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CN 11-5639/O4
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HighLights More»   
  • Antiferromagnetic–ferromagnetic transition in zigzag graphene nanoribbons induced by substitutional doping

    Shenyuan Yang(杨身园), Jing Li(李静), Shu-Shen Li(李树深)
    Chin. Phys. B 2018, 27 (11): 117102
    Using first-principles calculations based on density functional theory, we show that the ground state of zigzag-edged graphene nanoribbons (ZGNRs) can be transformed from antiferromagnetic (AFM) order to ferromagnetic (FM) order by changing the substitutional sites of N or B dopants. This AFM-FM tra...

     
  • A single-crystal neutron diffraction study on magnetic structure of CsCo2Se2

    Juanjuan Liu(刘娟娟), Jieming Sheng(盛洁明), Wei Luo(罗伟), Jinchen Wang(汪晋辰), Wei Bao(鲍威), Jinhu Yang(杨金虎), Minghu Fang(方明虎), S A Danilkin
    Chin. Phys. B 2018, 27 (11): 117401
    The magnetic structure of CsCo2Se2 was investigated using single-crystal neutron diffraction technique. An antiferromagnetic transition with the propagation vector (0,0,1) was observed at TN=78 K. The Co magnetic moment 0.772(6) μB at 10 K pointing in the basal plane couples ferromagnetically in ...

     
  • Formation and stability of ultrasonic generated bulk nanobubbles

    Chen-Ran Mo(莫宸冉), Jing Wang(王菁), Zhou Fang(方舟), Li-Min Zhou(周利民), Li-Juan Zhang(张立娟), Jun Hu(胡钧)
    Chin. Phys. B 2018, 27 (11): 118104
    Although various and unique properties of bulk nanobubbles have drawn researchers' attention over the last few years, their formation and stabilization mechanism has remained unsolved. In this paper, we use ultrasonic methods to produce bulk nanobubbles in the pure water and give a comprehensive stu...

     
  • High capacity sodium-rich layered oxide cathode for sodium-ion batteries

    Gen-Cai Guo(郭根材), Changhao Wang(王长昊), Bang-Ming Ming(明帮铭), Si-Wei Luo(罗斯玮), Heng Su(苏恒), Bo-Ya Wang(王博亚), Ming Zhang(张铭), Hai-Jun Yu(尉海军), Ru-Zhi Wang(王如志)
    Chin. Phys. B 2018, 27 (11): 118801
    Sodium-ion batteries have attracted significant recent attention currently considering the limited available lithium resource. However, the energy density of sodium-ion batteries is still insufficient compared to lithium-ion batteries, mainly because of the unavailability of high-energy cathode mate...

     
Chin. Phys. B  
  Chin. Phys. B--2018, Vol.27, No.11
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TOPICAL REVIEW—Magnetism, magnetic materials, and interdisciplinary research

Nanocrystalline and nanocomposite permanent magnets by melt spinning technique

Chuanbing Rong(荣传兵), Baogen Shen(沈保根)
Chin. Phys. B, 2018, 27 (11): 117502 doi: 10.1088/1674-1056/27/11/117502
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The melt-spinning technique offers an opportunity for tailoring magnetic properties by controlling the structures and microstructures in both single-phase and composite magnets. This review first broadly discusses the principle of cooling control, amorphization, crystallization, annealing, and consolidation of the melt-spun ribbons. The phase, microstructure, and magnetic properties of popular single-phase nanocrystalline magnets are reviewed, followed by the nanocomposite magnets consisting of magnetically hard and soft phases. The precipitation-hardened magnetic materials prepared by melt spinning are also discussed. Finally, the role of intergrain exchange coupling, thermal fluctuation, and reversible/irreversible magnetization processes are discussed and correlated to the magnetic phenomena in both single-phase and nanocomposite magnets.

Mn-based permanent magnets

Jinbo Yang(杨金波), Wenyun Yang(杨文云), Zhuyin Shao(邵珠印), Dong Liang(梁栋), Hui Zhao(赵辉), Yuanhua Xia(夏元华), Yunbo Yang(杨云波)
Chin. Phys. B, 2018, 27 (11): 117503 doi: 10.1088/1674-1056/27/11/117503
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Mn-based intermetallic compounds have attracted much attention due to their fascinating structural and physical properties, especially their interesting hard magnetic properties. In this paper, we have summarized the magnetic and structural properties of Mn-based intermetallic compounds (MnX, where X=Al, Bi, and Ga). Various methods for synthesizing single phases of MnAl, MnBi, and MnxGa were developed in our lab. A very high saturation magnetization of 125 emu/g, coercivity of 5 kOe, and maximum energy product (BH)max of 3.1 MG·Oe were achieved at room temperature for the pure τ-Mn-Al magnetic phase without carbon doping and the extrusion process. Low temperature phase (LTP) MnBi with a purity above 95 wt.% can be synthesized. An abnormal temperature coefficient of the coercivity was observed for the LTP MnBi magnet. Its coercivity increased with temperature from 100 K to 540 K, reached a maximum of 2.5 T at about 540 K, and then decreased slowly to 1.8 T at 610 K. The positive temperature coefficient of the coercivity is related to the evolution of the structure and magnetocrystalline anisotropy field of the LTP MnBi phase with temperature. The LTP MnBi bonded magnets show maximum energy products (BH)max of 8.9 MG·Oe (70 kJ/m3) and 5.0 MG·Oe (40 kJ/m3) at room temperature and 400 K, respectively. Ferrimagnetic MnxGa phases with L10 structures (x < 2.0) and D022 structures (x > 2.0) were obtained. All of the above structures can be described by a D022 supercell model in which 2a-Ga and 2b-Mn are simultaneously substituted. The tetragonal D022 phases of the MnxGa show high coercivities ranging from 7.2 kOe for low Mn content x=1.8 to 18.2 kOe for high Mn content x=3 at room temperature. The Mn1.2Ga sample exhibits a room temperature magnetization value of 80 emu/g. The hard magnetic properties of coercivity iHc=3.5 kOe, remanence Mr=43.6 emu/g, and (BH)max=2.5 MG·Oe were obtained at room temperature. Based on the above studies, we believe that Mn-based magnetic materials could be promising candidates for rare earth free permanent magnets exhibiting a high Curie temperature, high magnetocrystalline anisotropy, and very high coercivity.

Rare earth permanent magnets prepared by hot deformation process

Ren-Jie Chen(陈仁杰), Ze-Xuan Wang(王泽轩), Xu Tang(唐旭), Wen-Zong Yin(尹文宗), Chao-Xiang Jin(靳朝相), Jin-Yun Ju(剧锦云), Don Lee(李东), A-Ru Yan(闫阿儒)
Chin. Phys. B, 2018, 27 (11): 117504 doi: 10.1088/1674-1056/27/11/117504
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Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets. Firstly, rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precursors using the hot-pressing process. The prepared isotropic precursors are then hot-deformed to produce high-anisotropy uniaxial bulk rare earth permanent magnets and a highly textured structure is produced via this process. The resulting magnets possess many advantages such as near-net-shape, outstanding corrosion resistance, and ultrafine-grain structure. The influence of the preparation parameters utilized in the hot-pressing and deformation processes on the magnetic properties and microstructure of the permanent magnets are systemically summarized in this report. As a near-net-shape technique, the hot deformation process has notable advantages with regard to the production of irregular shapes, especially for radially oriented ring-shaped magnets with high length-diameter ratios or thin walls. The difficulties associated with the fabrication of crack-free, homogeneous, and non-decentered ring-shaped magnets are substantially resolved through an emphasis on mold design, adjustment of deformation parameters, and application of theoretical simulation. Considering the characteristics of hot-deformed magnets which include grain shape and size, anisotropic distribution of intergranular phases, etc., investigation and improvement of the mechanical and electric properties, in addition to thermal stability, with the objective of improving the application of hot-deformed magnets or ring-shaped magnets, is of practical significance.

TOPICAL REVIEW—Fundamental research under high magnetic fields

High-gradient magnetic field-controlled migration of solutes and particles and their effects on solidification microstructure: A review

Tie Liu(刘铁), Qiang Wang(王强), Yi Yuan(苑轶), Kai Wang(王凯), Guojian Li(李国建)
Chin. Phys. B, 2018, 27 (11): 118103 doi: 10.1088/1674-1056/27/11/118103
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We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidification microstructure of alloys. Diverse areas relevant to various aspects of theory and applications of high-gradient magnetic field-controlled migration of solutes and particles are surveyed. They include introduction, high-gradient magnetic field effects, migration behavior of solute and particles in high-gradient magnetic fields, microstructure evolution induced by high-gradient magnetic fieldcontrolled migrations of solute and particles, and properties of materials modified by high-gradient magnetic field-tailored microstructure. Selected examples of binary and multiphase alloy systems are presented and examined, with the main focus on the correlation between the high-gradient magnetic field-modified migration and the related solidification microstructure evolution. Particular attention is given to the mechanisms responsible for the microstructure evolution induced by highgradient magnetic fields.

TOPICAL REVIEW—Physics research in materials genome

MatCloud, a high-throughput computational materials infrastructure: Present, future visions, and challenges

Xiaoyu Yang(杨小渝), Zongguo Wang(王宗国), Xushan Zhao(赵旭山), Jianlong Song(宋健龙), Chao Yu(虞超), Jiaxin Zhou(周嘉欣), Kai Li(李凯)
Chin. Phys. B, 2018, 27 (11): 110301 doi: 10.1088/1674-1056/27/11/110301
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MatCloud provides a high-throughput computational materials infrastructure for the integrated management of materials simulation, data, and computing resources. In comparison to AFLOW, Material Project, and NoMad, MatCloud delivers two-fold functionalities:a computational materials platform where users can do on-line job setup, job submission and monitoring only via Web browser, and a materials properties simulation database. It is developed under Chinese Materials Genome Initiative and is a China own proprietary high-throughput computational materials infrastructure. MatCloud has been on line for about one year, receiving considerable registered users, feedbacks, and encouragements. Many users provided valuable input and requirements to MatCloud. In this paper, we describe the present MatCloud, future visions, and major challenges. Based on what we have achieved, we will endeavour to further develop MatCloud in an open and collaborative manner and make MatCloud a world known China-developed novel software in the pressing area of high-throughput materials calculations and materials properties simulation database within Material Genome Initiative.

Band structure engineering and defect control of oxides for energy applications

Hui-Xiong Deng(邓惠雄), Jun-Wei Luo(骆军委), Su-Huai Wei(魏苏淮)
Chin. Phys. B, 2018, 27 (11): 117104 doi: 10.1088/1674-1056/27/11/117104
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Metal oxides play an essential role in modern optoelectronic devices because they have many unique physical properties such as structure diversity, superb stability in solution, good catalytic activity, and simultaneous high electron conductivity and optical transmission. Therefore, they are widely used in energy-related optoelectronic applications such as photovoltaics and photoelectrochemical (PEC) fuel generation. In this review, we mainly discuss the structure engineering and defect control of oxides for energy applications, especially for transparent conducting oxides (TCOs) and oxide catalysts used for water splitting. We will review our current understanding with an emphasis on the contributions of our previous theoretical modeling, primarily based on density functional theory. In particular, we highlight our previous work:(i) the fundamental principles governing the crystal structures and the electrical and optical behaviors of TCOs; (ii) band structures and defect properties for n-type TCOs; (iii) why p-type TCOs are difficult to achieve; (iv) how to modify the band structure to achieve p-type TCOs or even bipolarly dopable TCOs; (v) the origin of the high-performance of amorphous TCOs; and (vi) band structure engineering of bulk and nano oxides for PEC water splitting. Based on the understanding above, we hope to clarify the key issues and the challenges facing the rational design of novel oxides and propose new and feasible strategies or models to improve the performance of existing oxides or design new oxides that are critical for the development of next-generation energy-related applications.

The materials data ecosystem: Materials data science and its role in data-driven materials discovery

Hai-Qing Yin(尹海清), Xue Jiang(姜雪), Guo-Quan Liu(刘国权), Sharon Elder, Bin Xu(徐斌), Qing-Jun Zheng(郑清军), Xuan-Hui Qu(曲选辉)
Chin. Phys. B, 2018, 27 (11): 118101 doi: 10.1088/1674-1056/27/11/118101
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Since its launch in 2011, the Materials Genome Initiative (MGI) has drawn the attention of researchers from academia, government, and industry worldwide. As one of the three tools of the MGI, the use of materials data, for the first time, has emerged as an extremely significant approach in materials discovery. Data science has been applied in different disciplines as an interdisciplinary field to extract knowledge from data. The concept of materials data science has been utilized to demonstrate its application in materials science. To explore its potential as an active research branch in the big data era, a three-tier system has been put forward to define the infrastructure for the classification, curation and knowledge extraction of materials data.

Combinatorial synthesis and high-throughput characterization of copper-oxide superconductors

J Wu, A T Bollinger, X He, I Božović
Chin. Phys. B, 2018, 27 (11): 118102 doi: 10.1088/1674-1056/27/11/118102
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Fast synthesis and screening of materials are vital to the advance of materials science and are an essential component of the Materials Genome Initiative. Here we use copper-oxide superconductors as an example to demonstrate the power of integrating combinatorial molecular beam epitaxy synthesis with high-throughput electric transport measurements. Leveraging this method, we have generated a phase diagram with more than 800 compositions in order to unravel the doping dependence of interface superconductivity. In another application of the same method, we have studied the superconductor-to-insulator quantum phase transition with unprecedented accuracy in tuning the chemical doping level.

Accomplishment and challenge of materials database toward big data

Yibin Xu(徐一斌)
Chin. Phys. B, 2018, 27 (11): 118901 doi: 10.1088/1674-1056/27/11/118901
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The history and current status of materials data activities from handbook to database are reviewed, with introduction to some important products. Through an example of prediction of interfacial thermal resistance based on data and data science methods, we show the advantages and potential of material informatics to study material issues which are too complicated or time consuming for conventional theoretical and experimental methods. Materials big data is the fundamental of material informatics. The challenges and strategy to construct materials big data are discussed, and some solutions are proposed as the results of our experiences to construct National Institute for Materials Science (NIMS) materials databases.

TOPICAL REVIEW—Nanolasers

Surface plasmon polariton nanolasers: Coherent light sources for new applications

Yu-Hsun Chou(周昱薰), Chia-Jui Chang(張家睿), Tzy-Rong Lin(林資榕), Tien-Chang Lu(盧廷昌)
Chin. Phys. B, 2018, 27 (11): 114208 doi: 10.1088/1674-1056/27/11/114208
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The invention of the Internet and mobile devices has caused tremendous changes in human lives over the past two decades. Information technology has broken through limitations of geospatial space, enabling extremely high-speed data transmission and new types of data services. In recent years, demands for data processing have shown an increasing trend. Furthermore, data generated from internet-related applications such as cloud services and self-driving technology are likely to grow exponentially over the coming years. Currently, data transmission inside integrated circuits mainly relies on metal wires. However, the substantial resistive-capacitive delay and energy loss that are caused by metal wires limit data transmission speeds. Optical interconnection has been regarded as a major solution to efficiently reduce energy consumption and increase data transmission speeds. The size of conventional semiconductor laser devices, which are the key component in optical interconnection, cannot be smaller than the wavelength of light, which is a fundamental physical obstacle to lasers integrating with current electronic integrated circuits in reasonable volumes. To realize optical interconnection, the volume of the laser device must match the existing electronic components. Recently, the use of diffraction-unlimited plasmonic lasers has been successfully demonstrated, and these have great potential in different applications. In this paper, we discuss the recent progress toward surface plasmon polariton lasers and provide practical insights into the challenges in realizing these novel devices.

Research progress of low-dimensional metal halide perovskites for lasing applications

Zhen Liu(刘镇), Chun Li(李淳), Qiu-Yu Shang(尚秋宇), Li-Yun Zhao(赵丽云), Yang-Guang Zhong(钟阳光), Yan Gao(高燕), Wen-Na Du(杜文娜), Yang Mi(米阳), Jie Chen(陈杰), Shuai Zhang(张帅), Xin-Feng Liu(刘新风), Ying-Shuang Fu(付英双), Qing Zhang(张青)
Chin. Phys. B, 2018, 27 (11): 114209 doi: 10.1088/1674-1056/27/11/114209
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Metal halide perovskites have been regarded as remarkable materials for next-generation light-harvesting and light emission devices. Due to their unique optical properties, such as high absorption coefficient, high optical gain, low trapping-state density, and ease of band gap engineering, perovskites promise to be used in lasing devices. In this article, the recent progresses of microlasers based on reduced-dimensional structures including nanoplatelets, nanowires, and quantum dots are reviewed from both fundamental photophysics and device applications. Furthermore, perovskite-based plasmonic nanolasers and polariton lasers are summarized. Perspectives on perovskite-based small lasers are also discussed. This review can serve as an overview and evaluation of state-of-the-art micro/nanolaser science.

Electrically pumped metallic and plasmonic nanolasers

Martin T Hill
Chin. Phys. B, 2018, 27 (11): 114210 doi: 10.1088/1674-1056/27/11/114210
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In recent years, there have been a significant number of demonstrations of small metallic and plasmonic lasers. The vast majority of these demonstrations have been for optically pumped devices. Electrically pumped devices are advantageous for applications and could demonstrate concepts not amenable for optical pumping. However, there have been relatively few demonstrations of electrically pumped small metal cavity lasers. This lack of results is due to the following reasons:there are limited types of electrically pumped gain media available; there is a significantly greater level of complexity required in the fabrication of electrically pumped devices; finally, the required components for electrical pumping restrict cavity design options and furthermore make it intrinsically more difficult to achieve lasing. This review looks at the motivation for electrically pumped nanolasers, the key issues that need addressing for them to be realized, the results that have been achieved so far including devices where lasing has not been achieved, and potential new directions that could be pursued.

Semiconductor photonic crystal laser

Wanhua Zheng(郑婉华)
Chin. Phys. B, 2018, 27 (11): 114211 doi: 10.1088/1674-1056/27/11/114211
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By combing artificial micro-nano structures, photonic crystals (PCs), with traditional semiconductor laser material to realize the dynamic collaborative control of photonic states and confined electrons, the band engineering of the PC has been confirmed. This brings new development space for the semiconductor laser, such as for low threshold and high efficiency. Based on a series of works by Zheng's group, this paper has reviewed kinds of PC lasers including electrical injection PC vertical cavity and lateral cavity surface-emitting lasers, and PC high beam quality lasers, to show that the PC is vital for promoting the continuous improvement of semiconductor laser performance at present and in the future.

Square microcavity semiconductor lasers

Yuede Yang(杨跃德), Haizhong Weng(翁海中), Youzeng Hao(郝友增), Jinlong Xiao(肖金龙), Yongzhen Huang(黄永箴)
Chin. Phys. B, 2018, 27 (11): 114212 doi: 10.1088/1674-1056/27/11/114212
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Square microcavities, which support whispering-gallery modes with total internal reflections, can be employed as high-quality laser resonators for fabricating compact, low-threshold semiconductor lasers. In this paper, we review the recent progress of square microcavity semiconductor lasers. The characteristics of confined optical modes in the square microcavities are introduced briefly. Based on the mode properties of the square microcavities, dual-mode lasers with tunable wavelength intervals are realized for generating microwave signals. Furthermore, deformed square microcavity lasers with the sidewalls replaced by circular sides are proposed and experimentally demonstrated to enhance the mode confinement and increase the dual-mode interval to the THz range. In order to further reduce the device size, metal-confined wavelength-scale square cavity lasers are also demonstrated.

Applications of nanostructures in wide-field, label-free super resolution microscopy

Xiaowei Liu(刘小威), Chao Meng(孟超), Xuechu Xu(徐雪初), Mingwei Tang(汤明炜), Chenlei Pang(庞陈雷), Qing Yang(杨青)
Chin. Phys. B, 2018, 27 (11): 118704 doi: 10.1088/1674-1056/27/11/118704
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Super resolution imaging capable of resolving details beyond the diffraction limit is highly desired in many scientific and application fields, including bio-medicine, nanomaterial science, and opto-electronic integration. Up to now, many different methods have been proposed, among which wide-field, label-free super resolution microscopy is indispensable due to its good applicability to diverse sample types, large field of view (FOV), and high imaging speed. In recent years, nanostructures have made a crucial contribution to the wide-field, label-free subdiffraction microscopy, with various working mechanisms and configuration designs. This review summarizes the recent applications of the nanostructures in the wide-field, label-free super resolution microscopy, with the emphasis on the designs of hyperlens with hyperbolic dispersion, microsphere with “nano-jets”, and nanowire ring illumination microscopy based on spatial frequency shift effect. The bottlenecks of the current techniques and possible solutions are also discussed.

TOPICAL REVIEW—80th Anniversary of Northwestern Polytechnical University (NPU)

Some new advance on the research of stochastic non-smooth systems

Wei Xu(徐伟), Liang Wang(王亮), Jinqian Feng(冯进钤), Yan Qiao(乔艳), Ping Han(韩平)
Chin. Phys. B, 2018, 27 (11): 110503 doi: 10.1088/1674-1056/27/11/110503
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Due to the extensive applicability in real life, the non-smooth system with random factors attracted much attention in past two decades. A lot of methods and techniques have been proposed to research these systems by scholars. In this paper, we will summarize some new research advance on the stochastic non-smooth systems. The existing results about the stochastic vibro-impact system, the stochastic friction system, and the stochastic hysteretic system are introduced respectively. Some conclusions and outlook are given at the end.

Three-dimensional modulations on the states of polarization of light fields

Peng Li(李鹏), Dongjing Wu(吴东京), Sheng Liu(刘圣), Yi Zhang(章毅), Xuyue Guo(郭旭岳), Shuxia Qi(齐淑霞), Yu Li(李渝), Jianlin Zhao(赵建林)
Chin. Phys. B, 2018, 27 (11): 114201 doi: 10.1088/1674-1056/27/11/114201
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Light fields with spatially structured states of polarization (SoPs) are gathering increasing attention because of their potential applications from optical imaging and micromanipulation to classical and quantum communications. Meanwhile, the concepts within structured light fields have been extended and applied to acoustic, electron, and matter waves. In this article, we review recent developments of the SoP modulation of light fields, especially focusing on three-dimensional (3D) modulations on the SoPs of light fields. The recent progress and novel implementations based on 3D spin-dependent separation are discussed. Following the discussions to this physical phenomenon, we then describe recent developments on the vector fields with 3D structured SoP and intensity distributions, namely, 3D vector fields. The discussed phenomena inspire us to explore other structured light fields for the expansion of applications in biomedical, information science, quantum optics, and so on.

Review of photoinduced effect in manganite films and their heterostructures

Xin-Yu Li(李欣谕), Long Zhao(赵龙), Xiang-Yang Wei(魏向洋), Hao Li(李豪), Ke-Xin Jin(金克新)
Chin. Phys. B, 2018, 27 (11): 117501 doi: 10.1088/1674-1056/27/11/117501
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Light-matter interaction plays an important role in the non-equilibrium physics, especially in strongly correlated electron systems with complex phases. Photoinduced effect can cause the variation in the physical properties and produce some emergent phases. As a classical archetype, manganites have received much attention due to their colossal magnetoresistance (CMR) effect and the strong interaction of charge, spin, orbital, and lattice degrees of freedom. In this paper, we give an overview of photoinduced effect in manganites and their heterostructures. In particular, some materials, including ZnO, Si, BiFeO3 (BFO), titanate-based oxides, and 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) have been integrated with manganites. Heterostructures composed of these materials display some exciting and intriguing properties. We do hope that this review offers a guiding idea and more meaningful physical phenomena will be discovered in active areas of solid state physics and materials science.

Review of photoresponsive properties at SrTiO3-based heterointerfaces

Hong Yan(闫虹), Zhaoting Zhang(张兆亭), Shuanhu Wang(王拴虎), Kexin Jin(金克新)
Chin. Phys. B, 2018, 27 (11): 117804 doi: 10.1088/1674-1056/27/11/117804
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The two-dimensional electron gas at SrTiO3-based heterointerfaces has received a great deal of attention in recent years owing to their potential for the exploration of emergent physics and the next generation of electronics. One of the most fascinating aspects in this system is that the light, as a powerful external perturbation, can modify its transport properties. Recent studies have reported that SrTiO3-based heterointerfaces exhibit the persistent photoconductivity and can be tuned by the surface and interface engineering. These researches not only reveal the intrinsic physical mechanisms in the photoresponsive process, but also highlight the ability to be used as a tool for novel all-oxide optical devices. This review mainly contraposes the studies of photoresponse at SrTiO3-based heterointerfaces.

Metamaterials and metasurfaces for designing metadevices: Perfect absorbers and microstrip patch antennas

Yahong Liu(刘亚红), Xiaopeng Zhao(赵晓鹏)
Chin. Phys. B, 2018, 27 (11): 117805 doi: 10.1088/1674-1056/27/11/117805
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In the past twenty years, electromagnetic metamaterials represented by left-handed metamaterials (LHMs) have attracted considerable attention due to the unique properties such as negative refraction, perfect lens, and electromagnetic cloaks. In this paper, we present a comprehensive review of our group's work on metamaterials and metasurfaces. We present several types of LHMs and chiral metamaterials. As a two-dimensional equivalent of bulk three-dimensional metamaterials, metasurfaces have led to a myriad of devices due to the advantages of lower profile, lower losses, and simpler to fabricate than bulk three-dimensional metamaterials. We demonstrate the novel microwave metadevices based on metamaterials and metasurfaces:perfect absorbers and microwave patch antennas, including novel transmission line antennas, high gain resonant cavity antennas, wide scanning phased array antennas, and circularly polarized antennas.

SPECIAL TOPIC—80th Anniversary of Northwestern Polytechnical University (NPU)

Heteroclinic cycles in a new class of four-dimensional discontinuous piecewise affine systems

Wenjing Xu(徐文静), Wei Xu(徐伟), Li Cai(蔡力)
Chin. Phys. B, 2018, 27 (11): 110201 doi: 10.1088/1674-1056/27/11/110201
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It is a huge challenge to give an existence theorem for heteroclinic cycles in the high-dimensional discontinuous piecewise systems (DPSs). This paper first provides a new class of four-dimensional (4D) two-zone discontinuous piecewise affine systems (DPASs), and then gives a useful criterion to ensure the existence of heteroclinic cycles in the systems by rigorous mathematical analysis. To illustrate the feasibility and efficiency of the theory, two numerical examples, exhibiting chaotic behaviors in a small neighborhood of heteroclinic cycles, are discussed.

Cascaded tilted fiber Bragg grating for enhanced refractive index sensing

Biqiang Jiang(姜碧强), Zhixuan Bi(毕芷瑄), Shouheng Wang(王守恒), Teli Xi(席特立), Kaiming Zhou, Lin Zhang, Jianlin Zhao(赵建林)
Chin. Phys. B, 2018, 27 (11): 114220 doi: 10.1088/1674-1056/27/11/114220
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We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating (TFBG) for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber (SMF) and reduced-diameter SMF with the same tilt angle, and then excites two sets of superposed spectral combs of cladding modes. The cascaded TFBG with total length of 18 mm has a much wider wavelength range over 100 nm and narrower wavelength separation than that of a TFBG only in the SMF, enabling an enlarged range and a higher accuracy of refractive index measurement. The fabricated TFBG with the merits of enhanced sensing capability and temperature self-calibration presents great potentials in the biochemical sensing applications.

Effect of the fluctuant acoustic channel on the gain of a linear array in the ocean waveguide

Lei Xie(谢磊), Chao Sun(孙超), Guang-Yu Jiang(蒋光禹), Xiong-Hou Liu(刘雄厚), De-Zhi Kong(孔德智)
Chin. Phys. B, 2018, 27 (11): 114301 doi: 10.1088/1674-1056/27/11/114301
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The inhomogenous ocean waveguide, which leads the amplitude and phase of the signal arriving at a hydrophone array to fluctuate, is one of the causes that make the array gain deviate from its ideal value. The relationship between the array gain and the fluctuant acoustic channel is studied theoretically. The analytical expression of the array gain is derived via an acoustic channel transfer function on the assumption that the ambient noise field is isotropic. The expression is expanded via the Euler formula to give an insight into the effect of the fluctuant acoustic channel on the array gain. The result demonstrates that the amplitude fluctuation of the acoustic channel transfer functions has a slight effect on the array gain; however, the uniformity of the phase difference between the weighting coefficient and the channel transfer function on all the hydrophones in the array is a major factor that leads the array gain to further deviate from its ideal value. The numerical verification is conducted in the downslope waveguide, in which the gain of a horizontal uniform linear array (HLA) with a wide-aperture operating in the continental slope area is considered. Numerical result is consistent with the theoretical analysis.

Discrete state space method and modal extension method based impact sound synthesis model

Xu-Hua Tian(田旭华), Ke-An Chen(陈克安), Yan-Ni Zhang(张燕妮), Han Li(李晗), Jian Xu(胥健)
Chin. Phys. B, 2018, 27 (11): 114302 doi: 10.1088/1674-1056/27/11/114302
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The efficient and accurate synthesis of physical parameter-controllable impact sounds is essential for sound source identification. In this study, an impact sound synthesis model of a cylinder is proposed based on discrete state space (DSS) method and modal extension method (MEM). This model is comprised of the whole three processes of the physical interaction, i.e., the Hertz contact process, the transient structural response process, and the sound radiation process. Firstly, the modal expanded DSS equations of the contact system are constructed and the transient structural response of the cylinder is obtained. Then the impact sound of the cylinder is acquired using improved discrete Raleigh integral. Finally, the proposed model is verified by comparing with existing models. The results show that the proposed impact sound synthesis model is more accurate and efficient than the existing methods and easy to be extended to the impact sound synthesis of other structures.

Three-dimensional human thermoregulation model based on pulsatile blood flow and heating mechanism

Si-Na Dang(党思娜), Hong-Jun Xue(薛红军), Xiao-Yan Zhang(张晓燕), Jue Qu(瞿珏), Cheng-Wen Zhong(钟诚文), Si-Yu Chen(陈思宇)
Chin. Phys. B, 2018, 27 (11): 114402 doi: 10.1088/1674-1056/27/11/114402
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A three-dimensional thermoregulation mathematical model of temperature fluctuations for the human body is developed based on predecessors' thermal models. The following improvements are necessary in real situations:ellipsoids and elliptical cylinders are used to adequately approximate body geometry, divided into 18 segments and five layers; the core layer consists of the organs; the pulsation of the heart cycle, the pulsatile laminar flow, the peripheral resistance, and the thermal effect of food are considered. The model is calculated by adopting computational fluid dynamics (CFD) technology, and the results of the model match with the experimental data. This paper can give a reasonable explanation for the temperature fluctuations.

Effect of the asymmetric geometry on the wake structures of a pitching foil

LiMing Chao(朝黎明), Guang Pan(潘光), Dong Zhang(张栋)
Chin. Phys. B, 2018, 27 (11): 114701 doi: 10.1088/1674-1056/27/11/114701
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The two-dimensional wake produced by a time-periodic pitching foil with the asymmetric geometry is investigated in the present work. Through numerically solving nonlinear Navier-Stokes equations, we discuss the relationship among the kinematics of the prescribed motion, the asymmetric parameter K ranged as -1 ≤ K ≤ 1, and the types of the wakes including the mP+nS wake, the Bénard-von Kármán wake, the reverse Bénard-von Kármán wake, and the deviated wake. Compared with previous studies, we reveal that the asymmetric geometry of a pitching foil directly affects the foil's wake structures. The numerical results show that the reverse Bénard-von Kármán wake is easily deviated at K<0, while the symmetry-breaking of the reverse Bénard-von Kármán wake is delayed at K>0. Through the vortex dynamic method, we understand that the initial velocity of the vortex affected by the foil's asymmetry plays a key role in the deviation of the reverse Bénard-von Kármán wake. Moreover, we provide a theoretical model to predict the wake deviation of the asymmetric foil.

Effect of elasticity mismatch on cell deformation and migration: A phase-field study

Yuanfeng Yin(尹元枫), Hui Xing(邢辉), Duyang Zang(臧渡洋), Kexin Jin(金克新)
Chin. Phys. B, 2018, 27 (11): 116201 doi: 10.1088/1674-1056/27/11/116201
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The phase-field model for cell migration is used to study the effect of elasticity mismatch on the migration dynamics of multiple cells in a confluent monolayer, where one tagged cell is embedded by a number of normal cells and both types of cells are supposed to have the same properties except elasticity. Our results show that a larger elasticity mismatch leads to a larger difference in shape change between the tagged cell and the normal cells. We find that the bursts of velocity always fall behind the peak of the perimeter, and the shape change of the tagged cell results in the accelerated motion of the tagged cell in the whole process. Moreover, the variation of the averaging cell perimeter ratio Ltag/Lnormal with the increase of the elasticity ratio γtag/γnormal for different active velocities|va|is analyzed. We find that Ltag/Lnormal decreases with the increase of γtag/γnormal, following a simple power law function. Our results highlight the important role played by the cell elasticity mismatch in cell deformation and migration.

Ab initio molecular dynamics simulations of nano-crystallization of Fe-based amorphous alloys with early transition metals

Yao-Cen Wang(汪姚岑), Yan Zhang(张岩), Yoshiyuki Kawazoe, Jun Shen(沈军), Chong-De Cao(曹崇德)
Chin. Phys. B, 2018, 27 (11): 116401 doi: 10.1088/1674-1056/27/11/116401
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The addition of early transition metals (ETMs) into Fe-based amorphous alloys is practically found to be effective in reducing the α-Fe grain size in crystallization process. In this paper, by using ab initio molecular dynamics simulations, the mechanism of the effect of two typical ETMs (Nb and W) on nano-crystallization is studied. It is found that the diffusion ability in amorphous alloy is mainly determined by the bonding energy of the atom rather than the size or weight of the atom. The alloying of B dramatically reduces the diffusion ability of the ETM atoms, which prevents the supply of Fe near the grain surface and consequently suppresses the growth of α-Fe grains. Moreover, the difference in grain refining effectiveness between Nb and W could be attributed to the larger bonding energy between Nb and B than that between W and B.

Metastable phase separation and rapid solidification of undercooled Co40Fe40Cu20 alloy

Xiaojun Bai(白晓军), Yaocen Wang(汪姚岑), Chongde Cao(曹崇德)
Chin. Phys. B, 2018, 27 (11): 116402 doi: 10.1088/1674-1056/27/11/116402
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The metastable liquid phase separation and rapid solidification behaviors of Co40Fe40Cu20 alloy were investigated by using differential thermal analysis (DTA) in combination with glass fluxing and electromagnetic levitation (EML) techniques. The critical liquid phase separation undercooling for this alloy was determined by DTA to be 174 K. Macrosegregation morphologies are formed in the bulk samples processed by both DTA and EML. It is revealed that undercooling level, cooling rate, convection, and surface tension difference between the two separated phases play a dominant role in the coalescence and segregation of the separated phases. The growth velocity of the (Fe,Co) dendrite has been measured as a function of undercooling up to 275 K. The temperature rise resulting from recalescence increases linearly with the increase of undercooling because of the enhancement of recalescence. The slope change of the recalescence temperature rise versus undercooling at the critical undercooling also implies the occurrence of liquid demixing.

Spin Seebeck effect and spin Hall magnetoresistance in the Pt/Y3Fe5O12 heterostructure under laser-heating

Shuanhu Wang(王拴虎), Gang Li(李刚), Jianyuan Wang(王建元), Yingyi Tian(田颖异), Hongrui Zhang(张洪瑞), Lvkuan Zou(邹吕宽), Jirong Sun(孙继荣), Kexin Jin(金克新)
Chin. Phys. B, 2018, 27 (11): 117201 doi: 10.1088/1674-1056/27/11/117201
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In the previous study of longitudinal spin Seebeck effect (LSSE), the thermal gradient was often generated by inserting the sample between the cool bath and the hot bath. For practical use, this method is too cumbersome to be easily integrated into modern electrical circuits. Since the laser can be easily focused into a small region, it will be more convenient and friendly to the integrated circuit. In this paper, we systematically investigate the LSSE and spin Hall magnetoresistance (SMR) of the Pt/Y3Fe5O12 heterostructure under focused laser-heating. We find that the extremely large voltage of inverse spin Hall effect (VISHE) can be obtained by reducing the diameter of laser or increasing the number of light spots. Meanwhile, even under the illumination of the ultraviolet light which will excite the electron from the valence band to the conduction band in yttrium iron garnet (YIG), the magnitude of SMR is nearly constant. It indicates that the spin transport behavior of the adjacent Pt is independent of the electron configuration of YIG. The laser-heating method to generate LSSE will be very promising for modern integrated electronic circuits and will promote the application of spin caloritronics in practice.

Twin boundary dominated electric field distribution in CdZnTe detectors

Jiangpeng Dong(董江鹏), Wanqi Jie(介万奇), Jingyi Yu(余竞一), Rongrong Guo(郭榕榕), Christian Teichert, Kevin-P Gradwohl, Bin-Bin Zhang(张滨滨), Xiangxiang Luo(罗翔祥), Shouzhi Xi(席守智), Yadong Xu(徐亚东)
Chin. Phys. B, 2018, 27 (11): 117202 doi: 10.1088/1674-1056/27/11/117202
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The performance of CdZnTe X/γ-ray detectors is strongly affected by the electric field distribution in terms of charge transport and charge collection. Factors which determine the electric field distribution are not only electric contact, but also intrinsic defects, especially grown-in twin boundaries. Here, the electric field distribution around twin boundaries is investigated in a CdZnTe bicrystal detector with a {111}-{111} twin plane using the Pockels electro-optic effect. The results of laser beam induced current pulses are also obtained by the transient current technique, and we discuss the influence of the twin boundary on the electric field evolution. These studies reveal a significant distortion of the electric field, which is attributed to the buildup of space charges at twin boundaries. Also, the position of these space charge regions depends on the polarity of the detector bias. An energy band model based on the formation of an n-n+-n junction across the twin boundary has been established to explain the observed results.

Subwavelength asymmetric Au-VO2 nanodisk dimer for switchable directional scattering

Han-Mou Zhang(张汉谋), Wu-Yun Shang(尚武云), Hua Lu(陆华), Fa-Jun Xiao(肖发俊), Jian-Lin Zhao(赵建林)
Chin. Phys. B, 2018, 27 (11): 117301 doi: 10.1088/1674-1056/27/11/117301
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We propose an asymmetric Au-VO2 nanodisk dimer for realizing a switchable directional scattering. Specifically, the directional scattering can be triggered on/off through controlling the phase transition of the VO2 nanodisk from metallic to semiconductor state. More strikingly, an obvious directional scattering with the directivity of~40 dB is achieved under the metallic state of VO2 nanodisk. This tunable directional scattering is further explained with an interference model where the Au and VO2 nanodisks are treated as two weakly interacting electric dipoles. The phase transition controlled scattering patterns of asymmetric Au-VO2 nanodisk dimer are then well interpreted from the phase difference between these two dipoles.

Coupling-induced spectral splitting for plasmonic sensing with ultra-high figure of merit

Hua Lu(陆华), Yi-Cun Fan(范奕村), Si-Qing Dai(戴思清), Dong Mao(毛东), Fa-Jun Xiao(肖发俊), Peng Li(李鹏), Jian-Lin Zhao(赵建林)
Chin. Phys. B, 2018, 27 (11): 117302 doi: 10.1088/1674-1056/27/11/117302
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We investigate a kind of spectral splitting effect in a plasmonic multilayer system, which consists of stacked Al2O3 and SiO2 layers, a thin metal film, and a dielectric prism substrate. The results illustrate that an obvious peak appears in the center of the surface plasmon resonance (SPR)-induced reflection spectral dip in the structure with the SiO2/Al2O3/SiO2 layers. This spectral splitting response can be regarded as an electromagnetically induced transparency (EIT) like effect, which is attributed to the coupling and interference between the SPR on the metal film and guided-mode resonance (GMR) in the Al2O3 layer. The theoretical calculations agree well with the numerical simulations. It is also found that the reflection spectrum will be further split by the introduction of another Al2O3 layer into the multilayer structure. The reintroduced GMR in the Al2O3 layer changes the coupling and interference process between the SPR and GMR field, giving rise to the generation of ultra-narrow reflection dip. Especially, the spectral splitting can facilitate the realization of plasmonic sensors with ultra-high figure of merit (583), which is about 5 times larger than that of traditional SPR sensors. These results will provide a new avenue to the light field manipulation and optical functionalities, especially biochemical and environmental sensing.

Effects of filler loading and surface modification on electrical and thermal properties of epoxy/montmorillonite composite

Zi-Rui Jia(贾梓睿), Zhen-Guo Gao(高振国), Di Lan(兰笛), Yong-Hong Cheng(成永红), Guang-Lei Wu(吴广磊), Hong-Jing Wu(吴宏景)
Chin. Phys. B, 2018, 27 (11): 117806 doi: 10.1088/1674-1056/27/11/117806
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Epoxy-based composites containing montmorillonite (MMT) modified by silylation reaction with γ-aminopropyltriethoxysilane (γ-APTES) and 3-(glycidyloxypropyl) trimethoxysilane (GPTMS) are successfully prepared. The effects of filler loading and surface modification on the electrical and thermal properties of the epoxy/MMT composites are investigated. Compared with the pure epoxy resin, the epoxy/MMT composite, whether MMT is surface-treated or not, shows low dielectric permittivity, low dielectric loss, and enhanced dielectric strength. The MMT in the epoxy/MMT composite also influences the thermal properties of the composite by improving the thermal conductivity and stability. Surface functionalization of MMT not only conduces to the better dispersion of the nanoparticles, but also significantly affects the electric and thermal properties of the hybrid by influencing the interfaces between MMT and epoxy resin. Improved interfaces are good for enhancing the electric and thermal properties of nanocomposites. What is more, the MMT modified with GPTMS rather than γ-APTES is found to have greater influence on improving the interface between the MMT filler and polymer matrices, thus resulting in lower dielectric loss, lower electric conductivity, higher breakdown strength, lower thermal conductivity, and higher thermal stability.

An infrared and visible image fusion method based uponmulti-scale and top-hat transforms

Gui-Qing He(何贵青), Qi-Qi Zhang(张琪琦), Jia-Qi Ji(纪佳琪), Dan-Dan Dong(董丹丹), Hai-Xi Zhang(张海曦), Jun Wang(王珺)
Chin. Phys. B, 2018, 27 (11): 118706 doi: 10.1088/1674-1056/27/11/118706
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The high-frequency components in the traditional multi-scale transform method are approximately sparse, which can represent different information of the details. But in the low-frequency component, the coefficients around the zero value are very few, so we cannot sparsely represent low-frequency image information. The low-frequency component contains the main energy of the image and depicts the profile of the image. Direct fusion of the low-frequency component will not be conducive to obtain highly accurate fusion result. Therefore, this paper presents an infrared and visible image fusion method combining the multi-scale and top-hat transforms. On one hand, the new top-hat-transform can effectively extract the salient features of the low-frequency component. On the other hand, the multi-scale transform can extract high-frequency detailed information in multiple scales and from diverse directions. The combination of the two methods is conducive to the acquisition of more characteristics and more accurate fusion results. Among them, for the low-frequency component, a new type of top-hat transform is used to extract low-frequency features, and then different fusion rules are applied to fuse the low-frequency features and low-frequency background; for high-frequency components, the product of characteristics method is used to integrate the detailed information in high-frequency. Experimental results show that the proposed algorithm can obtain more detailed information and clearer infrared target fusion results than the traditional multi-scale transform methods. Compared with the state-of-the-art fusion methods based on sparse representation, the proposed algorithm is simple and efficacious, and the time consumption is significantly reduced.

Effect of stochastic electromagnetic disturbances on autapse neuronal systems

Liang-Hui Qu(曲良辉), Lin Du(都琳), Zi-Chen Deng(邓子辰), Zi-Lu Cao(曹子露), Hai-Wei Hu(胡海威)
Chin. Phys. B, 2018, 27 (11): 118707 doi: 10.1088/1674-1056/27/11/118707
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With the help of a magnetic flux variable, the effects of stochastic electromagnetic disturbances on autapse Hodgkin-Huxley neuronal systems are studied systematically. Firstly, owing to the autaptic function, the inter-spike interval series of an autapse neuron not only bifurcates, but also presents a quasi-periodic characteristic. Secondly, an irregular mixed-mode oscillation induced by a specific electromagnetic disturbance is analyzed using the coefficient of variation of inter-spike intervals. It is shown that the neuronal discharge activity has certain selectivity to the noise intensity, and the appropriate noise intensity can induce the significant mixed-mode oscillations. Finally, the modulation effects of electromagnetic disturbances on a ring field-coupled neuronal network with autaptic structures are explored quantitatively using the average spiking frequency and the average coefficient of variation. The electromagnetic disturbances can not only destroy the continuous and synchronous discharge state, but also induce the resting neurons to generate the intermittent discharge mode and realize the transmission of neural signals in the neuronal network. The studies can provide some theoretical guidance for applying electromagnetic disturbances to effectively control the propagation of neural signals and treat mental illness.

GENERAL

Hierarchical and probabilistic quantum information splitting of an arbitrary two-qubit state via two cluster states

Wen-Ming Guo(郭文明), Lei-Ru Qin(秦蕾茹)
Chin. Phys. B, 2018, 27 (11): 110302 doi: 10.1088/1674-1056/27/11/110302
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Based on non-maximally entangled four-particle cluster states, we propose a new hierarchical information splitting protocol to probabilistically realize the quantum state sharing of an arbitrary unknown two-qubit state. In this scheme, the sender transmits the two-qubit secret state to three agents who are divided into two grades with two Bell-state measurements, and broadcasts the measurement results via a classical channel. One agent is in the upper grade and two agents are in the lower grade. The agent in the upper grade only needs to cooperate with one of the other two agents to recover the secret state but both of the agents in the lower grade need help from all of the agents. Every agent who wants to recover the secret state needs to introduce two ancillary qubits and performs a positive operator-valued measurement (POVM) instead of the usual projective measurement. Moreover, due to the symmetry of the cluster state, we extend this protocol to multiparty agents.

Modulating quantum Fisher information of qubit in dissipative cavity by coupling strength

Danping Lin(林丹萍), Yu Liu(刘禹), Hong-Mei Zou(邹红梅)
Chin. Phys. B, 2018, 27 (11): 110303 doi: 10.1088/1674-1056/27/11/110303
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By using the non-Markovian master equation, we investigate the effect of the cavity and the environment on the quantum Fisher information (QFI) of an atom qubit system in a dissipation cavity. We obtain the formulae of QFI for two different initial states and analyze the effect of the atom-cavity coupling and the cavity-reservoir coupling on the QFI. The results show that the dynamic behavior of the QFI is obviously dependent on the initial atomic states, the atom-cavity coupling, and the cavity-reservoir coupling. The stronger the atom-cavity coupling, the quicker the QFI oscillates, and the slower the QFI decreases. In particular, the QFI will tend to be a stable value rather than zero if the atom-cavity coupling is large enough. On the other hand, the smaller the cavity-reservoir coupling, the stronger the non-Markovian effect, and the slower the QFI decays. In other words, choosing the best parameter can improve the accuracy of the parameter estimation. In addition, the physical explanation of the dynamic behavior of the QFI is given by means of the QFI flow.

Rydberg quantum controlled-phase gate with one control and multiple target qubits

S L Su(苏石磊)
Chin. Phys. B, 2018, 27 (11): 110304 doi: 10.1088/1674-1056/27/11/110304
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We propose a scheme to construct the multiple-qubit Rydberg quantum controlled-phase gate with one control and multiple target qubits. The proposed quantum logic gate works under the asymmetric-Rydberg-interaction-induced dipole blockade and can be implemented with three operation steps. The most prominent characteristic of the scheme is that the required operation time and steps keep invariant as the number of qubits increases. The Rydberg state leakage and some practical situations are considered. The Lindblad master equation is used to evaluate and verify the feasibility of the scheme.

A new class of states of reversible entanglement manipulation under positive partial transpose operations

Jing Duan(段静), Yu Luo(罗宇), Yong-Ming Li(李永明)
Chin. Phys. B, 2018, 27 (11): 110305 doi: 10.1088/1674-1056/27/11/110305
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We first study the reversibility for a class of states under the operations which completely preserve the positivity of partial transpose (PPT) and show that the entanglement cost is equal to the distillable entanglement for a rank-two mixed state on the 4⊗4 antisymmetric subspace under PPT operations. By using a similar method in finding the irreversibility, we also find that the value of a new efficiently computable additive lower bound Eη(ρ) for the asymptotic PPT-relative entropy of entanglement presented in[Phys. Rev. Lett. 119, 180506 (2017)] is equal to the regularized Rains' bound and an upper bound EN(ρ) for distillable entanglement for these states. Furthermore, we find states on the symmetric subspace satisfying the relation mentioned above, generalize the antisymmetric states and symmetric states in higher dimensions, and give a specific value for distillable entanglement and entanglement cost for these states under the PPT operations.

On the usefulness of an assisted driving Hamiltonian for quantum adiabatic evolution

Jie Sun(孙杰), Songfeng Lu(路松峰)
Chin. Phys. B, 2018, 27 (11): 110306 doi: 10.1088/1674-1056/27/11/110306
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In our recent work we showed, by investigating the initialization of some unusual forms of assisted driving Hamiltonians, that the addition of an assisted driving Hamiltonian is not always useful in quantum adiabatic evolution. These unusual forms are those that are not the relatively fixed ones that are widely used in the literature. In this paper, we continue this study, providing further evidence for the validity of the conclusion above by researching some relatively more complex forms of assisted driving scheme, which generalize the ones studied in our previous work.

Bursting oscillations as well as the bifurcation mechanism in a non-smooth chaotic geomagnetic field model

Ran Zhang(张冉), Miao Peng(彭淼), Zhengdi Zhang(张正娣), Qinsheng Bi(毕勤胜)
Chin. Phys. B, 2018, 27 (11): 110501 doi: 10.1088/1674-1056/27/11/110501
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Based on the chaotic geomagnetic field model, a non-smooth factor is introduced to explore complex dynamical behaviors of a system with multiple time scales. By regarding the whole excitation term as a parameter, bifurcation sets are derived, which divide the generalized parameter space into several regions corresponding to different kinds of dynamic behaviors. Due to the existence of non-smooth factors, different types of bifurcations are presented in spiking states, such as grazing-sliding bifurcation and across-sliding bifurcation. In addition, the non-smooth fold bifurcation may lead to the appearance of a special quiescent state in the interface as well as a non-smooth homoclinic bifurcation phenomenon. Due to these bifurcation behaviors, a special transition between spiking and quiescent state can also occur.

A novel pseudo-random coupled LP spatiotemporal chaos and its application in image encryption

Xingyuan Wang(王兴元), Yu Wang(王宇), Siwei Wang(王思伟), Yingqian Zhang(张盈谦), Xiangjun Wu(武相军)
Chin. Phys. B, 2018, 27 (11): 110502 doi: 10.1088/1674-1056/27/11/110502
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In this paper, first, we investigate a novel one-dimensional logistic-PWLCM (LP) modulation map which is derived from the logistic and PWLCM maps. Second, we propose a novel PCLML spatiotemporal chaos in pseudo-random coupling method that can accelerate the system behavior of the fully spatial chaos. Here, because the better chaotic properties include a wide range of parameter settings and better ergodicity than a logistic map, the LP is used in PCLML as f(x). The Kolmogorov-Sinai entropy density and universality and the bifurcation diagram are employed to investigate the chaotic behaviors of the proposed PCLML model. Finally, we apply the LP and PCLML chaotic systems to image encryption to improve the effectiveness and security of the encryption scheme. By combining self-generating matrix model M and dynamic substitution box (S-Box) methods, we design a new image encryption algorithm. Numerical simulations and security analysis have been carried out to demonstrate that the proposed algorithm has a high security level and can efficiently encrypt several different kinds of images into random-like images.

Effect of different bending shapes on thermal properties of flexible light-emitting diode filament

Liping Wang(王立平), Wenbo Li(李文博), Yichao Xu(徐一超), Bobo Yang(杨波波), Mingming Shi(石明明), Jun Zou(邹军), Yang Li(李杨), Xinglu Qian(钱幸璐), Fei Zheng(郑飞), Lei Yang(杨磊)
Chin. Phys. B, 2018, 27 (11): 110701 doi: 10.1088/1674-1056/27/11/110701
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Heat dissipation is an important part of light-emitting diode (LED) filament research and has aroused constant concern. In this paper, we studied the thermal performance of flexible LED filament by numerical simulation and through experiment. The heat dissipation characteristics of spring-like structure flexible LED filament were computed by finite volume method, and it was found that the chip junction temperature was closely related to the pitch and the bending radius. The effect of inclination angle of lighting LED filament was discussed because it is relevant to the spring-like structure flexible LED filament in geometry. The results demonstrated that the temperature of the filament increases as the inclination angle improves.

RAPID COMMUNICATION

A single-crystal neutron diffraction study on magnetic structure of CsCo2Se2 Hot!

Juanjuan Liu(刘娟娟), Jieming Sheng(盛洁明), Wei Luo(罗伟), Jinchen Wang(汪晋辰), Wei Bao(鲍威), Jinhu Yang(杨金虎), Minghu Fang(方明虎), S A Danilkin
Chin. Phys. B, 2018, 27 (11): 117401 doi: 10.1088/1674-1056/27/11/117401
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The magnetic structure of CsCo2Se2 was investigated using single-crystal neutron diffraction technique. An antiferromagnetic transition with the propagation vector (0,0,1) was observed at TN=78 K. The Co magnetic moment 0.772(6) μB at 10 K pointing in the basal plane couples ferromagnetically in the plane, which stacks antiferromagnetically along the c direction. Tuning and suppressing the interplane antiferromagnetic interaction may be crucial to induce a superconducting state in the material.

Formation and stability of ultrasonic generated bulk nanobubbles Hot!

Chen-Ran Mo(莫宸冉), Jing Wang(王菁), Zhou Fang(方舟), Li-Min Zhou(周利民), Li-Juan Zhang(张立娟), Jun Hu(胡钧)
Chin. Phys. B, 2018, 27 (11): 118104 doi: 10.1088/1674-1056/27/11/118104
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Although various and unique properties of bulk nanobubbles have drawn researchers' attention over the last few years, their formation and stabilization mechanism has remained unsolved. In this paper, we use ultrasonic methods to produce bulk nanobubbles in the pure water and give a comprehensive study on the bulk nanobubbles properties and generation. The ultrasonic wave gives rise to constant oscillation in water where positive and negative pressure appears alternately. With the induced cavitation and presence of dissolved air, the bulk nanobubbles formed. “Nanosight” (which is a special instrument that combines dynamic light scattering with nanoparticle tracking analysis) was used to analyze the track and concentration of nanobubbles. Our results show that in our experiment, sufficient bulk nanobubbles were generated and we have proven they are not contaminations. We also found nanobubbles in the ultrasonic water change in both size and concentration with ultrasonic time.

INVITED REVIEW

Electronic structures of impurities and point defects in semiconductors

Yong Zhang(张勇)
Chin. Phys. B, 2018, 27 (11): 117103 doi: 10.1088/1674-1056/27/11/117103
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A brief history of the impurity theories in semiconductors is provided. A bound exciton model is proposed for both donor-and acceptor-like impurities and point defects, which offers a unified understanding for “shallow” and “deep” impurities and point defects. The underlying physics of computational results using different density-functional theory-based approaches are discussed and interpreted in the framework of the bound exciton model.

ATOMIC AND MOLECULAR PHYSICS

Landscape of s-triazine molecule on Si(100) by a theoretical x-ray photoelectron spectroscopy and x-ray absorption near-edge structure spectra study

Jing Hu(胡静), Xiu-Neng Song(宋秀能), Sheng-Yu Wang(王胜雨), Juan Lin(林娟), Jun-Rong Zhang(张俊荣), Yong Ma(马勇)
Chin. Phys. B, 2018, 27 (11): 113101 doi: 10.1088/1674-1056/27/11/113101
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The chemisorbed structure for an aromatic molecule on a silicon surface plays an important part in promoting the development of organic semiconductor material science. The carbon K-shell x-ray photoelectron spectroscopy (XPS) and the x-ray absorption near-edge structure (XANES) spectra of the interfacial structure of an s-triazine molecule adsorbed on Si(100) surface have been performed by the first principles, and the landscape of the s-triazine molecule on Si(100) surface has been described in detail. Both the XPS and XANES spectra have shown their dependence on different structures for the pristine s-triazine molecule and its several possible adsorbed configurations. By comparison with the XPS spectra, the XANES spectra display the strongest structural dependency of all of the studied systems and thus could be well applied to identify the chemisorbed s-triazine derivatives. The exploration of spectral components originated from non-equivalent carbons in disparate local environments has also been implemented for both the XPS and XANES spectra of s-triazine adsorbed configurations.

Ethylene glycol solution-induced DNA conformational transitions

Nan Zhang(张楠), Ming-Ru Li(李明儒), Feng-Shou Zhang(张丰收)
Chin. Phys. B, 2018, 27 (11): 113102 doi: 10.1088/1674-1056/27/11/113102
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We study the properties of the ethylene glycol solutions and the conformational transitions of DNA segment in the ethylene glycol solutions by molecular dynamics simulations based on GROMACS. The hydrogen network structures of water-water and ethylene glycol-water are reinforced by ethylene glycol molecules when the concentrations of the solutions increase from 0% to 80%. As illustrated by the results, conformation of the double-stranded DNA in ethylene glycol solutions, although more compact, is similar to the structure of DNA in the aqueous solutions. In contrast, the DNA structure is an A-B hybrid state in the ethanol/water mixed solution. A fraying of terminal base-pairs is observed for the terminal cytosine. The ethylene glycol molecules preferentially form a ring structure around the phosphate groups to influence DNA conformation by hydrogen interactions, while water molecules tend to reside in the grooves. The repulsion between the negatively charged phosphate groups is screened by ethylene glycol molecules, preventing the repulsion from unwinding and extending the helix and thus making the conformation of DNA more compact.

Low-order harmonic generation of hydrogen molecular ion in laser field studied by the two-state model

Ling-Ling Du(杜玲玲), Guo-Li Wang(王国利), Peng-Cheng Li(李鹏程), Xiao-Xin Zhou(周效信)
Chin. Phys. B, 2018, 27 (11): 113201 doi: 10.1088/1674-1056/27/11/113201
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The low-order harmonic generation of hydrogen molecular ion interacting with a linearly polarized laser field has been investigated theoretically by using a simple two-state model. The validity of the two-state model is carefully examined by comparing the harmonic spectra of hydrogen molecular ion obtained from this model with those from the three-dimensional time-dependent Schrödinger equation. When combined with the Morlet transform of quantum time-frequency spectrum, the two-state model can be used to study the dynamical origin of the low-order harmonic generation of hydrogen molecular ion driven by low-frequency pulses. In addition, some interesting structures of the time profiles for low order harmonics are obtained.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

Ultra-wideband low radar cross-section metasurface and its application on waveguide slot antenna array

Li-Li Cong(丛丽丽), Xiang-Yu Cao(曹祥玉), Tao Song(宋涛), Jun Gao(高军)
Chin. Phys. B, 2018, 27 (11): 114101 doi: 10.1088/1674-1056/27/11/114101
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A novel approach devoted to achieving ultra-wideband radar cross section reduction (RCSR) of a waveguide slot antenna array (WGSAA) while maintaining its radiation performance is proposed. Three kinds of artificial magnetic conductors (AMCs) tiles consisting of three types of basic units resonant at different frequencies are designed and arranged in a novel quadruple-triangle-type configuration to create a composite planar metasurface. The proposed metasurface is characterized by low radar feature over an ultra-wideband based on the principle of phase cancellation. Both simulated and measured results demonstrate that after the composite metasurface is used to cover part of the antenna array, an ultra-wideband RCSR involving in-band and out-of-band is achieved for co-and cross-polarized incident waves based on energy cancellation, while the radiation performance is well retained. The proposed method is simple, low-cost, and easy-to-fabricate, providing a new method for ultra-wideband RCSR of an antenna array. Moreover, the method proposed in this paper can easily be applied to other antenna architectures.

Modified physical optics algorithm for near field scattering

Bin Chen(陈彬), Chuangming Tong(童创明)
Chin. Phys. B, 2018, 27 (11): 114102 doi: 10.1088/1674-1056/27/11/114102
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A novel modified physical optics algorithm is proposed to overcome the difficulties of near field scattering prediction for classical physical optics. The method is applied to calculating the near field radar cross section of electrically large objects by taking into account the influence of the distinct wave propagation vector, the near field Green function, and the antenna radiation pattern. By setting up local reference coordinates, each partitioned facet has its own distinct wave front curvature. The radiation gain for every surface element is taken into consideration based on the modulation of the antenna radiation pattern. The Green function is refined both in amplitude and phase terms and allows for near field calculation. The scattered characteristics of the near field targets are studied by numerical simulations. The results show that the approach can achieve a satisfactory accuracy.

β-BaB2O4 with special cut-angle applied to single crystal cascaded third-harmonic generation

Hong-Kai Ren(任宏凯), Hong-Wei Qi(亓宏伟), Zheng-Ping Wang(王正平), Zhi-Xin Wu(吴志心), Meng-Xia Wang(王梦霞), Yu-Xiang Sun(孙玉祥), Xun Sun(孙洵), Xin-Guang Xu(许心光)
Chin. Phys. B, 2018, 27 (11): 114202 doi: 10.1088/1674-1056/27/11/114202
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High-efficiency single crystal cascaded third-harmonic generation (THG) was realized in β-BaB2O4 (BBO) material with special cut-angle. By analyzing effective nonlinear optical coefficient (deff) of the cascaded THG process, which was composed by type-Ⅱ frequency doubling and type-I sum-frequency, the optimum phase matching (PM) direction in BBO crystal was determined to be (θ=32.1°, φ=11°). With an optimized 9-mm long sample which was processed along this direction, the highest cascaded THG conversion efficiency reached 42.3%, which is much superior to the similar components reported previously, including ADP, KDP, and GdxY1-xCOB crystals.

Modulation transfer spectroscopy based on acousto-optic modulator with zero frequency shift

Chen-Fei Wu(吴晨菲), Xue-Shu Yan(颜学术), Li-Xun Wei(卫立勋), Pei Ma(马沛), Jian-Hui Tu(涂建辉), Jian-Wei Zhang(张建伟), Li-Jun Wang(王力军)
Chin. Phys. B, 2018, 27 (11): 114203 doi: 10.1088/1674-1056/27/11/114203
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We present a modulation transfer spectroscopy (MTS) configuration based on an acousto-optic modulator by using a variant of the typical double pass structure. One beam is modulated by using an acousto-optic modulator in opposite diffraction order to cancel the carrier frequency shift and produce a modulated pump beam. The line shape performance is investigated theoretically and experimentally. Laser frequency stabilization of the proposed configuration is demonstrated for the 133Cs|62S1/2, F=4> →|62 P3/2, F'=5> transition. The Allan deviations, which are measured by using beat note signals and the three-cornered hat method, are 3.6×10-11 in an integration time of 100 s and approximately 4×10-11 in a longer integration time.

Terahertz two-pixel imaging based on complementary compressive sensing

Yuye Wang(王与烨), Yuchen Ren(任宇琛), Linyu Chen(陈霖宇), Ci Song(宋词), Changzhao Li(李长昭), Chao Zhang(张超), Degang Xu(徐德刚), Jianquan Yao(姚建铨)
Chin. Phys. B, 2018, 27 (11): 114204 doi: 10.1088/1674-1056/27/11/114204
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A compact terahertz (THz) imaging system based on complementary compressive sensing has been proposed using two single-pixel detectors. By using a mechanical spatial light modulator, sampling in the transmission and reflection orientations was achieved simultaneously, which allows imaging with negative mask values. The improvement of THz image quality and anti-noise performance has been verified experimentally compared with the traditional reconstructed image, and is in good agreement with the numerical simulation. The demonstrated imaging system, with the advantages of high imaging quality and strong anti-noise property, opens up possibilities for new applications in the THz region.

Nonlinear coherent perfect photon absorber in asymmetrical atom-nanowires coupling system

Xiuwen Xia(夏秀文), Xinqin Zhang(张新琴), Jingping Xu(许静平), Mutian Cheng(程木田), Yaping Yang(羊亚平)
Chin. Phys. B, 2018, 27 (11): 114205 doi: 10.1088/1674-1056/27/11/114205
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Coherent perfect absorption provides a method of light-controlling-light and has practical applications in optical communications. Recently, a cavity-based nonlinear perfect photon absorption extends the coherent perfect absorber (CPA) beyond the linear regime. As nanowire-based system is a more competitive candidate for full-optical device, we introduce a nonlinear CPA in the single two-level atom-nanowires coupling system in this work. Nonlinear input-output relations are derived analytically, and three contributions of atomic saturation nonlinearity are explicit. The consociation of optical nonlinearity and destructive interference makes it feasible to fabricate a nonlinear monoatomic CPA. Our results also indicate that a nonlinear system may work linearly even when the incoming lights are not weak any more. Our findings show promising applications in full-optical devices.

On the nonclassical dynamics of cavity-assisted four-channel nonlinear coupler

Rafael Julius, Abdel-Baset M A Ibrahim, Pankaj Kumar Choudhury, Hichem Eleuch
Chin. Phys. B, 2018, 27 (11): 114206 doi: 10.1088/1674-1056/27/11/114206
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The non-classical properties of light propagating in four-channel Kerr waveguides, confined in an optical cavity, are studied. The solution to the Hamiltonian of field operators is obtained semi-analytically by using symmetrically ordered phase-space representation. Full quantum analysis of the input coherent fields displays a strong transition of photon property between the super-Poissonian and sub-Poissonian statistics. It is found that the cavity-assisted multichannel system exhibits enhanced squeezing both in single-and compound-mode. This multichannel system may be utilized as an efficient quantum-light generator.

Generation of sustained optimal entropy squeezing of a two-level atom via non-Hermitian operation

Yan-Yi Wang(王彦懿), Mao-Fa Fang(方卯发)
Chin. Phys. B, 2018, 27 (11): 114207 doi: 10.1088/1674-1056/27/11/114207
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We investigate the entropy squeezing of a two-level atom in the Jaynes-Cummings model, and provide a scheme to generate the sustained optimal entropy squeezing of the atom via non-Hermitian operation. Our results show that the squeezing degree and the persistence time of entropy squeezing of atomic polarization components greatly depend on the non-Hermiticity intensity in non-Hermitian operation. Especially, under a proper choice of non-Hermiticity parameters, the sustained optimal entropy squeezing of the atom can be generated even though the atom is initially prepared in a no entropy squeezing state.

Energy scaling and extended tunability of a ring cavity terahertz parametric oscillator based on KTiOPO4 crystal

Yuye Wang(王与烨), Yuchen Ren(任宇琛), Degang Xu(徐德刚), Longhuang Tang(唐隆煌), Yixin He(贺奕焮), Ci Song(宋词), Linyu Chen(陈霖宇), Changzhao Li(李长昭), Chao Yan(闫超), Jianquan Yao(姚建铨)
Chin. Phys. B, 2018, 27 (11): 114213 doi: 10.1088/1674-1056/27/11/114213
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A wide terahertz tuning range from 0.96 THz to 7.01 THz has been demonstrated based on ring-cavity THz wave parametric oscillator with a KTiOPO4 (KTP) crystal. The tuning range was observed intermittently from 0.96 THz to 1.87 THz, from 3.04 THz to 3.33 THz, from 4.17 THz to 4.48 THz, from 4.78 THz to 4.97 THz, from 5.125 THz to 5.168 THz, from 5.44 THz to 5.97 THz, and from 6.74 THz to 7.01 THz. The dual-Stokes wavelengths resonance phenomena were observed in some certain tuning angle ranges. Through the theoretical analysis of the dispersion curve of the KTP crystal, the intermittent THz wave tuning range and dual-wavelength Stokes waves operation during angle tuning process were explained. The theoretical analysis was in good agreement with the experiment results. The maximum THz output voltage detected by Golay cell was 1.7 V at 5.7 THz under the pump energy of 210 mJ, corresponding to the THz wave output energy of 5.47 μJ and conversion efficiency of 2.6×10-5.

Carboxyl graphene oxide solution saturable absorber for femtosecond mode-locked erbium-doped fiber laser

Rui-dong Lv(吕瑞东), Lu Li(李璐), Yong-gang Wang(王勇刚), Zhen-dong Chen(陈振东), Si-cong Liu(刘思聪), Xi Wang(王茜), Jiang Wang(王江), Yong-fang Li(李永放)
Chin. Phys. B, 2018, 27 (11): 114214 doi: 10.1088/1674-1056/27/11/114214
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The carboxyl-functionalized graphene oxide (GO-COOH) is a kind of unique two-dimensional (2D) material and possesses excellent nonlinear saturable absorption property and high water-solubility. In this paper, we prepare saturable absorber (SA) device by depositing GO-COOH nanosheets aqueous solution on a D-shaped fiber. The modulation depth (MD) and saturable intensity of the SA are measured to be 9.6% and 19 MW/cm2, respectively. By inserting the SA into the erbium-doped fiber (EDF) laser, a passively mode-locked EDF laser has been achieved with the spectrum center wavelength of 1562.76 nm. The pulse duration, repetition rate, and the signal-to-noise ratio (SNR) are 500 fs, 14.79 MHz, and 80 dB, respectively. The maximum average output power is measured to be 3.85 mW. These results indicate that the GO-COOH nanosheets SA can be used as a promising mode locker for the generation of ultrashort pulses.

Surface plasmon polariton at the interface of dielectric and graphene medium using Kerr effect

Bakhtawar, Muhammad Haneef, B A Bacha, H Khan, M Atif
Chin. Phys. B, 2018, 27 (11): 114215 doi: 10.1088/1674-1056/27/11/114215
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We theoretically investigate the control of surface plasmon polariton (SPP) generated at the interface of dielectric and graphene medium under Kerr nonlinearity. The controlled Kerr nonlinear signal of probe light beam in a dielectric medium is used to generate SPPs at the interface of dielectric and graphene medium. The positive, negative absorption, and dispersion properties of SPPs are modified and controlled by the control and Kerr fields. A large amplification (negative absorption) is noted for SPPs under the Kerr nonlinearity. The normal/anomalous slope of dispersion and propagation length of SPPs is modified and controlled with Kerr nonlinearity. This leads to significant variation in slow and fast SPP propagation. The controlled slow and fast SPP propagation may predict significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster, and sensing technology.

Generation of breathing solitons in the propagation and interactions of Airy-Gaussian beams in a cubic-quintic nonlinear medium

Weijun Chen(陈卫军), Ying Ju(鞠莹), Chunyang Liu(刘春阳), Liankai Wang(王连锴), Keqing Lu(卢克清)
Chin. Phys. B, 2018, 27 (11): 114216 doi: 10.1088/1674-1056/27/11/114216
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Using the split-step Fourier transform method, we numerically investigate the generation of breathing solitons in the propagation and interactions of Airy-Gaussian (AiG) beams in a cubic-quintic nonlinear medium in one transverse dimension. We show that the propagation of single AiG beams can generate stable breathing solitons that do not accelerate within a certain initial power range. The propagation direction of these breathing solitons can be controlled by introducing a launch angle to the incident AiG beams. When two AiG beams accelerated in opposite directions interact with each other, different breathing solitons and soliton pairs are observed by adjusting the phase shift, the beam interval, the amplitudes, and the light field distribution of the initial AiG beams.

Effect of Hf4+ doping on structure and enhancement of upconversion luminescence in Yb: Tm: LiNbO3 crystals

Li Dai(代丽), Chunrui Liu(刘春蕊), Xianbo Han(韩县博), Luping Wang(王路平), Yu Shao(邵瑀), Yuheng Xu(徐玉恒)
Chin. Phys. B, 2018, 27 (11): 114217 doi: 10.1088/1674-1056/27/11/114217
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A series of Yb:Tm:LiNbO3 crystals doped with x mol% Hf4+ ions (x=2, 4, and 6) were grown by the Czochralski method. The dopant occupancy and defect structure of Hf:Yb:Tm:LiNbO3 crystals were investigated by x-ray diffraction and infrared transmission spectra. The influence of Hf4+ ions concentration on UV-VIS-NIR absorption spectra of Hf:Yb:Tm:LiNbO3 crystals was discussed. The upconversion luminescence of Hf:Yb:Tm:LiNbO3 crystals was obtained under 980 nm excitation. Strong emissions were observed at 475 nm in the blue wavelength range and 651 nm in the red wavelength range. Remarkably, enhancement of the red and blue upconversion luminescence was achieved by tridoping Hf4+ ions.

Polymer waveguide thermo-optical switch with loss compensation based on NaYF4: 18% Yb3+, 2% Er3+ nanocrystals

Gui-Chao Xing(邢桂超), Mei-Ling Zhang(张美玲), Tong-He Sun(孙潼鹤), Yue-Wu Fu(符越吾), Ya-Li Huang(黄雅莉), Jian Shao(邵健), Jing-Rong Liu(刘静蓉), Fei Wang(王菲), Da-Ming Zhang(张大明)
Chin. Phys. B, 2018, 27 (11): 114218 doi: 10.1088/1674-1056/27/11/114218
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A polymer waveguide thermo-optical switch with loss compensation based on NaYF4:18% Yb3+, 2% Er3+ nanocrystals, fabricated by traditional semiconductor processes, has been investigated. NaYF4:18% Yb3+, 2% Er3+ nanocrystals were prepared by a pyrolysis method. The morphology and luminescent properties of the nanocrystals were characterized. The nanocrystals were doped into SU-8 as the core material of an optical waveguide amplifier. The size of the device was optimized for its optical and thermal fields as well as its transmission characteristics. The device was fabricated on a silica substrate by spin coating, photolithography, and wet etching. The insertion loss of the switch device is~15 dB. The rise and fall times of the device are 240 μs and 380 μs, respectively, as measured by application of a 304 Hz square wave voltage. The extinction ratio of the device is about 14 dB at an electrode-driving power of 7 mW. When the pump light power is 230 mW and the signal light power is 0.1 mW, the loss compensation of the device is 3.8 dB at a wavelength of 1530 nm. Optical devices with loss compensation have important research significance.

Supercontinuum manipulation based on the influence of chirp on soliton spectral tunneling

Saili Zhao(赵赛丽), Huan Yang(杨华), Yilin Zhao(赵奕霖), Yuzhe Xiao(肖宇哲)
Chin. Phys. B, 2018, 27 (11): 114219 doi: 10.1088/1674-1056/27/11/114219
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The soliton spectral tunneling (SST) effect, as a soliton spectral switching phenomenon, enables a soliton to tunnel through a spectrally limited regime of normal dispersion in the fiber with multiple zero dispersion wavelengths (ZDWs). Since initial chirp can affect the behavior of pulse evolution, we numerically study the influence of chirp on the SST in the process of supercontinuum (SC) occurring in a photonic crystal fiber (PCF) with three ZDWs. The linear chirp is imposed by a phase modulation of input pulse while maintaining a constant pulse duration. Interestingly, it is found that the spectral range and flatness can be flexibly tuned by adjusting the initial chirp value. More specifically, positive chirp facilitates soliton self-frequency shifting (SSFS), making the soliton quickly transfer from one anomalous dispersion regime to another accompanied by the generation of dispersive waves (DWs). In this case, the SST effect further expands the spectral range by enhancing both the red-shift of the fundamental soliton and the blue-shift of DWs, thus generating a broader SC. However, negative chirp suppresses the SST effect, resulting in a smoother SC at the expense of bandwidth. Therefore, the findings in this work provide interesting results relating to the influence of initial chirp on the SST to generate a considerably smoother and broader SC, which is extremely useful in many applications, such as wavelength conversion and SC generation.

Effect of graphene/ZnO hybrid transparent electrode on characteristics of GaN light-emitting diodes

Jun-Tian Tan(谭竣天), Shu-Fang Zhang(张淑芳), Ming-Can Qian(钱明灿), Hai-Jun Luo(罗海军), Fang Wu(吴芳), Xing-Ming Long(龙兴明), Liang Fang(方亮), Da-Peng Wei(魏大鹏), Bao-Shan Hu(胡宝山)
Chin. Phys. B, 2018, 27 (11): 114401 doi: 10.1088/1674-1056/27/11/114401
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In order to reduce the Schottky barrier height and sheet resistance between graphene (Gr) and the p-GaN layers in GaN-based light-emitting diodes (LEDs), conductive transparent thin films with large work function are required to be inserted between Gr and p-GaN layers. In the present work, three kinds of transparent conductive oxide (TCO) zinc oxide (ZnO) films, Al-, Ga-, and In-doped ZnO (AZO, GZO, and IZO), are introduced as a bridge layer between Gr and p-GaN, respectively. The influence of different combinations of Gr/ZnO hybrid transparent conducting layers (TCLs) on the optical and thermal characteristics of the GaN-LED was investigated by the finite element method through COMSOL software. It is found that both the TCL transmittance and the surface temperature of the LED chip reduce with the increase in Gr and ZnO thickness. In order to get the transmittance of the Gr/ZnO hybrid TCL higher than 80%, the appropriate combination of Gr/ZnO compound electrode should be a single layer of Gr with ZnO no thicker than 400 nm (1L Gr/400-nm ZnO), 2L Gr/300-nm ZnO, 3L Gr/200-nm ZnO, or 4L Gr/100-nm ZnO. The LEDs with hybrid TCLs consisting of 1L Gr/300-nm AZO, 2L Gr/300-nm GZO, and 2L Gr/300-nm IZO have good performance, among which the one with 1L Gr/300-nm GZO has the best thermal property. Typically, the temperature of LEDs with 1L Gr/300-nm GZO hybrid TCLs will drop by about 7 K compared with that of the LEDs with a TCL without ZnO film.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

First-principles study on the mechanics, optical, and phonon properties of carbon chains

Jin-Ping Li(李金平), Song-He Meng(孟松鹤), Han-Tao Lu(陆汉涛), Takami Tohyama(遠山貴巳)
Chin. Phys. B, 2018, 27 (11): 117101 doi: 10.1088/1674-1056/27/11/117101
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Besides graphite, diamond, graphene, carbon nanotubes, and fullerenes, there is another allotrope of carbon, carbyne, existing in the form of a one-dimensional chain of carbon atoms. It has been theoretically predicted that carbyne would be stronger, stiffer, and more exotic than other materials that have been synthesized before. In this article, two kinds of carbyne, i.e., cumulene and polyyne are investigated by the first principles, where the mechanical properties, electronic structure, optical and phonon properties of the carbynes are calculated. The results on the crystal binding energy and the formation energy show that though both are difficult to be synthesized from diamond or graphite, polyyne is more stable and harder than cummulene. The tensile stiffness, bond stiffness, and Young's modulus of cumulene are 94.669 eV/Å, 90.334 GPa, and 60.62 GPa, respectively, while the corresponding values of polyyne are 94.939 eV/Å, 101.42 GPa, and 60.06 GPa. The supercell calculation shows that carbyne is most stable at N=5, where N is the supercell number, which indicates that the carbon chain with 10 atoms is most stable. The calculation on the electronic band structure shows that cumulene is a conductor and polyyne is a semiconductor with a band gap of 0.37 eV. The dielectric function of carbynes varies along different directions, consistent with the one-dimensional nature of the carbon chains. In the phonon dispersion of cumulene, there are imaginary frequencies with the lowest value down to-3.817 THz, which indicates that cumulene could be unstable at room temperature and normal pressure.

Antiferromagnetic–ferromagnetic transition in zigzag graphene nanoribbons induced by substitutional doping Hot!

Shenyuan Yang(杨身园), Jing Li(李静), Shu-Shen Li(李树深)
Chin. Phys. B, 2018, 27 (11): 117102 doi: 10.1088/1674-1056/27/11/117102
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Using first-principles calculations based on density functional theory, we show that the ground state of zigzag-edged graphene nanoribbons (ZGNRs) can be transformed from antiferromagnetic (AFM) order to ferromagnetic (FM) order by changing the substitutional sites of N or B dopants. This AFM-FM transition induced by substitutional sites is found to be a consequence of the competition between the edge and bulk states. The energy sequence of the edge and bulk states near the Fermi level is reversed in the AFM and FM configurations. When the dopant is substituted near the edge of the ribbon, the extra charge from the dopant is energetically favorable to occupy the edge states in AFM configuration. When the dopant is substituted near the center, the extra charge is energetically favorable to occupy the bulk states in FM configuration. Proper substrate with weak interaction is necessary to maintain the magnetic properties of the doped ZGNRs. Our study can serve as a guide to synthesize graphene nanostructures with stable FM order for future applications to spintronic devices.

Phase diagram characterized by transmission in a triangular quantum dot

Jin Huang(黄金), Wei-Zhong Wang(王为忠)
Chin. Phys. B, 2018, 27 (11): 117303 doi: 10.1088/1674-1056/27/11/117303
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We propose a theoretical model to detect the quantum phase transition in a triangular quantum dot molecule with frustration. The boundaries of the phase diagram are accurately determined by the transmission. For small frustration t, as the interdot Coulomb repulsion V increases, the system undergoes a Kosterlitz-Thouless (KT) transition from the Kondo resonance state with a transmission peak at zero energy to the Coulomb blocked state with zero transmission, which is followed by a first transition to the V-induced resonance (VIR) state with unitary transmission. For large frustration t, as V increases, the orbital spin singlet without transmission transits to the VIR state through a KT transition.

Magnetism induced by Mn atom doping in SnO monolayer

Ruilin Han(韩瑞林), Yu Yan(闫羽)
Chin. Phys. B, 2018, 27 (11): 117505 doi: 10.1088/1674-1056/27/11/117505
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The structural, magnetic properties, and mechanism of magnetization of SnO monolayer doped with 3d transition metal Mn atom were studied using first-principles calculations. The calculated results show that the substitution doping is easier to realize under the condition of oxygen enrichment. Numerical results reveal that the spin-splitting defect state of the Mn doped system is produced in the band gap and the magnetic moment of 5.0 μB is formed. The induced magnetic moment by Mnsub is mostly derived from the 3d orbital of the doped Mn atom. The magnetic coupling between magnetic moments caused by two Mn atoms in SnO monolayer is a long-range ferromagnetic, which is due to the hole-mediated p-p and p-d interactions. The calculated results suggest that room-temperature ferromagnetism in a SnO monolayer can be induced after substitutional doping of a Mn atom.

Fabrication and characterization of Ge–Ga–Sb–S glass microsphere lasers operating at~1.9 μm

Kun Yang(杨坤), Shixun Dai(戴世勋), Yuehao Wu(吴越豪), Qiuhua Nie(聂秋华)
Chin. Phys. B, 2018, 27 (11): 117701 doi: 10.1088/1674-1056/27/11/117701
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We report the fabrication and characterization of germanium gallium antimony sulfide (Ge-Ga-Sb-S or 2S2G, doped with Tm3+ ions) microsphere lasers operating at~1.9-μm spectral band. Compared to the chalcogenide glasses that are used in previous microsphere lasers, this 2S2G glass has a lower transition temperature and a higher characteristic temperature. This implies that 2S2G microspheres can be fabricated at lower temperatures and the crystallization problem in the sphere-forming process can be alleviated. We show that hundreds of high-quality microspheres (quality factors higher than 105) of various diameters can be produced simultaneously via a droplet sphere-forming method. Microspheres are coupled with silica fiber tapers for optical characterizations. We demonstrate that Whispering Gallery mode (WGM) patterns in the 1.7-2.0 μm band can be conveniently obtained and that once the pump power exceeds a threshold, single-and multi-mode microsphere lasers can be generated. For a typical microsphere whose diameter is 258.64 μm, we demonstrate its laser threshold is 0.383 mW, the laser wavelength is 1907.38 nm, and the thermal sensitivity of the microsphere laser is 29.56 pm/℃.

Temperature-dependent Raman spectroscopic study of ferroelastic K2Sr(MoO4)

Ji Zhang(张季), De-Ming Zhang(张德明), Ran-Ran Zhang(张冉冉)
Chin. Phys. B, 2018, 27 (11): 117801 doi: 10.1088/1674-1056/27/11/117801
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Raman scattering measurements of K2Sr(MoO4)2 were performed in the temperature range of 25-750℃. The Raman spectrum of the low-temperature phase α-K2Sr(MoO4)2 that was obtained by first-principle calculations indicated that the Raman bands in the wavenumber region of 250-500 cm-1 are related to Mo-O bending vibrations in MoO4 tetrahedra, while the Raman bands in the wavenumber region of 650-950 cm-1 are attributed to stretching vibrations of Mo-O bonds. The temperature-dependent Raman spectra reveal that K2Sr(MoO4)2 exhibits two sets of modifications in the Raman spectra at~150℃ and~475℃, attributed to structural phase transitions. The large change of the Raman spectra in the temperature range of 150℃ to 475℃ suggests structural instability of the medium-temperature phase β-K2Sr(MoO4)2.

Photodynamics of GaZn-VZn complex defect in Ga-doped ZnO

Ai-Hua Tang(汤爱华), Zeng-Xia Mei(梅增霞), Yao-Nan Hou(侯尧楠), Xiao-Long Du(杜小龙)
Chin. Phys. B, 2018, 27 (11): 117802 doi: 10.1088/1674-1056/27/11/117802
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The wide-band-gap II-VI compound semiconductor ZnO is regarded as a promising single-photon emission (SPE) host material. In this work, we demonstrate that a (GaZn-VZn)- complex defect can readily be obtained and the density can be controlled in a certain range. In analogy to nitrogen vacancy centers, such a defect in ZnO is expected to be a new single photon source. The optical properties of the (GaZn-VZn)- complex defect are further studied by photoluminescence and time-resolved photoluminescence spectra measurements. The electron transitions between the defect levels emit light at~650 nm with a lifetime of 10-20 nanoseconds, indicating a good coherent length for SPE. Finally, a two-level emitter structure is proposed to explain the carrier dynamics. We believe that the photodynamics study of the (GaZn-VZn)- complex defect in this work is important for ZnO-based quantum emitters.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

Excellent thermal stability and thermoelectric properties of Pnma-phase SnSe in middle temperature aerobic environment

Yu Tang(唐语), Decong Li(李德聪), Zhong Chen(陈钟), Shuping Deng(邓书平), Luqi Sun(孙璐琪), Wenting Liu(刘文婷), Lanxian Shen(申兰先), Shukang Deng(邓书康)
Chin. Phys. B, 2018, 27 (11): 118105 doi: 10.1088/1674-1056/27/11/118105
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SnSe is considered to be a promising thermoelectric material due to a high ZT value and abundant and non-toxic composition elements. However, the thermal stability is an important issue for commercial application. In particular, thermoelectric materials are in the high temperature for a long time due to the working condition. The present work investigates the thermal stability and oxidation resistance of single crystal SnSe thermoelectric materials. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that the internal of SnSe crystal is not easily oxidized, while the x-ray photoelectron spectroscopy (XPS) results indicate that the surface of SnSe is slight oxidized to SnO2. Even if the surface is oxidized, the SnSe crystal still exhibits stable thermoelectric properties. Meanwhile, the crystallization quality of SnSe samples can be improved after the appropriate heat treatment in the air, which is in favor of the carrier mobility and can improve the electrical conduction properties of SnSe. Moreover, the decrease of defect density after heat treatment can further improve the Seebeck coefficient and electrical transport properties of SnSe. The density functional theory (DFT) calculation verifies the important role of defect on the electrical conductivity and electron configuration. In summary, appropriate temperature annealing is an effective way to improve the transmission properties of SnSe single crystal thermoelectric materials.

Electronic, optical property and carrier mobility of graphene, black phosphorus, and molybdenum disulfide based on the first principles

Congcong Wang(王聪聪), Xuesheng Liu(刘学胜), Zhiyong Wang(王智勇), Ming Zhao(赵明), Huan He(何欢), Jiyue Zou(邹吉跃)
Chin. Phys. B, 2018, 27 (11): 118106 doi: 10.1088/1674-1056/27/11/118106
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The band structure, density of states, optical properties, carrier mobility, and loss function of graphene, black phosphorus (BP), and molybdenum disulfide (MoS2) were investigated by the first-principles method with the generalized-gradient approximation. The graphene was a zero-band-gap semiconductor. The band gaps of BP and MoS2 were strongly dependent on the number of layers. The relationships between layers and band gap were built to predict the band gap of few-layer BP and MoS2. The absorption showed an explicit anisotropy for light polarized in (100) and (001) directions of graphene, BP, and MoS2. This behavior may be readily detected in spectroscopic measurements and exploited for optoelectronic applications. Moreover, graphene (5.27×104 cm2·V-1·s-1), BP (1.5×104 cm2·V-1·s-1),and MoS2(2.57×102 cm2·V-1·s-1) have high carrier mobility. These results show that graphene, BP, and MoS2 are promising candidates for future electronic applications.

Dual-polarized lens antenna based on multimode metasurfaces

Hao-Fang Wang(王浩放), Zheng-Bin Wang(王正斌), Yong Cheng(程勇), Ye-Rong Zhang(张业荣)
Chin. Phys. B, 2018, 27 (11): 118401 doi: 10.1088/1674-1056/27/11/118401
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We propose a dual-polarized lens antenna system based on isotropic metasurfaces for 12 GHz applications. The metasurface lens is composed of subwavelength unit cells (0.24λ0) with metallic strips etched on the top and bottom sides of the unit cell, and a cross-slots metallic layer in the middle that serves as the ground. The multimode resonance in the unit cell can realize a large phase shift (covering 0°-360°), and the total transmission efficiency of the lens is above 80%. The feed antenna at the focal point of the lens is a broadband dual-polarized microstrip antenna. Both the simulated and the measured results demonstrate that the dual-polarized lens antenna system can realize a gain of more than 16.1 dB, and an input port isolation of more than 25.0 dB.

Design and development of radio frequency output window for circular electron-positron collider klystron

Zhijun Lu(陆志军), Shigeki Fukuda, Zusheng Zhou(周祖圣), Shilun Pei(裴士伦), Shengchang Wang(王盛昌), Ouzheng Xiao(肖欧正), UnNisa Zaib, Bowen Bai(白博文), Guoxi Pei(裴国玺), Dong Dong(董东), Ningchuang Zhou(周宁闯), Shaozhe Wang(王少哲), Yunlong Chi(池云龙)
Chin. Phys. B, 2018, 27 (11): 118402 doi: 10.1088/1674-1056/27/11/118402
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This paper presents the first phase of design, analysis, and simulation for the klystron coaxial radio frequency (RF) output window. This study is motivated by 800 kW continuous wave (CW), 650 MHz klystrons for the future plan of circular electron-positron collider (CEPC) project. The RF window which is used in the klystron output section has a function to separate the klystron from the inner vacuum side to the outside, and high RF power propagates through the window with small power dissipation. Therefore, the window is a key component for the high power klystron. However, it is vulnerable to the high thermal stress and multipacting, so this paper presents the window design and analysis for these problems. The microwave design has been performed by using the computer simulation technology (CST) microwave studio and the return loss of the window has been established to be less than-90 dB. The multipacting simulation of the window has been carried out using MultiPac and CST particles studio. Through the multipacting analysis, it is shown that with thin coating of TiN, the multipacting effect has been suppressed effectively on the ceramic surface. The thermal analysis is carried out using ANSYS code and the temperature of alumina ceramic is lower than 310 K with water cooling. The design result successfully meets the requirement of the CEPC 650 MHz klystron. The manufacturing and high power test plan are also described in this paper.

Analysis of tail bits generation of multilevel storage in resistive switching memory

Jing Liu(刘璟), Xiaoxin Xu(许晓欣), Chuanbing Chen(陈传兵), Tiancheng Gong(龚天成), Zhaoan Yu(余兆安), Qing Luo(罗庆), Peng Yuan(袁鹏), Danian Dong(董大年), Qi Liu(刘琦), Shibing Long(龙世兵), Hangbing Lv(吕杭炳), Ming Liu(刘明)
Chin. Phys. B, 2018, 27 (11): 118501 doi: 10.1088/1674-1056/27/11/118501
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The tail bits of intermediate resistance states (IRSs) achieved in the SET process (IRSS) and the RESET process (IRSR) of conductive-bridge random-access memory were investigated. Two types of tail bits were observed, depending on the filament morphology after the SET/RESET operation. (i) Tail bits resulting from lateral diffusion of Cu ions introduced an abrupt increase of device resistance from IRS to ultrahigh-resistance state, which mainly happened in IRSS. (ii) Tail bits induced by the vertical diffusion of Cu ions showed a gradual shift of resistance toward lower value. Statistical results show that more than 95% of tail bits are generated in IRSS. To achieve a reliable IRS for multilevel cell (MLC) operation, it is desirable to program the IRS in RESET operation. The mechanism of tail bit generation that is disclosed here provides a clear guideline for the data retention optimization of MLC resistive random-access memory cells.

Impact of variations of threshold voltage and hold voltage of threshold switching selectors in 1S1R crossbar array

Yu-Jia Li(李雨佳), Hua-Qiang Wu(吴华强), Bin Gao(高滨), Qi-Lin Hua(化麒麟), Zhao Zhang(张昭), Wan-Rong Zhang(张万荣), He Qian(钱鹤)
Chin. Phys. B, 2018, 27 (11): 118502 doi: 10.1088/1674-1056/27/11/118502
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The impact of the variations of threshold voltage (Vth) and hold voltage (Vhold) of threshold switching (TS) selector in 1S1R crossbar array is investigated. Based on ON/OFF state I-V curves measurements from a large number of Ag-filament TS selectors, Vth and Vhold are extracted and their variations distribution expressions are obtained, which are then employed to evaluate the impact on read process and write process in 32×32 1S1R crossbar array under different bias schemes. The results indicate that Vth and Vhold variations of TS selector can lead to degradation of 1S1R array performance parameters, such as minimum read/write voltage, bit error rate (BER), and power consumption. For the read process, a small Vhold variation not only results in the minimum read voltage increasing but it also leads to serious degradation of BER. As the standard deviation of Vhold and Vth increases, the BER and the power consumption of 1S1R crossbar array under 1/2 bias, 1/3 bias, and floating scheme degrade, and the case under 1/2 bias tends to be more serious compared with other two schemes. For the write process, the minimum write voltage also increases with the variation of Vhold from small to large value. A slight increase of Vth standard deviation not only decreases write power efficiency markedly but also increases write power consumption. These results have reference significance to understand the voltage variation impacts and design of selector properly.

Unidirectional rotation of circles driven by chiral active particles

Jiamin Chen(陈佳敏), Xiaolin Zhou(周晓琳), Linxi Zhang(章林溪)
Chin. Phys. B, 2018, 27 (11): 118701 doi: 10.1088/1674-1056/27/11/118701
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The dynamics of two-dimensional rigid circles filled with chiral active particles are investigated by employing the overdamped Langevin dynamics simulations. Unidirectional rotation of rigid circles is observed, and the rotational angular velocity (ω') relies mainly on the length (l), the number (nB), and tilt angle (γ) of boards, and the angular velocity (ω) and area fraction (ρ) of chiral active particles. There are optimum values for these parameters at which the average angular velocity of circle reaches its maximum. The center-of-mass mean square displacement for circles drops by about two orders of magnitude for large angular velocity ω of chiral active particles with oscillations in the short-time regime. Our work demonstrates that nanofabricated objects with suitable designs immersed in a bath of chiral active particles can extract and rectify energy in a unidirectional motion.

Mechanochemical model for myosin II dimer that can explain the spontaneous oscillatory contraction of muscle

Wei Sun(孙伟), Xiao-Yang Zhao(赵晓阳), Jun-Ping Zhang(张俊萍), Tala(塔拉), Wei-Sheng Guo(郭维生)
Chin. Phys. B, 2018, 27 (11): 118702 doi: 10.1088/1674-1056/27/11/118702
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The spontaneous oscillatory contraction (SPOC) of myofibrils is the essential property inherent to the contractile system of muscle. Muscle contraction results from cyclic interactions between actin filament and myosin Ⅱ which is a dimeric motor protein with two heads. Taking the two heads of myosin Ⅱ as an indivisible element and considering the effects of cooperative behavior between the two heads on rate constants in the mechanochemical cycle, the present work proposes the tenstate mechanochemical cycle model for myosin Ⅱ dimer. The simulations of this model show that the proportion of myosin Ⅱ in different states periodically changes with time, which results in the sustained oscillations of contractive tension, and serves as the primary factor for SPOC. The good fit of this model to experimental results suggests that the cooperative interaction between the two heads of myosin Ⅱ dimer may be one of the underlying mechanisms for muscle contraction.

Effects of 3.7 T–24.5 T high magnetic fields on tumor-bearing mice

Xiaofei Tian(田小飞), Ze Wang(王泽), Lei Zhang(张磊), Chuanying Xi(郗传英), Li Pi(皮雳), Ziping Qi(齐紫平), Qingyou Lu(陆轻铀), Xin Zhang(张欣)
Chin. Phys. B, 2018, 27 (11): 118703 doi: 10.1088/1674-1056/27/11/118703
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Since high magnetic field (MF) intensity can improve the image quality and reduce magnetic resonance imaging (MRI) acquisition time, the field intensity of MRIs has continued to increase over the past few decades. Although MRIs in most current hospitals are 0.5 T-3 T, there are preclinical studies have been carried out using 9.4 T MRI, and engineers are also putting efforts on building MRIs with even higher MFs. However, the accompanied safety issue of high-field MRIs is an emergent question to address before their clinical applications. In the meantime, the static magnetic field (SMF) has been shown to inhibit tumor growth in previous studies. Here, we investigated both the safety issue and the anti-tumor potentials of 3.7 T-24.5 T SMFs on GIST-T1 gastrointestinal stromal tumor-bearing nude mice. We followed up the mice three weeks after their exposure to high SMF and found that none of the mice died or had severe organ damage, except for slightly decreased food intake, weight gain, and liver function. Moreover, the tumor growth was inhibited by 3.7 T-24.5 T SMFs (up to~54%). It is interesting that the effects are more dependent on MF gradient than intensities, and for the same gradient and intensity, mice responded differently to hypogravity and hypergravity conditions. Therefore, our study not only demonstrated the safeness of high SMFs up to 24.5 T on mice but also revealed their anti-tumor potentials in the future.

Probing conformational change of T7 RNA polymerase and DNA complex by solid-state nanopores

Xin Tong(童鑫), Rui Hu(胡蕊), Xiaoqing Li(李晓晴), Qing Zhao(赵清)
Chin. Phys. B, 2018, 27 (11): 118705 doi: 10.1088/1674-1056/27/11/118705
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Proteins are crucial to most biological processes, such as enzymes, and in various catalytic processes a dynamic motion is required. The dynamics of protein are embodied as a conformational change, which is closely related to the flexibility of protein. Recently, nanopore sensors have become accepted as a low cost and high throughput method to study the features of proteins. In this article, we used a SiN nanopore device to study the flexibility of T7 RNA polymerase (RNAP) and its complex with DNA promoter. By calculating full-width at half-maximum (FWHM) of Gaussian fits to the blockade histograms, we found that T7 RNAP becomes more flexible after binding DNA promoter. Moreover, the distribution of fractional current blockade suggests that flexibility alters due to a breath-like change of the volume.

High capacity sodium-rich layered oxide cathode for sodium-ion batteries Hot!

Gen-Cai Guo(郭根材), Changhao Wang(王长昊), Bang-Ming Ming(明帮铭), Si-Wei Luo(罗斯玮), Heng Su(苏恒), Bo-Ya Wang(王博亚), Ming Zhang(张铭), Hai-Jun Yu(尉海军), Ru-Zhi Wang(王如志)
Chin. Phys. B, 2018, 27 (11): 118801 doi: 10.1088/1674-1056/27/11/118801
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Sodium-ion batteries have attracted significant recent attention currently considering the limited available lithium resource. However, the energy density of sodium-ion batteries is still insufficient compared to lithium-ion batteries, mainly because of the unavailability of high-energy cathode materials. In this work, a novel sodium-rich layered oxide material (Na2MnO3) is reported with a dynamical stability similar to that of the Li2MnO3 structure and a high capacity of 269.69 mA·h·g1, based on first-principles calculations. Sodium ion de-intercalation and anionic reaction processes are systematically investigated, in association with sodium ions migration phenomenon and structure stability during cycling of NaxMnO3 (1 ≤ x ≤ 2). In addition, the charge compensation during the initial charging process is mainly contributed by oxygen, where the small differences of the energy barriers of the paths 2c→4h, 4h→2c, 4h→4h, 2c→2b, and 4h→2b indicate the reversible sodium ion occupancy in transitional metal and sodium layers. Moreover, the slow decrease of the elastic constants is a clear indication of the high cycle stability. These results provide a framework to exploit the potential of sodium-rich layered oxide, which may facilitate the development of high-performance electrode materials for sodium-ion batteries.

Coordinated chaos control of urban expressway based on synchronization of complex networks

Ming-bao Pang(庞明宝), Yu-man Huang(黄玉满)
Chin. Phys. B, 2018, 27 (11): 118902 doi: 10.1088/1674-1056/27/11/118902
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We investigate the problem of coordinated chaos control on an urban expressway based on pinning synchronization of complex networks. A node coupling model of an urban expressway based on complex networks has been established using the cell transmission model (CTM). The pinning controller corresponding to multi-ramp coordinated controller was designed by using the delayed feedback control (DFC) method, whose objective is to realize periodical orbits from chaotic states. The concrete pinning control nodes corresponding to the subsystems of regulating the inflows from the on-ramps to the mainline were obtained and the parameters of the controller were optimized by using the stability theory of complex networks to ensure the network synchronization. The validity of the proposed coordinated chaos control method was proven via the simulation experiment. The results of the examples indicated that the order motion on urban expressway can be realized, the wide-moving traffic jam can be suppressed, and the operating efficiency is superior to that of the traditional control methods.

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