenuation performance in the frequency range below 1000 Hz and the vibration of the hydraulic system is effectively suppressed. All the results are validated by experiment. The experimental results show a good agreement with the numerical calculations, thus the flexural vibration transfer properties of the high-pressure periodic pipe can be precisely calculated by taking the fluid structure interaction between the pipe and oil into consideration. This study provides an effective way for the vibration control of the hydraulic system.
Examination of the Thermal Cloaking Effectiveness with Layered Engineering Materials
Run Hu, Jin-Yan Hu, Rui-Kang Wu, Bin Xie, Xing-Jian Yu, Xiao-Bing Luo
Chin. Phys. Lett. 2016, 33 (04): 044401 .   DOI: 10.1088/0256-307X/33/4/044401
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The concentrically layered thermal cloaks with isotropic materials could realize the equivalent thermal cloaking effect with Pendry's cloak, while the effectiveness is scarcely investigated quantitatively. Here we examine the cloaking effectiveness quantitatively by evaluating the standard deviation of the temperature difference between the simulated plane with the layered thermal cloak and Pendry's thermal cloak. The design rules for the isotropic materials in terms of thermal conductivity and layer thickness are presented. The present method could quantitatively evaluate the cloaking effectiveness, and could open avenues for analyzing the cloaking effect, detecting the (anti-) cloaks, etc.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Spatial-Resolved Measurement and Analysis of Extreme-Ultraviolet Emission Spectra from Laser-Produced Al Plasmas
Shi-Quan Cao, Mao-Gen Su, Dui-Xiong Sun, Qi Min, Chen-Zhong Dong
Chin. Phys. Lett. 2016, 33 (04): 045201 .   DOI: 10.1088/0256-307X/33/4/045201
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Extreme ultraviolet emission from laser-produced Al plasma is experimentally and theoretically investigated. Spatial-evolution emission spectra are measured by using the spatio-temporally resolved laser produced plasma technique. Based on the assumptions of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model, we succeed in reproducing the spectra at different detection positions, which are in good agreement with experiments. The decay curves about the electron temperature and electron density, as well as the fractions of individual Al ions and average ionization stage with increasing the detection distance are obtained by comparison with the experimental measurements. These parameters are critical points for deeply understanding the expanding and cooling of laser produced plasmas in vacuum.
Formation Process of Magnetized Fusion Target on the YingGuang 1 Device
Lu-Lu Li, Yue-Song Jia, Qi-Zhi Sun, Wei Liu, Zheng-Fen Liu, Wei-Dong Qin, Jun Li, Yuan Chi, Xian-Jun Yang
Chin. Phys. Lett. 2016, 33 (04): 045202 .   DOI: 10.1088/0256-307X/33/4/045202
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Magnetized target fusion is an alternative method to fulfill the goal of controlled fusion, which combines advantages of both magnetic confinement fusion and inertial confinement fusion since its parameter space lies between the two traditional ways. Field reversed configuration (FRC) is a good candidate of magnetized targets due to its translatable, compressible, high $\beta$ and high energy density properties. Dynamic formation process of high density FRC is observed on the YingGuang 1 device for the first time in China. The evolution of a magnetic field is detected with magnetic probes, and the compression process can be clearly seen from images taken with a high-speed multi-frame CCD camera. The process is also studied with two-dimensional magneto hydrodynamic code MPF-2D theoretically, and the results agree well with the experiment. Combining the experimental data and the theoretical analysis, the length of the formed FRC is about 39 cm, the diameter is about 2–2.7 cm, the average density is $1.3 \times 10^{16}$ cm$^{-3}$, and the average temperature is 137 eV.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
The Magnetic Order in Ion Irradiated Graphite
Li-Juan Li, Xin-Mei Yang, Hui-Hao Xia, Zhou-Tong He, Xing-Tai Zhou, Xiang-Dong Liu
Chin. Phys. Lett. 2016, 33 (04): 046101 .   DOI: 10.1088/0256-307X/33/4/046101
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The magnetism of highly oriented pyrolytic graphite (HOPG) induced by ion implantation is investigated with electron spin resonance (ESR) spectroscopy and magnetization measurements. The results indicate that the ESR spectra of the HOPG sample correlate with ion species, incident energy and dose of implantation. The correlation of the ESR spectra and magnetism of the HOPG sample with $^{12}$C$^{+}$ ion implantation and H$^{+}$ ion implantation are studied in detail. The ferromagnetism of the HOPG sample is likely related to the asymmetric L1 line, which may be attributed to the interaction between localized defects and itinerant electrons occupied in the 'impurity' band induced by ion implantation.
Raman Scattering Modification in Monolayer ReS$_{2}$ Controlled by Strain Engineering
Ting-Hui Li, Zi-Heng Zhou, Jun-Hong Guo, Fang-Ren Hu
Chin. Phys. Lett. 2016, 33 (04): 046201 .   DOI: 10.1088/0256-307X/33/4/046201
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Regulation of optical properties and electronic structure of two-dimensional layered ReS$_{2}$ materials has attracted much attention due to their potential in electronic devices. However, the identification of structure transformation of monolayer ReS$_{2}$ induced by strain is greatly lacking. In this work, the Raman spectra of monolayer ReS$_{2}$ with external strain are determined theoretically based on the density function theory. Due to the lower structural symmetry, deformation induced by external strain can only regulate the Raman mode intensity but cannot lead to Raman mode shifts. Our calculations suggest that structural deformation induced by external strain can be identified by Raman scattering.
An Attempt to Prepare Metallic Glasses from Quasicrystals
Zi-Jing Li, Lin-Ran Zhao, Yu-Ting Wang, Ze-Ming Chen, Wen-Kang Tu, Ya-Qi Zhang, Hong Bo, Ying-Dan Liu, Li-Min Wang
Chin. Phys. Lett. 2016, 33 (04): 046401 .   DOI: 10.1088/0256-307X/33/4/046401
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Icosahedrons in supercooled liquids and glasses are considered to be of significance for the glass formation in alloy systems. Starting from the similarity of the local structure of quasicrystals to the icosahedrons in metallic glasses, a scheme is put forward to prepare metallic glasses based on a well-known quasicrystal Zr$_{40}$Ti$_{40}$Ni$_{20}$. A series of (Zr$_{40}$Ti$_{40}$Ni$_{20}$)$_{100-x}$Co$_{x}$ metallic glasses are fabricated, and the optimized glass forming composition is determined at (Zr$_{40}$Ti$_{40}$Ni$_{20}$)$_{92}$Co$_{8}$. The results show that the glass-forming ability of the alloys is closely related to the quasicrystalline phases. The mechanism of the enhanced glass-forming ability is discussed.
Thermal Expansion and Deformation of Graphene
Zheng-Fu Cheng, Rui-Lun Zheng
Chin. Phys. Lett. 2016, 33 (04): 046501 .   DOI: 10.1088/0256-307X/33/4/046501
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Taking into consideration short-atomic-range interactions and anharmonic effects, we calculate the thermal expansion coefficients, Gruneisen parameters, the elastic modulus of graphene varying with temperature and the phonon frequency. The anharmonic effects associated with the graphene deformation are also discussed. The results show that the value of thermal expansion coefficient is negative in the moderate temperature range, and it becomes positive when the temperature grows to be higher than a certain value. The change rate of elastic modulus with respect to temperature and pressure are calculated, and phonon frequencies are estimated. In the process of graphene thermal expansion, it is accompanied with the change of bond length and the rotation around the axis normal to the plane. Our results indicate that the effects due to the bond change are more significant than that of the rotation. We also show that if anharmonic effects are ignored, the thermal expansion coefficient and the Gruneisen parameters are zero, and the elastic modulus and the phonon frequency are constant. If anharmonic effects are considered up to the second term, these values will vary with temperature, and become closer to the experimental value. The higher the temperature is, the more significant the anharmonic effects become.
Thermal Expansion of Ni$_{3}$Al Intermetallic Compound: Experiment and Simulation
Hai-Peng Wang, Peng Lü, Kai Zhou, Bing-Bo Wei
Chin. Phys. Lett. 2016, 33 (04): 046502 .   DOI: 10.1088/0256-307X/33/4/046502
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The thermal expansion of Ni$_{3}$Al intermetallic compound is determined by a thermal dilatometer and simulated by the molecular dynamics method. The results of the linear thermal expansion coefficients are presented from 200 K up to the maximum temperature of 1600 K. The single phase of Ni$_{3}$Al intermetallic compound is confirmed by x-ray diffraction together with DSC melting and solidification peaks, from which the solidus and the liquidus temperatures are obtained to be 1660 and 1695 K, respectively. The measured linear thermal expansion coefficient increases from $1.5\times10^{-5}$ to $2.7\times10^{-5}$ K$^{-1}$ in the experimental temperature range, in good agreement with the data obtained by the molecular dynamics simulation, just a slight difference from the temperature dependence coefficient. Furthermore, the atomic structure and position are presented to reveal the atom distribution change during thermal expansion of Ni$_{3}$Al compound.
Phase Transition and Negative Thermal Expansion Property of ZrMnMo$_{3}$O$_{12}$
Xiang-Hong Ge, Yan-Chao Mao, Lin Li, Li-Ping Li, Na Yuan, Yong-Guang Cheng, Juan Guo, Ming-Ju Chao, Er-Jun Liang
Chin. Phys. Lett. 2016, 33 (04): 046503 .   DOI: 10.1088/0256-307X/33/4/046503
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A novel material of ZrMnMo$_{3}$O$_{12}$ with negative thermal expansion is presented. The phase transition temperature and coefficient of thermal expansion (CTE) are investigated by temperature-dependent x-ray diffraction and Raman spectra. It is shown that ZrMnMo$_{3}$O$_{12}$ adopts monoclinic structure with space group $P21/a$ (No. 14) from 298 to 358 K and transforms to orthorhombic with space group $Pnma$ (No. 62) above 363 K. The linear CTE obtained from the results of XRD refinement is $-2.80\times10^{-6}$ K$^{-1}$ from 363 to 873 K. The CTE of the bulk cylinder ceramic measured by a thermal dilatometer is $-4.7\times10^{-6}$ K$^{-1}$ from 373 to 773 K approximatively.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Effect of Chirality on the Electronic Transport Properties of the Thioxanthene-Based Molecular Switch
Cai-Juan Xia, Bo-Qun Zhang, Mao Yang, Chun-Lan Wang, Ai-Yun Yang
Chin. Phys. Lett. 2016, 33 (04): 047101 .   DOI: 10.1088/0256-307X/33/4/047101
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Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. Furthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.
Detecting Spin Bias with Circularly Polarized Light
Feng Liang, Ben-Ling Gao, Yu Gu, Cheng Yang
Chin. Phys. Lett. 2016, 33 (04): 047201 .   DOI: 10.1088/0256-307X/33/4/047201
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We theoretically study the spin transport through a two-terminal quantum dot device under the influence of a symmetric spin bias and circularly polarized light. It is found that the combination of the circularly polarized light and the applied spin bias can result in a net charge current. The resultant charge current is large enough to be measured when properly choosing the system parameters. The resultant charge current can be used to deduce the spin bias due to the fact that there exists a simple linear relation between them. When the external circuit is open, a charge bias instead of a charge current can be induced, which is also measurable by present technologies. These findings indicate a new approach to detect the spin bias by using circularly polarized light.
Multiplexing Read-Out of Charge Qubits by a Superconducting Resonator
Tian-Yi Han, Guang-Wei Deng, Da Wei, Guo-Ping Guo
Chin. Phys. Lett. 2016, 33 (04): 047301 .   DOI: 10.1088/0256-307X/33/4/047301
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Wavelength division multiplexing (WDM) is widely used in modern optics and electronics. For future quantum computers, the integration of readout is also vitally important. Here we incorporate an idea of WDM to demonstrate multiplexing readout of charge qubits by using a single integrated on-chip superconducting microwave resonator. Two distant qubits formed by two graphene double quantum dots (DQDs) are simultaneously readout by an interconnected superconducting resonator. This readout device is found to have 2 MHz bandwidth and $1.1\times 10^{-4}\,{\rm e}/\sqrt{\rm Hz}$ charge sensitivity. Different frequency gate-modulations, which are used selectively to change the impedance of the qubits, are applied to different DQDs, which results in separated sidebands in the spectrum. These sidebands enable a multiplexing readout for the multi-qubits circuit. This architecture can largely reduce the amount of detectors and can improve the prospect for scaling-up of semiconductor qubits.
Programmable Logic Based on Large Magnetoresistance of Germanium
Jiao-Jiao Chen, Hong-Guang Piao, Zhao-Chu Luo, Cheng-Yue Xiong, Xiao-Zhong Zhang
Chin. Phys. Lett. 2016, 33 (04): 047501 .   DOI: 10.1088/0256-307X/33/4/047501
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We find extremely large low-magnetic-field magnetoresistance ($\sim$350% at 0.2 T and $\sim$180% at 0.1 T) in germanium at room temperature and the magnetoresistance is highly sensitive to the surface roughness. This unique magnetoelectric property is applied to fabricate logic architecture which could perform basic Boolean logic including AND, OR, NOR and NAND. Our logic device may pave the way for a high performance microprocessor and may make the germanium family more advanced.
Evolution of Magnetic Domain Structure in a YIG Thin Film
Ran Wang, Ya-Xuan Shang, Rui Wu, Jin-Bo Yang, Yang Ji
Chin. Phys. Lett. 2016, 33 (04): 047502 .   DOI: 10.1088/0256-307X/33/4/047502
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The evolution of a magnetic domain structure induced by temperature and magnetic field is reported in silicon-doped yttrium iron garnet (YIG) films with perpendicular anisotropy. During a cooling-down procedure from 300 K to 7 K, a 20% change in the domain width is observed, with the long tails of the stripes being shortened and the twisting stripes being straightened. Under the influence of the stray field of a barium ferrite, the garnet presents an interesting domain structure, which shows an appearance of branching protrusions. The intrinsic mechanisms in these two processes are also discussed.
Broad-Band FMR Linewidth of Co2MnSi Thin Films with Low Damping Factor: The Role of Two-Magnon Scattering
Shi-Zhu Qiao, Quan-Nian Ren, Run-Run Hao, Hai Zhong, Yun Kang, Shi-Shou Kang, Yu-Feng Qin, Shu-Yun Yu, Guang-Bing Han, Shi-Shen Yan, Liang-Mo Mei
Chin. Phys. Lett. 2016, 33 (04): 047601 .   DOI: 10.1088/0256-307X/33/4/047601
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The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonality of the ferromagnetic resonance mode and other degenerate spin wave modes was broken by magnetic anisotropy, voids, second phase, surface defects, etc., which is important in analysis of ferromagnetic resonance linewidth. Direct fitting to linewidth with Gilbert damping is advisable only when the measured linewidth is a linear function of measuring frequency in a broad band measurement. We observe the nonlinear ferromagnetic resonance linewidth of Co2MnSi thin films with respect to measuring frequency in broad band measurement. Experimental data could be well fitted with the model including two-magnon scattering with no fixed parameters. The fitting results show that two-magnon scattering results in the nonlinear linewidth behavior, and the Gilbert damping factor is much smaller than reported ones, indicating that our Co2MnSi films are more suitable for the applications of spin transfer torque.

First-Principles Investigations of Pb$_{0.5}$Ba$_{0.5}$TiO$_3$ Alloys Based on Structure Predictions
Hong-Bo Wu, Yi-Feng Duan, Chang-Ming Zhao, Kun Liu, Li-Xia Qin
Chin. Phys. Lett. 2016, 33 (04): 047701 .   DOI: 10.1088/0256-307X/33/4/047701
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Crystal structure predictions of Pb$_{0.5}$Ba$_{0.5}$TiO$_3$ alloys under different pressures are performed based on the particle swarming optimization algorithm. The predicted stable ground-state and high-pressure phases are tetragonal ferroelectric ($I4mm$) and cubic para-electric ($Fm\bar{3}m$), respectively, whose structural details have not been reported. The pressure-induced colossal enhancements in piezoelectric response are associated with the mechanical and dynamical instabilities instead of polarization rotation. The band gap of the tetragonal phase is indirect and that of the cubic phase is always direct. As pressure increases, the alloy displays the similar band-gap behaviors to PbTiO$_3$, while different from BaTiO$_3$, which is attributed to the different orbital contributions to the valence bands. Our calculated results are in good agreement with the available data.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Growth of InAlGaN Quaternary Alloys by Pulsed Metalorganic Chemical Vapor Deposition
Ru-Dai Quan, Jin-Cheng Zhang, Sheng-Rui Xu, Jun-Shuai Xue, Yi Zhao, Jing Ning, Zhi-Yu Lin, Ze-Yang Ren, Yue Hao
Chin. Phys. Lett. 2016, 33 (04): 048101 .   DOI: 10.1088/0256-307X/33/4/048101
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Epitaxial growth of InAlGaN/GaN structures are performed on the $c$-plane sapphire by pulsed metal organic chemical vapor deposition with different triethylgallium (TEGa) flows in the growth process of InAlGaN quaternary alloys. X-ray photoelectron spectroscopy results show that the Al/In ratio of the samples increases as the TEGa flows increase in the InAlGaN quaternary growth process. High-resolution x-ray diffraction results show that the crystal quality is improved with increasing TEGa flows. Morphology of the InAlGaN/GaN heterostructures is characterized by an atomic force microscopy, and the growth mode of the InAlGaN quaternary shows a 2D island growth mode. The minimum surface roughness is 0.20 nm with the TEGa flows equaling to 3.6 $\mu$mol/min in rms. Hall effect measurement results show that the highest electron mobility $\mu$ is 1005.49 cm$^{2}$/Vs and the maximal two-dimensional electron gas is $1.63\times10^{13}$ cm$^{-2}$.
Prediction of Henry Constants and Adsorption Mechanism of Volatile Organic Compounds on Multi-Walled Carbon Nanotubes by Using Support Vector Regression
Wen-De Cheng, Cong-Zhong Cai
Chin. Phys. Lett. 2016, 33 (04): 048201 .   DOI: 10.1088/0256-307X/33/4/048201
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Support vector regression (SVR) combined with particle swarm optimization for its parameter optimization is employed to establish a model for predicting the Henry constants of multi-walled carbon nanotubes (MWNTs) for adsorption of volatile organic compounds (VOCs). The prediction performance of SVR is compared with those of the model of theoretical linear salvation energy relationship (TLSER). By using leave-one-out cross validation of SVR test Henry constants for adsorption of 35 VOCs on MWNTs, the root mean square error is 0.080, the mean absolute percentage error is only 1.19%, and the correlation coefficient $(R^{2})$ is as high as 0.997. Compared with the results of the TLSER model, it is shown that the estimated errors by SVR are all smaller than those achieved by TLSER. It reveals that the generalization ability of SVR is superior to that of the TLSER model. Meanwhile, multifactor analysis is adopted for investigation of the influences of each molecular structure descriptor on the Henry constants. According to the TLSER model, the adsorption mechanism of adsorption of carbon nanotubes of VOCs is mainly a result of van der Waals and interactions of hydrogen bonds. These can provide the theoretical support for the application of carbon nanotube adsorption of VOCs and can make up for the lack of experimental data.
A Mixed Host Emitting Interlayer Based on CBP:TPBi in Green Phosphorescent Organic Light-Emitting Diodes
Yao Xu, Yu-Ting Zhang, Zhi-Qi Kou, Shuang Cheng, Sheng-Li Bu
Chin. Phys. Lett. 2016, 33 (04): 048501 .   DOI: 10.1088/0256-307X/33/4/048501
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A series of green phosphorescent organic light-emitting diodes based on bipolar-transporting material 4,4'-bis-(carbazol-9-yl) biphenyl (CBP) are prepared. We insert a mixed host emitting interlayer (CBP$_{x}$: electron-transporting material 1,3,5-tris (N-phenylbenzimidazole-2yl) (TPBi)$_{1-x}$) in the middle of the emitting layer, and the best performance appears when $x$ is 2/3. The position of this interlayer can also affect the performance of phosphorescent organic light-emitting diodes. When this interlayer is close to the side of the electron transporting layer, the maximum value of luminance, the current efficiency and the power efficiency are 34090 cd/m$^{2}$ at 12 V, 60.6 cd/A and 56.6 lm/W, respectively.
Low Crosstalk Three-Color Infrared Detector by Controlling the Minority Carriers Type of InAs/GaSb Superlattices for Middle-Long and Very-Long Wavelength
Dong-Wei Jiang, Wei Xiang, Feng-Yun Guo, Hong-Yue Hao, Xi Han, Xiao-Chao Li, Guo-Wei Wang, Ying-Qiang Xu, Qing-Jiang Yu, Zhi-Chuan Niu
Chin. Phys. Lett. 2016, 33 (04): 048502 .   DOI: 10.1088/0256-307X/33/4/048502
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We report a type-II InAs/GaSb superlattice three-color infrared detector for mid-wave (MW), long-wave (LW), and very long-wave (VLW) detections. The detector structure consists of three contacts of NIPIN architecture for MW and LW detections, and hetero-junction NIP architecture for VLW detection. It is found that the spectral crosstalks can be significantly reduced by controlling the minority carriers transport via doping beryllium in the two active regions of NIPIN section. The crosstalk detection at MW, LW, and VLW signals are achieved by selecting the bias voltages on the device. At 77 K, the cutoff wavelengths of the three-color detection are 5.3 μm (at 0 mV), 14 μm (at 300 mV) and 19 μm (at $-$20 mV) with the detectivities of 4.6$\times$10$^{11}$ cm$\cdot$Hz$^{1/2}$W$^{-1}$, 2.3$\times$10$^{10}$ cm$\cdot$Hz$^{1/2}$W$^{-1}$, and 1.0$\times$10$^{10}$ cm$\cdot$Hz$^{1/2}$W$^{-1}$ for MW, LW and VLW. The crosstalks of the MW channel, LW channel, and VLW channel are almost 0, 0.25, and 0.6, respectively.
Off-Axis Imaging in Keel-Edge Pinhole Single Photon Emission Computed Tomography System Based on Monte Carlo Simulation
Su-Ying Li, Zhao-Heng Xie, Zhi-Yu Huang, Kun Yang, Bai-Xuan Xu, Qiu-Shi Ren
Chin. Phys. Lett. 2016, 33 (04): 048701 .   DOI: 10.1088/0256-307X/33/4/048701
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Monte Carlo simulation is applied to investigate the off-axis effect in keel-edge pinhole single photon emission computed tomography imaging. Aiming at finding the effective field of view (FOV) for imaging, we simulate point source in off-axis imaging (0, 4, 8 and 12 mm from the central rotation axis) of different collimator designs (channel height with 1.38, 1 and 0.5 mm) with a fixed aperture diameter. Tradeoff curves of rms resolution and sensitivity are plotted to determine the effective FOV for different channel height pinhole collimators. The parameterized model can be further incorporated into image reconstruction algorithms, which compensates for the off-axis effect and is used as a reference for multi-pinhole design.
A Collaboration Network Model with Multiple Evolving Factors
Xiu-Lian Xu, Chun-Ping Liu, Da-Ren He
Chin. Phys. Lett. 2016, 33 (04): 048901 .   DOI: 10.1088/0256-307X/33/4/048901
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To describe the empirical data of collaboration networks, several evolving mechanisms have been proposed, which usually introduce different dynamics factors controlling the network growth. These models can reasonably reproduce the empirical degree distributions for a number of well-studied real-world collaboration networks. On the basis of the previous studies, in this work we propose a collaboration network model in which the network growth is simultaneously controlled by three factors, including partial preferential attachment, partial random attachment and network growth speed. By using a rate equation method, we obtain an analytical formula for the act degree distribution. We discuss the dependence of the act degree distribution on these different dynamics factors. By fitting to the empirical data of two typical collaboration networks, we can extract the respective contributions of these dynamics factors to the evolution of each networks.
39 articles