Chin. Phys. B

A more general form of lump solution, lumpoff, and instanton/rogue wave solutions of a reduced (3+1)-dimensional nonlinear evolution equation Suggested by editors

Panfeng Zheng(郑攀峰), Man Jia(贾曼)

Chin. Phys. B, 2018, 27 (12): 120201. DOI: 10.1088/1674-1056/27/12/120201

Abstract ( 721 )

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In this manuscript, a reduced (3+1)-dimensional nonlinear evolution equation is studied. We first construct the bilinear formalism of the equation by using the binary Bell polynomials theory, then explore a lump solution to the special case for z=x. Furthermore, a more general form of lump solution of the equation is found which possesses seven arbitrary parameters and four constraint conditions. By cutting the lump by the induced soliton(s), lumpoff and instanton/rogue wave solutions are also constructed by the more general form of lump solution.

N-soliton solutions for the nonlocal two-wave interaction system via the Riemann-Hilbert method

Si-Qi Xu(徐思齐), Xian-Guo Geng(耿献国)

Chin. Phys. B, 2018, 27 (12): 120202. DOI: 10.1088/1674-1056/27/12/120202

Abstract ( 663 )

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In this paper, a nonlocal two-wave interaction system from the Manakov hierarchy is investigated via the Riemann-Hilbert approach. Based on the spectral analysis of the Lax pair, a Riemann-Hilbert problem for the nonlocal two-wave interaction system is constructed. By discussing the solutions of this Riemann-Hilbert problem in both the regular and non-regular cases, we explicitly present the N-soliton solution formula of the nonlocal two-wave interaction system. Moreover, the dynamical behaviour of the single-soliton solution is shown graphically.

Effects of the planarity and heterogeneity of networks on evolutionary two-player games

Xu-Sheng Liu(刘旭升), Zhi-Xi Wu(吴枝喜), Jian-Yue Guan(关剑月)

Chin. Phys. B, 2018, 27 (12): 120203. DOI: 10.1088/1674-1056/27/12/120203

Abstract ( 666 )

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We study the effects of the planarity and heterogeneity of networks on evolutionary two-player symmetric games by considering four different kinds of networks, including two types of heterogeneous networks:the weighted planar stochastic lattice (a planar scale-free network) and the random uncorrelated scale-free network with the same degree distribution as the weighted planar stochastic lattice; and two types of homogeneous networks:the hexagonal lattice and the random regular network with the same degree k₀=6 as the hexagonal lattice. Using extensive computer simulations, we found that both the planarity and heterogeneity of the network have a significant influence on the evolution of cooperation, either promotion or inhibition, depending not only on the specific kind of game (the Harmony, Snowdrift, Stag Hunt or Prisoner's Dilemma games), but also on the update rule (the Fermi, replicator or unconditional imitation rules).

Quantum metrology with a non-Markovian qubit system

Jiang Huang(黄江), Wen-Qing Shi(师文庆), Yu-Ping Xie(谢玉萍), Guo-Bao Xu(徐国保), Hui-Xian Wu(巫慧娴)

Chin. Phys. B, 2018, 27 (12): 120301. DOI: 10.1088/1674-1056/27/12/120301

Abstract ( 605 )

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The dynamics of the quantum Fisher information (QFI) of phase parameter estimation in a non-Markovian dissipative qubit system is investigated within the structure of single and double Lorentzian spectra. We use the time-convolutionless method with fourth-order perturbation expansion to obtain the general forms of QFI for the qubit system in terms of a non-Markovian master equation. We find that the phase parameter estimation can be enhanced in our model within both single and double Lorentzian spectra. What is more, the detuning and spectral width are two significant factors affecting the enhancement of parameter-estimation precision.

Optomechanical state transfer between two distant membranes in the presence of non-Markovian environments Suggested by editors

Jiong Cheng(程泂), Xian-Ting Liang(梁先庭), Wen-Zhao Zhang(张闻钊), Xiangmei Duan(段香梅)

Chin. Phys. B, 2018, 27 (12): 120302. DOI: 10.1088/1674-1056/27/12/120302

Abstract ( 742 )

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The quantum state transfer between two membranes in coupled cavities is studied when the system is surrounded by non-Markovian environments. An analytical approach for describing non-Markovian memory effects that impact on the state transfer between distant membranes is presented. We show that quantum state transfer can be implemented with high efficiency by utilizing the experimental spectral density, and the performance of state transfer in non-Markovian environments is much better than that in Markovian environments, especially when the tunneling strength between the two cavities is not very large.

Effects of imperfect pulses on dynamical decoupling using quantum trajectory method

Lin-Ze He(何林泽), Man-Chao Zhang(张满超), Chun-Wang Wu(吴春旺), Yi Xie(谢艺), Wei Wu(吴伟), Ping-Xing Chen(陈平形)

Chin. Phys. B, 2018, 27 (12): 120303. DOI: 10.1088/1674-1056/27/12/120303

Abstract ( 650 )

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The dynamical decoupling (DD) method is widely adopted to preserve coherence in different quantum systems. In the case of ideal pulses, its effects on the suppression of noise can be analytically described by the mathematical form of filter function. However, in practical experiments, the unavoidable pulse errors limit the efficiency of DD. In this paper, we study the effects of imperfect pulses on DD efficiency based on quantum trajectories. By directly generating a pseudo noise sequence correlated in time, we can explore the performance of DD with different pulse errors in the typical noise environment. It shows that, for the typical 1/f noise environment, the phase error of operational pulses severely affects the performance of noise suppression, while the detuning and intensity errors have less influence. Also, we get the thresholds of these errors for efficient DD under the given experimental conditions. Our method can be widely applied to guide practical DD experimental implementation.

Quantum steering in Heisenberg models with Dzyaloshinskii-Moriya interactions

Hui-Zhen Li(李慧贞), Rong-Sheng Han(韩榕生), Ye-Qi Zhang(张业奇), Liang Chen(陈亮)

Chin. Phys. B, 2018, 27 (12): 120304. DOI: 10.1088/1674-1056/27/12/120304

Abstract ( 674 )

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In this work, we study the quantum steering in two-qubit Heisenberg models with Dzyaloshinskii-Moriya (DM) interaction and an external magnetic field. We find that the steerable weight (SW) and the critical temperature where SW→0 can be enhanced by the DM interactions. In the special case where the magnetic field is vanishing and the two spins are ferromagnetically coupled, the DM interaction can tune the zero-temperature SW from zero to a finite value. In addition to the SW, some other measurements used to identify the quantum entanglement and quantum correlations are investigated, i.e., the concurrence, the quantum discord, and the robustness of coherence. In the strong magnetic field limit, our results show that the SW is dramatically different from the other measurements.

The entanglement of deterministic aperiodic quantum walks

Ting-Ting Liu(刘婷婷), Ya-Yun Hu(胡亚运), Jing Zhao(赵静), Ming Zhong(钟鸣), Pei-Qing Tong(童培庆)

Chin. Phys. B, 2018, 27 (12): 120305. DOI: 10.1088/1674-1056/27/12/120305

Abstract ( 668 )

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We study the entanglement between the internal (coin) and the external (position) degrees of freedom in the dynamic and the static deterministic aperiodic quantum walks (QWs). For the dynamic (static) aperiodic QWs, the coin depends on the time (position) and takes two coins C(α) and C(β) arranged in the two classes of generalized Fibonacci (GF) and the Thue-Morse (TM) sequences. We found that for the dynamic QWs, the entanglement of three kinds of the aperiodic QWs are close to the maximal value, which are all much larger than that of the homogeneous QWs. Further, the first class of GF (1st GF) QWs can achieve the maximum entangled state, which is similar to that of the dynamic disordered QWs. And the entanglement of 1st GF QWs is greater than that of the TM QWs, being followed closely by the entanglement of the second class of GF (2nd GF) QWs. For the static QWs, the entanglement of three kinds of the aperiodic QWs are also close to the maximal value and 1st GF QWs can achieve the maximum entangled state. The entanglement of the TM QWs is between 1st GF QWs and 2nd GF QWs. However, the entanglement of the static disordered QWs is less than that of three kinds of the aperiodic QWs. This is different from those of the dynamic QWs. From these results, we can conclude that the dynamic and static 1st GF QWs can also be considered as maximal entanglement generators.

Possible generation of π-condensation in a free space by collisions between photons and protons Suggested by editors

Qi-Ren Zhang(张启仁)

Chin. Phys. B, 2018, 27 (12): 120306. DOI: 10.1088/1674-1056/27/12/120306

Abstract ( 640 )

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A sharply peaked structure is found in the angular distribution of emitted π⁺ mesons from photon-proton collisions. This offers a possible way to generate a π⁺-condensation in free space. To make the stimulated emission of π⁺-mesons efficient, a ring resonator is designed.

Trapped Bose-Einstein condensates with quadrupole-quadrupole interactions ^Hot!

An-Bang Wang(王安邦), Su Yi(易俗)

Chin. Phys. B, 2018, 27 (12): 120307. DOI: 10.1088/1674-1056/27/12/120307

Abstract ( 642 )

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We numerically investigate the ground-state properties of a trapped Bose-Einstein condensate with quadrupole-quadrupole interaction. We quantitatively characterize the deformations of the condensate induced by the quadrupolar interaction. We also map out the stability diagram of the condensates and explore the trap geometry dependence of the stability.

Evolution of the Internet AS-level topology:From nodes and edges to components

Xiao Liu(刘晓), Jinfa Wang(王进法), Wei Jing(景薇), Menno de Jong, Jeroen S Tummers, Hai Zhao(赵海)

Chin. Phys. B, 2018, 27 (12): 120501. DOI: 10.1088/1674-1056/27/12/120501

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Studying the topology of infrastructure communication networks (e.g., the Internet) has become a means to understand and develop complex systems. Therefore, investigating the evolution of Internet network topology might elucidate disciplines governing the dynamic process of complex systems. It may also contribute to a more intelligent communication network framework based on its autonomous behavior. In this paper, the Internet Autonomous Systems (ASes) topology from 1998 to 2013 was studied by deconstructing and analysing topological entities on three different scales (i.e., nodes, edges and 3 network components:single-edge component M1, binary component M2 and triangle component M3). The results indicate that:a) 95% of the Internet edges are internal edges (as opposed to external and boundary edges); b) the Internet network consists mainly of internal components, particularly M2 internal components; c) in most cases, a node initially connects with multiple nodes to form an M2 component to take part in the network; d) the Internet network evolves to lower entropy. Furthermore, we find that, as a complex system, the evolution of the Internet exhibits a behavioral series, which is similar to the biological phenomena concerned with the study on metabolism and replication. To the best of our knowledge, this is the first study of the evolution of the Internet network through analysis of dynamic features of its nodes, edges and components, and therefore our study represents an innovative approach to the subject.

Primary resonance of fractional-order Duffing-van der Pol oscillator by harmonic balance method Suggested by editors

Sujuan Li(李素娟), Jiangchuan Niu(牛江川), Xianghong Li(李向红)

Chin. Phys. B, 2018, 27 (12): 120502. DOI: 10.1088/1674-1056/27/12/120502

Abstract ( 562 )

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The dynamical properties of fractional-order Duffing-van der Pol oscillator are studied, and the amplitude-frequency response equation of primary resonance is obtained by the harmonic balance method. The stability condition for steady-state solution is obtained based on Lyapunov theory. The comparison of the approximate analytical results with the numerical results is fulfilled, and the approximations obtained are in good agreement with the numerical solutions. The bifurcations of primary resonance for system parameters are analyzed. The results show that the harmonic balance method is effective and convenient for solving this problem, and it provides a reference for the dynamical analysis of similar nonlinear systems.

Effect of temporal disorder on wave packet dynamics in one-dimensional kicked lattices

Yuting Wang(王雨婷), Yi Gao(高绎), Peiqing Tong(童培庆)

Chin. Phys. B, 2018, 27 (12): 120503. DOI: 10.1088/1674-1056/27/12/120503

Abstract ( 606 )

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Inspired by the recent experimental progress in noisy kicked rotor systems, we investigate the effect of temporal disorder or quasi-periodicity in one-dimensional kicked lattices with pulsed on-site potential. We found that, unlike the spatial disorder or quasi-periodicity which usually leads to localization, the effect of the temporal one is more complex and depends on the spatial configuration. If the kicked on-site potential is periodic in real space, then the wave packet will stay diffusive in the presence of temporal disorder or quasi-periodicity. On the other hand, if the kicked on-site potential is spatially quasi-periodic, then the temporal disorder or quasi-periodicity may lead to a shift of the transition point of the dynamical localization and destroy the dynamical localization in a certain parameter range. The results we obtained can be readily tested by experiments and may help us better understand the dynamical localization.

Theoretical study of the radiative decay processes in H⁺(D⁺, T⁺)-Be collisions Suggested by editors

Huilin Wei(魏惠琳), Xiaojun Liu(刘晓军)

Chin. Phys. B, 2018, 27 (12): 123101. DOI: 10.1088/1674-1056/27/12/123101

Abstract ( 490 )

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The potential energy curves of X¹Σ⁺, A¹Σ⁺, C¹Σ⁺, and B¹Π are calculated with high-level MRDCI method, and the calculated spectroscopic constants of those states are in good agreement with most recent experimental data. On the basis of high precision PECs, the radiative processes of H⁺+Be collisions are studied by using the fully quantum, optical potential and semiclassical methods in the energy ranges of 10^-8 eV/u-0.1 eV/u, and the radiative decay, the radiative charge transfer, and the radiative association cross-sections are computed. It is found that the radiative association process is dominant in the energy region of 10^-8 eV/u-0.02 eV/u, while radiative charge transfer becomes important at higher energies. Rich resonance structures are present in the radiative association and charge transfer cross-sections in the whole energy region considered, which result from the interaction between the quasi-bound rovibrational (^{J, v}) states in the entrance channel with the final continuum state. Significant isotope effects have been found in the radiative decay processes of H⁺+Be collisions.

Up-conversion luminescence tuning in Er³⁺-doped ceramic glass by femtosecond laser pulse at different laser powers Suggested by editors

Wen-Jing Cheng(程文静), Guo Liang(梁果), Ping Wu(吴萍), Shi-Hua Zhao(赵世华), Tian-Qing Jia(贾天卿), Zhen-Rong Sun(孙真荣), Shi-An Zhang(张诗按)

Chin. Phys. B, 2018, 27 (12): 123201. DOI: 10.1088/1674-1056/27/12/123201

Abstract ( 566 )

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The up-conversion luminescence tuning of rare-earth ions is an important research topic for understanding luminescence mechanisms and promoting related applications. In this paper, we experimentally study the up-conversion luminescence tuning of Er³⁺-doped ceramic glass excited by the unshaped, V-shaped and cosine-shaped femtosecond laser field with different laser powers. The results show that green and red up-conversion luminescence can be effectively tuned by varying the power or spectral phase of the femtosecond laser field. We further analyze the up-conversion luminescence tuning mechanism by considering different excitation processes, including single-photon absorption (SPA), two-photon absorption (TPA), excited state absorption (ESA), and energy transfer up-conversion (ETU). The relative weight of TPA in the whole excitation process can increase with the increase of the laser power, thereby enhancing the intensity ratio between green and red luminescence (I₅₄₇/I₆₅₆). However, the second ETU (ETU2) process can generate red luminescence and reduce the green and red luminescence intensity ratio I₅₄₇/I₆₅₆, while the third ESA (ESA3) process can produce green luminescence and enhance its control efficiency. Moreover, the up-conversion luminescence tuning mechanism is further validated by observing the up-conversion luminescence intensity, depending on the laser power and the down-conversion luminescence spectrum under the excitation of 400-nm femtosecond laser pulse. These studies can present a clear physical picture that enables us to understand the up-conversion luminescence tuning mechanism in rare-earth ions, and can also provide an opportunity to tune up-conversion luminescence to promote its related applications.

Tracking coherent low frequency vibrational information of Rh101 in ground and excited electronic states by broadband transient grating spectroscopy

Wei Zhang(张伟), Xiao-Song Liu(刘小嵩), Zan-Hao Wang(王赞浩), Yun-Fei Song(宋云飞), Yan-Qiang Yang(杨延强)

Chin. Phys. B, 2018, 27 (12): 123301. DOI: 10.1088/1674-1056/27/12/123301

Abstract ( 526 )

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Time- and frequency-resolved broadband transient grating (BB-TG) spectroscopy is used to distinguish between ground- and excite-electronic state vibrational coherence at different wavelengths. Qualitative theoretical analysis using double-sided Feynman diagrams indicates that a superposition of ground and excited state vibrational coherence are contained in the ground state absorption (GSA) and stimulated emission (SE) overlap band, while only the excited state is contained in the excited state absorption (ESA) band. The TG experiment, in which a white light continuum (WLC) is adopted as a probe, is conducted with rhodamine101 (Rh101⁺) as the target molecule. Fourier analysis of TG dynamics in a positive delay time range at specific wavelengths enables us to distinguish the low-frequency vibrational modes of Rh101 in ground- and excite-electronic states.

Ghost images reconstructed from fractional-order moments with thermal light

De-Zhong Cao(曹德忠), Qing-Chen Li(李清晨), Xu-Cai Zhuang(庄绪财), Cheng Ren(任承), Su-Heng Zhang(张素恒), Xin-Bing Song(宋新兵)

Chin. Phys. B, 2018, 27 (12): 123401. DOI: 10.1088/1674-1056/27/12/123401

Abstract ( 689 )

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We present the joint probability density function (PDF) between the bucket signals and reference signals in thermal light ghost imaging, by regarding these signals as stochastic variables. The joint PDF allows us to examine the fractional-order moments of the bucket and the reference signals, in which the correlation orders are fractional numbers, other than positive integers in previous studies. The experimental results show that various images can be reconstructed from fractional-order moments. Negative (positive) ghost images are obtained with negative (positive) orders of the bucket signals. The visibility and peak signal-to-noise ratios of the diverse ghost images depend greatly on the fractional orders.

Resonances for positron-helium and positron-lithium systems in kappa-distribution plasma

Zi-Shi Jiang(姜子实), Ya-Chen Gao(高亚臣), Sabyasachi Kar, Kurunathan Ratnavelu

Chin. Phys. B, 2018, 27 (12): 123402. DOI: 10.1088/1674-1056/27/12/123402

Abstract ( 725 )

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S-wave resonances of positron-helium and positron-lithium systems in kappa-distribution plasmas are investigated using Hylleraas-type wave functions in the framework of the stabilization method. A model potential approach is used to represent the interactions between the outer electron, the positron and the core. The resonance parameters (position and width) of positron-helium and positron-lithium systems below the Ps(2s) threshold are reported as a function of screening parameter and spectral index of plasma.

Calibration of the superconducting gravimeter based on a cold atom absolute gravimeter at NIM ^Hot!

Qiyu Wang(王启宇), Jinyang Feng(冯金扬), Shaokai Wang(王少凯), Wei Zhuang(庄伟), Yang Zhao(赵阳), Lishuang Mou(牟丽爽), Shuqing Wu(吴书清)

Chin. Phys. B, 2018, 27 (12): 123701. DOI: 10.1088/1674-1056/27/12/123701

Abstract ( 820 )

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The scale factor of a superconducting gravimeter (SG) is usually calibrated by using simultaneous and co-located gravity measurements with the FG5-type absolute gravimeter (AG). In this paper, another new kind of absolute gravimeter-cold atom gravimeter (CAG) is first reported to calibrate the SG. Five-day side-by-side gravity measurements have been carried out by using our CAG (NIM-AGRb-1) to calibrate the SG (iGrav-012) located at Changping Campus of the National Institute of Metrology (NIM) of China. A weighted least-squares method is applied to determine the scale factor and the result is given as (-928.01±0.73) nm·^-2·V^-1 with a precision of 0.79‰. We have demonstrated that a calibration precision of 1‰ level can be achieved after 3 days of parallel observations at spring tide. The obtained calibration results are then compared with the previous calibration by FG5X-249, which shows that the calibration precision obtained by using NIM-AGRb-1 was slightly higher than FG5X-249 with the same time interval. The factors affecting the calibration precision are analyzed in the calibrations by means of different AGs. Finally, several calibration experiments for SG iGrav-012 are discussed. The final scale factor is estimated as (-927.58±0.36) nm·^-2·V^-1 with an accuracy of 0.39‰. Our main results demonstrate that the CAGs can be used for high-precision calibrations of SGs.

Homogeneous transparent device and its layered realization

Cheng-Fu Yang(杨成福), Ming Huang(黄铭), Jing-Jing Yang(杨晶晶), Fu-Chun Mao(毛福春), Ting-Hua Li(李廷华), Peng Li(黎鹏), Peng-Shan Ren(任鹏姗)

Chin. Phys. B, 2018, 27 (12): 124101. DOI: 10.1088/1674-1056/27/12/124101

Abstract ( 634 )

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Arbitrarily shaped electromagnetic transparent devices with homogeneous, non-negative, anisotropic and generic constitutive parameters are proposed based on linear transformation optics, which provides the flexibility for device design that is applicable for the practical fabrication. To remove the anisotropic property, a layered structure is developed based on effective medium theory. Simulation results show that with sufficient layers, the performance of the layered transparent device is nearly as perfect as an ideal device, and it is able to protect an antenna without sacrificing its performance. The feasibility of designing a transparent device by using natural isotropic materials instead of metamaterials would dramatically reduce the difficulty of fabrication and further promote the practicality of the device.

Polarization ratio characteristics of electromagnetic scattering from sea ice in polar areas Suggested by editors

Li Zhao(赵立), Tao Xie(谢涛), Lei Meng(孟雷), William Perrie, Jin-Song Yang(杨劲松), He Fang(方贺), Han Chen(陈韩), Run-Bing Ai(艾润冰)

Chin. Phys. B, 2018, 27 (12): 124102. DOI: 10.1088/1674-1056/27/12/124102

Abstract ( 605 )

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In the global climate system, the polar regions are sensitive indicators of climate change, in which sea ice plays an important role. Satellite remote sensing is a significant tool for monitoring sea ice. The use of synthetic aperture radar (SAR) images to distinguish sea ice from sea water is one of the current research hotspots in this topic. To distinguish sea ice from the open sea, the polarization ratio characteristics of sea ice and sea water are studied for L-band and C-band radars, based on an electromagnetic scattering model of sea ice derived from the integral equation method (IEM) and the radiative transfer (RT) model. Numerical experiments are carried out based on the model and the results are given as follows. For L-band, the polarization ratio for sea water depends only on the incident angle, while the polarization ratio for sea ice is related to the incident angle and the ice thickness. For C-band, the sea water polarization ratio is influenced by the incident angle and the root mean square (RMS) height of the sea surface. For C-band, for small to medium incident angles, the polarization ratio for bare sea ice is mainly determined by the incident angle and ice thickness. When the incident angle increases, the RMS height will also affect the polarization ratio for bare sea ice. If snow covers the sea ice, then the polarization ratio for sea ice decreases and is affected by the RMS height of snow surface, snow thickness, volume fraction and the radius of scatterers. The results show that the sea ice and the open sea can be distinguished by using either L-band or C-band radar according to their polarization ratio difference. However, the ability of L-band to make this differentiation is higher than that of C-band.

Generation of Mathieu beams using angular pupil modulation

Zhijun Ren(任志君), Jinping He(何晋平), Yile Shi(施逸乐)

Chin. Phys. B, 2018, 27 (12): 124201. DOI: 10.1088/1674-1056/27/12/124201

Abstract ( 560 )

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By using an amplitude-type spatial light modulator to load angular spectrum of Mathieu function distribution along a narrow annular pupils, the Durnin's experimental setup is extended to generate various types of Mathieu beams. As a special type of Mathieu beams, Bessel beams are also generated using this optical setup. Furthermore, the optical morphology of the Mathieu beams family are also presented and analyzed.

Physical manipulation of ultrathin-film optical interference for super absorption and two-dimensional heterojunction photoconversion

Guo-Yang Cao(曹国洋), Cheng Zhang(张程), Shao-Long Wu(吴绍龙), Dong Ma(马冬), Xiao-Feng Li(李孝峰)

Chin. Phys. B, 2018, 27 (12): 124202. DOI: 10.1088/1674-1056/27/12/124202

Abstract ( 698 )

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Ultrathin optical interference in a system composed of absorbing material and metal reflector has attracted extensive attention due to its potential application in realizing highly efficient optical absorption by using extremely thin semiconductor material. In this paper, we study the physics behind the high absorption of ultrathin film from the viewpoint of destructive interference and admittance matching, particularly addressing the phase evolution by light propagation and interface reflection. The physical manipulations of the ultrathin interference effect by controlling the substrate material and semiconductor material/thickness are examined. We introduce typical two-dimensional materials–i.e., MoS₂ and WSe₂–as the absorbing layer with thickness below 10 nm, which exhibits~90% absorption in a large range of incident angle (0°~70°). According to the ultrathin interference mechanism, we propose the ultrathin (<20 nm) MoS₂/WSe₂ heterojunction for photovoltaic application and carefully examine the detailed optoelectronic responses by coupled multiphysics simulation. By comparing the same cells on SiO₂ substrate, both the short-circuit current density (up to 20 mA/cm²) and the photoelectric conversion efficiency (up to 9.5%) are found to be increased by~200%.

Polarization-based range-gated imaging in birefringent medium:Effect of size parameter

Heng Tian(田恒), Jing-Ping Zhu(朱京平), Shu-Wen Tan(谭树文), Jing-Jing Tian(田晶晶), Yun-Yao Zhang(张云尧), Xun Hou(侯洵)

Chin. Phys. B, 2018, 27 (12): 124203. DOI: 10.1088/1674-1056/27/12/124203

Abstract ( 559 )

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We have investigated the effect of size parameter of the scatterer on the image quality obtained with polarization-based range-gated imaging in birefringent turbid medium. Both linearly and circularly polarized light were utilized for imaging. The simulated results indicate that the improvement of visibility is more pronounced using circularly polarized light for the birefringent medium composed of smaller-sized scatterers at lower values of optical thickness and the birefringent medium comprising larger-sized scatterers. In contrast, linearly polarized light provides better image quality for the birefringent medium composed of smaller-sized scatterers at larger values of optical thickness. The evolution of the polarization characteristics of backscattered light and target light under the conditions mentioned above was measured to account for these numerical results.

Geometrical condition for observing Talbot effect in plasmonics infinite metallic groove arrays

Afshari-Bavil Mehdi, Xiao-Ping Lou(娄小平), Ming-Li Dong(董明利), Chuan-Bo Li(李传波), Shuai Feng(冯帅), Parsa Saviz, Lian-Qing Zhu(祝连庆)

Chin. Phys. B, 2018, 27 (12): 124204. DOI: 10.1088/1674-1056/27/12/124204

Abstract ( 568 )

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The plasmonics Talbot effect in metallic layer with infinite periodic grooves is presented in this study. Numerical approach based on the finite element method is employed to verify the derived Talbot carpet on the non-illumination side. The groove depth is less than the metallic layer thickness; however, for specific conditions, surface plasmons polaritons (SPPs) can penetrate through grooves, propagate under the metallic layer, and form Talbot revivals. The geometrical parameters are specified via groove width, gap size, period, and wavelength, and their proper values are determined by introducing two opening ratio parameters. To quantitatively compare different Talbot carpets, we introduce new parameters such as R-square that characterizes the periodicity of Talbot images. The higher the R-square of a carpet, the more coincident with non-paraxial approximation the Talbot distance becomes. We believe that our results can help to understand the nature of SPPs and also contribute to exploring this phenomenon in Talbot-image-based applications, including imaging, optical systems, and measurements.

Tunable plasmon-induced transparency based on asymmetric H-shaped graphene metamaterials

Yu-Chen Tian(田雨宸), Wei Jia(贾微), Pei-Wen Ren(任佩雯), Chun-Zhen Fan(范春珍)

Chin. Phys. B, 2018, 27 (12): 124205. DOI: 10.1088/1674-1056/27/12/124205

Abstract ( 522 )

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We propose and numerically demonstrate a tunable plasmon-induced transparency (PIT) phenomenon based on asymmetric H-shaped graphene metamaterials. The tunable PIT effect is realized through varying the applied polarization angles rather than changing the structure geometry. By simply adjusting the polarization angle, the transmission spectra can be controlled between the switch-on state and switch-off state. The physical mechanism of the induced transparency is revealed from magnetic dipole inductive coupling and phase coupling. Importantly, by varying the Fermi energy of the graphene or the refractive index of the substrate, the resonant position of the PIT can be dynamically controlled and the maximum modulation depths can reach up to 60.7%. The sensitivity (nm/RIU) of the graphene structure, which is the shift of resonance wavelength per unit change of refractive index, is 5619.56 nm/RIU. Moreover, we also extend our research to the x-axis symmetric H-shaped structure, and the tunable PIT transmission window can also be realized. The physical mechanism of the induced transparency is revealed from the electric dipole hybridization coupling. Our designed H-shaped graphene-based structures is a promising candidate for compact elements such as tunable sensors, switches and slow-light devices.

Dynamic properties of atomic collective decay in cavity quantum electrodynamics

Yu-Feng Han(韩玉峰), Cheng-Jie Zhu(朱成杰), Xian-Shan Huang(黄仙山), Ya-Ping Yang(羊亚平)

Chin. Phys. B, 2018, 27 (12): 124206. DOI: 10.1088/1674-1056/27/12/124206

Abstract ( 520 )

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We theoretically study the collective decay of two atoms trapped in a single mode cavity and describe the evolution of the population of Dicke states. We show that the collective decay property is strongly dependent on the phase of atomic radiation and the speeding up of collective decay can be observed in bad cavity regime. For in- or out-phase case, it occurs due to the quantum interference enhancement no matter which atom is excited initially. For π/2 phase, the speeding up of collective decay takes place if the first atom is excited at the beginning. However, it disappears due to the quantum interference cancelation if the second atom is excited. Compared with the in-phase and out-phase cases, we also show that the speeding up of collective decay can be significantly enhanced in strong coupling regime for π/2 phase although one atom is decoupled to the cavity in this condition. The study presented here is helpful to understand the physical mechanism of collective decay in cavity quantum electrodynamics, and provide a useful method to control the collective decay phenomenon via quantum interference effect.

Room-temperature continuous-wave interband cascade laser emitting at 3.45 μm

Yi Zhang(张一), Fu-Hui Shao(邵福会), Cheng-Ao Yang(杨成奥), Sheng-Wen Xie(谢圣文), Shu-Shan Huang(黄书山), Ye Yuan(袁野), Jin-Ming Shang(尚金铭), Yu Zhang(张宇), Ying-Qiang Xu(徐应强), Hai-Qiao Ni(倪海桥), Zhi-Chuan Niu(牛智川)

Chin. Phys. B, 2018, 27 (12): 124207. DOI: 10.1088/1674-1056/27/12/124207

Abstract ( 581 )

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We report a type-Ⅱ GaSb-based interband cascade laser operating a continuous wave at room temperature. The cascade region of interband cascade laser was designed using the ‘W’ configuration of the active quantum wells and the ‘Carrier Rebalancing’ method in the electron injector. The devices were processed into narrow ridges and mounted epitaxial side down on a copper heat sink. The 25-μm-wide, 3-mm-long ridge without coated facets generated 41.4 mW of continuous wave output power at T=15℃. And a low threshold current density of 267 A/cm² is achieved. The emission wavelength of the ICL is 3452.3 nm at 0.5 A.

16-channel dual-tuning wavelength division multiplexer/demultiplexer

Pei Yuan(袁配), Yue Wang(王玥), Yuan-Da Wu(吴远大), Jun-Ming An(安俊明), Xiong-Wei Hu(胡雄伟)

Chin. Phys. B, 2018, 27 (12): 124208. DOI: 10.1088/1674-1056/27/12/124208

Abstract ( 576 )

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A 16-channel dual tuning wavelength division multiplexer/demultiplexer based on silicon on insulator platform is demonstrated, which is both peak wavelength tunable and output optical power tunable. The wavelength division multiplexer/demultiplexer consists of an arrayed waveguide grating for wavelength division multiplexing/demultiplexing, a heater for peak wavelength tuning and a variable optical attenuator based on p-i-n carrier-injection structure for optical power tuning. The experimental results show that the insertion loss on chip of the device is 3.7 dB-5.7 dB and the crosstalk is 7.5 dB-9 dB. For the tunability of the peak wavelength, 1.058-nm wavelength tunability is achieved with 271.2-mW power consumption, and the average modulation efficiency is 3.9244 nm/W; for the tunability of the optical power, the optical power equalization is achieved in all 16 channels, 20-dB attenuation is achieved with 144.07-mW power consumption, and the raise/fall time of VOA is 35 ns/42 ns.

Thermoacoustic-reflected focusing lens based on acoustic Bessel-like beam with phase manipulation

An-Ru Hou(侯安茹), Wen-Ting Gao(高文婷), Jiao Qian(钱姣), Hong-Xiang Sun(孙宏祥), Yong Ge(葛勇), Shou-Qi Yuan(袁寿其), Qiao-Rui Si(司乔瑞), Xiao-Jun Liu(刘晓峻)

Chin. Phys. B, 2018, 27 (12): 124301. DOI: 10.1088/1674-1056/27/12/124301

Abstract ( 636 )

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We report the realization of broadband reflected acoustic focusing lenses based on thermoacoustic phased arrays of Bessel-like beams, in which the units of phase manipulation are composed of three rigid insulated boundaries and a thermal insulation film in air with different temperatures. Based on these units, we realize a reflected focusing lens which can focus reflected acoustic energy on a line, and its fractional bandwidth can reach about 0.29. In addition, we discuss the influences of the base angle of Bessel-like beam, the number of basic unit, and the variation of unit temperature on focusing performances in details. Furthermore, the reflected focusing lens for the cylindrical acoustic wave based on the Bessel-like beam is also demonstrated. The proposed focusing lens has the advantages of a broad working bandwidth, large focus size, and high robustness, which may provide possibilities for the design and application of acoustic lenses.

Bidirectional asymmetric acoustic focusing with two flat acoustic metasurfaces

Di-Chao Chen(陈帝超), Xing-Feng Zhu(朱兴凤), Qi Wei(魏琦), Da-Jian Wu(吴大建)

Chin. Phys. B, 2018, 27 (12): 124302. DOI: 10.1088/1674-1056/27/12/124302

Abstract ( 648 )

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We design an asymmetric transmission system (ATS) with two flat acoustic metasurfaces (AMs) to yield bidirectional asymmetric acoustic focusing (BAAF). The acoustic waves could be focused on both sides of the ATS with different focal lengths and intensities. To achieve high intensity energy concentration, the accelerating acoustic beams are selected to realize the BAAF. The working bandwidth of the BAAF based on our ATS could reach~0.4 kHz. It is found that by adjusting the distance between two flat AMs, the focal length and intensity of the bidirectional focusing could easily be modulated. Because the distance between two flat AMs is large enough, the BAAF even could be converted into a unidirectional acoustic focusing. The proposed BAAF may find applications in non-destructive evaluation, biomedical imaging and medical diagnosis.

Cellular automaton modeling of pedestrian movement behavior on an escalator

Fu-Rong Yue(岳芙蓉), Juan Chen(陈娟), Jian Ma(马剑), Wei-Guo Song(宋卫国), Siu-Ming Lo(卢兆明)

Chin. Phys. B, 2018, 27 (12): 124501. DOI: 10.1088/1674-1056/27/12/124501

Abstract ( 680 )

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As a convenient passenger transit facility between floors with different heights, escalators have been extensively used in shopping malls, metro stations, airport terminals, etc. Compared with other vertical transit facilities including stairs and elevators, escalators usually have large transit capacity. It is expected to reduce pedestrian traveling time and thus improve the quality of pedestrian's experiences especially in jamming conditions. However, it is noticed that pedestrians may present different movement patterns, e.g., queuing on each step of the escalator, walking on the left-side and meanwhile standing on the right-side of the escalator. These different patterns affect the actual escalator traffic volume and finally the passenger spatiotemporal distribution in different built environments. Thus, in the present study, a microscopic cellular automaton (CA) simulation model considering pedestrian movement behavior on escalators is built. Simulations are performed considering different pedestrian movement speeds, queuing modes, and segregation on escalators with different escalator speeds. The actual escalator capacities under different pedestrian movement patterns are investigated. It is found that walking on escalators will not always benefit escalator transit volume improvement, especially in jamming conditions.

Traffic flow velocity disturbance characteristics and control strategy at the bottleneck of expressway Suggested by editors

Jun-Wei Zeng(曾俊伟), Yong-Sheng Qian(钱勇生), Xu-Ting Wei(魏谞婷), Xiao Feng(冯骁)

Chin. Phys. B, 2018, 27 (12): 124502. DOI: 10.1088/1674-1056/27/12/124502

Abstract ( 632 )

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In the three-phase traffic flow studies, the traffic flow characteristic at the bottleneck section is a hot spot in the academic field. The controversy about the characteristics of the synchronized flow at bottleneck is also the main contradiction between the three-phase traffic flow theory and the traditional traffic flow theory. Under the framework of three-phase traffic flow theory, this paper takes the on-ramp as an example to discuss the traffic flow characteristics at the bottleneck section. In particular, this paper mainly conducts the micro-analysis to the effect of lane change under the two lane conditions, as well as the effect of the on-ramp on the main line traffic flow. It is found that when the main road flow is low, the greater the on-ramp inflow rate, the higher the average speed of the whole road section. As the probability of vehicles entering from the on-ramp increases, the flow and the average speed of the main road are gradually stabilized, and then the on-ramp inflow vehicles no longer have a significant impact on the traffic flow. In addition, this paper focuses on the velocity disturbance generated at the on-ramp, and proposes the corresponding on-ramp control strategy based on it, and the simulation verified that the control strategy can reasonably control the traffic flow by the on-ramp, which can meet the control strategy requirements to some extent.

Gas flow characteristics of argon inductively coupled plasma and advections of plasma species under incompressible and compressible flows

Shu-Xia Zhao(赵书霞), Zhao Feng(丰曌)

Chin. Phys. B, 2018, 27 (12): 124701. DOI: 10.1088/1674-1056/27/12/124701

Abstract ( 660 )

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In this work, incompressible and compressible flows of background gas are characterized in argon inductively coupled plasma by using a fluid model, and the respective influence of the two flows on the plasma properties is specified. In the incompressible flow, only the velocity variable is calculated, while in the compressible flow, both the velocity and density variables are calculated. The compressible flow is more realistic; nevertheless, a comparison of the two types of flow is convenient for people to investigate the respective role of velocity and density variables. The peripheral symmetric profile of metastable density near the chamber sidewall is broken in the incompressible flow. At the compressible flow, the electron density increases and the electron temperature decreases. Meanwhile, the metastable density peak shifts to the dielectric window from the discharge center, besides for the peripheral density profile distortion, similar to the incompressible flow. The velocity profile at incompressible flow is not altered when changing the inlet velocity, whereas clear peak shift of velocity profile from the inlet to the outlet at compressible flow is observed as increasing the gas flow rate. The shift of velocity peak is more obvious at low pressures for it is easy to compress the rarefied gas. The velocity profile variations at compressible flow show people the concrete residing processes of background molecule and plasma species in the chamber at different flow rates. Of more significance is it implied that in the usual linear method that people use to calculate the residence time, one important parameter in the gas flow dynamics, needs to be rectified. The spatial profile of pressure simulated exhibits obvious spatial gradient. This is helpful for experimentalists to understand their gas pressure measurements that are always taken at the chamber outlet. At the end, the work specification and limitations are listed.

Numerical simulation of metal evaporation based on the kinetic model equation and the direct simulation Monte Carlo method

Xiaoyong Lu(卢肖勇), Xiaozhang Zhang(张小章), Zhizhong Zhang(张志忠)

Chin. Phys. B, 2018, 27 (12): 124702. DOI: 10.1088/1674-1056/27/12/124702

Abstract ( 588 )

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Metal evaporation on the basis of the kinetic model equations (BGK and S-model) and the direct simulation Monte Carlo (DSMC) method was investigated computationally under the circumstances of collimators existing or not. Numerical data of distributions of number density, bulk velocity and temperature were reported over a wide range of evaporation rate. It was shown that these results reached a good agreement for the case of small evaporation rate, while the deviations became increasingly obvious with the increase of evaporation rate, especially when the collimators existed. Moreover, the deposition thickness over substrate obtained from the kinetic model equations were inaccurate even though the evaporation rate was small. All of the comparisons showed the reliability of the kinetic model equations, which require less computational cost at small evaporation rate and simple structure.

Drag reduction characteristics of heated spheres falling into water

Jia-Chuan Li(李佳川), Ying-Jie Wei(魏英杰), Cong Wang(王聪), Wei-Xue Xia(夏维学)

Chin. Phys. B, 2018, 27 (12): 124703. DOI: 10.1088/1674-1056/27/12/124703

Abstract ( 669 )

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We experimentally investigate the drag reduction characteristics of heated spheres falling into water by using a high-speed camera. In 25-℃ water, with the increase of the sphere temperature the average velocity increases to a maximum value at a temperature of 400℃ and then decreases until the temperature reaches 700℃, the average velocity will increase while the sphere temperature continually rises until the temperature reaches 900℃. The average and the maximum velocity of the heated sphere are larger than those of the room-temperature sphere. The flow separates at the rear of the heated sphere, leading to low pressure drag. The drag reduction effect of the stable film boiling is lower than that of the nucleate boiling. In the nucleate boiling regime, the average velocity decreases with the increase of water temperature, the drag of the sphere with gentle boiling intensity is smaller. The vapor layer formed in the stable film boiling regime can improve the stability of the fall trajectory. The intense turbulence caused by the nucleate boiling can make the sphere largely deviate from rectilinear motion.

Numerical simulations of dense granular flow in a two-dimensional channel:The role of exit position

Tingwei Wang(王廷伟), Xin Li(李鑫), Qianqian Wu(武倩倩), Tengfei Jiao(矫滕菲), Xingyi Liu(刘行易), Min Sun(孙敏), Fenglan Hu(胡凤兰), Decai Huang(黄德财)

Chin. Phys. B, 2018, 27 (12): 124704. DOI: 10.1088/1674-1056/27/12/124704

Abstract ( 632 )

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Molecular dynamics simulations have been performed to elucidate the influence of exit position on a dense granular flow in a two-dimensional channel. The results show that the dense flow rate remains constant when the exit is far from the channel wall and increases exponentially when the exit moves close to the lateral position. Beverloo's law proves to be successful in describing the relation between the dense flow rate and the exit size for both the center and the lateral exits. Further simulated results confirm the existence of arch-like structure of contact force above the exit. The effective exit size is enlarged when the exit moves from the center to the lateral position. As compared with the granular flow of the center exit, both the vertical velocities of the grains and the flow rate increase for the lateral exit.

Preliminary computation of the gap eigenmode of shear Alfvén waves on the LAPD

Lei Chang(苌磊)

Chin. Phys. B, 2018, 27 (12): 125201. DOI: 10.1088/1674-1056/27/12/125201

Abstract ( 454 )

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Characterizing the gap eigenmode of shear Alfvén waves (SAWs) and its interaction with energetic ions is important to the success of magnetically confined fusion. Previous studies have reported an experimental observation of the spectral gap of SAW on the on Large Plasma Device (LAPD) (Zhang et al. 2008 Phys. Plasmas 15 012103), a linear large plasma device (Gekelman et al. 1991 Rev. Sci. Instrum. 62 2875) possessing easier diagnostic access and lower cost compared with traditional fusion devices, and analytical theory and numerical gap eigenmode using ideal conditions (Chang 2014 Ph.D Thesis at Australian National University). To guide experimental implementation, the present work models the gap eigenmode of SAWs using exact LAPD parameters. A full picture of the wave field for previous experiment reveals that the previously observed spectral gap is not global but an axially local result. To form a global spectral gap, the number of magnetic mirrors has to be increased and stronger static magnetic field makes it clearer. Such a spectral gap is obtained for the magnetic field of B₀(z)=1.2+0.6cos[2π (z-33.68)/3.63] with 7.74-m magnetic beach. By introducing two types of local defects (corresponding to E_θ(z₀)=0 and E_θ'(z₀)=0 respectively), odd-parity and even-parity discrete eigenmodes are formed clearly inside the gap. The strength of these gap eigenmodes decreases significantly with collision frequency, which is consistent with previous studies. Parameter scans show that these gap eigenmodes can be even formed successfully for the field strength of B₀(z)=0.2+0.1cos[2π (z-33.68)/3.63] and with only four magnetic mirrors, which are achievable by the LAPD at its present status. This work can serve as a strong motivation and direct reference for the experimental implementation of the gap eigenmode of SAWs on the LAPD and other linear plasma devices.

Numerical simulation of the multiple reversed shear Alfvén eigenmodes associated with the triangularity Alfvén gap

Wenjia Wang(王文家), Deng Zhou(周登), Youjun Hu(胡友俊), Yue Ming(明玥), Baolong Hao(郝保龙)

Chin. Phys. B, 2018, 27 (12): 125202. DOI: 10.1088/1674-1056/27/12/125202

Abstract ( 538 )

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It was found that there are multiplicity of low shear toroidicity-induced Alfvén eigenmodes in a zero beta limit if the inverse aspect ratio is larger than the magnetic shear at the mode location (Candy 1996 Phys. Lett. A 215 299). Because the reversed shear Alfvén eigenmode (RSAE) and even the RSAE associated with the non-circular triangularity-induced Alfvén eigenmode (NAE) gap (NAE-RSAE) usually reside near the shear-reversal point, the condition that the inverse aspect ratio is larger than the magnetic shear is naturally satisfied. For this reason, we numerically investigate the existence of multiplicity of core-localized NAE-RSAEs and mode characteristics in the present work. We firstly verify the existence of the multiplicity for zero beta plasma by using a D-shaped equilibrium. It is pointed out that, for a given toroidal mode number, the Alfvén cascade spectrum accommodates down-sweeping and up-sweeping modes above and below the NAE range of frequencies. An analytical model for the existence of multiple RSAE modes is in good agreement with the simulation results. One notices that the triangularity has a greater effect on the odd-type modes than that on the even-type modes:the odd-type modes come into existence because of the plasma triangularity.

Review of improved spectral response of ultraviolet photodetectors by surface plasmon

You Wu(吴忧), Xiao-Juan Sun(孙晓娟), Yu-Ping Jia(贾玉萍), Da-Bing Li(黎大兵)

Chin. Phys. B, 2018, 27 (12): 126101. DOI: 10.1088/1674-1056/27/12/126101

Abstract ( 577 )

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Ultraviolet (UV) photodetectors based on wide band gap semiconductor have attracted much attention for their small volume, low working voltage, long lifetime, good chemical and thermal stability. Up to now, many researches have been done on the semiconductors based UV detectors and some kinds of detectors have been made, such as metal-semiconductor-metal (MSM), Schottky, and PIN-type detectors. However, the sensitivity values of those detectors are still far from the expectation. Recent years, surface plasmon (SP) has been considered to be an effective way to enhance the sensitivity of semiconductor based UV photodetector. When the light is matched with the resonance frequency of surface plasmon, the localized field enhancement or scattering effect will happen and thus the spectral response will be enhanced. Here, we present an overview of surface plasmon enhancing the performance of UV detectors, including the GaN, ZnO, and other wide band gap semiconductor UV detectors. Both fundamental and experimental achievements are contained in this review.

First-principles investigations on structural stability, mechanical, and thermodynamic properties of LaT₂Al₂₀ (T=Ti, V, Cr, Nb, and Ta) intermetallic cage compounds

Shanyu Quan(权善玉), Xudong Zhang(张旭东), Cong Liu(刘聪), Wei Jiang(姜伟)

Chin. Phys. B, 2018, 27 (12): 126201. DOI: 10.1088/1674-1056/27/12/126201

Abstract ( 488 )

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First principles calculations were used to explore the structural stability, mechanical properties, and thermodynamic properties of LaT₂Al₂₀ (T=Ti, V, Cr, Nb, and Ta) intermetallics. The calculated formation enthalpy and phonon frequencies indicate that LaT₂Al₂₀ intermetallics exhibit the structural stability. The elastic moduli (B, G, E, and H_v) indicate that these intermetallics possess the better elastic properties than pure Al. The values of Poisson's ratio v and B/G demonstrate that LaT₂Al₂₀ intermetallics are all brittle materials. The anisotropy of elasticity and Young's modulus (three- and two-dimensional figures) indicate that LaT₂Al₂₀ compounds are anisotropic. Importantly, the calculated thermal quantities demonstrate that LaT₂Al₂₀ intermetallics possess the better thermal physical properties than pure Al at high temperatures.

Shock temperature and reflectivity of precompressed H₂O up to 350 GPa:Approaching the interior of planets Suggested by editors

Zhi-Yu He(贺芝宇), Hua Shu(舒桦), Xiu-Guang Huang(黄秀光), Qi-Li Zhang(张其黎), Guo Jia(贾果), Fan Zhang(张帆), Yu-Chun Tu(涂昱淳), Jun-Yue Wang(王寯越), Jun-Jian Ye(叶君建), Zhi-Yong Xie(谢志勇), Zhi-Heng Fang(方智恒), Wen-Bing Pei(裴文兵), Si-Zu Fu(傅思祖)

Chin. Phys. B, 2018, 27 (12): 126202. DOI: 10.1088/1674-1056/27/12/126202

Abstract ( 635 )

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Using a combination of static precompression and laser-driven shock compression, shock temperature and reflectivity of H₂O have been measured up to 350 GPa and 2.1×10⁴ K. Here, two calibration standards were applied to enhance temperature measurement reliability. Additionally, in temperature calculations, the discrepancy in reflectivity between active probe beam wavelength and self-emission wavelength has been taken into account to improve the data's precision. Precompressed water's temperature-pressure data are in very good agreement with our quantum molecular dynamics model, suggesting a superionic conductor of H₂O in the icy planets' deep interior. A sluggish slope gradually approaching Dulong-Petit limit at high temperature was found at a specific heat capacity. Also, high reflectivity and conductivity were observed at the same state. By analyzing the temperature-pressure diagram, reflectivity, conductivity and specific heat comprehensively at conditions simulating the interior of planets in this work, we found that as the pressure rises, a change in ionization appears; it is supposedly attributed to energetics of bond-breaking in the H₂O as it transforms from a bonded molecular fluid to an ionic state. Such molecular dissociation in H₂O is associated with the conducting transition because the dissociated hydrogen atoms contribute to electrical properties.

Simulation and experimental investigation of low-frequency vibration reduction of honeycomb phononic crystals

Han-Bo Shao(邵瀚波), Guo-Ping Chen(陈国平), Huan He(何欢), Jin-Hui Jiang(姜金辉)

Chin. Phys. B, 2018, 27 (12): 126301. DOI: 10.1088/1674-1056/27/12/126301

Abstract ( 563 )

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The honeycomb phononic crystal displays good performance in reducing vibration, especially at low frequency, but there are few corresponding experiments involving this kind of phononic crystal and the influence of geometric parameters on the bandgap is unclear. We design a honeycomb phononic crystal, which is assembled by using a chemigum plate and a steel column, calculate the bandgaps of the phononic crystal, and analyze the vibration modes. In the experiment, we attach a same-sized rubber plate and a phononic crystal to a steel plate separately in order to compare their vibration reduction performances. We use 8×8 unit cells as a complete phononic crystal plate to imitate an infinite period structure and choose a string suspension arrangement to support the experiment. The results show that the honeycomb phononic crystal can reduce the vibrating plate magnitude by up to 60 dB in a frequency range of 600 Hz-900 Hz, while the rubber plate can reduce only about 20 dB. In addition, we study the effect of the thickness of plate and the height and the radius of the column in order to choose the most superior parameters to achieve low frequency and wide bandgap.

The superconducting properties of a Pb/MoTe₂/Pb heterostructure:First-principles calculations within the anisotropic Migdal-Eliashberg theory

Wei Xia(夏威), Jie Zhang(张洁), Gui-Qin Huang(黄桂芹)

Chin. Phys. B, 2018, 27 (12): 126302. DOI: 10.1088/1674-1056/27/12/126302

Abstract ( 644 )

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The spin-polarized band structures of an ultrathin Pb/MoTe₂/Pb heterostructure are calculated via first-principles density functional theory. The electron-phonon interaction and the superconducting properties of the ultrathin Pb/MoTe₂/Pb heterostructure are studied by using the fully anisotropic Migdal-Eliashberg theory powered by Wannier-Fourier interpolation. Due to the complex Fermi surface in this low-dimensional system, the electron-phonon interaction and the superconducting gap display significant anisotropy. The temperature dependence of the superconducting gap can be fitted by solving numerically the Bardeen-Cooper-Schrieffer (BCS) gap equation with an adjustable parameter α, suggesting that phonon-mediated mechanism as its superconducting origin. Large Rashba spin-splitting and superconductivity coexist in this heterostructure, suggesting that this hybrid low-dimensional system will have some specific applications.

Exact solitary wave solutions of a nonlinear Schrödinger equation model with saturable-like nonlinearities governing modulated waves in a discrete electrical lattice

Serge Bruno Yamgoué, Guy Roger Deffo, Eric Tala-Tebue, François Beceau Pelap

Chin. Phys. B, 2018, 27 (12): 126303. DOI: 10.1088/1674-1056/27/12/126303

Abstract ( 509 )

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In this paper, we introduce and propose exact and explicit analytical solutions to a novel model of the nonlinear Schrödinger (NLS) equation. This model is derived as the equation governing the dynamics of modulated cutoff waves in a discrete nonlinear electrical lattice. It is characterized by the addition of two terms that involve time derivatives to the classical equation. Through those terms, our model is also tantamount to a generalized NLS equation with saturable; which suggests that the discrete electrical transmission lines can potentially be used to experimentally investigate wave propagation in media that are modeled by such type of nonlinearity. We demonstrate that the new terms can enlarge considerably the forms of the solutions as compared to similar NLS-type equations. Sine-Gordon expansion-method is used to derive numerous kink, antikink, dark, and bright soliton solutions.

Multilayer graphene refractive index tuning by optical power Suggested by editors

Lijun Li(李丽君), Yilin Liu(刘仪琳), Yinming Liu(刘荫明), Lin Xu(徐琳), Fei Yu(于飞), Tianzong Xu(徐天纵), Zhihui Shi(石志辉), Weikang Jia(贾伟康)

Chin. Phys. B, 2018, 27 (12): 126304. DOI: 10.1088/1674-1056/27/12/126304

Abstract ( 753 )

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Graphene's optical absorption coefficient increases linearly with the number of layers making it more effective in the construction of optical tuning graphene-based devices. Refractive index (RI) is one of the important optical parameters of the graphene for accurately describing its optical characteristics and further applications. In view of the RI research of the multilayer graphene is lacking and existing measurement methods are complicated. Optical power tuning RI of multilayer graphene is investigated using a simple measurement and no temperature cross sensitivity all optical fiber sensing structure. Optical power tuning RI characteristics of multilayer graphene are studied by tuning the introducing broad band light power from 0.57 mW to 22.7 mW. Different thickness graphene coating shows different tuning efficiency. At 4.86-μm thickness, a 3.433-nm Bragg wavelength shift is obtained with 156.2-pm/mW wavelength versus optical power tuning sensitivity corresponding to 3.25×10³ RI change and 0.154 URI/W (URI, unit of RI) RI optical power tuning efficiency.

Bloch oscillation of Weyl metal along synthetic dimensions

Ye Xiong(熊烨)

Chin. Phys. B, 2018, 27 (12): 126701. DOI: 10.1088/1674-1056/27/12/126701

Abstract ( 555 )

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Synthetic dimensions in time (Sambe space) can be utilized in a periodic time-dependent system. By subjecting the system into a time-periodic potential and measuring the physical quantities at distinct time in one period, one is able to simulate the models in higher dimension. To verify this approach, we show that the Bloch oscillation of wave packets along the magnetic field in a three-dimensional (3D) Weyl metal can be simulated on a two-dimensional (2D) insulator. Different from the chiral anomaly, this Bloch oscillation is anisotropic when the initial wave packet is not on the 0-th Landau level.

Effects of dielectric decrement on surface potential in a mixed electrolyte solution

Jing Peng(彭景), Wen-Xin Zou(邹温馨), Rui Tian(田锐), Hang Li(李航), Xin-Min Liu(刘新敏)

Chin. Phys. B, 2018, 27 (12): 126801. DOI: 10.1088/1674-1056/27/12/126801

Abstract ( 528 )

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Surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson-Boltzmann theory with the consideration of the dielectric decrement in mixed electrolyte. The analytical relationships between surface potential and charge density are derived in different mixed electrolytes with monovalent and bivalent ions. The dielectric decrease on the charged surface strongly affects the surface potential at a high charge density with different ion strengths and concentration ratios of counter-ions. The surface potential based on the Gouy-Chapman model is underestimated because of the dielectric decrement on the surface. The diffuse layer can be regarded as a continuous uniform medium only when the surface charge density is lower than 0.3 C·m^-2. However, the surface charge densities of many materials in practical applications are higher than 0.3 C·m^-2. The new model for the estimation of surface potential can return to the results obtained based on the Gouy-Chapman model at a low charge density. Therefore, it is implied that the established model that considers the dielectric decrement is valid and widely applicable.

Theoretical design of multifunctional half-Heusler materials based on first-principles calculations

Xiuwen Zhang(张秀文)

Chin. Phys. B, 2018, 27 (12): 127101. DOI: 10.1088/1674-1056/27/12/127101

Abstract ( 771 )

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The family of ABX half-Heusler materials, also called filled-tetrahedral structures, is a special class of ternary compounds hosting a variety of material functionalities including thermoelectricity, topological insulation, magnetism, transparent conductivity and superconductivity. This class of compounds can be derived from two substitution approaches, i.e., from Heusler materials by removing a portion of atoms forming ordered vacancies thus becoming half-Heusler, or from tetrahedral zinc blende compounds by adding atoms on the interstitial sites thus become filled-tetrahedral structures. In this paper, we briefly review the substitution approaches for material design along with their application in the design of half-Heusler compounds; then we will review the high-throughput search of new half-Heusler filled-tetrahedral structures and the study of their physical properties and functionalities.

Effects of the band-filling and Fe/Mo disorder on physical properties of Ca₂FeMoO₆

Jin-Feng Wang(王金凤), Zhao-Tong Zhuang(庄照通), Shuai-Shuai Liu(刘帅帅), Qian-Qian Gao(高迁迁)

Chin. Phys. B, 2018, 27 (12): 127201. DOI: 10.1088/1674-1056/27/12/127201

Abstract ( 563 )

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Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca₂FeMoO₆. Two series of Ca₂FeMoO₆ and Nd_0.3Ca_1.7FeMoO₆ ceramics sintered at (1050℃, 1200℃, and 1300℃) were specially designed to comparatively investigate the band-filling effect and Fe/Mo disorder on the physical properties of Ca₂FeMoO₆. The x-ray diffraction indicates that Fe/Mo disorder is sensitive to the sintering temperature. The magnetization behavior is mainly controlled by the Fe/Mo disorder not by the band filling effect, manifested by a close correlation of saturated magnetization (M_s) with the Fe/Mo disorder. Interestingly, magnetoresistance (MR) property of the same composition is dominantly contributed by the grain boundary strength, which can be expressed by the macroscopic resistivity values. However, the band filling effect caused by the Nd-substitution can decrease the spin polarization, and thus suppress the MR performance fundamentally. Contrary to the MR response, the Curie temperature (T_C) shows an obvious optimization due to the band filling effect, which increases the carrier density near the Fermi level responsible for the ferromagnetic coupling interaction strengthen. Maybe, our work can provoke further research interests into the correlation of the band-filling effects and Fe/Mo disorder with the physical properties of other Fe/Mo-based double perovskites.

Temporal pulsed x-ray response of CdZnTe:In detector ^Hot!

Rong-Rong Guo(郭榕榕), Ya-Dong Xu(徐亚东), Gang-Qiang Zha(查钢强), Tao Wang(王涛), Wan-Qi Jie(介万奇)

Chin. Phys. B, 2018, 27 (12): 127202. DOI: 10.1088/1674-1056/27/12/127202

Abstract ( 671 )

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The temporal response of cadmium-zinc-telluride (CZT) crystals is evaluated at room temperature by using an ultrafast-pulsed x-ray source. The dynamics of carrier relaxation in a CZT single crystal is modeled at a microscopic level based on a multi-trapping effect. The effects of the irradiation flux and bias voltage on the amplitude and full width at half maximum (FWHM) of the transient currents are investigated. It is demonstrated that the temporal response process is affected by defect level occupation fraction. A fast photon current can be achieved under intense pulsed x-ray irradiation to be up to 2.78×10⁹ photons mm^-2·s^-1. Meanwhile, it is found that high bias voltage could enhance carrier detrapping by suppressing the capture of structure defects and thus improve the temporal response of CZT detectors.

Valley-polarized pumping current in zigzag graphene nanoribbons with different spatial symmetries

Zhizhou Yu(俞之舟), Fuming Xu(许富明)

Chin. Phys. B, 2018, 27 (12): 127203. DOI: 10.1088/1674-1056/27/12/127203

Abstract ( 744 )

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We numerically investigate the valley-polarized current in symmetric and asymmetric zigzag graphene nanoribbons (ZGNRs) by the adiabatic pump, and the effect of spatial symmetry is considered by introducing different pumping regions. It is found that pumping potentials with the symmetry V_p(x,y)=V_p(-x,y) can generate the largest valley-polarized current. The valley-polarized currents I₁₃^L with the pumping potential symmetry V_p(x,y)=V_p(x,-y) and I₁₄^L with V_p(x,y)=V_p(-x,-y) of symmetric ZGNRs are much smaller than those of asymmetric ZGNRs. We also find I₁₃^L and I₁₄^L of symmetric ZGNRs decrease and increase with the increasing pumping amplitude, respectively. Moreover, the dephasing effect from the electron-phonon coupling within the Buttiker dephasing scheme is introduced. The valley-polarized current of the symmetric ZGNRs with V_p(x,y)=V_p(x,-y) increases with the increase of the dephasing strength while that with V_p(x,y)=V_p(-x,-y) decreases as the dephasing strength increases.

Tunable edge bands and optical properties in black phosphorus nanoribbons under electric field

Hong Liu(刘红)

Chin. Phys. B, 2018, 27 (12): 127301. DOI: 10.1088/1674-1056/27/12/127301

Abstract ( 628 )

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For several types of the applied electric field configuration on the normal-zigzag black phosphorus nanoribbon (nZZ-BPNR) we investigate the band structure and the linear optical absorption spectrum, especially for the edge states and the corresponding low-energy absorption peaks. The obtained results show that the applied electric field can not only open another band gap at k=0.5 point, but also can change completely the spacial probabilities of edge states in the two edge bands. The strength of electric field can tune the two band gaps at the Γ point and 0.5 point. Further, one remarkable feature is that the forbidden transition E₁₂ and E₂₁ are allowed. The lowest-excited-energy linear absorption peak E₁₁ originates from the transition between two edge bands at the Γ point. Finally, in comparison with the lowest-excited-energy peaks among various configurations, the second type of electric field configuration can move this peak blue-shift larger than other configurations.

A simulation study of field plate termination in Ga₂O₃ Schottky barrier diodes

Hui Wang(王辉), Ling-Li Jiang(蒋苓利), Xin-Peng Lin(林新鹏), Si-Qi Lei(雷思琦), Hong-Yu Yu(于洪宇)

Chin. Phys. B, 2018, 27 (12): 127302. DOI: 10.1088/1674-1056/27/12/127302

Abstract ( 617 )

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In this work, the field plate termination is studied for Ga₂O₃ Schottky barrier diodes (SBDs) by simulation. The influence of field plate overlap, dielectric material and thickness on the termination electric field distribution are demonstrated. It is found that the optimal thickness increases with reverse bias increasing for all the three dielectrics of SiO₂, Al₂O₃, and HfO₂. As the thickness increases, the maximum electric field intensity decreases in SiO₂ and Al₂O₃, but increases in HfO₂. Furthermore, it is found that SiO₂ and HfO₂ are suitable for the 600 V rate Ga₂O₃ SBD, and Al₂O₃ is suitable for both 600 V and 1200 V rate Ga₂O₃ SBD. In addition, the comparison of Ga₂O₃ SBDs between the SiC and GaN counterpart reveals that for Ga₂O₃, the breakdown voltage bottleneck is the dielectric. While, for SiC and GaN, the bottleneck is mainly the semiconductor itself.

Enhanced performance of a solar cell based on a layer-by-layer self-assembled luminescence down-shifting layer of core-shell quantum dots

Ni Liu(刘妮), Shu-Xin Li(李淑鑫), Ying-Chun Ye(叶迎春), Yan-Li Yao(姚延立)

Chin. Phys. B, 2018, 27 (12): 127303. DOI: 10.1088/1674-1056/27/12/127303

Abstract ( 543 )

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In this paper, core-shell quantum dots (QDs) with two polar surface functional groups (ZnSe/ZnS-COOH QDs and ZnSe/ZnS-NH₂ QDs) are synthesized in an aqueous phase. Photoluminescence (PL) and absorption spectra clearly indicate luminescence down-shifting (LDS) properties. On the basis of QDs, surface functional group multilayer LDS films (M-LDSs) are fabricated through an electrostatic layer-by-layer (LBL) self-assembly method. The PL intensity increases linearly with the number of bilayers, showing a regular and uniform film growth. When the M-LDS is placed on the surface of a Si-based solar cell as an optical conversion layer for the first time, the external quantum efficiency (EQE) and short-circuit current density (J_sc) notably increases for the LDS process. The EQE response improves in a wavelength region extending from the UV region to the blue region, and its maximum increase reaches more than 15% between 350 nm and 460 nm.

The nonlocal transport and switch effect in light- and electric-controlled silicene-superconductor hybrid structure

Fenghua Qi(戚凤华), Jun Cao(曹军), Jie Cao(曹杰), Lifa Zhang(张力发)

Chin. Phys. B, 2018, 27 (12): 127401. DOI: 10.1088/1674-1056/27/12/127401

Abstract ( 518 )

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We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junction. Owing to the tunable band structure of silicene, a pure crossed Andreev reflection process can be realized under the optical and electrical coaction. Moreover, a switch effect among the exclusive crossed Andreev reflection, the exclusive elastic cotunneling and the exclusive Andreev reflection, where the former two are the nonlocal transports and the third one is the local transport, can be obtained in our system by the modulation of the electric and light fields. In addition, the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.

High-throughput research on superconductivity

Mingyang Qin(秦明阳), Zefeng Lin(林泽丰), Zhongxu Wei(魏忠旭), Beiyi Zhu(朱北沂), Jie Yuan(袁洁), Ichiro Takeuchi, Kui Jin(金魁)

Chin. Phys. B, 2018, 27 (12): 127402. DOI: 10.1088/1674-1056/27/12/127402

Abstract ( 664 )

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As an essential component of the Materials Genome Initiative aiming to shorten the period of materials research and development, combinatorial synthesis and rapid characterization technologies have been playing a more and more important role in exploring new materials and comprehensively understanding materials properties. In this review, we discuss the advantages of high-throughput experimental techniques in researches on superconductors. The evolution of combinatorial thin-film technology and several high-speed screening devices are briefly introduced. We emphasize the necessity to develop new high-throughput research modes such as a combination of high-throughput techniques and conventional methods.

Dyson-Maleev theory of an X X Z ferrimagnetic spin chain with single-ion anisotropy

Yu-Ge Chen(陈宇戈), Yin-Xiang Li(李殷翔), Li-Jun Tian(田立君), Bin Chen(陈斌)

Chin. Phys. B, 2018, 27 (12): 127501. DOI: 10.1088/1674-1056/27/12/127501

Abstract ( 619 )

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We use the mean-field approximation of Dyson-Maleev representation to study an XXZ Heisenberg ferrimagnetic spin chain with single-ion anisotropy. By solving the self-consistent equations with different anisotropies, λ and D respectively, the energy spectrums, internal energy, static susceptibility and specific heat are calculated. Especially, the quantum phase transition of the magnetization plateau induced by single-ion anisotropy D is obtained in the model of the ferrimagnetic spin chain by using Dyson-Maleev mean-field theory.

Temperature-dependent interlayer exchange coupling strength in synthetic antiferromagnetic[Pt/Co]₂/Ru/[Co/Pt]₄ multilayers

Yong Li(李勇), Xiangjun Jin(金香君), Pengfei Pan(潘鹏飞), Fu Nan Tan, Wen Siang Lew, Fusheng Ma(马付胜)

Chin. Phys. B, 2018, 27 (12): 127502. DOI: 10.1088/1674-1056/27/12/127502

Abstract ( 731 )

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In this work, we experimentally investigated the thermal stability of the interlayer exchange coupling field (H_ex) and strength (-J_iec) in synthetic antiferromagnetic (SAF) structure of[Pt(0.6)/Co(0.6)]₂/Ru(t_Ru)/[Co(0.6)/Pt(0.6)]₄ multilayers with perpendicular anisotropy. Depending on the thickness of the spacing ruthenium (Ru) layer, the observed interlayer exchange coupling can be either ferromagnetic or antiferromagnetic. The H_ex were studied by measuring the magnetization hysteresis loops in the temperature range from 100 K to 700 K as well as the theoretical calculation of the -J_iec. It is found that the interlayer coupling in the multilayers is very sensitive to the thickness of Ru and temperature. The H_ex exhibits either a linear or a non-linear dependence on the temperature for different thickness of Ru. Furthermore, our SAF multilayers show a high thermal stability even up to 600 K (H_ex=3.19 kOe, -J_iec=1.97 erg/cm² for t_Ru=0.6 nm, the unit 1 Oe=79.5775 A·m^-1), which was higher than the previous studies.

Realization of artificial skyrmion in CoCrPt/NiFe bilayers

Yi Liu(刘益), Yong-Ming Luo(骆泳铭), Zheng-Hong Qian(钱正洪), Jian-Guo Zhu(朱建国)

Chin. Phys. B, 2018, 27 (12): 127503. DOI: 10.1088/1674-1056/27/12/127503

Abstract ( 615 )

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Skyrmion, as a quasi-particle structure, has attracted much attention due to its potential applications in future spintronic devices. Artificial skyrmion structure has aroused great interest as it can be stabilized at room temperature, without needing to incorporate materials with Dzyaloshinskii-Moriya interaction (DMI) into it. In this paper, it is found that the artificial skyrmion structure can be realized in CoCrPt/NiFe bilayers by micromagnetic simulations. The critical magnetic field of the core decreases as the diameter of the NiFe soft magnetic layer increases. The artificial skyrmion has excellent topological protection, and the critical magnetic field of plane is about 76 mT (760 Oe, 1 Oe=79.5775 A·m^-1). The external magnetic field plays a key role in determining the core diameter of the skyrmion, and the artificial skyrmion can be realized in CoCrPt/Cu/CoCrPt/NiFe four-layer with a diameter of 13 nm.

Dynamic nucleation of domain-chains in magnetic nanotracks

Xiangjun Jin(金香君), Yong Li(李勇), Fusheng Ma(马付胜)

Chin. Phys. B, 2018, 27 (12): 127504. DOI: 10.1088/1674-1056/27/12/127504

Abstract ( 573 )

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Most of the reported observations are about the dynamic properties of individual domain-walls in magnetic nanowires, but the properties of multiple stripe-domains have rarely been investigated. Here, we demonstrate a simple but efficient scenario for multiple domains injection in magnetic nanowires. The domain-chains (DCs), a cluster of multiple domains, can be dynamically generated with tunable static properties. It is found that the number of domains in a single DC can be dynamically adjusted by varying the frequency of microwave field (MF) and the period of spin-polarized current (SPC) intensity. The static properties of the DCs, i.e., its length, spacing, and period between neighboring DCs, can be dynamically controlled by regulating the frequency of MF and the intensity of SPC. We have also discussed the possibility of using domain-chains as information carries, which provides a meaningful approach for flexible multi-bit information storage applications.

Effect of an electric field on the electrocaloric response of ferroelectrics

Hongbo Liu(刘宏波)

Chin. Phys. B, 2018, 27 (12): 127701. DOI: 10.1088/1674-1056/27/12/127701

Abstract ( 455 )

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The electrocaloric effect of the model ferroelectric BaTiO₃ was investigated using phenomenological theory. The results indicate that the applied electric field strength is a key factor for the induced electrocaloric response and there are two distinguishing electrocaloric responses. When a moderate electric field is applied, the electrocaloric temperature variation is small but the electrocaloric strength is high. In contrast, the electrocaloric temperature variation is large but electrocaloric strength is low when a very high electric field is applied. These results are consistent with the experimental observations on BaTiO₃ based bulk and thin film ferroelectric materials.

Epitaxially strained SnTiO₃ at finite temperatures

Dawei Wang(王大威), Laijun Liu(刘来君), Jia Liu(刘佳), Nan Zhang(张楠), Xiaoyong Wei(魏晓勇)

Chin. Phys. B, 2018, 27 (12): 127702. DOI: 10.1088/1674-1056/27/12/127702

Abstract ( 365 )

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By combining the effective Hamiltonian approach and direct ab initio computation, we obtain the phase diagram of SnTiO₃ with respect to epitaxial strain and temperature. This demonstrates the complex features of the phase diagram and provides an insight into this system, which is a presumably simple perovskite. Two triple points, as shown in the phase diagram, may be exploited to achieve high-performance piezoelectric effects. Despite the inclusion of the degree of freedom related to oxygen octahedron tilting, the ferroelectric displacements dominate the structural phases over the whole misfit strain range. Finally, we show that SnTiO₃ can change from hard to soft ferroelectrics with the epitaxial strain.

Broadband microwave absorption properties of polyurethane foam absorber optimized by sandwiched cross-shaped metamaterial

Long-Hui He(贺龙辉), Lian-Wen Deng(邓联文), Heng Luo(罗衡), Jun He(贺君), Yu-Han Li(李宇涵), Yun-Chao Xu(徐运超), Sheng-Xiang Huang(黄生祥)

Chin. Phys. B, 2018, 27 (12): 127801. DOI: 10.1088/1674-1056/27/12/127801

Abstract ( 491 )

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The effect of a sandwiched cross-shaped metamaterial absorber (CMMA) on microwave absorption properties of the double-layered polyurethane foam absorber (PUFA) is investigated. Combining with the sandwiched CMMA, the bandwidth of -10-dB reflection loss for PUFA is broadened from 7.4 GHz to 9.1 GHz, which is attributed to the overlap of two absorption peaks originating from CMMA and PUFA, respectively. The values of the two absorption peaks located at 10.15 GHz and 14.7 GHz are -38.44 dB and -40.91 dB, respectively. Additionally, distribution of surface current, electromagnetic field and power loss density are introduced to investigate the absorption mechanism of the CMMA. The electromagnetic field distribution of the double-layered PUFA and the three-layered hybrid absorber are comparatively analyzed to ascertain the influence of CMMA. The results show that the proposed hybrid absorber can be applied to the anti-electromagnetic interference and stealth technology.

Influences on oxidation voltage and holding time on poly(3-methylthiophene) film for electrochromic stability

Bo Zhang(张波), Chen Xu(徐晨), Guo-Yue Xu(徐国跃), Chu-Yang Liu(刘初阳), Hong-Han Bu(卜红寒), Jian-Chao Zhang(张建超)

Chin. Phys. B, 2018, 27 (12): 127802. DOI: 10.1088/1674-1056/27/12/127802

Abstract ( 570 )

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In this study, we report the influences of oxidation potential and holding time on the electrochromic (EC) stability of poly(3-methylthiophene) (P3MT) film during the electrochemical reaction. The cycle stability and transmittance changes of the film were investigated by optimizing the oxidation potential, and its chemical compositions were measured by x-ray photoelectron spectra after multiple electrochemical cycles. High oxidation potentials can increase the P3MT film color contrast and decrease its cycle stability because of accelerating chemical decomposition. Moreover, the holding time with potential pulsing was analyzed by using the optical memory of P3MT at an optimized oxidation potential, which revealed the reduced voltage duration saved energy consumption by 11.6% and improved the EC cycle stability without changing in color contrast.

Influence of carrier gas H₂ flow rate on quality of p-type GaN epilayer grown and annealed at lower temperatures

Shuang-Tao Liu(刘双韬), Jing Yang(杨静), De-Gang Zhao(赵德刚), De-Sheng Jiang(江德生), Feng Liang(梁锋), Ping Chen(陈平), Jian-Jun Zhu(朱建军), Zong-Shun Liu(刘宗顺), Wei Liu(刘炜), Yao Xing(邢瑶), Li-Yuan Peng(彭莉媛), Li-Qun Zhang(张立群), Wen-Jie Wang(王文杰), Mo Li(李沫)

Chin. Phys. B, 2018, 27 (12): 127803. DOI: 10.1088/1674-1056/27/12/127803

Abstract ( 616 )

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In this work, we study the influence of carrier gas H₂ flow rate on the quality of p-type GaN grown and annealed at lower temperatures. It is found that the concentration of H atoms in Mg-doped GaN epilayer can effectively decrease with appropriately reducing the carrier gas H₂ flow rate, and a high-quality p-type GaN layer could be obtained at a comparatively low annealing temperature by reducing the carrier gas H₂ flow rate. Meanwhile, it is found that the intensity and wavelength of DAP peak are changed as the annealing temperature varies, which shows that the thermal annealing has a remarkable effect not only on the activation of acceptors but also on the compensation donors.

Increase of photoluminescence blinking frequency of 3C-SiC nanocrystals with excitation power

Zhixing Gan(甘志星), Weiping Zhou(周卫平), Ming Meng(孟明)

Chin. Phys. B, 2018, 27 (12): 127804. DOI: 10.1088/1674-1056/27/12/127804

Abstract ( 742 )

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Super-resolution optical fluctuation imaging is dependent on the blinking frequency of fluorophores. Consequently, improvement of the photoluminescence (PL) blink frequency is important. This is achieved for 3C-SiC nanocrystals (NCs) by simply increasing the excitation power. Using an excitation of 488 nm with powers of 5 μW to 50 μW, individual 3C-SiC NC always exhibits PL blinking with a short on-state sojourn time (<0.1 s). A fast Fourier transform method is exploited to determine the PL switching frequency. It is found that the frequency of the bright state increases from 2 Hz to 20 Hz as the excitation power increases from 5 μW to 50 μW, which is explained by the Auger photonionization model.

Suppression of indium-composition fluctuations in InGaN epitaxial layers by periodically-pulsed mixture of N₂ and H₂ carrier gas Suggested by editors

Hai-Long Wang(王海龙), Xiao-Han Zhang(张晓涵), Hong-Xia Wang(王红霞), Bin Li(黎斌), Chong Chen(陈冲), Yong-Xian Li(李永贤), Huan Yan(颜欢), Zhi-Sheng Wu(吴志盛), Hao Jiang(江灏)

Chin. Phys. B, 2018, 27 (12): 127805. DOI: 10.1088/1674-1056/27/12/127805

Abstract ( 496 )

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Indium-composition fluctuations in InGaN epitaxial layers are suppressed by using periodically-pulsed mixture (PPM) of N₂ and H₂ carrier gas. Photoluminescence, optical transmission, reciprocal space map and space-resolved cathodoluminescence are employed to characterize the InGaN epilayers. It is shown that the lateral In-fluctuations mainly occur as hillock-like In-rich regions. Both the number and size of In-rich regions are reduced by introducing the PPM carrier gas. Moreover, the measurements first experimentally demonstrate that the H₂ carrier gas has a stronger decomposition effect on the In-rich region. As the duration time of the PPM carrier gas increases, the reduction of In-content in the In-rich region reaches up to 12%, however, only 2% for the In-homogeneous region. These factors lead to the suppression of In-fluctuations.

Recent research process on perovskite photodetectors:A review for photodetector – materials, physics, and applications

Yan Zhao(赵岩), Chenglong Li(李成龙), Liang Shen(沈亮)

Chin. Phys. B, 2018, 27 (12): 127806. DOI: 10.1088/1674-1056/27/12/127806

Abstract ( 646 )

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The perovskite photodetectors can be used for image sensing, environmental monitoring, optical communication, and chemical/biological detection. In the recent five years, the perovskite photoelectric detectors with various devices are well-designed and have made unprecedented progress of light detection. It is necessary to emphasize the most interesting works and summarize them to provide researchers with systematic information. In this review, we report the recent progress in perovskite photodetectors, including highly sensitive, ultrafast response speed, high gain, low noise, flexibility, and narrowband, concentrating on the photodetection performance of versatile halide perovskites (organic-inorganic hybrid and all inorganic compositions). Currently, organic-inorganic hybrid and all-inorganic halide microcrystals with polycrystalline film, nanoparticle/wire/chip, and block monocrystalline morphology control show important performance in response rate, decomposition rate, noise equivalent power, linear dynamic range, and response speed. It is expected that a comprehensive compendium of the research status of perovskite photodetectors will contribute to the development of this area.

Large magnetic moment at sheared ends of single-walled carbon nanotubes Suggested by editors

Jian Zhang(张健), Ya Deng(邓娅), Ting-Ting Hao(郝婷婷), Xiao Hu(胡潇), Ya-Yun Liu(刘雅芸), Zhi-Sheng Peng(彭志盛), Jean Pierre Nshimiyimana, Xian-Nian Chi(池宪念), Pei Wu(武佩), Si-Yu Liu(刘思雨), Zhong Zhang(张忠), Jun-Jie Li(李俊杰), Gong-Tang Wang(王公堂), Wei-Guo Chu(褚卫国), Chang-Zhi Gu(顾长志), Lian-Feng Sun(孙连峰)

Chin. Phys. B, 2018, 27 (12): 128101. DOI: 10.1088/1674-1056/27/12/128101

Abstract ( 539 )

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In this work we report that after single-walled carbon nanotubes (SWNTs) are sheared with a pair of titanium scissors, the magnetization becomes larger than that of the corresponding pristine ones. The magnetization increases proportionally with the number of SWNTs with sheared ends, suggesting that there exist magnetic moments at the sheared ends of SWNTs. By using the coefficient of this linear relation, the average magnetic moment is estimated to be 41.5±9.8 μ_B (Bohr magneton) per carbon atom in the edge state at temperature of 300.0 K, suggesting that ultrahigh magnetic fields can be produced. The dangling sigma and pi bonds of the carbon atoms at sheared ends play important roles in determining the unexpectedly high magnetic moments, which may have great potential applications.

Short-wave infrared InGaAs photodetectors and focal plane arrays

Yong-Gang Zhang(张永刚), Yi Gu(顾溢), Xiu-Mei Shao(邵秀梅), Xue Li(李雪), Hai-Mei Gong(龚海梅), Jia-Xiong Fang(方家熊)

Chin. Phys. B, 2018, 27 (12): 128102. DOI: 10.1088/1674-1056/27/12/128102

Abstract ( 560 )

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In this article, unique spectral features of short-wave infrared band of 1 μ-3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, the different material systems for the devices in this band are outlined. Based on the background, the development of lattice-matched and wavelength-extended InGaAs photodetectors and focal plane arrays, including our continuous efforts in this field, are reviewed. These devices are concentrated on the applications in spectral sensing and imaging, exclusive of optical fiber communication.

High-throughput design of functional materials using materials genome approach

Kesong Yang(杨可松)

Chin. Phys. B, 2018, 27 (12): 128103. DOI: 10.1088/1674-1056/27/12/128103

Abstract ( 643 )

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High-throughput computational materials design provides one efficient solution to accelerate the discovery and development of functional materials. Its core concept is to build a large quantum materials repository and to search for target materials with desired properties via appropriate materials descriptors in a high-throughput fashion, which shares the same idea with the materials genome approach. This article reviews recent progress of discovering and developing new functional materials using high-throughput computational materials design approach. Emphasis is placed on the rational design of high-throughput screening procedure and the development of appropriate materials descriptors, concentrating on the electronic and magnetic properties of functional materials for various types of industrial applications in nanoelectronics.

Enhanced dielectric and optical properties of nanoscale barium hexaferrites for optoelectronics and high frequency application

J Mohammed, A B Suleiman, Tchouank Tekou Carol T, H Y Hafeez, Jyoti Sharma, Pradip K Maji, Sachin Godara Kumar, A K Srivastava

Chin. Phys. B, 2018, 27 (12): 128104. DOI: 10.1088/1674-1056/27/12/128104

Abstract ( 515 )

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M-type barium hexaferrites with chemical composition Ba_1-xDy_xFe_12-yCr_yO₁₉ (x=0.0, 0.1, 0.2, and y=0.0, 0.4, 0.5) were synthesized via sol-gel auto-combustion method. The samples were pre-sintered at 400℃ for 3 h and sintered at 950℃ for 5 h. The changes in the structural, dielectric, and optical properties were studied after the substitution of Dy³⁺ and Cr³⁺ ions. X-ray diffraction (XRD) analysis confirms the formation of single phase hexaferrites with the absence of secondary phase. FTIR analysis gives an idea of the formation of hexaferrites with the appearance of two peaks at 438 cm^-1 and 589 cm^-1. The field emission scanning electron micrographs (FESEM) show a combination of crystallites with large shapes close to hexagonal platelet-like shape and others with rice or rod-like shapes, whereas EDX and elemental analysis confirm the stoichiometry of prepared samples. The calculated band gap from UV-vis NIR spectroscopy spectra was found to decreases with increase in Dy³⁺-Cr³⁺ substitution. The dielectric properties were explained on the basis of Maxwell-Wagner model. Enhancement of dielectric constant at higher frequencies was observed in all the samples. Low dielectric loss is also observed in all the samples and Cole-Cole plot shows that grain boundary resistance (R_gb) contribute most to the dielectric properties. The prepared samples exhibit properties that could be useful for optoelectronics and high frequency application.

1.3-μm InAs/GaAs quantum dots grown on Si substrates Suggested by editors

Fu-Hui Shao(邵福会), Yi Zhang(张一), Xiang-Bin Su(苏向斌), Sheng-Wen Xie(谢圣文), Jin-Ming Shang(尚金铭), Yun-Hao Zhao(赵云昊), Chen-Yuan Cai(蔡晨元), Ren-Chao Che(车仁超), Ying-Qiang Xu(徐应强), Hai-Qiao Ni(倪海桥), Zhi-Chuan Niu(牛智川)

Chin. Phys. B, 2018, 27 (12): 128105. DOI: 10.1088/1674-1056/27/12/128105

Abstract ( 827 )

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We compare the effect of InGaAs/GaAs strained-layer superlattice (SLS) with that of GaAs thick buffer layer (TBL) serving as a dislocation filter layer. The InGaAs/GaAs SLS is found to be more effective than GaAs TBL in blocking the propagation of threading dislocations, which are generated at the interface between the GaAs buffer layer and the Si substrate. Through testing and analysis, we conclude that the weaker photoluminescence for quantum dots (QDs) on Si substrate is caused by the quality of capping In_0.15Ga_0.85As and upper GaAs. We also find that the periodic misfits at the interface are related to the initial stress release of GaAs islands, which guarantees that the upper layers are stress-free.

Imaging the diffusion pathway of Al³⁺ ion in NASICON-type (Al_0.2Zr_0.8)_20/19Nb(PO₄)₃ as electrolyte for rechargeable solid-state Al batteries ^Hot!

Jie Wang(王捷), Chun-Wen Sun(孙春文), Yu-Dong Gong(巩玉栋), Huai-Ruo Zhang(张怀若), Jose Antonio Alonso, María Teresa Fernández-Díaz, Zhong-Lin Wang(王中林), John B Goodenough

Chin. Phys. B, 2018, 27 (12): 128201. DOI: 10.1088/1674-1056/27/12/128201

Abstract ( 843 )

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Among all-solid-state batteries, rechargeable Al-ion batteries have attracted most attention because they involve three-electron-redox reactions with high theoretic specific capacity. However, the solid Al-ion conductor electrolytes are less studied. Here, the microscopic path of Al³⁺-ion conduction of NASICON-type (Al_0.2Zr_0.8)_20/19Nb(PO₄)₃ oxide is identified by temperature-dependent neutron powder diffraction and aberration-corrected scanning transmission electron microscopy experiments. (Al_0.2Zr_0.8)_20/19Nb(PO₄)₃ shows a rhombohedral structure consisting of a framework of (Zr,Nb)O₆ octahedra sharing corners with (PO₄) tetrahedra; the Al occupy trigonal antiprisms exhibiting extremely large displacement factors. This suggests a strong displacement of Al ions along the c axis of the unit cell as they diffuse across the structure by a vacancy mechanism. Negative thermal expansion behavior is also identified along a and b axes, due to folding of the framework as temperature increases.

Nonlinear fast-slow dynamics of a coupled fractional order hydropower generation system

Xiang Gao(高翔), Diyi Chen(陈帝伊), Hao Zhang(张浩), Beibei Xu(许贝贝), Xiangyu Wang(王翔宇)

Chin. Phys. B, 2018, 27 (12): 128202. DOI: 10.1088/1674-1056/27/12/128202

Abstract ( 578 )

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Internal effects of the dynamic behaviors and nonlinear characteristics of a coupled fractional order hydropower generation system (HGS) are analyzed. A mathematical model of hydro-turbine governing system (HTGS) with rigid water hammer and hydro-turbine generator unit (HTGU) with fractional order damping forces are proposed. Based on Lagrange equations, a coupled fractional order HGS is established. Considering the dynamic transfer coefficient e is variational during the operation, introduced e as a periodic excitation into the HGS. The internal relationship of the dynamic behaviors between HTGS and HTGU is analyzed under different parameter values and fractional order. The results show obvious fast-slow dynamic behaviors in the HGS, causing corresponding vibration of the system, and some remarkable evolution phenomena take place with the changing of the periodic excitation parameter values.

“Refractivity-from-clutter” based on local empirical refractivity model

Xiaofeng Zhao(赵小峰)

Chin. Phys. B, 2018, 27 (12): 128401. DOI: 10.1088/1674-1056/27/12/128401

Abstract ( 617 )

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Constructing sophisticated refractivity models is one of the key problems for the RFC (refractivity from clutter) technology. If prior knowledge of the local refractivity environment is available, more accurate parameterized model can be constructed from the statistical information, which in turn can be used to improve the quality of the local refractivity retrievals. The validity of this proposal was demonstrated by range-dependent refractivity profile inversions using the adjoint parabolic equation method to the Wallops'98 experimental data.

Influence of characteristics' measurement sequence on total ionizing dose effect in PDSOI nMOSFET

Xin Xie(解鑫), Da-Wei Bi(毕大伟), Zhi-Yuan Hu(胡志远), Hui-Long Zhu(朱慧龙), Meng-Ying Zhang(张梦映), Zheng-Xuan Zhang(张正选), Shi-Chang Zou(邹世昌)

Chin. Phys. B, 2018, 27 (12): 128501. DOI: 10.1088/1674-1056/27/12/128501

Abstract ( 605 )

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The influence of characteristics' measurement sequence on total ionizing dose effect in partially-depleted SOI nMOSFET is comprehensively studied. We find that measuring the front-gate curves has no influence on total ionizing dose effect. However, the back-gate curves' measurement has a great influence on total ionizing dose effect due to high electric field in the buried oxide during measuring. In this paper, we analyze their mechanisms and we find that there are three kinds of electrons tunneling mechanisms at the bottom corner of the shallow trench isolation and in the buried oxide during the back-gate curves' measurement, which are:Fowler-Nordheim tunneling, trap-assisted tunneling, and charge-assisted tunneling. The tunneling electrons neutralize the radiation-induced positive trapped charges, which weakens the total ionizing dose effect. As the total ionizing dose level increases, the charge-assisted tunneling is enhanced by the radiation-induced positive trapped charges. Hence, the influence of the back-gate curves' measurement is enhanced as the total ionizing dose level increases. Different irradiation biases are compared with each other. An appropriate measurement sequence and voltage bias are proposed to eliminate the influence of measurement.

Photovoltaic effects in reconfigurable heterostructured black phosphorus transistors

Siqi Hu(胡思奇), Ruijuan Tian(田睿娟), Xiaoguang Luo(罗小光), Rui Yin(殷瑞), Yingchun Cheng(程迎春), Jianlin Zhao(赵建林), Xiaomu Wang(王肖沐), Xuetao Gan(甘雪涛)

Chin. Phys. B, 2018, 27 (12): 128502. DOI: 10.1088/1674-1056/27/12/128502

Abstract ( 799 )

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We demonstrate a reconfigurable black phosphorus electrical field transistor, which is van der Waals heterostructured with few-layer graphene and hexagonal boron nitride flakes. Varied homojunctions could be realized by controlling both source-drain and top-gate voltages. With the spatially resolved scanning photocurrent microscopy technique, photovoltaic photocurrents originated from the band-bending regions are observed, confirming nine different configurations for each set of fixed voltages. In addition, as a phototransistor, high responsivity (~800 mA/W) and fast response speed (~230 μs) are obtained from the device. The reconfigurable van der Waals heterostructured transistors may offer a promising structure towards electrically tunable black phosphorus-based optoelectronic devices.

Efficiency of collective myosin Ⅱ motors studied with an elastic coupling power-stroke ratchet model

Zi-Qing Wang(汪自庆), Jin-Fang Li(李金芳), Ying-Ge Xie(解迎革), Guo-Dong Wang(王国栋), Yao-Gen Shu(舒咬根)

Chin. Phys. B, 2018, 27 (12): 128701. DOI: 10.1088/1674-1056/27/12/128701

Abstract ( 550 )

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We proposed a modified ratchet model including power-stroke and elastic coupling to study the efficiency of collective non-processive motors such as myosin Ⅱ in muscle. Our theoretical results are in good agreement with the experimental data. Our study not only reveals that the maximum efficiency depends on elasticity and is independent of transition rates but also indicates that the parameters fitted to fast muscle are different from those fitted to a slow one. The latter may imply that the structure of the fast muscle is different from that of the slow one. The main reason that our model succeeds is that velocity in this model is an independent variable.

The determinant factors for map resolutions obtained using CryoEM single particle imaging method Suggested by editors

Yihua Wang(王义华), Daqi Yu(余大启), Qi Ouyang(欧阳颀), Haiguang Liu(刘海广)

Chin. Phys. B, 2018, 27 (12): 128702. DOI: 10.1088/1674-1056/27/12/128702

Abstract ( 561 )

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The CryoEM single particle structure determination method has recently received broad attention in the field of structural biology. The structures can be resolved to near-atomic resolutions after model reconstructions from a large number of CryoEM images measuring molecules in different orientations. However, the determining factors for reconstructed map resolution need to be further explored. Here, we provide a theoretical framework in conjunction with numerical simulations to gauge the influence of several key factors to CryoEM map resolutions. If the projection image quality allows orientation assignment, then the number of measured projection images and the quality of each measurement (quantified using average signal-to-noise ratio) can be combined to a single factor, which is dominant to the resolution of reconstructed maps. Furthermore, the intrinsic thermal motion of molecules has significant effects on the resolution. These effects can be quantitatively summarized with an analytical formula that provides a theoretical guideline on structure resolutions for given experimental measurements.

Controlled generation of cell-laden hydrogel microspheres with core-shell scaffold mimicking microenvironment of tumor

Yuenan Li(李岳南), Miaomiao Hai(海苗苗), Yu Zhao(赵宇), Yalei Lv(吕亚蕾), Yi He(何益), Guo Chen(陈果), Liyu Liu(刘雳宇), Ruchuan Liu(刘如川), Guigen Zhang

Chin. Phys. B, 2018, 27 (12): 128703. DOI: 10.1088/1674-1056/27/12/128703

Abstract ( 589 )

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Development of an in vitro three-dimensional (3D) model that closely mimics actual environment of tissue has become extraordinarily important for anti-cancer study. In recent years, various 3D cell culture systems have been developed, with multicellular tumor spheroids being the most popular and effective model. In this work, we present a microfluidic device used as a robust platform for generating core-shell hydrogel microspheres with precisely controlled sizes and varied components of hydrogel matrix. To gain a better understanding of the governing mechanism of microsphere formation, computational models based on multiphase flow were developed to numerically model the droplet generation and velocity field evolution process with COMSOL Multiphysics software. Our modeling results show good agreement with experiments in size dependence on flow rate as well as effect of vortex flow on microsphere formation. With real-time tuning of the flow rates of aqueous phase and oil phase, tumor cells were encapsulated into the microspheres with controllable core-shell structure and different volume ratios of core (comprised of alginate, Matrigel, and/or Collagen) and shell (comprised of alginate). Viability of cells in four different hydrogel matrices were evaluated by standard acridine orange (AO) and propidium iodide (PI) staining. The proposed microfluidic system can play an important role in engineering the in vitro micro-environment of tumor spheroids to better mimic the actual in vivo 3D spatial structure of a tumor and perfect the 3D tumor models for more effective clinical therapies.

Discovery and design of lithium battery materials via high-throughput modeling

Xuelong Wang(王雪龙), Ruijuan Xiao(肖睿娟), Hong Li(李泓), Liquan Chen(陈立泉)

Chin. Phys. B, 2018, 27 (12): 128801. DOI: 10.1088/1674-1056/27/12/128801

Abstract ( 663 )

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This paper reviews the rapid progress in the field of high-throughput modeling based on the Materials Genome Initiative, and its application in the discovery and design of lithium battery materials. It offers examples of screening, optimization and design of electrodes, electrolytes, coatings, additives, etc. and the possibility of introducing the machine learning method into material design. The application of the material genome method in the development of lithium battery materials provides the possibility to speed up the upgrading of new candidates in the discovery of lots of functional materials.

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