Table of contents

05 February 2019, Volume 28 Issue 2 Previous issue    Next issue

GENERAL

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Influence of random phase modulation on the imaging quality of computational ghost imaging Chao Gao(高超), Xiao-Qian Wang(王晓茜), Hong-Ji Cai(蔡宏吉), Jie Ren(任捷), Ji-Yuan Liu(刘籍元), Zhi-Hai Yao(姚治海) Chin. Phys. B, 2019, 28 (2):  020201.  DOI: 10.1088/1674-1056/28/2/020201 Abstract ( 802 )   HTML   PDF (2622KB) ( 358 )   In this paper, we investigated phase modulation-based computational ghost imaging. According to the results of numerical simulations, we found that the range of the random phase affects the quality of the reconstructed image. Besides, compared with those amplitude modulation-based computational ghost imaging schemes, introducing random phase modulation into the computational ghost imaging scheme could significantly improve the spatial resolution of the reconstructed image, and also extend the field of view.

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Dynamics of three nonisospectral nonlinear Schrödinger equations Abdselam Silem, Cheng Zhang(张成), Da-Jun Zhang(张大军) Chin. Phys. B, 2019, 28 (2):  020202.  DOI: 10.1088/1674-1056/28/2/020202 Abstract ( 823 )   HTML   PDF (5645KB) ( 279 )   Dynamics of three nonisospectral nonlinear Schrödinger equations (NNLSEs), following different time dependencies of the spectral parameter, are investigated. First, we discuss the gauge transformations between the standard nonlinear Schrödinger equation (NLSE) and its first two nonisospectral counterparts, for which we derive solutions and infinitely many conserved quantities. Then, exact solutions of the three NNLSEs are derived in double Wronskian terms. Moreover, we analyze the dynamics of the solitons in the presence of the nonisospectral effects by demonstrating how the shapes, velocities, and wave energies change in time. In particular, we obtain a rogue wave type of soliton solutions to the third NNLSE.

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Evolutionary game dynamics of combining the Moran and imitation processes Xian-Jia Wang(王先甲), Cui-Ling Gu(顾翠伶), Shao-Jie Lv(吕少杰), Ji Quan(全吉) Chin. Phys. B, 2019, 28 (2):  020203.  DOI: 10.1088/1674-1056/28/2/020203 Abstract ( 646 )   HTML   PDF (499KB) ( 214 )   One of the assumptions of previous research in evolutionary game dynamics is that individuals use only one rule to update their strategy. In reality, an individual's strategy update rules may change with the environment, and it is possible for an individual to use two or more rules to update their strategy. We consider the case where an individual updates strategies based on the Moran and imitation processes, and establish mixed stochastic evolutionary game dynamics by combining both processes. Our aim is to study how individuals change strategies based on two update rules and how this affects evolutionary game dynamics. We obtain an analytic expression and properties of the fixation probability and fixation times (the unconditional fixation time or conditional average fixation time) associated with our proposed process. We find unexpected results. The fixation probability within the proposed model is independent of the probabilities that the individual adopts the imitation rule update strategy. This implies that the fixation probability within the proposed model is equal to that from the Moran and imitation processes. The one-third rule holds in the proposed mixed model. However, under weak selection, the fixation times are different from those of the Moran and imitation processes because it is connected with the probability that individuals adopt an imitation update rule. Numerical examples are presented to illustrate the relationships between fixation times and the probability that an individual adopts the imitation update rule, as well as between fixation times and selection intensity. From the simulated analysis, we find that the fixation time for a mixed process is greater than that of the Moran process, but is less than that of the imitation process. Moreover, the fixation times for a cooperator in the proposed process increase as the probability of adopting an imitation update increases; however, the relationship becomes more complex than a linear relationship.

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Competitive and synergistic adsorption of binary volatile organic compound mixtures on activated carbon Jing Zhu(祝静), Hong-Lei Zhan(詹洪磊), Kun Zhao(赵昆), Xin-Yang Miao(苗昕扬), Qiong Zhou(周琼), Wen-Zheng Yue(岳文正) Chin. Phys. B, 2019, 28 (2):  020204.  DOI: 10.1088/1674-1056/28/2/020204 Abstract ( 721 )   HTML   PDF (1249KB) ( 207 )   The adsorption of four substances and their binary mixture is investigated via the terahertz time domain spectroscopy (THz-TDS). The selected unary compound (ethanol, acetone, ethyl acetate, and n-propyl acetate) and binary mixture (solution 1 is composed of ethanol and acetone, and solution 2 is composed of ethyl acetate and n-propyl acetate) exhibit different adsorption behaviors with varied polarities. In comparison with single component, solution 1 shows shorter adsorption equilibrium time, faster adsorption rate, and stronger adsorption capacity, which conform to a synergistic adsorption mechanism, while the competitive behavior is attributed to the slower adsorption in solution 2. In addition, the pseudo-second-order equation with terahertz parameter is used to assess the rate of binary component organics. The present results indicate a further understanding of multicomponent adsorption mechanisms.

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Error-detected single-photon quantum routing using a quantum dot and a double-sided microcavity system A-Peng Liu(刘阿鹏), Liu-Yong Cheng(程留永), Qi Guo(郭奇), Shi-Lei Su(苏石磊), Hong-Fu Wang(王洪福), Shou Zhang(张寿) Chin. Phys. B, 2019, 28 (2):  020301.  DOI: 10.1088/1674-1056/28/2/020301 Abstract ( 739 )   HTML   PDF (914KB) ( 276 )   Based on a hybrid system consisting of a quantum dot coupled with a double-sided micropillar cavity, we investigate the implementation of an error-detected photonic quantum routing controlled by the other photon. The computational errors from unexpected experimental imperfections are heralded by single photon detections, resulting in a unit fidelity for the present scheme, so that this scheme is intrinsically robust. We discuss the performance of the scheme with currently achievable experimental parameters. Our results show that the present scheme is efficient. Furthermore, our scheme could provide a promising building block for quantum networks and distributed quantum information processing in the future.

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Realization of t-bit semiclassical quantum Fourier transform on IBM's quantum cloud computer Xiang-Qun Fu(付向群), Wan-Su Bao(鲍皖苏), He-Liang Huang(黄合良), Tan Li(李坦), Jian-Hong Shi(史建红), Xiang Wang(汪翔), Shuo Zhang(张硕), Feng-Guang Li(李风光) Chin. Phys. B, 2019, 28 (2):  020302.  DOI: 10.1088/1674-1056/28/2/020302 Abstract ( 766 )   HTML   PDF (502KB) ( 270 )   To overcome the difficulty of realizing large-scale quantum Fourier transform (QFT) within existing technology, this paper implements a resource-saving method (named t-bit semiclassical QFT over Z2n), which could realize large-scale QFT using an arbitrary-scale quantum register. By developing a feasible method to realize the control quantum gate Rk, we experimentally realize the 2-bit semiclassical QFT over Z23 on IBM's quantum cloud computer, which shows the feasibility of the method. Then, we compare the actual performance of 2-bit semiclassical QFT with standard QFT in the experiments. The squared statistical overlap experimental data shows that the fidelity of 2-bit semiclassical QFT is higher than that of standard QFT, which is mainly due to fewer two-qubit gates in the semiclassical QFT. Furthermore, based on the proposed method, N=15 is successfully factorized by implementing Shor's algorithm.

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Phase diagram of interacting fermionic two-leg ladder with pair hopping Hot! Wan-Li Liu(刘万里), Tian-Zhong Yuan(原天忠), Zhi Lin(林志), Wei Yan(闫伟) Chin. Phys. B, 2019, 28 (2):  020303.  DOI: 10.1088/1674-1056/28/2/020303 Abstract ( 910 )   HTML   PDF (795KB) ( 297 )   We study the phase diagram of the interacting fermionic two-leg ladder, which is featured by pair hopping and interactions of singlet and triplet superconducting channels. By using Abelian bosonization method, we obtain the full phase diagram of our model. The superconducting triplet pairing phase is characterized by a fractional edge spin and interpreted as two Kitaev chains under the mean filed approximation. The pair hopping will give rise to spin-density-wave (SDW) orders and can also support Majorana edge modes in spin channel. At half filling, the resulting Majorana-SDW phase shows additional fractionalization in charge channel, and can be interpreted as two Su-Schrieffer-Heeger (SSH) chains in the mean field regime.

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Nodes and layers PageRank centrality for multilayer networks Lai-Shui Lv(吕来水), Kun Zhang(张琨), Ting Zhang(张婷), Meng-Yue Ma(麻孟越) Chin. Phys. B, 2019, 28 (2):  020501.  DOI: 10.1088/1674-1056/28/2/020501 Abstract ( 917 )   HTML   PDF (1096KB) ( 279 )   In this paper, we propose a new centrality algorithm that can simultaneously rank the nodes and layers of multilayer networks, referred to as the MRFNL centrality. The centrality of nodes and layers are obtained by developing a novel iterative algorithm for computing a set of tensor equations. Under some conditions, the existence and uniqueness of this centrality were proven by applying the Brouwer fixed point theorem. Furthermore, the convergence of the proposed iterative algorithm was established. Finally, numerical experiments on a simple multilayer network and two real-world multilayer networks (i.e., Pierre Auger Collaboration and European Air Transportation Networks) are proposed to illustrate the effectiveness of the proposed algorithm and to compare it to other existing centrality measures.

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Energy feedback and synchronous dynamics of Hindmarsh-Rose neuron model with memristor K Usha, P A Subha Chin. Phys. B, 2019, 28 (2):  020502.  DOI: 10.1088/1674-1056/28/2/020502 Abstract ( 883 )   HTML   PDF (2937KB) ( 452 )   We analyze the energy aspects of single and coupled Hindmarsh-Rose (HR) neuron models with a quadratic flux controlled memristor. The energy function for HR neuron with memristor has been derived and the dynamics have been analyzed in the presence of various external stimuli. We found that the bursting mode of the system changes with external forcing. The negative feedback in Hamilton energy function effectively stabilizes the chaotic trajectories and controls the phase space. The Lyapunov exponents have been plotted to verify the stabilization of trajectories. The energy aspects during the synchronous dynamics of electrically coupled neurons have been analyzed. As the coupling strength increases, the average energy fluctuates and stabilizes at the point of synchronization. When the neurons are coupled via chemical synapse, the average energy variations show three important regimes:a fluctuating regime corresponding to the desynchronized, a stable region indicating synchronized and a linearly increasing regime corresponding to the amplitude death states have been observed. The synchronization transitions are verified by plotting the transverse Lyapunov exponents. The proposed method has a large number of applications in controlling coupled chaotic systems and in analyzing the energy change during various metabolic processes.

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Design new chaotic maps based on dimension expansion Abdulaziz O A Alamodi, Kehui Sun(孙克辉), Wei Ai(艾维), Chen Chen(陈晨), Dong Peng(彭冬) Chin. Phys. B, 2019, 28 (2):  020503.  DOI: 10.1088/1674-1056/28/2/020503 Abstract ( 750 )   HTML   PDF (19412KB) ( 246 )   Based on the high-dimensional (HD) chaotic maps and the sine function, a new methodology of designing new chaotic maps using dimension expansion is proposed. This method accepts N dimensions of any existing HD chaotic map as inputs to generate new dimensions based on the combined results of those inputs. The main principle of the proposed method is to combine the results of the input dimensions, and then performs a sine-transformation on them to generate new dimensions. The characteristics of the generated dimensions are totally different compared to the input dimensions. Thus, both of the generated dimensions and the input dimensions are used to create a new HD chaotic map. An example is illustrated using one of the existing HD chaotic maps. Results show that the generated dimensions have better chaotic performance and higher complexity compared to the input dimensions. Results also show that, in the most cases, the generated dimensions can obtain robust chaos which makes them attractive to usage in a different practical application.

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Dynamical stable-jump-stable-jump picture in a non-periodically driven quantum relativistic kicked rotor system Hsincheng Yu(于心澄), Zhongzhou Ren(任中洲), Xin Zhang(张欣) Chin. Phys. B, 2019, 28 (2):  020504.  DOI: 10.1088/1674-1056/28/2/020504 Abstract ( 793 )   HTML   PDF (945KB) ( 218 )   We study a non-periodically driven kicked rotor based on the one-dimensional quantum relativistic kicked rotor (QRKR). In our model, we add a small constant to the interval of the one-dimensional QRKR after each kick process. It is found that the momentum spreading is stable in finite kicked times, it then jumps up or down and becomes stable again. This interesting phenomenon is understood by quantum resonance. Moreover, the stable-jump-stable-jump phenomenon persists, even though the interval of kick process is randomly increased. This result means that the quantum resonance is independent of the periodic perturbation in the QRKR model.

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One-dimensional mass transport with dynamic external potentials Xingxing Zhang(张星星), Dongqin Zheng(郑冬琴), Weirong Zhong(钟伟荣) Chin. Phys. B, 2019, 28 (2):  020505.  DOI: 10.1088/1674-1056/28/2/020505 Abstract ( 722 )   HTML   PDF (648KB) ( 168 )   Using non-equilibrium molecular dynamics and the Monte Carlo method, we simulated mass transport in a one-dimensional channel with dynamic external potentials. This study focuses on the influence of the dynamic external potential field on the mass transport. Traveling wave and standing wave potential fields have been employed as our dynamic potential field. We found that mass transport can be promoted by the traveling wave field when the external potential moves along the direction of the mass current. When the standing wave field is exerted on the channel, the channel is found to work like a switch. The mass current can be “on” or “off” by adjusting the standing wave frequency. The effects of the period number, the amplitude and the velocity of the external potential on the mass transport are also discussed. Our research provides valuable advice for the control o particle transport through one-dimensional channels.

TOPICAL REVIEW—Photodetector: materials, physics, and applications

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Recent progress of infrared photodetectors based on lead chalcogenide colloidal quantum dots Jinming Hu(胡津铭), Yuansheng Shi(史源盛), Zhenheng Zhang(张珍衡), Ruonan Zhi(智若楠), Shengyi Yang(杨盛谊), Bingsuo Zou(邹炳锁) Chin. Phys. B, 2019, 28 (2):  020701.  DOI: 10.1088/1674-1056/28/2/020701 Abstract ( 1085 )   HTML   PDF (5611KB) ( 759 )   Commercial photodetectors based on silicon are extensively applied in numerous fields. Except for their high performance, their maximum absorption wavelength is not over than 1100 nm and incident light with longer wavelengths cannot be detected; in addition, their cost is high and their manufacturing process is complex. Therefore, it is meaningful and significant to extend absorption wavelength, to decrease cost, and to simplify the manufacturing process while maintaining high performance for photodetectors. Due to the properties of size-dependent bandgap tunability, low cost, facile processing, and substrate compatibility, solution-processed colloidal quantum dots (CQDs) have recently gained significant attention and become one of the most competitive and promising candidates for optoelectronic devices. Among these CQDs, lead chalcogenide CQDs are getting very prominent and are widely investigated. In this paper, the recent progress of infrared (IR) photodetectors based on lead sulfide (PbS), lead selenide (PbSe), and ternary PbSxSe1-x CQDs, and their underlying concepts, breakthroughs, and remaining challenges are reviewed, thus providing guidance for designing high-performance quantum-dot IR photodetectors.

ATOMIC AND MOLECULAR PHYSICS

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Imaging alignment of rotational state-selected CH3I molecule Le-Le Song(宋乐乐), Yan-Hui Wang(王艳辉), Xiao-Chun Wang(王晓春), Hong-Tao Sun(孙洪涛), Lan-Hai He(赫兰海), Si-Zuo Luo(罗嗣佐), Wen-Hui Hu(胡文惠), Dong-Xu Li(李东旭), Wen-Hui Zhu(朱文会), Ya-Nan Sun(孙亚楠), Da-Jun Ding(丁大军), Fu-Chun Liu(刘福春) Chin. Phys. B, 2019, 28 (2):  023101.  DOI: 10.1088/1674-1056/28/2/023101 Abstract ( 723 )   HTML   PDF (967KB) ( 257 )   We experimentally and numerically investigate CH3I molecular alignment by using a femtosecond laser and a hexapole. The hexapole provides the |111> rotational state condition at 4.5-kV hexapole rod voltage. Based on this single rotational state, an enhanced alignment degree of 0.73 is achieved. Our experimental results are in agreement with the simulation results. We experimentally obtain the ion velocity map images and show the influence of the initial rotational-state population. With the I+ ion images and angular distributions at different pump-probe delay time, the alignment and anti-alignment phenomena are further demonstrated. The molecules will be under field-free conditions when the laser effect disappears completely at the full revival time. Our work shows that the quantum control and spatial control on CH3I molecules can be realized and molecular coordinate frame can be obtained for further molecular experiment.

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Reaction mechanism of D+ND→N+D2 and its state-to-state quantum dynamics Ting Xu(许婷), Juan Zhao(赵娟), Xian-Long Wang(王宪龙), Qing-Tian Meng(孟庆田) Chin. Phys. B, 2019, 28 (2):  023102.  DOI: 10.1088/1674-1056/28/2/023102 Abstract ( 868 )   HTML   PDF (863KB) ( 236 )   The quantum state-to-state calculations of the D+ND→N+D2 reaction are performed on a potential energy surface of 4A" state. The state-resolved integral and differential cross sections and product state distributions are calculated and discussed. It is found that the rotational distribution, rather than the vibrational distribution, of the product has an obvious inversion. Due to the fact that it is a small-impact-parameter collision, its product D2 is mainly dominated by rebound mechanism, which can lead to backward scattering at low collision energy. As the collision energy increases, the forward scattering and sideward scattering begin to appear. In addition, the backward collision is also found to happen at high collision energy, through which we can know that both the rebound mechanism and stripping mechanism exist at high collision energy.

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Quantum photodetachment of hydrogen negative ion in a harmonic potential subjected to static electric field Azmat Iqbal, Kiran Humayun, Sana Maqsood, Saba Jawaid, Afaq Ahmad, Amin Ur Rahman, Bakht Amin Bacha Chin. Phys. B, 2019, 28 (2):  023201.  DOI: 10.1088/1674-1056/28/2/023201 Abstract ( 802 )   HTML   PDF (560KB) ( 846 )   Photodetachment of negative ions has attracted immense interest owing to its fundamental nature and practical implications with regard to technology. In this study, we explore the quantum dynamics of the photodetachment cross section of negative ion of hydrogen H- in the perturbed one dimensional linear harmonic potential via static electric field. To this end, the quantum formula for total photodetachment cross section of the H- ion is derived by calculating the dipole matrix element in spherical coordinates. In order to obtain the detached electron wave function, we have solved the time-independent Schrödinger wave equation for the perturbed Hamiltonian of the harmonic oscillator in momentum representation. To acquire the corresponding normalized final state detached electron wave function in momentum space, we have employed an approach analogous to the WKB (Wenzel-Kramers-Brillouin) approximation. The resulting analytical formula of total photodetachment cross section depicts interesting oscillator structure that varies considerably with incident-photon energy, oscillator potential frequency, and electric field strength as elucidated by the numerical results. The current problem having close analogy with the Stark effect in charged harmonic oscillator may have potential implications in atomic and molecular physics and quantum optics.

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Angle-resolved spectra of the direct above-threshold ionization of diatomic molecule in IR+XUV laser fields Shang Shi(石尚), Fa-Cheng Jin(金发成), Bing-Bing Wang(王兵兵) Chin. Phys. B, 2019, 28 (2):  023202.  DOI: 10.1088/1674-1056/28/2/023202 Abstract ( 839 )   HTML   PDF (2369KB) ( 245 )   The direct above-threshold ionization (ATI) of diatomic molecules in linearly-polarized infrared and extreme ultraviolet (IR+XUV) laser fields is investigated by the frequency-domain theory based on the nonperturbative quantum electrodynamics. The destructive interference fringes on the angle-resolved ATI spectra, which are closely related to the molecular structure, can be well fitted by a simple predictive formula for any alignment of the molecular axis. By comparing the direct ATI spectra for monochromatic and two-color laser fields, we found that the XUV laser field can both raise the ionization probability and the kinetic energy of the ionized electron, while the infrared (IR) laser field can broaden the energy distribution of the ionized electron. Our results demonstrate that, by using IR+XUV two-color laser fields, the angle-resolved spectra of the direct ATI can image the structural information of molecules without considering the recollision process of the ionized electron.

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Comparison of single-neutral-atom qubit between in bright trap and in dark trap Ya-Li Tian(田亚莉), Zhi-Hui Wang(王志辉), Peng-Fei Yang(杨鹏飞), Peng-Fei Zhang(张鹏飞), Gang Li(李刚), Tian-Cai Zhang(张天才) Chin. Phys. B, 2019, 28 (2):  023701.  DOI: 10.1088/1674-1056/28/2/023701 Abstract ( 943 )   HTML   PDF (1150KB) ( 200 )   A single neutral atom is one of the most promising candidates to encode a quantum bit (qubit). In a real experiment, a single neutral atom is always confined in a micro-sized far off-resonant optical trap (FORT). There are generally two types of traps:red-detuned trap and blue-detuned trap. We experimentally compare the qubits encoded in “clock states” of single cesium atoms confined separately in either 1064-nm red-detuned (bright) trap or 780-nm blue-detuned (dark) trap:both traps have almost the same trap depth. A longer lifetime of 117 s and a longer coherence time of about 10 ms are achieved in the dark trap. This provides a direct proof of the superiority of the dark trap over the bright trap. The measures to further improve the coherence are discussed.

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

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Nonreciprocal transmission of electromagnetic waves by three-layer magneto-optical mediums Guan-Xia Yu(余观夏), Jing-Jing Fu(付晶晶), Wen-Wen Du(杜文文), Yi-Hang Lv(吕一航), Min Luo(骆敏) Chin. Phys. B, 2019, 28 (2):  024101.  DOI: 10.1088/1674-1056/28/2/024101 Abstract ( 831 )   HTML   PDF (1619KB) ( 214 )   We investigate the non-reciprocal transmission properties of a three-layer structure filled with magneto-optical medium and normal medium. Based on the transfer matrix method, we deduce the total transmission coefficient for a one-dimensional (1D) structure with anisotropic mediums. When two-side layers with magneto-optical medium loaded in opposite external magnetic field, the time-reversal symmetry of transmission properties will be broken. Our numerical results show that the non-reciprocal transmission properties are influenced by external magnetic fields, incident angle, and thickness of the normal medium layer. Since the non-reciprocal properties can be easily realized and adjusted by the simple structure, such a design has potential applications in integrated circulators and isolators.

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Key design parameters and optimum method of medium- and high-velocity synchronous induction coilgun based on orthogonal experimental design Kai-Pei Liu(刘开培), Xiao-Bo Niu(牛小波), Ya-Dong Zhang(张亚东), Zeng-Chao Ji(季曾超), Jian-Yuan Feng(冯建源), Wen-Qi Li(李文琦) Chin. Phys. B, 2019, 28 (2):  024102.  DOI: 10.1088/1674-1056/28/2/024102 Abstract ( 673 )   HTML   PDF (754KB) ( 264 )   The energy conversion efficiency of a multistage synchronous induction coilgun (MSSICG) has become one of the key factors that restricts its industrialization. To improve the launch efficiency of medium- and high-velocity MSSICG, we propose an optimization design scheme combining orthogonal experimental design (OED) and self-consistent design method in this paper. The OED is introduced to reduce the number of iterations and improve the identification accuracy and efficiency. A self-consistent design model is established to overcome a defect that the parameters that need to be optimized will multiply as the number of coil stages increases. The influence of six factors (radial thickness of armature, axial length of armature, axial length of coil, capacitance, wire diameter, and slip speed) on the launch efficiency are then evaluated by range analysis. This work presents a valuable reference for optimizing medium- and high-velocity MSSICG.

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Propagation of a Pearcey beam in uniaxial crystals Chuangjie Xu(许创杰), Ludong Lin(林露东), Zhengzhong Huang(黄郑重), Donglong He(何东龙), Dongmei Deng(邓冬梅) Chin. Phys. B, 2019, 28 (2):  024201.  DOI: 10.1088/1674-1056/28/2/024201 Abstract ( 855 )   HTML   PDF (3193KB) ( 214 )   An analytical propagation expression of a Pearcey beam in uniaxial crystals orthogonal to the optical axis is derived. The propagations of the Pearcey beam in the tourmaline and the quartz are investigated. The phase distribution and the angular momentum of the Pearcey beam in the tourmaline are also performed. The result shows that the positions of the auto-focusing and the inversion simply relate to the extraordinary refractive index of the crystals. In other words, we can choose the suitable crystals to adjust the positions of auto-focusing and inversion of the Pearcey beam to meet the actual needs.

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Reflected and transmitted powers of arbitrarily polarized plane waves at interface between chiral and achiral media Yan-Feng Lu(路彦峰), Yi-Ping Han(韩一平) Chin. Phys. B, 2019, 28 (2):  024202.  DOI: 10.1088/1674-1056/28/2/024202 Abstract ( 598 )   HTML   PDF (1068KB) ( 170 )   A study has been made on the reflected and transmitted powers generated when an arbitrarily polarized plane wave impinges at a planar interface separating an isotropic achiral medium (IAM) and an isotropic chiral medium (ICM). It follows that the theoretical formulas are derived for the normalized reflection and transmission powers from an IAM-ICM interface for an arbitrary polarized incident wave, and those at an ICM-IAM interface for right-hand circularly polarized (RCP) or left-hand circularly polarized (LCP) incident wave are also obtained. The behavior of the reflected and transmitted waves in different cases is studied, and the dependence of the reflection/transmission of the incident wave on the incident angle and the parameters of the media is investigated in detail. Our numerical results show that high transmission is exhibited under the impedance matching condition and the incident wave can be split into two waves of the same circular polarization state in the case of the ICM-IAM interface, which indicates that circular polarizing beam splitter is achieved.

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Numerical study of optical trapping properties of nanoparticle on metallic film with periodic structure Cheng-Xian Ge(葛城显), Zhen-Sen Wu(吴振森), Jing Bai(白靖), Lei Gong(巩蕾) Chin. Phys. B, 2019, 28 (2):  024203.  DOI: 10.1088/1674-1056/28/2/024203 Abstract ( 688 )   HTML   PDF (2343KB) ( 180 )   Based on the three-dimensional dispersive finite difference time domain method and Maxwell stress tensor equation, the optical trapping properties of nanoparticle placed on the gold film with periodic circular holes are investigated numerically. Surface plasmon polaritons are excited on the metal-dielectric interface, with particular emphasis on the crucial role in tailoring the optical force acting on a nearby nanoparticle. Utilizing a first order corrected electromagnetic field components for a fundamental Gaussian beam, the incident beam is added into the calculation model of the proposed method. To obtain the detailed trapping properties of nanoparticle, the selected calculations on the effects of beam waist radius, sizes of nanoparticle and circular holes, distance between incident Gaussian beam and gold film, material of nanoparticle and polarization angles of incident wave are analyzed in detail to demonstrate that the optical-trapping force can be explained as a virtual spring which has a restoring force to perform positive and negative forces as a nanoparticle moves closer to or away from the centers of circular holes. The results of optical trapping properties of nanoparticle in the vicinity of the gold film could provide guidelines for further research on the optical system design and manipulation of arbitrary composite nanoparticles.

TOPICAL REVIEW—Fundamental research under high magnetic fields

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Physics of quantum coherence in spin systems Maimaitiyiming Tusun(麦麦提依明·吐孙), Xing Rong(荣星), Jiangfeng Du(杜江峰) Chin. Phys. B, 2019, 28 (2):  024204.  DOI: 10.1088/1674-1056/28/2/024204 Abstract ( 1140 )   HTML   PDF (9653KB) ( 572 )   Quantum computation provides a great speedup over its classical counterpart in solving some hard problems. The advantages of quantum computation come from the coherent superposition principle of quantum mechanics. Spin system is one of the most significant candidates to realize quantum computation. In this review, we focus on the recent experimental progress related to quantum coherence and some fundamental concepts such as the uncertainty principle in the spin systems. We shall first briefly introduce the quantum description of qubit, coherence, and decoherence. Based on this picture, preserving quantum coherence and detection of weak magnetic fields are presented. We also discuss the realization of precise quantum coherent control, adiabatic quantum factorization algorithm, and two aspects of uncertainty relations.

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

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Effect of thermally induced birefringence on high power picosecond azimuthal polarization Nd:YAG laser system Hongpan Peng(彭红攀), Ce Yang(杨策), Shang Lu(卢尚), Ning Ma(马宁), Meng Chen(陈檬) Chin. Phys. B, 2019, 28 (2):  024205.  DOI: 10.1088/1674-1056/28/2/024205 Abstract ( 790 )   HTML   PDF (1381KB) ( 233 )   Pulse-burst 1064-nm picosecond azimuthal polarization beam amplification up to an average power of 16.32 W using side-pumped Nd: YAG amplifiers has been demonstrated. The maximum envelop energy as much as 16.32 mJ, corresponding to a power amplification factor of 299.5%. A simple criterion was defined to help estimate the amount of depolarization in Nd:YAG amplifier stages. The degree of depolarization of the beam was 7.1% and the beam quality was measured to be M2 = 3.69. The reason for the azimuthal polarization depolarization and beam quality degradation were explained theoretically and experimentally during the amplification process.

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Amplitude and phase controlled absorption and dispersion of coherently driven five-level atom in double-band photonic crystal Li Jiang(姜丽), Ren-Gang Wan(万仁刚) Chin. Phys. B, 2019, 28 (2):  024206.  DOI: 10.1088/1674-1056/28/2/024206 Abstract ( 696 )   HTML   PDF (889KB) ( 155 )   The absorption-dispersion properties of a microwave-driven five-level atom embedded in an isotropic photonic bandgap (PBG) have been studied. Due to the singular density of modes (DOM) in the isotropic PBG and the dynamically coherence induced by the coupling fields, modified reservoir-induced transparency and quantum interference-induced transparency emerge simultaneously. Their interaction leads to ultra-narrow spectral structure. As a result of closed-loop configuration, these features can be manipulated by the amplitudes and relative phase of the coherently driven fields. The position and width of PBG also have an influence on the spectra. The theoretical studies can provide us with more efficient methods to control the atomic absorption-dispersion properties, which have applications in optical switching and slow light.

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Controllable photon echo phase induced by modulated pulses and chirped beat detection Xian-Yang Zhang(张显扬), Shuang-Gen Zhang(张双根), Hua-Di Zhang(张化迪), Xiu-Rong Ma(马秀荣) Chin. Phys. B, 2019, 28 (2):  024207.  DOI: 10.1088/1674-1056/28/2/024207 Abstract ( 735 )   HTML   PDF (902KB) ( 230 )   In this paper, we propose a scheme for photon echo chirped detection process composed of additional modulation pulses to obtain controllable geometric phase. The geometric phases are observed and measured by a beat signal between the photon echo field and the chirped field. The chirped detection model reveals that the period of the beat signal increases as the chirped rate and delay time increase. Additionally, a two-fold relationship between the modulation phase and the echo shift phase is obtained. The numerical simulations accord with the theoretical results obtained by the finite difference time domain (FDTD) method.

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Power of all-fiber amplifier increasing from 1030 W to 2280 W through suppressing mode instability by increasing the seed power Xue-Xue Luo(罗雪雪), Ru-Mao Tao(陶汝茂), Chen Shi(史尘), Han-Wei Zhang(张汉伟), Xiao-Lin Wang(王小林), Pu Zhou(周朴), Xiao-Jun Xu(许晓军) Chin. Phys. B, 2019, 28 (2):  024208.  DOI: 10.1088/1674-1056/28/2/024208 Abstract ( 682 )   HTML   PDF (817KB) ( 233 )   In this work, we investigate suppressing mode instability in detail by varying the seed power in a large mode area all-fiber amplifier with a fiber core diameter of 25 μm. The transverse mode instability (TMI) thresholds are systematically measured for different seed power. Our experimental results reveal that increasing the seed power has a positive influence on enhancing the output power before the TMI effect appears, and finally the TMI threshold is approximately doubled from 1030 W to 2280 W when the seed power is increased from 27 W to 875 W. Almost 84.7% slope efficiency is reached with different seed power before the TMI threshold power. During our operation, we also find that in this type of LMA fiber the beam quality of the amplifier is degraded gradually instead of a sudden change as the pump power increases.

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Experimental and numerical investigation of mid-infrared laser in Pr3+-doped chalcogenide fiber Hua Chen(陈华), Ke-Lun Xia(夏克伦), Zi-Jun Liu(刘自军), Xun-Si Wang(王训四), Xiang-Hua Zhang(章向华), Yin-Sheng Xu(许银生), Shi-Xun Dai(戴世勋) Chin. Phys. B, 2019, 28 (2):  024209.  DOI: 10.1088/1674-1056/28/2/024209 Abstract ( 809 )   HTML   PDF (868KB) ( 270 )   We report on a chalcogenide glass fiber doped with Pr3+ that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm-5.5 μm fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89-μm wavelength, with a pump power of 5 W, excitation wavelength at 2.04 μm, Pr3+ ion concentration at 4.22×1025 ions/m3, fiber length at 0.94 m, and fiber background loss at 3 dB/m.

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Analysis of CV mode selected resonator based on vectorial eigenvector method You-You Hu(胡友友), Jian-Tai Dou(窦健泰), Bo-Wei Luo(罗博伟), Chang-Yu He(贺昌玉) Chin. Phys. B, 2019, 28 (2):  024210.  DOI: 10.1088/1674-1056/28/2/024210 Abstract ( 672 )   HTML   PDF (3438KB) ( 183 )   The vectorial eigenvector method was applied to compute the cylindrical vector (CV) modes of polarization-dependent resonators and multiple modes in the CV mode selected resonator were tracked. Then, the mode characteristics of CV mode selected resonator depending on the Fresnel number, geometry parameters, and polarization parameters were simulated. When the difference in reflection coefficient between radial and azimuthal polarization is greater than 0.021 for spherical semi-confocal cavity, the radially polarized TM01* mode most probably appears in the resonator due to its lowest loss, which is consistent with an azimuthal polarization-selective resonant cavity. Moreover, the appropriate phase shift factor contributes to suppress non-rotationally symmetrical modes, which promotes the selection of CV modes. The Fresnel number between 2 and 2.5 are the appropriate range of values when the value of geometry parameters g2 is 0.5, both of which decide the effective Fresnel number.

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Nonlinear behavior of the population dynamics of three-level systems in the presence of single photon absorption Allam Srinivasa Rao Chin. Phys. B, 2019, 28 (2):  024211.  DOI: 10.1088/1674-1056/28/2/024211 Abstract ( 827 )   HTML   PDF (1289KB) ( 218 )   We numerically investigate the population dynamics in a single photon resonant three-level cascade and non-cascade energy level molecules at 532-nm wavelength. The time-dependent population in the energy levels in the presence of 100 ps (pico-second) and 100 ns (nano-second) laser pulses is described in the form of rate equations. We provide a brief idea of how the optical energy transfer takes place in the light-matter interaction and we also discuss the absorption as a function of pulse width and repetition rate. We also plot the z-scan transmittance curve as a function of number of excitation pulses participating in the absorption.

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High-gain and low-distortion Brillouin amplification based on pump multi-frequency intensity modulation Li-Wen Sheng(盛立文), De-Xin Ba(巴德欣), Zhi-Wei Lv(吕志伟) Chin. Phys. B, 2019, 28 (2):  024212.  DOI: 10.1088/1674-1056/28/2/024212 Abstract ( 693 )   HTML   PDF (562KB) ( 206 )   Using a pump with a multi-line spectrum to broaden the Brillouin gain bandwidth is an effective way to achieve low-distortion amplification with high gain. Here, we theoretically and experimentally investigate the generation of a broadband Brillouin gain spectrum based on multi-frequency intensity modulation in an optical fiber. The arbitrary bandwidth of the Brillouin gain spectrum of stimulated Brillouin scattering (SBS) can be obtained as expected. In our experiment, a broadband Brillouin gain spectrum with a bandwidth of about 200 MHz is demonstrated. We also achieve a low-distortion amplification of a weak signal, whose maximum magnification is 65 dB for a -68-dBm input power signal.

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Feasibility analysis for acquiring visibility based on lidar signal using genetic algorithm-optimized back propagation algorithm Guo-Dong Sun(孙国栋), Lai-An Qin(秦来安), Zai-Hong Hou(侯再红), Xu Jing(靖旭), Feng He(何枫), Feng-Fu Tan(谭逢富), Si-Long Zhang(张巳龙), Shou-Chuan Zhang(张守川) Chin. Phys. B, 2019, 28 (2):  024213.  DOI: 10.1088/1674-1056/28/2/024213 Abstract ( 938 )   HTML   PDF (2572KB) ( 196 )   Visibility is an important atmospheric parameter that is gaining increasing global attention. This study introduces a back-propagation neural network method based on genetic algorithm optimization to obtain visibility directly using light detection and ranging (lidar) signals instead of acquiring extinction coefficient. We have validated the performance of the novel method by comparing it with the traditional inversion method, the back-propagation (BP) neural network method, and the Belfort, which is used as a standard value. The mean square error (MSE) and mean absolute percentage error (MAPE) values of the genetic algorithm-optimized back propagation (GABP) method are located in the range of 0.002 km2-0.005 km2 and 1%-3%, respectively. However, the MSE and MAPE values of the traditional inversion method and the BP method are significantly higher than those of the GABP method. Our results indicate that the proposed algorithm achieves better performance and can be used as a valuable new approach for visibility estimation.

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Influence of low-temperature sulfidation on the structure of ZnS thin films Shuzhen Chen(陈书真), Ligang Song(宋力刚), Peng Zhang(张鹏), Xingzhong Cao(曹兴忠), Runsheng Yu(于润升), Baoyi Wang(王宝义), Long Wei(魏龙), Rengang Zhang(张仁刚) Chin. Phys. B, 2019, 28 (2):  024214.  DOI: 10.1088/1674-1056/28/2/024214 Abstract ( 747 )   HTML   PDF (881KB) ( 203 )   ZnS thin films were prepared by sulfuring zinc thin films at different sulfuration temperatures. The crystal structure, surface morphology, defects, and optical properties of the thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), positron annihilation Doppler broadening, and UV-Vis spectrophotometer, respectively. It was found that the (200)-plane preferred orientation of the ZnS thin films changed to (111)-plane with increasing sulfidation temperature. Moreover, a number of large holes were generated at 420℃ and eliminated at 440℃. The concentration of defects was lowest when the sulfuration temperature was 440℃. The optical transmission of all samples was maintained at 60%-80% in the wavelength range of 400 nm-800 nm, and the band energy of the ZnS thin films was approximately 3.5 eV for all treatment temperatures except 430℃.

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Laser-induced damage threshold in HfO2/SiO2 multilayer films irradiated by β-ray Mei-Hua Fang(方美华), Peng-Yu Tian(田鹏宇), Mao-Dong Zhu(朱茂东), Hong-Ji Qi(齐红基), Tao Fei(费涛), Jin-Peng Lv(吕金鹏), Hui-Ping Liu(刘会平) Chin. Phys. B, 2019, 28 (2):  024215.  DOI: 10.1088/1674-1056/28/2/024215 Abstract ( 736 )   HTML   PDF (1450KB) ( 274 )   Post-processing can effectively improve the resistance to laser damage in multilayer films used in a high power laser system. In this work, HfO2/SiO2 multilayer films are prepared by e-beam evaporation and then β-ray irradiation is employed as the post-processing method. The particle irradiation affects the laser induced damage threshold (LIDT), which includes defects, surface roughness, packing density and residual stress. The residual stress that is relaxed during irradiation changes from compressive stress into tensile stress. Our results indicate that appropriate tensile stress can improve LIDT remarkably. In view of the fact that LIDT rises from 8 J/cm2 to 12 J/cm2, i.e., 50% increase, after the film has been irradiated by 2.2×1013/cm2 β-ray, the particle irradiation can be used as a controllable and desirable post-processing method to improve the resistance to laser induced damage.

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Simultaneous polarization separation and switching for 100-Gbps DP-QPSK signals in backbone networks Yu-Long Su(苏玉龙), Huan Feng(冯欢), Hui Hu(胡辉), Wei Wang(汪伟), Tao Duan(段弢), Yi-Shan Wang(王屹山), Jin-Hai Si(司金海), Xiao-Ping Xie(谢小平), He-Ning Yang(杨合宁), Xin-Ning Huang(黄新宁) Chin. Phys. B, 2019, 28 (2):  024216.  DOI: 10.1088/1674-1056/28/2/024216 Abstract ( 873 )   HTML   PDF (1529KB) ( 222 )   We propose a novel scheme of simultaneous polarization separation and switching, based on the orthogonally-polarized four-wave mixing (FWM) effect, for ultra-high-speed polarization multiplexing (Pol-MUX) fiber networks such as 100-Gbps and 400-Gbps backbone networks. We use theoretical and experimental analysis of the vector theory of FWM to successfully achieve polarization separation and all-optical switching by utilizing a 100-Gbps dual polarization-quadrature phase shift keying (DP-QPSK) signal and two orthogonally-polarized pumps. Both of the polarization-separated QPSK signals have clear constellation diagrams, with root mean square (RMS) error vector magnitudes (EVMs) of 14.32% and 14.11% respectively. The wavelengths of idlers can be created at 30 different wavelengths, which are consistent with International Telecommunication Union-Telecommunication (ITU-T) wavelengths, by flexibly changing the wavelength of the pump light. Moreover, the idlers that have distinct wavelengths have power distributed in a range from -10 dBm to -15 dBm, which can support error-free transmission. The power penaltyis 5 dB lower than that of back-to-back (BTB) signal for both the X- and Y-polarization components measured at a bit error ratio (BER) of 3.8×10-3. Our experimental results indicate that this scheme has promising applications in future backbone networks.

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Manipulation of acoustic wavefront by transmissive metasurface based on pentamode metamaterials Ying Liu(刘颖), Yi-Feng Li(李义丰), Xiao-Zhou Liu(刘晓宙) Chin. Phys. B, 2019, 28 (2):  024301.  DOI: 10.1088/1674-1056/28/2/024301 Abstract ( 709 )   HTML   PDF (646KB) ( 249 )   An underwater acoustic metasurface with sub-wavelength thickness is designed for acoustic wavefront manipulation. In this paper, a pentamode lattice and a frequency-independent generalized acoustic Snell's law are introduced to overcome the limitations of narrow bandwidth and low transmittance. The bulk modulus and effective density of each unit cell can be tuned simultaneously, which are modulated to guarantee the achievement of refractive index profile and high transmission. Here, we actualize anomalous refraction, generation of non-diffracting Bessel beam, sub-wavelength flat focusing, and surface wave conversion by constructing inhomogeneous acoustic metasurface. This design approach has potential applications in medical ultrasound imaging and underwater acoustic communications.

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Ultrasonic backscatter characterization of cancellous bone using a general Nakagami statistical model Hot! Chengcheng Liu(刘成成), Rui Dong(东蕊), Boyi Li(李博艺), Ying Li(李颖), Feng Xu(徐峰), Dean Ta(他得安), Weiqi Wang(王威琪) Chin. Phys. B, 2019, 28 (2):  024302.  DOI: 10.1088/1674-1056/28/2/024302 Abstract ( 980 )   HTML   PDF (563KB) ( 293 )   The goal of this study is to analyze the statistics of the backscatter signal from bovine cancellous bone using a Nakagami model and to evaluate the feasibility of Nakagami-model parameters for cancellous bone characterization. Ultrasonic backscatter measurements were performed on 24 bovine cancellous bone specimens in vitro and the backscatter signals were compensated for the frequency-dependent attenuation prior to the envelope detection. The statistics of the backscatter envelope were modeled using the Nakagami distribution. Our results reveal that the backscatter envelope mainly followed pre-Rayleigh distributions, and the deviations of the backscatter envelope from Rayleigh distribution decreased with increasing bone density. The Nakagami shape parameter (i.e., m) was significantly correlated with bone densities (R=0.78-0.81, p<0.001) and trabecular microstructures (|R|=0.46-0.78, p<0.05). The scale parameter (i.e., Ω) and signal-to-noise ratio (SNR) also yielded significant correlations with bone density and structural features. Multiple linear regressions showed that bone volume fraction (BV/TV) was the main predictor of the Nakagami parameters, and microstructure produced significantly independent contribution to the prediction of Nakagami distribution parameters, explaining an additional 10.2% of the variance at most. The in vitro study showed that statistical parameters derived with Nakagami model might be useful for cancellous bone characterization, and statistical analysis has potential for ultrasonic backscatter bone evaluation.

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Aerodynamic actuation characteristics of radio-frequency discharge plasma and control of supersonic flow Zhen Yang(杨臻), Hui-Min Song(宋慧敏), Hong-Yu Wang(王宏宇), Shan-Guang Guo(郭善广), Min Jia(贾敏), Kang Wang(王康) Chin. Phys. B, 2019, 28 (2):  024701.  DOI: 10.1088/1674-1056/28/2/024701 Abstract ( 735 )   HTML   PDF (3562KB) ( 200 )   In this paper, aerodynamic actuation characteristics of radio-frequency (RF) discharge plasma are studied and a method is proposed for shock wave control based on RF discharge. Under the static condition, a RF diffuse glow discharge can be observed; under the supersonic inflow, the plasma is blown downstream but remains continuous and stable. Time-resolved schlieren is used for flow field visualization. It is found that RF discharge not only leads to continuous energy deposition on the electrode surface but also induces a compression wave. Under the supersonic inflow condition, a weak oblique shock wave is induced by discharge. Experimental results of the shock wave control indicate that the applied actuation can disperse the bottom structure of the ramp-induced oblique shock wave, which is also observed in the extracted shock wave structure after image processing. More importantly, this control effect can be maintained steadily due to the continuous high-frequency (MHz) discharge. Finally, correlations for schlieren images and numerical simulations are employed to further explore the flow control mechanism. It is observed that the vortex in the boundary layer increases after the application of actuation, meaning that the boundary layer in the downstream of the actuation position is thickened. This is equivalent to covering a layer of low-density smooth wall around the compression corner and on the ramp surface, thereby weakening the compressibility at the compression corner. Our results demonstrate the ability of RF plasma aerodynamic actuation to control the supersonic airflow.

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Hydrodynamic binary coalescence of droplets under air flow in a hydrophobic microchannel Chao Wang(王超), Chao-qun Shen(沈超群), Su-chen Wu(吴苏晨), Xiang-dong Liu(刘向东), Fang-ping Tang(汤方平) Chin. Phys. B, 2019, 28 (2):  024702.  DOI: 10.1088/1674-1056/28/2/024702 Abstract ( 695 )   HTML   PDF (3990KB) ( 190 )   Based on the volume of fluid (VOF) method, we conduct a numerical simulation to study the hydrodynamic binary coalescence of droplets under air flow in a hydrophobic rectangular microchannel. Two distinct regimes, coalescence followed by sliding motion and that followed by detaching motion, are identified and discussed. Additionally, the detailed hydrodynamic information behind the binary coalescence is provided, based on which a dynamic mechanical analysis is conducted to reveal the hydrodynamic mechanisms underlying these two regimes. The simulation results indicate that the sliding motion of droplets is driven by the drag force and restrained by the adhesion force induced by the interfacial tension along the main flow direction. The detachment (i.e., upward motion) of the droplet is driven by the lift force associated with an aerodynamic lifting pressure difference imposed on the coalescent droplet, and also restrained by the adhesion force perpendicular to the main flow direction. Especially, the lift force is mainly induced by an aerodynamic lifting pressure difference imposed on the coalescent droplet. Two typical regimes can be quantitatively recognized by a regime diagram depending on Re and We. The higher Re and We respectively lead to relatively larger lift forces and smaller adhesion forces acting on the droplet, both of which are helpful to detachment of the coalesced droplet.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Numerical simulation on modulational instability of ion-acoustic waves in plasma Yi-Rong Ma(马艺荣), Lie-Juan Li(李烈娟), Wen-Shan Duan(段文山) Chin. Phys. B, 2019, 28 (2):  025201.  DOI: 10.1088/1674-1056/28/2/025201 Abstract ( 821 )   HTML   PDF (453KB) ( 207 )   In this paper, the one-dimensional (1D) particle-in-cell (PIC) simulation is used to study the modulation instability of ion acoustic waves in electron-ion plasmas. The ion acoustic wave is described by using a nonlinear Schrödinger equation (NLSE) derived from the reductive perturbation method. Form our numerical simulations, we are able to demonstrate that, after the modulation, the amplitude increases steadily over time. Furthermore, by comparing the numerical results with traditional analytical solutions, we acquire the application scope for the reductive perturbation method to obtain the NLSE. We also find this method can also be extended to other fields such as fluid dynamics, nonlinear optics, solid state physics, and the Bose-Einstein condensate to validate the application scope of the results from the traditional perturbation method.

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Effects of secondary electron emission on plasma characteristics in dual-frequency atmospheric pressure helium discharge by fluid modeling Yi-Nan Wang(王一男), Shuai-Xing Li(李帅星), Yue Liu(刘悦), Li Wang(王莉) Chin. Phys. B, 2019, 28 (2):  025202.  DOI: 10.1088/1674-1056/28/2/025202 Abstract ( 925 )   HTML   PDF (678KB) ( 366 )   A one-dimensional (1D) fluid simulation of dual frequency discharge in helium gas at atmospheric pressure is carried out to investigate the role of the secondary electron emission on the surfaces of the electrodes. In the simulation, electrons, ions of He+ and He2+, metastable atoms of Heast and metastable molecules of He2* are included. It is found that the secondary electron emission coefficient significantly influences plasma density and electric field as well as electron heating mechanisms and ionization rate. The particle densities increase with increasing SEE coefficient from 0 to 0.3 as well as the sheath's electric field and electron source. Moreover, the SEE coefficient also influences the electron heating mechanism and electron power dissipation in the plasma and both of them increase with increasing SEE coefficient within the range from 0 to 0.3 as a result of increasing of electron density.

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Preliminary investigation on electrothermal instabilities in early phases of cylindrical foil implosions on primary test stand facility Guanqiong Wang(王冠琼), Delong Xiao(肖德龙), Jiakun Dan(但家坤), Yang Zhang(张扬), Ning Ding(丁宁), Xianbin Huang(黄显宾), Xiaoguang Wang(王小光), Shunkai Sun(孙顺凯), Chuang Xue(薛创), Xiaojian Shu(束小建) Chin. Phys. B, 2019, 28 (2):  025203.  DOI: 10.1088/1674-1056/28/2/025203 Abstract ( 649 )   HTML   PDF (2548KB) ( 225 )   Recent experiments on the implosions of 15-mm long and 2-μm thick aluminum liners having a diameter of 12.8 mm have been performed on the primary test stand (PTS) facility. The stratified structures are observed as alternating dark and light transverse stripes in the laser shadowgraph images. These striations perpendicular to the current flow are formed early in the implosion, i.e., at the stage when the bulk of the material mass was almost at rest. A two-dimensional (2D) magnetohydrodynamics (MHD) code is employed to simulate the behavior of liner dynamics in the early phases. It is found that the striations may be produced by the electrothermal instability (ETI) that results from non-uniform Joule heating due to the characteristic relation between the resistivity and the temperature. In 2D simulations, the stratified structures can be seen obviously in both density and temperature contours as the liner expands rapidly. By analyzing instability spectrum, the dominant wavelengths of the perturbations are 8.33 μm-20.0 μm, which agree qualitatively with the theoretical predictions. It is also interesting to show that ETI provides a significant seed to the subsequent magneto Rayleigh-Taylor (MRT) instability.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Enhanced structural and magnetic properties of microwave sintered Li-Ni-Co ferrites prepared by sol-gel method Nandeibam Nilima, M Maisnam, Sumitra Phanjoubam Chin. Phys. B, 2019, 28 (2):  026101.  DOI: 10.1088/1674-1056/28/2/026101 Abstract ( 757 )   HTML   PDF (3079KB) ( 206 )   The properties of lithium ferrites are very sensitive to chemical composition, synthesis method, and sintering techniques. Li-Ni-Co ferrites with compositional formula Li0.45-0.5xNi0.1CoxFe2.45-0.5xO4, where 0.00 ≤ x ≤ 0.1 in steps of 0.02 were prepared by chemical sol-gel method and sintered by microwave sintering technique. The x-ray diffraction patterns confirmed the formation of single phase with spinel structure in all the samples. The structural parameter viz. lattice constant, crystallite size, and x-ray density for these samples were studied and compared with those measured from samples of similar composition prepared by the sol-gel method and sintered by conventional sintering technique. Enhancement in the magnetic properties like Curie temperature, hysteresis parameters was observed by employing sol-gel synthesis combined with microwave sintering. The results obtained and mechanisms involved are discussed in the paper.

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Dynamically tunable optical properties in graphene-based plasmon-induced transparency metamaterials Wei Jia(贾微), Pei-Wen Ren(任佩雯), Yu-Chen Tian(田雨宸), Chun-Zhen Fan(范春珍) Chin. Phys. B, 2019, 28 (2):  026102.  DOI: 10.1088/1674-1056/28/2/026102 Abstract ( 706 )   HTML   PDF (1695KB) ( 298 )   A graphene-based metamaterial for THz plasmon induced transparency (PIT) is presented and numerically studied in this paper, which consists of two horizontal graphene strips attached to a continuous vertical wire separately. The calculated surface current distributions demonstrate that the distinct PIT window results from the near-field coupling of two bright modes. To explore the physical mechanism of PIT effect, we employ the coupled Lorentz oscillator model. The transmission spectra obtained with this model fits well with the simulation results. The performance of the PIT system can be controlled through the geometry parameters of graphene strips. Moreover, the transparency window can be dynamically tuned by varying the Fermi energy and the carrier mobility of the graphene strips. The slow light effect is also explored in our proposed structure and it can achieve 1.25 ps when Fermi energy is 1.3 eV. Finally, the position of the transmission window with the variation of the nearby medium refractive index is examined. Such a proposed graphene-based PIT system may have great potential applications in photonic devices.

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Orientation dependence of elastic properties in orthorhombic Ca3Mn2O7 Gang Jian(简刚), Mei-Rui Liu(刘美瑞), Chen Zhang(张晨), Jie Lu(卢杰), Chao Yan(晏超) Chin. Phys. B, 2019, 28 (2):  026201.  DOI: 10.1088/1674-1056/28/2/026201 Abstract ( 734 )   HTML   PDF (3736KB) ( 230 )   Elastic properties are important in fundamental understanding of multiferroic materials. However, up to now, there is no work about anisotropy of elastic properties in orthorhombic Ca3Mn2O7. In this study, using coordinate transformation method, we investigated basic elastic parameters (elastic constants c'ij) and engineering elastic parameters (Young's modulus E', Poisson's ratio v', and the rigidity modulus G') of orthorhombic Ca3Mn2O7 along arbitrary orientations. The detailed anisotropic characteristics of these parameters were presented. The results reveal the orientation related elastic properties in mm2 point group orthorhombic Ca3Mn2O7.

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PEALD-deposited crystalline GaN films on Si (100) substrates with sharp interfaces San-Jie Liu(刘三姐), Ying-Feng He(何荧峰), Hui-Yun Wei(卫会云), Peng Qiu(仇鹏), Yi-Meng Song(宋祎萌), Yun-Lai An(安运来), Abdul Rehman(阿布度-拉赫曼), Ming-Zeng Peng(彭铭曾), Xin-He Zheng(郑新和) Chin. Phys. B, 2019, 28 (2):  026801.  DOI: 10.1088/1674-1056/28/2/026801 Abstract ( 908 )   HTML   PDF (2416KB) ( 267 )   Polycrystalline gallium nitride (GaN) thin films were deposited on Si (100) substrates via plasma-enhanced atomic layer deposition (PEALD) under optimal deposition parameters. In this work, we focus on the research of the GaN/Si (100) interfacial properties. The x-ray reflectivity measurements show the clearly-resolved fringes for all the as-grown GaN films, which reveals a perfectly smooth interface between the GaN film and Si (100), and this feature of sharp interface is further confirmed by high resolution transmission electron microscopy (HRTEM). However, an amorphous interfacial layer (~2 nm) can be observed from the HRTEM images, and is determined to be mixture of GaxOy and GaN by x-ray photoelectron spectroscopy. To investigate the effect of this interlayer on the GaN growth, an AlN buffer layer was employed for GaN deposition. No interlayer is observed between GaN and AlN, and GaN shows better crystallization and lower oxygen impurity during the initial growth stage than the GaN with an interlayer.

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Effect of scanning speeds on electrochemical corrosion resistance of laser cladding TC4 alloy Xiaotian Feng(冯晓甜), Jianbo Lei(雷剑波), Hong Gu(顾宏), Shengfeng Zhou(周圣丰) Chin. Phys. B, 2019, 28 (2):  026802.  DOI: 10.1088/1674-1056/28/2/026802 Abstract ( 729 )   HTML   PDF (5330KB) ( 242 )   In order to study the effect of scanning speed on the electrochemical corrosion resistance of laser cladding TC4 alloy in artificial seawater, the x-ray diffraction analysis, microstructure of cross-section, microhardness variation, and impedance spectrum have been studied in comparison with the TC4 titanium alloy. The results show that the main phase of cladding coating is α-Ti, and the change of scanning speed has no obvious effect on it; therefore, the supersaturated α-Ti solid solution is formed, and the acicular α' martensite is obtained. As the scanning speed increases, the microstructure of cladding coating is orthogonal basket-weave, the crystal surface spacing decreases, and the average microhardness of laser cladding TC4 alloy slightly increases. When the scanning speed increases to 10 mm/s, the microhardness is about 14.71% higher than that of the substrate, and the electrochemical corrosion resistance of laser cladding TC4 alloy is also improved, which is about 2.48 times more than the substrate. Grain refinement has a great effect on enhancing the anti-electrochemical corrosion.

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

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1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor Sheng-Lei Zhao(赵胜雷), Zhi-Zhe Wang(王之哲), Da-Zheng Chen(陈大正), Mao-Jun Wang(王茂俊), Yang Dai(戴扬), Xiao-Hua Ma(马晓华), Jin-Cheng Zhang(张进成), Yue Hao(郝跃) Chin. Phys. B, 2019, 28 (2):  027301.  DOI: 10.1088/1674-1056/28/2/027301 Abstract ( 865 )   HTML   PDF (507KB) ( 267 )   In this paper, we present a 1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor (DH HEMT) with a gate-drain spacing LGD=18.8 μm. Compared with the regular DH HEMT, our circular structure has a high average breakdown electric-field strength that increases from 0.42 MV/cm to 0.96 MV/cm. The power figure of merit VBR2/RON for the circular HEMT is as high as 1.03×109 V2·Ω-1·cm-2. The divergence of electric field lines at the gate edge and no edge effect account for the breakdown enhancement capability of the circular structure. Experiments and analysis indicate that the circular structure is an effective method to modulate the electric field.

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Theoretical analytic model for RESURF AlGaN/GaN HEMTs Hao Wu(吴浩), Bao-Xing Duan(段宝兴), Luo-Yun Yang(杨珞云), Yin-Tang Yang(杨银堂) Chin. Phys. B, 2019, 28 (2):  027302.  DOI: 10.1088/1674-1056/28/2/027302 Abstract ( 1281 )   HTML   PDF (504KB) ( 316 )   In this paper, we propose a two-dimensional (2D) analytic model for the channel potential and electric field distribution of the RESURF AlGaN/GaN high electron mobility transistors (HEMTs). The model is constructed by two-dimensional Poisson's equation with appropriate boundary conditions. In the RESURF AlGaN/GaN HEMTs, we utilize the RESURF effect generated by doped negative charge in the AlGaN layer and introduce new electric field peaks in the device channels, thus, homogenizing the distribution of electric field in channel and improving the breakdown voltage of the device. In order to reveal the influence of doped negative charge on the electric field distribution, we demonstrate in detail the influences of the charge doping density and doping position on the potential and electric field distribution of the RESURF AlGaN/GaN HEMTs with double low density drain (LDD). The validity of the model is verified by comparing the results obtained from the analytical model with the simulation results from the ISE software. This analysis method gives a physical insight into the mechanism of the AlGaN/GaN HEMTs and provides reference to modeling other AlGaN/GaN HEMTs device.

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Influence of deep defects on electrical properties of Ni/4H-SiC Schottky diode Jin-Lan Li(李金岚), Yun Li(李赟), Ling Wang(汪玲), Yue Xu(徐跃), Feng Yan(闫锋), Ping Han(韩平), Xiao-Li Ji(纪小丽) Chin. Phys. B, 2019, 28 (2):  027303.  DOI: 10.1088/1674-1056/28/2/027303 Abstract ( 869 )   HTML   PDF (929KB) ( 349 )   In this paper, we investigate the influence of deep level defects on the electrical properties of Ni/4H-SiC Schottky diodes by analyzing device current-voltage (I-V) characteristics and deep-level transient spectra (DLTS). Two Schottky barrier heights (SBHs) with different temperature dependences are found in Ni/4H-SiC Schottky diode above room temperature. DLTS measurements further reveal that two kinds of defects Z1/2 and Ti(c)a are located near the interface between Ni and SiC with the energy levels of EC-0.67 eV and EC-0.16 eV respectively. The latter one as the ionized titanium acceptor residing at cubic Si lattice site is thought to be responsible for the low SBH in the localized region of the diode, and therefore inducing the high reverse leakage current of the diode. The experimental results indicate that the Ti(c)rm a defect has a strong influence on the electrical and thermal properties of the 4H-SiC Schottky diode.

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Low-energy (40 keV) proton irradiation of YBa2Cu3O7-x thin films:Micro-Raman characterization and electrical transport properties San-Sheng Wang(王三胜), Fang Li(李方), Han Wu(吴晗), Yu Zhang(张玉), Suleman Mu?ammad(穆罕默德苏尔曼), Peng Zhao(赵鹏), Xiao-Yun Le(乐小云), Zhi-Song Xiao(肖志松), Li-Xiang Jiang(姜利祥), Xue-Dong Ou(欧学东), Xiao-Ping Ouyang(欧阳晓平) Chin. Phys. B, 2019, 28 (2):  027401.  DOI: 10.1088/1674-1056/28/2/027401 Abstract ( 1101 )   HTML   PDF (2452KB) ( 321 )   To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa2Cu3O7-x (YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TC with the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TC0 is not observed at a fluence of 1015 p/cm2. Furthermore, the variation of activation energy U0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.

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Phase diagrams and magnetic properties of the mixed spin-1 and spin-3/2 Ising ferromagnetic thin film:Monte Carlo treatment B Boughazi, M Boughrara, M Kerouad Chin. Phys. B, 2019, 28 (2):  027501.  DOI: 10.1088/1674-1056/28/2/027501 Abstract ( 721 )   HTML   PDF (1233KB) ( 177 )   Phase diagrams and magnetic properties of the mixed spin-1 and spin-3/2 Ising film with different single-ion anisotropies are investigated, by the use of Monte Carlo simulation based on heat bath algorithms. The effects of the crystal-fields and the surface coupling on the phase diagrams are investigated in detail and the obtained phase diagrams are presented. Depending on the Hamiltonian parameters, the system exhibits both second- and first-order phase transitions besides tricritical point, triple point, and isolated critical end point.

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Unusual tunability of multiferroicity in GdMn2O5 by electric field poling far above multiferroic ordering point Hot! Xiang Li(李翔), Shuhan Zheng(郑书翰), Liman Tian(田礼漫), Rui Shi(石锐), Meifeng Liu(刘美风), Yunlong Xie(谢云龙), Lun Yang(杨伦), Nian Zhao(赵念), Lin Lin(林林), Zhibo Yan(颜志波), Xiuzhang Wang(王秀章), Junming Liu(刘俊明) Chin. Phys. B, 2019, 28 (2):  027502.  DOI: 10.1088/1674-1056/28/2/027502 Abstract ( 905 )   HTML   PDF (1067KB) ( 344 )   The multiferroicity in the RMn2O5 family remains unclear, and less attention has been paid to its dependence on high-temperature (high-T) polarized configuration. Moreover, no consensus on the high-T space group symmetry has been reached so far. In view of this consideration, one may argue that the multiferroicity of RMn2O5 in the low-T range depends on the poling sequence starting far above the multiferroic ordering temperature. In this work, we investigate in detail the variation of magnetically induced electric polarization in GdMn2O5 and its dependence on electric field poling routine in the high-T range. It is revealed that the multiferroicity does exhibit qualitatively different behaviors if the high-T poling routine changes, indicating the close correlation with the possible high-T polarized state. These emergent phenomena may be qualitatively explained by the co-existence of two low-T polarization components, a scenario that was proposed earlier. One is the component associated with the Mn3+-Mn4+-Mn3+ exchange striction that seems to be tightly clamped by the high-T polarized state, and the other is the component associated with the Gd3+-Mn4+-Gd3+ exchange striction that is free of the clamping. The present findings may offer a different scheme for the electric control of the multiferroicity in RMn2O5.

TOPICAL REVIEW—Photodetector: materials, physics, and applications

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Progress in quantum well and quantum cascade infrared photodetectors in SITP Xiaohao Zhou(周孝好), Ning Li(李宁), Wei Lu(陆卫) Chin. Phys. B, 2019, 28 (2):  027801.  DOI: 10.1088/1674-1056/28/2/027801 Abstract ( 844 )   HTML   PDF (6844KB) ( 435 )   This paper presents a review of recent advances in quantum well and quantum cascade infrared photodetectors developed in Shanghai Institute of Technical Physics, Chinese Academy of Sciences (SITP/CAS). Firstly, the temperature- and bias-dependent photocurrent spectra of very long wavelength (VLW) GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) are studied using spectroscopic measurements and corresponding theoretical calculations in detail. We confirm that the first excited state, which belongs to the quasi-bound state, can be converted into a quasi-continuum state induced by bias and temperature. Aided by band structure calculations, we propose a model of the double excited states that determine the working mechanism in VLW QWIPs. Secondly, we present an overview of a VLW QWIP focal plane array (FPA) with 320×256 pixels based on the bound to quasi-bound (BTQB) design. The technology of the manufacturing FPA based on the QWIP structures has been demonstrated. At the operating temperature of 45 K, the detectivity of QWIP FPA is larger than 1.4×1010 cm·Hz1/2/W with a cutoff wavelength larger than 16 μm. Finally, to meet the needs of space applications, we proposed a new long wavelength quantum cascade detector with a broadband detection ranging from 7.6 μm to 10.4 μm. With a pair of identical coupled quantum wells separated by a thin barrier, acting as absorption regions, the relative linewidth (Δ E/E) of response can be dramatically broadened to 30.7%. It is shown that the spectral shape and linewidth can be tuned by the thickness of the thin barrier, while it is insensitive to the working temperature. The device can work above liquid nitrogen temperature with a peak responsivity of 63 mA/W and Johnson noise limited detectivity of 5.1×109 cm·Hz1/2/W.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Effects of growth temperature and metamorphic buffer on electron mobility of InAs film grown on Si substrate by molecular beam epitaxy Jing Zhang(张静), Hongliang Lv(吕红亮), Haiqiao Ni(倪海桥), Shizheng Yang(杨施政), Xiaoran Cui(崔晓然), Zhichuan Niu(牛智川), Yimen Zhang(张义门), Yuming Zhang(张玉明) Chin. Phys. B, 2019, 28 (2):  028101.  DOI: 10.1088/1674-1056/28/2/028101 Abstract ( 912 )   HTML   PDF (1447KB) ( 200 )   The growth of the InAs film directly on the Si substrate deflected from the plane (100) at 4° towards (110) has been performed using a two-step procedure. The effect of the growth and annealing temperature on the electron mobility and surface topography has been investigated for a set of samples. The results show that the highest electron mobility is 4640 cm2/V·in the sample, in which the 10-nm InAs nucleation layer is grown at a low temperature of 320℃ followed by ramping up to 560℃, and the nucleation layer was annealed for 15 min and the second layer of InAs is grown at 520℃. The influence of different buffer layers on the electron mobility of the samples has also been investigated, which shows that the highest electron mobility of 9222 cm2/V·at 300 K is obtained in the sample grown on a thick and linearly graded InGaAlAs metamorphic buffer layer deposited at 420℃.

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Superlubricity enabled dry transfer of non-encapsulated graphene Zhe Ying(应哲), Aolin Deng(邓奥林), Bosai Lyu(吕博赛), Lele Wang(王乐乐), Takashi Taniguchi, Kenji Watanabe, Zhiwen Shi(史志文) Chin. Phys. B, 2019, 28 (2):  028102.  DOI: 10.1088/1674-1056/28/2/028102 Abstract ( 854 )   HTML   PDF (2969KB) ( 431 )   Transferring high-quality exfoliated graphene flakes onto different substrates while keeping the graphene free of polymer residues is of great importance, but at the same time very challenging. Currently, the only feasible way is the so-called all-dry “pick-and-lift” method, in which a hexagonal boron nitride (hBN) flake is employed to serve as a stamp to pick up graphene from one substrate and to lift it down onto another substrate. The transferred graphene samples, however, are always covered or encapsulated by hBN flakes, which leads to difficulties in further characterizations. Here, we report an improved “pick-and-lift” method, which allows ultra-clean graphene flakes to be transferred onto a variety of substrates without hBN coverage. Basically, by exploiting the superlubricity at the graphene/hBN stack interface, we are able to remove the top-layer hBN stamp by applying a tangential force and expose the underneath graphene.

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Inclusions in large diamond single crystals at different temperatures of synthesis Fei Han(韩飞), Shang-Sheng Li(李尚升), Xue-Fei Jia(贾雪菲), Wei-Qin Chen(陈玮琴), Tai-Chao Su(宿太超), Mei-Hua Hu(胡美华), Kun-Peng Yu(于昆鹏), Jian-Kang Wang(王健康), Yu-Min Wu(吴玉敏), Hong-An Ma(马红安), Xiao-Peng Jia(贾晓鹏) Chin. Phys. B, 2019, 28 (2):  028103.  DOI: 10.1088/1674-1056/28/2/028103 Abstract ( 890 )   HTML   PDF (2160KB) ( 360 )   The inclusions in large diamond single crystals have effects on its ultimate performance, which restricts its industrial applications to a great extent. Therefore, it is necessary to study the inclusions systematically. In this paper, large diamond single crystals with different content values of inclusions are synthesized along the (100) surface by the temperature gradient method (TGM) under 5.6 GPa at different temperatures. With the synthetic temperature changing from 1200℃ to 1270℃, the shapes of diamonds change from plate to low tower, to high tower, even to steeple. From the microscopic photographs of the diamond samples, it can be observed that with the shapes of the samples changing at different temperatures, the content values of inclusions in diamonds become zero, a little, much and most, correspondingly. Consequently, with the temperature growing from low to high, the content values of inclusions in crystals increase. The origin of inclusions is explained by the difference in growth rate between diamond crystal and its surface. The content values of inclusions in diamond samples are quantitatively calculated by testing the densities of diamond samples. And the composition and inclusion content are analyzed by energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). From contrasting scanning electron microscopy (SEM) photographs, it can be found that the more the inclusions in diamond, the more imperfect the diamond surface is.

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Synthesis and characterization of β-Ga2O3@GaN nanowires Shuang Wang(王爽), Yue-Wen Li(李悦文), Xiang-Qian Xiu(修向前), Li-Ying Zhang(张丽颖), Xue-Mei Hua(华雪梅), Zi-Li Xie(谢自力), Tao Tao(陶涛), Bin Liu(刘斌), Peng Chen(陈鹏), Rong Zhang(张荣), You-Dou Zheng(郑有炓) Chin. Phys. B, 2019, 28 (2):  028104.  DOI: 10.1088/1674-1056/28/2/028104 Abstract ( 584 )   HTML   PDF (1510KB) ( 185 )   In this work, we prepared the β-Ga2O3@GaN nanowires (NWs) by oxidizing GaN NWs. High-quality hexagonal wurtzite GaN NWs were achieved and the conversion from GaN to β-Ga2O3 was confirmed by x-ray diffraction, Raman spectroscopy and transmission electron microscopy. The effect of the oxidation temperature and time on the oxidation degree of GaN NWs was investigated systematically. The oxidation rate of GaN NWs was estimated at different temperatures.

SPECIAL TOPIC—Photodetector: Materials, physics, and applications

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Transition of photoconductive and photovoltaic operation modes in amorphous Ga2O3-based solar-blind detectors tuned by oxygen vacancies Yan-Fang Zhang(张彦芳), Xuan-Hu Chen(陈选虎), Yang Xu(徐阳), Fang-Fang Ren(任芳芳), Shu-Lin Gu(顾书林), Rong Zhang(张荣), You-Dou Zheng(郑有炓), Jian-Dong Ye(叶建东) Chin. Phys. B, 2019, 28 (2):  028501.  DOI: 10.1088/1674-1056/28/2/028501 Abstract ( 890 )   HTML   PDF (645KB) ( 456 )   We report on the transition of photovoltaic and photoconductive operation modes of the amorphous Ga2O3-based solar-blind photodetectors in metal-semiconductor-metal (MSM) configurations. The conversion from Ohmic to Schottky contacts at Ti/Ga2O3 interface is realized by tuning the conductivity of amorphous Ga2O3 films with delicate control of oxygen flux in the sputtering process. The abundant donor-like oxygen vacancies distributed near the Ti/Ga2O3 interface fascinate the tunneling process across the barrier and result in the formation of Ohmic contacts. As a consequence, the serious sub-gap absorption and persistent photoconductivity (PPC) effect degrades the performance of the photoconductive detectors. In contrast, the photovoltaic device with a Schottky contact exhibits an ultra-low dark current less than 1 pA, a high detectivity of 9.82×1012 cm·Hz1/2·W-1, a fast response time of 243.9 μs, and a high ultraviolet C (UVC)-to-ultraviolet A (UVA) rejection ratio of 103. The promoting performance is attributed primarily to the reduction of the sub-gap states and the resultant suppression of PPC effect. With simple architecture, low fabrication cost, and easy fusion with modern high-speed integrated circuitry, these results provide a cost-effective way to realize high performance solar-blind photodetectors towards versatile practical applications.

TOPICAL REVIEW—Photodetector: materials, physics, and applications

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Recent advances in Ga-based solar-blind photodetectors Ming-sheng Xu(徐明升), Lei Ge(葛磊), Ming-ming Han(韩明明), Jing Huang(黄静), Hua-yong Xu(徐化勇), Zai-xing Yang(杨再兴) Chin. Phys. B, 2019, 28 (2):  028502.  DOI: 10.1088/1674-1056/28/2/028502 Abstract ( 931 )   HTML   PDF (4881KB) ( 408 )   Solar-blind ultraviolet photodetectors have many advantages, such as low false alarm rates, the ability to detect weak signals, and high signal-to-noise ratios. Among the various functional solar-blind ultraviolet photodetectors, Ga-based alloys of AlGaN and Ga2O3 are the most commonly adopted channel semiconductor materials and have attracted extensive research attention in the past decades. This review presents an overview of the recent progress in Ga-based solar-blind photodetectors. In case of AlGaN-based solar-blind ultraviolet photodetectors, the response properties can be improved by optimizing the AlN nucleation layer and designing the avalanche structure. On the other hand, we also discuss the morphology and growth methods of Ga2O3 nanomaterials and their effect on the performance of the corresponding solar-blind photodetectors. The mechanically exfoliated Ga2O3 flakes show good potential for ultraviolet detection. Also, Ga2O3 nanoflowers and nanowires reveal perfect response to ultraviolet light. Finally, the challenges and future development of Ga-based functional solar-blind ultraviolet photodetectors are summarized.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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High material quality growth of AlInAsSb thin films on GaSb substrate by molecular beam epitaxy Fa-Ran Chang(常发冉), Rui-Ting Hao(郝瑞亭), Tong-Tong Qi(齐通通), Qi-Chen Zhao(赵其琛), Xin-Xing Liu(刘欣星), Yong Li(李勇), Kang Gu(顾康), Jie Guo(郭杰), Guo-Wei Wang(王国伟), Ying-Qiang Xu(徐应强), Zhi-Chuan Niu(牛智川) Chin. Phys. B, 2019, 28 (2):  028503.  DOI: 10.1088/1674-1056/28/2/028503 Abstract ( 816 )   HTML   PDF (1094KB) ( 539 )   In this paper, high material quality Al0.4In0.6AsSb quaternary alloy on GaSb substrates is demonstrated. The quality of these epilayers is assessed using a high-resolution x-ray diffraction, Fourier transform infrared (FTIR) spectrometer, and atomic force microscope (AFM). The x-ray diffraction exhibits high order satellite peaks with a measured period of 31.06 Å (theoretical value is 30.48 Å), the mismatch between the GaSb substrate and AlInAsSb achieves -162 arcsec, and the root-mean square (RMS) roughness for typical material growths has achieved around 1.6 Å over an area of 10 μm×10 μm. At room temperature, the photoluminescence (PL) spectrum shows a cutoff wavelength of 1.617 μm.

TOPICAL REVIEW—Photodetector: materials, physics, and applications

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Development of long-wavelength infrared detector and its space-based application requirements Junku Liu(刘军库), Lin Xiao(肖林), Yang Liu(刘阳), Longfei Cao(曹龙飞), Zhengkun Shen(申正坤) Chin. Phys. B, 2019, 28 (2):  028504.  DOI: 10.1088/1674-1056/28/2/028504 Abstract ( 1058 )   HTML   PDF (4773KB) ( 1512 )   Infrared detection technology has greatly expanded the ability of mankind to study the earth and the universe. In recent years, the demand for long-wavelength infrared detectors is increasing for their advantages in exploring the earth and the universe. A variety of long-wavelength infrared detectors have been made based on thermal resistive effect, photoelectric effect, etc., in the past few decades. Remarkable achievements have been made in infrared materials, device fabrication, readout circuit, and device package. However, high performance long-wavelength infrared detectors, especially those for large format long-wavelength infrared detector focus plane array, are still unsatisfactory. Low noise, high detectivity, and large format long-wavelength infrared detector is necessary to satisfy space-based application requirements.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Modeling for heterogeneous multi-stage information propagation networks and maximizing information Ren-Jie Mei(梅人杰), Li Ding(丁李), Xu-Ming An(安栩明), Ping Hu(胡萍) Chin. Phys. B, 2019, 28 (2):  028701.  DOI: 10.1088/1674-1056/28/2/028701 Abstract ( 716 )   HTML   PDF (1988KB) ( 213 )   In this paper, we propose a heterogeneous multi-stage model to study the effect of social reinforcement on information propagation. Both heterogeneity of network components and the heterogeneity of individual reinforcement thresholds are considered. An information outbreak condition is derived, according to which the outbreak scale and individual density of each state under specific propagation parameters can be deduced. Monte Carlo experiments are conducted in Facebook networks to demonstrate the outbreak condition, and we find that social reinforcement effects generally inhibit the propagation of information though it contributes to the emergence of certain hot spots simultaneously. Additionally, by applying Pontryagin's Maximum Principle, we derive the optimal control strategy in the case of limited control resources to maximize the information propagation. Then the forward-backward sweep method is utilized to verify its performance with numerical simulation.