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Chin. Phys. B  
  Chin. Phys. B--2018, Vol.27, No.6
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SPECIAL TOPIC—Recent advances in thermoelectric materials and devices
GENERAL

Enhancement of water self-diffusion at super-hydrophilic surface with ordered water

Xiao-Meng Yu, Chong-Hai Qi, Chun-Lei Wang
Chin. Phys. B 2018, 27 (6): 060101;  doi: 10.1088/1674-1056/27/6/060101
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It has been well acknowledged that molecular water structures at the interface play an important role in the surface properties, such as wetting behavior or surface frictions. Using molecular dynamics simulation, we show that the water self-diffusion on the top of the first ordered water layer can be enhanced near a super-hydrophilic solid surface. This is attributed to the fewer number of hydrogen bonds between the first ordered water layer and water molecules above this layer, where the ordered water structures induce much slower relaxation behavior of water dipole and longer lifetime of hydrogen bonds formed within the first layer.

Multiple Darboux-Bäcklund transformations via truncated Painlevé expansion and Lie point symmetry approach

Shuai-Jun Liu, Xiao-Yan Tang, Sen-Yue Lou
Chin. Phys. B 2018, 27 (6): 060201;  doi: 10.1088/1674-1056/27/6/060201
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For a given truncated Painlevé expansion of an arbitrary nonlinear Painlevé integrable system, the residue with respect to the singularity manifold is known as a nonlocal symmetry, called the residual symmetry, which is proved to be localized to Lie point symmetries for suitable prolonged systems. Taking the Korteweg-de Vries equation as an example, the n-th binary Darboux-Bäcklund transformation is re-obtained by the Lie point symmetry approach accompanied by the localization of the n-fold residual symmetries.

Distance-based formation tracking control of multi-agent systems with double-integrator dynamics

Zixing Wu, Jinsheng Sun, Ximing Wang
Chin. Phys. B 2018, 27 (6): 060202;  doi: 10.1088/1674-1056/27/6/060202
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This paper addresses the distance-based formation tracking problem for a double-integrator modeled multi-agent system (MAS) in the presence of a moving leader in d-dimensional space. Under the assumption that the state of leader can be obtained over fixed graphs, a distributed distance-based control protocol is designed for each double-integrator follower agent. The protocol consists of three terms:a gradient function term, a velocity consensus term, and a leader tracking term. Different shape stabilizing functions proposed in the literature can be applied to the gradient function term. The proposed controller allows all agents to both achieve the desired shape and reach the same velocity with moving leader by controlling the distances and velocity. Finally, we analyze the local asymptotic stability of the equilibrium set with center manifold theory. We validate the effectiveness of our approach through two examples.

Stochastic evolutionary public goods game with first and second order costly punishments in finite populations

Ji Quan, Yu-Qing Chu, Wei Liu, Xian-Jia Wang, Xiu-Kang Yang
Chin. Phys. B 2018, 27 (6): 060203;  doi: 10.1088/1674-1056/27/6/060203
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We study the stochastic evolutionary public goods game with punishment in a finite size population. Two kinds of costly punishments are considered, i.e., first-order punishment in which only the defectors are punished, and second-order punishment in which both the defectors and the cooperators who do not punish the defective behaviors are punished. We focus on the stochastic stable equilibrium of the system. In the population, the evolutionary process of strategies is described as a finite state Markov process. The evolutionary equilibrium of the system and its stochastic stability are analyzed by the limit distribution of the Markov process. By numerical experiments, our findings are as follows. (i) The first-order costly punishment can change the evolutionary dynamics and equilibrium of the public goods game, and it can promote cooperation only when both the intensity of punishment and the return on investment parameters are large enough. (ii) Under the first-order punishment, the further imposition of the second-order punishment cannot change the evolutionary dynamics of the system dramatically, but can only change the probability of the system to select the equilibrium points in the “C+P” states, which refer to the co-existence states of cooperation and punishment. The second-order punishment has limited roles in promoting cooperation, except for some critical combinations of parameters. (iii) When the system chooses “C+P” states with probability one, the increase of the punishment probability under second-order punishment will further increase the proportion of the “P” strategy in the “C+P” states.

Frequency response range of terahertz pulse coherent detection based on THz-induced time-resolved luminescence quenching

Man Zhang, Zhen-Gang Yang, Jin-Song Liu, Ke-Jia Wang, Jiao-Li Gong, Sheng-Lie Wang
Chin. Phys. B 2018, 27 (6): 060204;  doi: 10.1088/1674-1056/27/6/060204
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It has been proposed previously that the coherent detection of a terahertz (THz) pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide (GaAs) by the ensemble Monte Carlo method. At room temperature, for a direct-current (DC) voltage of 20 kV/cm applied to the semiconductor (GaAs) and sampling time of 140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied. The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range of 0.1 THz-4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency. Therefore, the frequency response range is 0.1 THz-4 THz. Moreover, when the sampling time is changed to 100 fs, the frequency response range is extended to be approximately 0.1 THz-5.6 THz. This study of the frequency-dependent characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.

Growth mode of helium crystal near dislocations in titanium

Bao-Ling Zhang, Bao-Wen Wang, Xue Su, Xiao-Yong Song, Min Li
Chin. Phys. B 2018, 27 (6): 060205;  doi: 10.1088/1674-1056/27/6/060205
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The helium bubble structure and growth modes near dislocations in titanium are studied using the molecular dynamics method. A helium crystal with an HCP structure in titanium is found to have a lattice constant of 1.977 Å at 0 K. On either side of the slip plane, helium bubbles form in the (001) plane, but they are in different growth modes. On the side of the slip plane with full atomic layers, helium bubbles grow toward the slip plane and easily cross the slip plane. In the growth process, the position of the top surface of the helium bubble remains almost unchanged. On the other side of the slip plane, the helium bubble grows initially toward the dislocation core, but it is difficult to cross the slip plane, which results in growth in the opposite direction upon reaching the slip plane.

Monogamy quantum correlation near the quantum phase transitions in the two-dimensional XY spin systems

Meng Qin, Zhongzhou Ren, Xin Zhang
Chin. Phys. B 2018, 27 (6): 060301;  doi: 10.1088/1674-1056/27/6/060301
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We investigate the role of quantum correlation around the quantum phase transitions by using quantum renormalization group theory. Numerical analysis indicates that quantum correlation as well as quantum nonlocality can efficiently detect the quantum critical point in the two-dimensional XY systems. The nonanalytic behavior of the first derivative of quantum correlation is observed at the critical point as the size of the model increases. Furthermore, we discuss the quantum correlation distribution in this system based on the square of concurrence (SC) and square of quantum discord (SQD). The monogamous properties of SC and SQD are obtained. Particularly, we prove that the quantum critical point can also be achieved by monogamy score.

Quantum speed-up capacity in different types of quantum channels for two-qubit open systems

Wei Wu, Xin Liu, Chao Wang
Chin. Phys. B 2018, 27 (6): 060302;  doi: 10.1088/1674-1056/27/6/060302
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A potential acceleration of a quantum open system is of fundamental interest in quantum computation, quantum communication, and quantum metrology. In this paper, we investigate the “quantum speed-up capacity” which reveals the potential ability of a quantum system to be accelerated. We explore the evolutions of the speed-up capacity in different quantum channels for two-qubit states. We find that although the dynamics of the capacity is varying in different kinds of channels, it is positive in most situations which are considered in the context except one case in the amplitude-damping channel. We give the reasons for the different features of the dynamics. Anyway, the speed-up capacity can be improved by the memory effect. We find two ways which may be used to control the capacity in an experiment:selecting an appropriate coefficient of an initial state or changing the memory degree of environments.

Quantum estimation of detection efficiency with no-knowledge quantum feedback

Dong Xie, Chunling Xu
Chin. Phys. B 2018, 27 (6): 060303;  doi: 10.1088/1674-1056/27/6/060303
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We investigate that no-knowledge measurement-based feedback control is utilized to obtain the estimation precision of the detection efficiency. We show that no-knowledge measurement is the optimal way to estimate the detection efficiency. The higher precision can be achieved for the lower or larger detection efficiency. It is found that no-knowledge feedback can be used to cancel decoherence. No-knowledge feedback with a high detection efficiency can perform well in estimating frequency and detection efficiency parameters simultaneously; simultaneous estimation is better than independent estimation given by the same probes.

Classical-driving-assisted coherence dynamics and its conservation

De-Ying Gao, Qiang Gao, Yun-Jie Xia
Chin. Phys. B 2018, 27 (6): 060304;  doi: 10.1088/1674-1056/27/6/060304
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We investigate the quantum coherence and quantum entanglement dynamics of a classical driven single atom coupled to a single-mode cavity. It is shown that the transformation between the atomic coherence and the atom-field entanglement exists, and can be improved by adjusting the classical driving field. The joint evolution of two identical single-body systems is also studied. The results show the quantum coherence transfers among composite subsystems, and the coherence conservation of composite subsystems is obtained. Moreover, the classical driving field can be used to suppress the decay of the coherence and entanglement, owing to considering the leaky cavity. The non-Markovian dynamics of the system is also discussed finally.

Demonstration of quantum permutation parity determine algorithm in a superconducting qutrit Hot!

Kunzhe Dai, Peng Zhao, Mengmeng Li, Xinsheng Tan, Haifeng Yu, Yang Yu
Chin. Phys. B 2018, 27 (6): 060305;  doi: 10.1088/1674-1056/27/6/060305
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A quantum algorithm provides a new way in solving certain computing problems and usually faster than classical algorithms. Here we report an implementation of a quantum algorithm to determine the parity of permutation in a single three-dimensional (3D) superconducting transmon qutrit system. The experiment shows the capacity to speed up in a qutrit, which can also be extended to a multi-level system for solving high-dimensional permutation parity determination problem.

Electronic and magnetic properties of semihydrogenated, fully hydrogenated monolayer and bilayer MoN2 sheets

Yan-Chao She, Zhao Wei, Kai-Wu Luo, Yong Li, Yun Zhang, Wei-Xi Zhang
Chin. Phys. B 2018, 27 (6): 060306;  doi: 10.1088/1674-1056/27/6/060306
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Based on density functional theory, we investigate the electronic and magnetic properties of semi-hydrogenated, fully hydrogenated monolayer and bilayer MoN2. We find that the AB stacking bilayer MoN2 exhibits ferromagnetic coupling of intralayer and antiferromagnetic coupling of interlayer, however, the ground states of the semi-hydrogenated, fully hydrogenated monolayer and AA stcaking bilayer MoN2 are nonmagnetic. The fully hydrogenated system has a quasi-direct band-gap of 2.5 eV, which has potential applications in light-emitting diode and photovoltaics. The AB stacking bilayer MoN2 shows the Dirac cone at K point in BZ around Fermi energy. Furthermore, the interlayer of the AB stacking bilayer MoN2 is subjected to a weak van der Waals force, while the interlayer of the AA stacking forms N-N covalent bond.

Topologically protected edge gap solitons of interacting Bosons in one-dimensional superlattices

Xi-Hua Guo, Tian-Fu Xu, Cheng-Shi Liu
Chin. Phys. B 2018, 27 (6): 060307;  doi: 10.1088/1674-1056/27/6/060307
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We comprehensively investigate the nontrivial states of an interacting Bose system in a cosine potential under the open boundary condition. Our results show that there exists a kind of stable localized state:edge gap solitons. We argue that the states originate from the eigenstates of independent edge parabolas. In particular, the edge gap solitons exhibit a nonzero topological-invariant behavior. The topological nature is due to the connection of the present model to the quantized adiabatic particle transport problem. In addition, the composition relations between the gap solitons and the extended states are also discussed.

General series expression of eddy-current impedance for coil placed above multi-layer plate conductor

Yin-Zhao Lei
Chin. Phys. B 2018, 27 (6): 060308;  doi: 10.1088/1674-1056/27/6/060308
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This paper presents a closed expression of the layered-plate factor used to calculate the coil eddy-current impedance over the multi-layer plate conductor. By using this expression, the general series of eddy-current impedance can be written directly without solving the undetermined constant equations. The series expression is easy to use for theoretical analysis and programming. Experimental results show that calculated values and measured values are in agreement. As an application, when the bottom layer of the layered plate is a non-ferromagnetic thin layer conductor and the product of the thickness and conductivity of the layer remains unchanged, using the layered-plate factor expression proposed in this paper, it can be theoretically predicted that the eddy-current impedance curves corresponding to different thin layer thickness values will coincide.

Dynamic characteristics in an external-cavity multi-quantum-well laser

Sen-Lin Yan
Chin. Phys. B 2018, 27 (6): 060501;  doi: 10.1088/1674-1056/27/6/060501
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This paper outlines our studies of bifurcation, quasi-periodic road to chaos and other dynamic characteristics in an external-cavity multi-quantum-well laser with delay optical feedback. The bistable state of the laser is predicted by finding theoretically that the gain shifts abruptly between two values due to the feedback. We make a linear stability analysis of the dynamic behavior of the laser. We predict the stability scenario by using the characteristic equation while we make an approximate analysis of the stability of the equilibrium point and discuss the quantitative criteria of bifurcation. We deduce a formula for the relaxation oscillation frequency and prove theoretically that this formula function relates to the loss of carriers transferring between well regime and barrier regime, the feedback level, the delayed time and the other intrinsic parameters. We demonstrate the dynamic distribution and double relaxation oscillation frequency abruptly changing in periodic states and find the multi-frequency characteristic in a chaotic state. We illustrate a road to chaos from a stable state to quasi-periodic states by increasing the feedback level. The effects of the transfers of carriers and the escaping of carriers on dynamic behavior are analyzed, showing that they are contrary to each other via the bifurcation diagram. Also, we show another road to chaos after bifurcation through changing the linewidth enhancement factor, the photon loss rate and the transfer rate of carriers.

The heat and work of quantum thermodynamic processes with quantum coherence

Shanhe Su, Jinfu Chen, Yuhan Ma, Jincan Chen, Changpu Sun
Chin. Phys. B 2018, 27 (6): 060502;  doi: 10.1088/1674-1056/27/6/060502
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Energy is often partitioned into heat and work by two independent paths corresponding to the change in the eigenenergies or the probability distributions of a quantum system. The discrepancies of the heat and work for various quantum thermodynamic processes have not been well characterized in literature. Here we show how the work in quantum machines is differentially related to the isochoric, isothermal, and adiabatic processes. We prove that the energy exchanges during the quantum isochoric and isothermal processes are simply depending on the change in the eigenenergies or the probability distributions. However, for a time-dependent system in a non-adiabatic quantum evolution, the transitions between the different quantum states representing the quantum coherence can affect the essential thermodynamic properties, and thus the general definitions of the heat and work should be clarified with respect to the microscopic generic time-dependent system. By integrating the coherence effects in the exactly-solvable dynamics of quantum-spin precession, the internal energy is rigorously transferred as the work in the thermodynamic adiabatic process. The present study demonstrates that the quantum adiabatic process is sufficient but not necessary for the thermodynamic adiabatic process.

Superconducting membrane mechanical oscillator based on vacuum-gap capacitor

Yong-Chao Li, Xin Dai, Jun-Liang Jiang, Jia-Zheng Pan, Xing-Yu Wei, Ya-Peng Lu, Sheng Lu, Xue-Cou Tu, Guo-Zhu Sun, Pei-Heng Wu
Chin. Phys. B 2018, 27 (6): 060701;  doi: 10.1088/1674-1056/27/6/060701
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Using the diluted S1813 UV photoresist as a sacrificial layer, we successfully fabricate a superconducting suspended parallel-plate capacitor, in which the top layer of aluminum film acts as a membrane mechanical resonator. Together with a superconducting octagonal spiral inductor, this parallel-plate capacitor constitutes a superconducting microwave resonator. At mK temperature, the transmission characteristic and spectrum of the microwave resonator are measured. Sideband frequencies caused by the vibration of the membrane mechanical resonator are clearly demonstrated. By down-converting with a mixer, the dependence of fundamental frequency and its harmonics on the input microwave power are clearly demonstrated, which is consistent with the numerical simulation.

Cryogenic amplifier with low input-referred voltage noise calibrated by shot noise measurement

Wuhao Yang, Jian Wei
Chin. Phys. B 2018, 27 (6): 060702;  doi: 10.1088/1674-1056/27/6/060702
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A low-noise cryogenic amplifier for the bandwidth from 100 kHz to 2 MHz with commercially available components is presented. The amplifier is mounted on the cold finger of our home-made liquid helium dipstick. The input impedance of the amplifier is 2 kΩ. The input-referred voltage noise of the amplifier at approximately 2 MHz is around 1 nV/√Hz. We demonstrate the performance of the amplifier by measuring shot noise on the Al/AlOx/Al tunneling junction with resistance about 17 kΩ at liquid helium temperature.

Baseline optimization for scalar magnetometer array and its application in magnetic target localization

Li-Ming Fan, Quan Zheng, Xi-Yuan Kang, Xiao-Jun Zhang, Chong Kang
Chin. Phys. B 2018, 27 (6): 060703;  doi: 10.1088/1674-1056/27/6/060703
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Generally, a magnetic target can be described with six parameters, three describing the position and three describing the magnetic moment. Due to a lack of sufficient components from one magnetometer, we need more than one magnetometer when locating the magnetic target. Thus, a magnetometer array should be designed. The baseline of the array is an important factor that affects the localization accuracy of the target. In this paper, we focus on the localization of a static target by using a scalar magnetometer array. We present the scalar magnetometer array with a cross-shaped structure. We propose a method of determining the optimal baseline according to the parameters of the magnetometer and detection requirements. In the method, we use the traditional signal-to-noise ratio (SNR) as a performance index, and obtain the optimal baseline of the array by using the Monte Carlo method. The proposed method of determining the optimal baseline is verified in simulation. The arrays with different baselines are used to locate a static magnetic target. The results show that the location performance is better when using the array with the optimal baseline determined by the proposed method.
TOPICAL REVIEW—Electron microscopy methods for the emergent materials and life sciences
ATOMIC AND MOLECULAR PHYSICS

Determination of static dipole polarizabilities of Yb atom

Zhi-Ming Tang, Yan-Mei Yu, Chen-Zhong Dong
Chin. Phys. B 2018, 27 (6): 063101;  doi: 10.1088/1674-1056/27/6/063101
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We determine the static values of the scalar and tensor dipole polarizabilities of the ground, 6s6p3P0o, and 6s6p3P1o states of the Yb atom. These results can be useful in many experiments undertaken using this atom. We employed a combined configuration interaction (CI) method and a second-order many-body perturbation theory (MBPT) to evaluate energies and electric dipole (E1) matrix elements of many low-lying excited states of the above atom. These values are compared with the other available theoretical calculations and experimental values. By combining these E1 matrix elements with the experimental excitation energies, we estimate the dominant valence correlation contributions to the dipole polarizabilities of the above states. The core contribution is obtained from the finite field approach. We also compare these values with the other theoretical results as there are no precise experimental values that are available for these properties.

Structure, stability, catalytic activity, and polarizabilities of small iridium clusters

Francisco E Jorge, José R da Costa Venâncio
Chin. Phys. B 2018, 27 (6): 063102;  doi: 10.1088/1674-1056/27/6/063102
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At the second order Douglas-Kroll-Hess (DKH2) level, the B3PW91 functional in conjunction with the relativistic all-electron basis set of valence triple zeta quality plus polarization functions are employed to compute bond lengths, dissociation energies, vertical ionization potentials, and the highest occupied molecular orbital-lowest unoccupied molecular orbital energy gaps of the small iridium clusters (Irn, n ≤ 8). These results are compared with the experimental and theoretical data available in the literature. Our results confirm the theoretical predictions made by Feng et al. about the catalytic activities of the Ir4 and Ir6 clusters. From the optimized geometries, DKH2 calculations of static electric mean dipole polarizabilities and polarizability anisotropies are also carried out. It is the first time that the polarizabilities of small iridium clusters have been studied. For n ≤ 4, the mean dipole polarizabilities per atom present an odd-even oscillatory behavior, whereas from Ir5 to Ir8, they decrease with the cluster size increasing. The dependence of the polarizability anisotropy on the structure symmetry of the iridium cluster is verified.

Effect of nickel segregation on CuΣ9 grain boundary undergone shear deformations

Xiang-Yue Liu, Hong Zhang, Xin-Lu Cheng
Chin. Phys. B 2018, 27 (6): 063103;  doi: 10.1088/1674-1056/27/6/063103
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Impurity segregation at grain boundary (GB) can significantly affect the mechanical behaviors of polycrystalline metal. The effect of nickel impurity segregated at Cu GB on the deformation mechanism relating to loading direction is comprehensively studied by atomic simulation. The atomic structures and shear responses of CuΣ9(114) <110> and Σ9(221) <110> symmetrical tilt grain boundary with different quantities of nickel segregation are analyzed. The results show that multiple accommodative evolutions involving GB gliding, GB shear-coupling migration, and dislocation gliding can be at play, where for the[221] shear of Σ9(114) <110> the segregated GBs tend to maintain their initial configurations and a segregated GB with a higher impurity concentration is more inclined to be a dislocation emission source while maintaining the high mechanical strength undergone plastic deformation for the[114] shear of Σ9(221) <110>. It is found that the nickel segregated GB exerts a cohesion enhancement effect on Cu under deformation:strong nickel segregation increases the work of separation of GB, which is proved by the first-principles calculations.

Single and double Auger decay of 4f-ionized mercury including cascade and direct processes

Yu-Long Ma, Fu-Yang Zhou, Zhen-Qi Liu, Yi-Zhi Qu
Chin. Phys. B 2018, 27 (6): 063201;  doi: 10.1088/1674-1056/27/6/063201
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Single (SA) and double (DA) Auger decay including cascade and direct processes are investigated for Hg 4f-1 with multiconfiguration Dirac-Fock method and two-step approaches, i.e., knockout and shakeoff mechanisms. Due to the computational effort, only the major transitions are considered to describe the SA and DA decays for the Hg+ ions with complex electronic configurations. In order to estimate the Auger transition energies and amplitudes, the reference configuration sets producing the configuration state functions are carefully chosen for balancing electron correlations among the successive singly, doubly and triply ionized mercury. The Auger rates and electron spectra, DA probabilities as well as the populations of the final Hg3+ states are obtained. Our results well explain the recent experimental data about the 4f hole states of Hg[Palaudoux J et al., Phys. Rev. A 91 012513 (2015)], and could provide guidance for further studies on complex atoms. Particularly for the DA decay, the contributions of the direct processes, which are neglected in their calculations, are found to be important, accounting for as high as about 38% and 34% of the total DA decays for the 4f7/2-1 and 4f5/2-1, respectively.

Demonstration of superadiabatic population transfer in superconducting qubit

Mengmeng Li, Xinsheng Tan, Kunzhe Dai, Peng Zhao, Haifeng Yu, Yang Yu
Chin. Phys. B 2018, 27 (6): 063202;  doi: 10.1088/1674-1056/27/6/063202
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We implemented the superadiabatic population transfer within the nonadiabatic regime in a two-level superconducting qubit system. To realize the superadiabatic procedure, we added an additional term in the Hamiltonian, introducing an auxiliary counter-diabatic field to cancel the nonadiabatic contribution in the evolution. Based on the superadiabatic procedure, we further demonstrated quantum Phase and NOT gates. These operations, which possess both of the fast and robust features, are promising for quantum information processing.

Enhanced ionization of vibrational hot carbon disulfide molecules in strong femtosecond laser fields

Wan-Long Zuo, Hang Lv, Hong-Jing Liang, Shi-Min Shan, Ri Ma, Bing Yan, Hai-Feng Xu
Chin. Phys. B 2018, 27 (6): 063301;  doi: 10.1088/1674-1056/27/6/063301
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By using a heated molecular beam in combination with a time-of-flight mass spectrometer, we experimentally study the ionization of vibrational-hot carbon disulfide (CS2) molecules irradiated by a linearly polarized 800-nm 50-fs strong laser field. The ion yields are measured in a laser intensity range of 7.0×1012 W/cm2-1.5×1014 W/cm2 at different molecular temperatures of up to 1400 K. Enhanced ionization yield is observed for vibrationally excited CS2 molecules. The results show that the enhancement decreases as the laser intensity increases, and exhibits non-monotonical dependence on the molecular temperature. According to the calculated potential energy curves of the neutral and ionic electronic states of CS2, as well as the theoretical models of molecular strong-field ionization available in the literature, we discuss the mechanism of the enhanced ionization of vibrational-hot molecules. It is indicated that the enhanced ionization could be attributed to both the reduced ionization potential with vibrational excitation and the Frank-Condon factors between the neutral and ionic electronic states. Our study paves the way to understanding the effect of nuclear motion on the strong-field ionization of molecules, which would give a further insight into theoretical and experimental investigations on the interaction of polyatomic molecules with strong laser fields.

Dynamics of the CH4+O(3P)→CH3(ν=0)+OH(ν'=0) reaction

Zhong-An Jiang, Ya Peng, Ju-Shi Chen, Gui Lan, Hao-Yu Lin
Chin. Phys. B 2018, 27 (6): 063401;  doi: 10.1088/1674-1056/27/6/063401
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The dynamics of the ground-state reaction of CH4+O(3P) → CH3(ν=0) +OH(ν'=0) have attracted a great deal of attention both theoretically and experimentally. This rapid communication represents extensive quasi-classical trajectory calculations of the vibrational distributions on a unique full-dimensional ab initio potential energy surface for the title reaction, at the collision energy of relevance to previous crossed molecular beam experiments. The surface is constructed using the all electrons coupled-cluster singles and doubles approach plus quasi-perturbative triple excitations with optimized basis sets. A modified Shepard interpolation method is also employed for the construction. Good agreement between our calculations and the available experimental results has been achieved, opening the door for accurate dynamics on this surface.

Investigations of the dielectronic recombination of phosphorus-like tin at CSRm

Xin Xu, Shu-Xing Wang, Zhong-Kui Huang, Wei-Qiang Wen, Han-Bing Wang, Tian-Heng Xu, Xiao-Ya Chuai, Li-Jun Dou, Wei-Qing Xu, Chong-Yang Chen, Chuan-Ying Li, Jian-Guo Wang, Ying-Long Shi, Chen-Zhong Dong, Li-Jun Mao, Da-Yu Yin, Jie Li, Xiao-Ming Ma, Jian-Cheng Yang, You-Jin Yuan, Xin-Wen Ma, Lin-Fan Zhu
Chin. Phys. B 2018, 27 (6): 063402;  doi: 10.1088/1674-1056/27/6/063402
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The electron-ion recombination for phosphorus-like 112Sn35+ has been measured at the main cooler storage ring of the Heavy Ion Research Facility in Lanzhou, China, employing an electron-ion merged-beams technique. The absolute total recombination rate coefficients for electron-ion collision energies from 0 eV-14 eV are presented. Theoretical calculations of recombination rate coefficients were performed using the Flexible Atomic Code to compare with the experimental results. The contributions of dielectronic recombination and trielectronic recombination on the experimental rate coefficients have been identified with the help of the theoretical calculation. The present results show that the trielectronic recombination has a substantial contribution to the measured electron-ion recombination spectrum of 112Sn35+. Although a reasonable agreement is found between the experimental and theoretical results the precise calculation of the electron-ion recombination rate coefficients for M-shell ions is still challengeable for the current theory.

Overrun phenomenon and neutron yield in Coulomb explosion of deuterated alkane clusters driven by intense laser field

Hong-Yu Li, Mei-Dong Huang, Ming Kang, De-Jun Li
Chin. Phys. B 2018, 27 (6): 063602;  doi: 10.1088/1674-1056/27/6/063602
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By using a simplified Coulomb explosion model, the laser-driven Coulomb explosion processes of three deuterated alkane clusters, i.e., deuterated methane (CD4)N, ethane (C2D6)N and propane (C3D8)N clusters are simulated numerically. The overrun phenomenon that the deuterons overtake the carbon ions inside the expanding clusters, as well as the dependence of the energetic deuterons and fusion neutron yield on cluster size, is discussed in detail. Researches show that the average kinetic energy of deuterons and neutron yield generated in the Coulomb explosion of (C2D6)N cluster are higher than those of (CD4)N cluster with the same size, in qualitative agreement with the reported conclusions from the experiments of (C2H6)N and (CH4) N clusters. It is indicated that (C2D6)N clusters are superior to (CD4)N clusters as a target for the laser-induced nuclear fusion reaction to achieve a higher neutron yield. In addition, by comparing the relevant data of (C3D8)N cluster with those of (C2D6)N cluster with the same size, it is theoretically concluded that (C3D8)N clusters with a larger competitive parameter might be a potential candidate for improving neutron generation. This will provide a theoretical basis for target selection in developing experimental schemes on laser-driven nuclear fusion in the future.

Optimization of endcap trap for single-ion manipulation

Yuan Qian, Chang-Da-Ren Fang, Yao Huang, Hua Guan, Ke-Lin Gao
Chin. Phys. B 2018, 27 (6): 063701;  doi: 10.1088/1674-1056/27/6/063701
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Potential distribution is an important characteristic for evaluating the performance of an ion trap. Here, we analyze and optimize the potential distribution of an endcap ion trap for single-ion trapping.We obtain an optimal endcap radius of 225 μm-250 μm, endcap-shield gap of~250 μm, and inter-endcap distance of 540 μm-590 μm. The simulation method for analysis can also be applied to other ion traps, which is useful for improving the design and assembly of ion traps.

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

Propagation of acoustic waves in a fluid-filled pipe with periodic elastic Helmholtz resonators

Dian-Long Yu, Hui-Jie Shen, Jiang-Wei Liu, Jian-Fei Yin, Zhen-Fang Zhang, Ji-Hong Wen
Chin. Phys. B 2018, 27 (6): 064301;  doi: 10.1088/1674-1056/27/6/064301
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Helmholtz resonators are widely used to reduce noise in a fluid-filled pipe system. It is a challenge to obtain low-frequency and broadband attenuation with a small sized cavity. In this paper, the propagation of acoustic waves in a fluid-filled pipe system with periodic elastic Helmholtz resonators is studied theoretically. The resonance frequency and sound transmission loss of one unit are analyzed to validate the correctness of simplified acoustic impedance. The band structure of infinite periodic cells and sound transmission loss of finite periodic cells are calculated by the transfer matrix method and finite element software. The effects of several parameters on band gap and sound transmission loss are probed. Further, the negative bulk modulus of periodic cells with elastic Helmholtz resonators is analyzed. Numerical results show that the acoustic propagation properties in the periodic pipe, such as low frequency, broadband sound transmission, can be improved.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

Reversed rotation of limit cycle oscillation and dynamics of low-intermediate-high confinement transition

Dan-Dan Cao, Feng Wan, Ya-Juan Hou, Hai-Bo Sang, Bai-Song Xie
Chin. Phys. B 2018, 27 (6): 065201;  doi: 10.1088/1674-1056/27/6/065201
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The dynamics of the confinement transition from L mode to H mode (LH) is investigated in detail theoretically via the extended three-wave coupling model describing the interaction of turbulence and zonal flow (ZF) for the first time. Thereinto, turbulence is divided into a positive-frequency (PF) wave and a negative-frequency (NF) one, and the gradient of pressure is added as the auxiliary energy for the system. The LH confinement transition is observed for a sufficiently high input energy. Moreover, it is found that the rotation direction of the limit cycle oscillation (LCO) of PF wave and pressure gradient is reversed during the transition. The mechanism is illustrated by exploring the wave phases. The results presented here provide a new insight into the analysis of the LH transition, which is helpful for the experiments on the fusion devices.

Measurements of argon metastable density using the tunable diode laser absorption spectroscopy in Ar and Ar/O2

Dao-Man Han, Yong-Xin Liu, Fei Gao, Wen-Yao Liu, Jun Xu, You-Nian Wang
Chin. Phys. B 2018, 27 (6): 065202;  doi: 10.1088/1674-1056/27/6/065202
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Densities of Ar metastable states 1s5 and 1s3 are measured by using the tunable diode laser absorption spectroscopy (TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma (DF-CCP). We investigate the effects of high-frequency (HF, 60 MHz) power, low-frequency (LF, 2 MHz) power, and working pressure on the density of Ar metastable states for three different gas components (0%, 5%, and 10% oxygen mixed in argon). The dependence of Ar metastable state density on the oxygen content is also studied at different working pressures. It is found that densities of Ar metastable states in discharges with different gas components exhibit different behaviors as HF power increases. With the increase of HF power, the metastable density increases rapidly at the initial stage, and then tends to be saturated at a higher HF power. With a small fraction (5% or 10%) of oxygen added in argon plasma, a similar change of the Ar metastable density with HF power can be observed, but the metastable density is saturated at a higher HF power than in the pure argon discharge. In the DF-CCP, the metastable density is found to be higher than in a single frequency discharge, and has weak dependence on LF power. As working pressure increases, the metastable state density first increases and then decreases, and the pressure value, at which the density maximum occurs, decreases with oxygen content increasing. Besides, adding a small fraction of oxygen into argon plasma will significantly dwindle the metastable state density as a result of quenching loss by oxygen molecules.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

Fractional Stokes-Einstein relation in TIP5P water at high temperatures

Gan Ren, Ge Sang
Chin. Phys. B 2018, 27 (6): 066101;  doi: 10.1088/1674-1056/27/6/066101
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Fractional Stokes-Einstein relation described by D~(τ/T ight)ξ is observed in supercooled water, where D is the diffusion constant, τ the structural relaxation time, T the temperature, and the exponent ξ≠-1. In this work, the Stokes-Einstein relation in TIP5P water is examined at high temperatures within 400 K-800 K. Our results indicate that the fractional Stokes-Einstein relation is explicitly existent in TIP5P water at high temperatures, demonstrated by the two usually adopted variants of the Stokes-Einstein relation, D-1and D~T/τ, as well as by D~T/η, where η is the shear viscosity. Both D-1 and D~T/τ are crossed at temperature Tx=510 K. The D-1 is in a fractional form as Dξ with ξ=-2.09 for TTx and otherwise ξ=-1.25. The D~T/τ is valid with ξ=-1.01 for TTx but in a fractional form for T> Tx. The Stokes-Einstein relation D~T/η is satisfied below Tx=620 K but in a fractional form above Tx. We propose that the breakdown of D~T/η may result from the system entering into the super critical region, the fractional forms of D-1 and D~T/τ are due to the disruption of the hydration shell and the local tetrahedral structure as well as the increase of the shear viscosity.

Jamming of packings of frictionless particles with and without shear

Wen Zheng, Shiyun Zhang, Ning Xu
Chin. Phys. B 2018, 27 (6): 066102;  doi: 10.1088/1674-1056/27/6/066102
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By minimizing the enthalpy of packings of frictionless particles, we obtain jammed solids at desired pressures and hence investigate the jamming transition with and without shear. Typical scaling relations of the jamming transition are recovered in both cases. In contrast to systems without shear, shear-driven jamming transition occurs at a higher packing fraction and the jammed solids are more rigid with an anisotropic force network. Furthermore, by introducing the macro-friction coefficient, we propose an explanation of the packing fraction gap between sheared and non-sheared systems at fixed pressure.

Li adsorption on monolayer and bilayer MoS2 as an ideal substrate for hydrogen storage

Cheng Zhang, Shaolong Tang, Mingsen Deng, Youwei Du
Chin. Phys. B 2018, 27 (6): 066103;  doi: 10.1088/1674-1056/27/6/066103
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Based on the first-principles plane wave calculations, we show that Li adsorbed on monolayer and bilayer MoS2 forming a uniform and stable coverage can serve as a high-capacity hydrogen storage medium, and Li-coated MoS2 can be recycled by operations at room temperature due to Li having strength binding, big separation and is stable against clustering. The full Li coverage MoS2 system (2*2 hexagonal MoS2 supercell) can reach up to eight H2 molecules on every side, corresponding to the gravimetric density of hydrogen storage up to 4.8 wt% and 2.5 wt% in monolayer and bilayer MoS2, respectively. The adsorption energies of hydrogen molecules are in the range of 0.10eV/H2-0.25 eV/H2, which are acceptable for reversible H2 adsorption/desorption near ambient temperature. In addition, compared with light metals decorated low dimension carbon-based materials, the sandwiched structure of MoS2 exhibits the greatly enhanced binding stability of Li atoms as well as slightly decreased Li-Li interaction and thus avoids the problem of metal clustering. It is interesting to note that the Li atom apart from the electrostatic interaction, acts as a bridge of hybridization between the S atoms of MoS2 and adsorbed H2 molecules. The encouraging results show that such light metals decorated with MoS2 have great potential in developing high performance hydrogen storage materials.

Effects of temperature and point defects on the stability of C15 Laves phase in iron: A molecular dynamics investigation

Hao Wang, Ning Gao, Guang-Hong Lü, Zhong-Wen Yao
Chin. Phys. B 2018, 27 (6): 066104;  doi: 10.1088/1674-1056/27/6/066104
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Molecular dynamics simulations are used to investigate the stabilities of C15 Laves phase structures subjected to temperature and point defects. The simulations based on different empirical potentials show that the bulk perfect C15 Laves phase appears to be stable under a critical temperature in a range from 350 K to 450 K, beyond which it becomes disordered and experiences an abrupt decrement of elastic modulus. In the presence of both vacancy and self-interstitial, the bulk C15 Laves phase becomes unstable at room temperature and prefers to transform into an imperfect body centered cubic (BCC) structure containing free vacancies or vacancy clusters. When a C15 cluster is embedded in BCC iron, the annihilation of interstitials occurs due to the presence of the vacancy, while it exhibits a phase transformation into a (1/2)<111> dislocation loop due to the presence of the self-interstitial.

Mechanisms of atmospheric neutron-induced single event upsets in nanometric SOI and bulk SRAM devices based on experiment-verified simulation tool

Zhi-Feng Lei, Zhan-Gang Zhang, Yun-Fei En, Yun Huang
Chin. Phys. B 2018, 27 (6): 066105;  doi: 10.1088/1674-1056/27/6/066105
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In this paper, a simulation tool named the neutron-induced single event effect predictive platform (NSEEP2) is proposed to reveal the mechanism of atmospheric neutron-induced single event effect (SEE) in an electronic device, based on heavy-ion data and Monte-Carlo neutron transport simulation. The detailed metallization architecture and sensitive volume topology of a nanometric static random access memory (SRAM) device can be considered to calculate the real-time soft error rate (RTSER) in the applied environment accurately. The validity of this tool is verified by real-time experimental results. In addition, based on the NSEEP2, RTSERs of 90 nm-32 nm silicon on insulator (SOI) and bulk SRAM device under various ambient conditions are predicted and analyzed to evaluate the neutron SEE sensitivity and reveal the underlying mechanism. It is found that as the feature size shrinks, the change trends of neutron SEE sensitivity of bulk and SOI technologies are opposite, which can be attributed to the different MBU performances. The RTSER of bulk technology is always 2.8-64 times higher than that of SOI technology, depending on the technology node, solar activity, and flight height.

Non-monotonic dependence of current upon i-width in silicon p-i-n diodes

Zheng-Peng Pang, Xin Wang, Jian Chen, Pan Yang, Yang Zhang, Yong-Hui Tian, Jian-Hong Yang
Chin. Phys. B 2018, 27 (6): 066106;  doi: 10.1088/1674-1056/27/6/066106
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Silicon p-i-n diodes with different i-region widths are fabricated and tested. It is found that the current shows the non-monotonic behavior as a function of i-region width at a bias voltage of 1.0 V. In this paper, an analytical model is presented to explain the non-monotonic behavior, which mainly takes into account the diffusion current and recombination current contributing to the total current. The calculation results indicate that the concentration ratio of p-region to n-region plays a crucial role in the non-monotonic behavior, and the carrier lifetime also has a great influence on this abnormal phenomenon.

Pressure-induced enhancement of optoelectronic properties in PtS2

Yi-Fang Yuan, Zhi-Tao Zhang, Wei-Ke Wang, Yong-Hui Zhou, Xu-Liang Chen, Chao An, Ran-Ran Zhang, Ying Zhou, Chuan-Chuan Gu, Liang Li, Xin-Jian Li, Zhao-Rong Yang
Chin. Phys. B 2018, 27 (6): 066201;  doi: 10.1088/1674-1056/27/6/066201
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PtS2, which is one of the group-10 transition metal dichalcogenides, attracts increasing attention due to its extraordinary properties under external modulations as predicted by theory, such as tunable bandgap and indirect-to-direct gap transition under strain; however, these properties have not been verified experimentally. Here we report the first experimental exploration of its optoelectronic properties under external pressure. We find that the photocurrent is weakly pressure-dependent below 3 GPa but increases significantly in the pressure range of 3 GPa-4 GPa, with a maximum~6 times higher than that at ambient pressure. X-ray diffraction data shows that no structural phase transition can be observed up to 26.8 GPa, which indicates a stable lattice structure of PtS2 under high pressure. This is further supported by our Raman measurements with an observation of linear blue-shifts of the two Raman-active modes to 6.4 GPa. The pressure-enhanced photocurrent is related to the indirect-to-direct/quasi-direct bandgap transition under pressure, resembling the gap behavior under compression strain as predicted theoretically.

Phase transition and near-zero thermal expansion of Zr0.5Hf0.5VPO7

Jun-Ping Wang, Qing-Dong Chen, Sai-Lei Li, Yan-Jun Ji, Wen-Ying Mu, Wei-Wei Feng, Gao-Jie Zeng, You-Wen Liu, Er-Jun Liang
Chin. Phys. B 2018, 27 (6): 066501;  doi: 10.1088/1674-1056/27/6/066501
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The Zr0.5Hf0.5VPO7 is successfully synthesized by the solid-state method with near-zero thermal expansion. Powder x-ray diffraction (XRD), Raman spectroscopy, thermal dilatometry, and scanning electron microscopy (SEM) are used to investigate the structure, the phase transition, and the coefficient of thermal expansion (CTE) of Zr0.5Hf0.5VPO7. The investigation results show that the samples are of the single cubic type with a space group of Pa3 at room temperature (RT). It can be inferred that the superstructure is transformed from the 3×3×3 superstructure to the 1×1×1 ideal crystal in a temperature range between 310 K and 323 K. The CTE is measured by a dilatometer to be 0.59×10-6 K-1 (310 K-673 K). The values of intrinsic (XRD) and extrinsic (dilatometric) thermal expansion are both near zero. The results show that Zr0.5Hf0.5VPO7 has near-zero thermal expansion behavior over a wide temperature range.
RAPID COMMUNICATION
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Explicit forms of zero modes in symmetric interacting Kitaev chain without and with dimerization

Yiming Wang, Zhidan Li, Qiang Han
Chin. Phys. B 2018, 27 (6): 067101;  doi: 10.1088/1674-1056/27/6/067101
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The fermionic and bosonic zero modes of the one-dimensional (1D) interacting Kitaev chain at the symmetric point are unveiled. The many-body structures of the Majorana zero modes in the topological region are given explicitly by carrying out a perturbation expansion up to infinite order. We also give the analytic expressions of the bosonic zero modes in the topologically trivial phase. Our results are generalized to the hybrid fermion system comprised of the interacting Kitaev model and the Su-Schrieffer-Heeger (SSH) model, in which we show that these two types of zero modes can coexist in a certain region of its phase diagram.

The structural, electronic, and optical properties of organic-inorganic mixed halide perovskites CH3NH3Pb(I1-y Xy)3 (X=Cl, Br)

Miao Jiang, Naihang Deng, Li Wang, Haiming Xie, Yongqing Qiu
Chin. Phys. B 2018, 27 (6): 067102;  doi: 10.1088/1674-1056/27/6/067102
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Methylammmonium lead iodide perovskites (CH3NH3PbI3) have received wide attention due to their superior optoelectronic properties. We performed first-principles calculations to investigate the structural, electronic, and optical properties of mixed halide perovskites CH3NH3Pb(I1-yXy)3 (X=Cl, Br; y=0, 0.33, 0.67). Our results reveal the reduction of the lattice constants and dielectric constants and enhancement of band gaps with increasing doping concentration of Cl-/Br- at I-. Electronic structure calculations indicate that the valance band maximum (VBM) is mainly governed by the halide p orbitals and Pb 6s orbitals, Pb 6p orbitals contribute the conduction band minimum (CBM) and doping does not change the direct semiconductor material. The organic cation[CH3NH3]+ does not take part in the formation of the band and only one electron donates to the considered materials. The increasing trends of the band gap with Cl content from y=0 (0.793 eV) to y=0.33 (0.953 eV) then to y=0.67 (1.126 eV). The optical absorption of the considered structures in the visible spectrum range is decreased but after doping the stability of the material is improving.

Magnetic interactions in a proposed diluted magnetic semiconductor (Ba1-xKx)(Zn1-yMny)2P2

Huan-Cheng Yang, Kai Liu, Zhong-Yi Lu
Chin. Phys. B 2018, 27 (6): 067103;  doi: 10.1088/1674-1056/27/6/067103
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By using first-principles electronic structure calculations, we have studied the magnetic interactions in a proposed BaZn2P2-based diluted magnetic semiconductor (DMS). For a typical compound Ba(Zn0.944Mn0.056)2P2 with only spin doping, due to the superexchange interaction between Mn atoms and the lack of itinerant carriers, the short-range antiferromagnetic coupling dominates. Partially substituting K atoms for Ba atoms, which introduces itinerant hole carriers into the p orbitals of P atoms so as to link distant Mn moments with the spin-polarized hole carriers via the p-d hybridization between P and Mn atoms, is very crucial for the appearance of ferromagnetism in the compound. Furthermore, applying hydrostatic pressure first enhances and then decreases the ferromagnetic coupling in (Ba0.75K0.25)(Zn0.944Mn0.056)2P2 at a turning point around 15 GPa, which results from the combined effects of the pressure-induced variations of electron delocalization and p-d hybridization. Compared with the BaZn2As2-based DMS, the substitution of P for As can modulate the magnetic coupling effectively. Both the results for BaZn2P2-based and BaZn2As2-based DMSs demonstrate that the robust antiferromagnetic (AFM) coupling between the nearest Mn-Mn pairs bridged by anions is harmful to improving the performance of these Ⅱ-Ⅱ-V based DMS materials.

Complex alloying effect on thermoelectric transport properties of Cu2Ge(Se1-xTex)3

Ruifeng Wang, Lu Dai, Yanci Yan, Kunling Peng, Xu Lu, Xiaoyuan Zhou, Guoyu Wang
Chin. Phys. B 2018, 27 (6): 067201;  doi: 10.1088/1674-1056/27/6/067201
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To enhance the thermoelectric performance of Cu2GeSe3, a series of Te-alloyed samples Cu2Ge(Se1-xTex)3 are synthesized and investigated in this work. It is found that the lattice thermal conductivity is reduced drastically for x=0.1 sample, which may be attributed to the point defects introduced by alloying. However, for samples with x ≥ 0.2, the lattice thermal conductivity increases with increasing x, which is related to a less distorted structure. The structure evolution, together with the change in carrier concentration, also leads to a systemically change in electrical properties. Finally, a zT of 0.55@750 K is obtained for the sample with x=0.3, about 62% higher than that for the pristine sample.

How to characterize capacitance of organic optoelectronic devices accurately

Hao-Miao Yu, Yun He
Chin. Phys. B 2018, 27 (6): 067202;  doi: 10.1088/1674-1056/27/6/067202
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The selection of circuit model (i.e., parallel or series model) is critical when using a capacitance-frequency and capacitance-voltage technique to probe properties of organic materials and physical processes of organic optoelectronic devices. In the present work, capacitances of ITO/Alq3/Al and ITO/CuPc/Al are characterized by series and parallel model, respectively. It is found that the large series resistance comes from the ITO electrode and results in the inapplicability of the parallel model to measuring the capacitances of organic devices at high frequencies. An equivalent circuit model with consideration of the parasitical inductance of cables is constructed to derive the capacitance, and actual capacitance-frequency spectra of Alq3 and CuPc devices are obtained. Further investigation of temperature-dependent capacitance-frequency and capacitance-voltage characteristics indicates that CuPc and Al form the Schottky contact, the density and ionization energy of impurities in CuPc are obtained. Moreover, more practical guidelines for accurate capacitance measurement are introduced instead of the impedance magnitude, which will be very helpful for the organic community to investigate capacitance-related characteristics when dealing with various organic optoelectronic devices.

Electrical controllable spin valves in a zigzag silicene nanoribbon ferromagnetic junction

Lin Zhang
Chin. Phys. B 2018, 27 (6): 067203;  doi: 10.1088/1674-1056/27/6/067203
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We propose two possible spin valves based on a zigzag silicene nanoribbon (ZSR) ferromagnetic junction. By using the Landauer-Bütikker formula, we calculate the spin-resolved conductance spectrum of the system and find that the spin transport is crucially dependent on the band structure of the ZSR tuned by a perpendicular electric field. When the ZSR is in the topological insulator phase under a zero electric field, the low-energy spin transport and its ON and OFF states in the tunneling junction mainly rely on the valley valve effect and the edge state of the energy band, which can be electrically modulated by the Fermi level, the spin-orbit coupling, and the local magnetization. When a nonzero perpendicular electric field is applied, the ZSR is a band insulator with a finite energy gap, the spin switch phenomenon is still preserved in the device and it does not come from the valley valve effect, but from the energy gap opened by the perpendicular electric field. The proposed device might be designed as electrical tunable spin valves to manipulate the spin degree of freedom of electrons in silicene.

Room-temperature large photoinduced magnetoresistance in semi-insulating gallium arsenide-based device

Xiong He, Zhi-Gang Sun
Chin. Phys. B 2018, 27 (6): 067204;  doi: 10.1088/1674-1056/27/6/067204
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It is still a great challenge for semiconductor based-devices to obtain a large magnetoresistance (MR) effect under a low magnetic field at room temperature. In this paper, the photoinduced MR effects under different intensities of illumination at room temperature are investigated in a semi-insulating gallium arsenide (SI-GaAs)-based Ag/SI-GaAs/Ag device. The device is subjected to the irradiation of light which is supplied by light-emitting diode (LED) lamp beads with a wavelength in a range of about 395 nm-405 nm and the working power of each LED lamp bead is about 33 mW. The photoinduced MR shows no saturation under magnetic fields (B) up to 1 T and the MR sensitivity S (S=MR/B) at low magnetic field (B=0.001 T) can reach 15 T-1. It is found that the recombination of photoinduced electron and hole results in a positive photoinduced MR effect. This work implies that a high photoinduced S under a low magnetic field may be obtained in a non-magnetic semiconductor device with a very low intrinsic carrier concentration.

Enhanced photoresponse performance in Ga/Ga2O3 nanocomposite solar-blind ultraviolet photodetectors

Shu-Juan Cui, Zeng-Xia Mei, Yao-Nan Hou, Quan-Sheng Chen, Hui-Li Liang, Yong-Hui Zhang, Wen-Xing Huo, Xiao-Long Du
Chin. Phys. B 2018, 27 (6): 067301;  doi: 10.1088/1674-1056/27/6/067301
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In the present work, we explore the solar-blind ultraviolet (UV) photodetectors (PDs) with enhanced photoresponse, fabricated on Ga/Ga2O3 nanocomposite films. Through pre-burying metal Ga layers and thermally post-annealing the laminated Ga2O3/Ga/Ga2O3 structures, Ga/Ga2O3 nanocomposite films incorporated with Ga nanospheres are obtained. For the prototype PD, it is found that the photocurrent and photoresponsivity will first increase and then decrease monotonically with the thickness of the pre-buried Ga layer increasing. Each of all PDs shows a spectrum response peak at 260 nm, demonstrating the ability to detect solar-blind UV light. Adjustable photoresponse enhancement factors are achieved by means of the surface plasmon in the nanocomposite films. The PD with a 20 nm thick Ga interlayer exhibits the best solar-blind UV photoresponse characteristics with an extremely low dark current of 8.52 pA at 10-V bias, a very high light-to-dark ratio of~8×105, a large photoresponsivity of 2.85 A/W at 15-V bias, and a maximum enhancement factor of~220. Our research provides a simple and practical route to high performance solar-blind UV PDs and potential applications in the field of optoelectronics.

Resonant surface plasmons of a metal nanosphere treated as propagating surface plasmons

Yu-Rui Fang, Xiao-Rui Tian
Chin. Phys. B 2018, 27 (6): 067302;  doi: 10.1088/1674-1056/27/6/067302
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On the assumption that the resonant surface plasmons on a spherical nanoparticle are formed by standing waves of two counter-propagating surface plasmon waves along the surface, by using Mie theory simulation, we find that the dispersions of surface plasmon resonant modes supported by silver nanospheres match with those of the surface plasmons on a semi-infinite medium-silver interface very well. This suggests that the resonant surface plasmons of a metal nanosphere can be treated as a propagating surface plasmon wave.

Improved performance of Au nanocrystal nonvolatile memory by N2-plasma treatment on HfO2 blocking layer

Chen Wang, Yi-Hong Xu, Song-Yan Chen, Cheng Li, Jian-Yuan Wang, Wei Huang, Hong-Kai Lai, Rong-Rong Guo
Chin. Phys. B 2018, 27 (6): 067303;  doi: 10.1088/1674-1056/27/6/067303
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The N2-plasma treatment on a HfO2 blocking layer of Au nanocrystal nonvolatile memory without any post annealing is investigated. The electrical characteristics of the MOS capacitor with structure of Al-TaN/HfO2/SiO2/p-Si are also characterized. After N2-plasma treatment, the nitrogen atoms are incorporated into HfO2 film and may passivate the oxygen vacancy states. The surface roughness of HfO2 film can also be reduced. Those improvements of HfO2 film lead to a smaller hysteresis and lower leakage current density of the MOS capacitor. The N2-plasma is introduced into Au nanocrystal (NC) nonvolatile memory to treat the HfO2 blocking layer. For the N2-plasma treated device, it shows a better retention characteristic and is twice as large in the memory window than that for the no N2-plasma treated device. It can be concluded that the N2-plasma treatment method can be applied to future nonvolatile memory applications.

Enhanced transient photovoltaic characteristics of core-shell ZnSe/ZnS/L-Cys quantum-dot-sensitized TiO2 thin-film

Kui-Ying Li, Lun Ren, Tong-De Shen
Chin. Phys. B 2018, 27 (6): 067305;  doi: 10.1088/1674-1056/27/6/067305
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Photoanodic properties greatly determine the overall performance of quantum-dot-sensitized solar cells (QDSCs). In the present report, the microdynamic behaviors of carriers in the nanocomposite thin-film, a ZnSe QD-sensitized mesoporous La-doped nano-TiO2 thin-film, as a potential candidate for photoanode, are probed via nanosecond transient photovoltaic (TPV) spectroscopy. The results confirm that the L-Cys ligand has a dual function serving as a stabilizer and molecular linker. Large quantities of interface states are located at the energy level with a photoelectric threshold of 1.58 eV and a quantum well (QW) depth of 0.67 eV. This QW depth is approximately 0.14 eV deeper than the depth of QW buried in the ZnSe QDs, and a deeper QW results in a higher quantum confinement energy. A strong quantum confinement effect of the interface state may be responsible for the excellent TPV characteristics of the photoanode. For example, the peak intensity of the TPV response of the QD-sensitized thin-film lasts a long time, from 9.40×10-7 s to 2.96×10-4 s, and the end time of the PTV response of the QD-sensitized thin-film is extended by approximately an order of magnitude compared with those of the TiO2 substrate and the QDs. The TPV characteristics of the QD-sensitized thin-film change from p-type to n-type for the QDs before and after sensitizing. These properties strongly depend on the extended diffusion length of the photogenerated carries and the reduced recombination rate of photogenerated electron-hole pairs, resulting in prolonged carrier lifetime and an increased level of electron injection into the TiO2 thin-film substrate.

Enhancement of off-state characteristics in junctionless field effect transistor using a field plate

Bin Wang, He-Ming Zhang, Hui-Yong Hu, Xiao-Wei Shi
Chin. Phys. B 2018, 27 (6): 067402;  doi: 10.1088/1674-1056/27/6/067402
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In this paper, a novel junctionless field effect transistor (JLFET) is proposed. In the presence of a field plate between gate and drain, the gate-induced drain leakage (GIDL) effect is suppressed due to the decrease of lateral band-to-band tunneling probability. Thus, the off-state current Ioff, which is mainly provided by the GIDL current, is reduced. Sentaurus simulation shows that the Ioff of the new optimized JLFET is reduced by~2 orders and its sub-threshold swing can reach 76.8 mV/decade with little influence on its on-state current Ion, so its Ion/Ioff ratio is improved by 2 orders of magnitude compared with that of the normal JLFET. Optimization of device parameters such as Φfps (the work difference between field plate and substrate) and LFP (the length of field plate), is also discussed in detail.

Superconductivity of bilayer titanium/indium thin film grown on SiO2/Si (001)

Zhao-Hong Mo, Chao Lu, Yi Liu, Wei Feng, Yun Zhang, Wen Zhang, Shi-Yong Tan, Hong-Jun Zhang, Chun-Yu Guo, Xiao-Dong Wang, Liang Wang, Rui-Zhu Yang, Zhong-Guo Ren, Xie-Gang Zhu, Zhong-Hua Xiong, Qi An, Xin-Chun Lai
Chin. Phys. B 2018, 27 (6): 067403;  doi: 10.1088/1674-1056/27/6/067403
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Bilayer superconducting films with tunable transition temperature (Tc) are a critical ingredient to the fabrication of high-performance transition edge sensors. Commonly chosen materials include Mo/Au, Mo/Cu, Ti/Au, and Ti/Al systems. Here in this work, titanium/indium (Ti/In) bilayer superconducting films are successfully fabricated on SiO2/Si (001) substrates by molecular beam epitaxy (MBE). The success in the epitaxial growth of indium on titanium is achieved by lowering the substrate temperature to -150℃ during indium evaporation. We measure the critical temperature under a bias current of 10 μA, and obtain different superconducting transition temperatures ranging from 645 mK to 2.7 K by adjusting the thickness ratio of Ti/In. Our results demonstrate that the transition temperature decreases as the thickness ratio of Ti/In increases.

Current-induced synchronized magnetization reversal of two-body Stoner particles with dipolar interaction

Zhou-Zhou Sun, Yu Yang, J Schliemann
Chin. Phys. B 2018, 27 (6): 067501;  doi: 10.1088/1674-1056/27/6/067501
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We investigate magnetization reversal of two-body uniaxial Stoner particles, by injecting spin-polarized current through a spin-valve structure. The two-body Stoner particles perform synchronized dynamics and can act as an information bit in computer technology. In the presence of magnetic dipole-dipole interaction (DDI) between the two particles, the critical switching current Ic for reversing the two dipoles is analytically obtained and numerically verified in two typical geometric configurations. The Ic bifurcates at a critical DDI strength, where Ic can decrease to about 70% of the usual value without DDI. Moreover, we also numerically investigate the magnetic hysteresis loop, magnetization self-precession, reversal time and synchronization stability phase diagram for the two-body system in the synchronized dynamics regime.

Voltage control of magnetization switching and dynamics

Hong-Yu Wen, Jian-Bai Xia
Chin. Phys. B 2018, 27 (6): 067502;  doi: 10.1088/1674-1056/27/6/067502
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The voltage controlled magnetic switching effect is verified experimentally. The Landau-Lifshitz-Gilbert (LLG) equation is used to study the voltage controlled magnetic switching. It is found that the initial values of magnetic moment components are critical for the switching effect, which should satisfy a definite condition. The external magnetic field which affects only the oscillation period should be comparable to the internal magnetic field. If the external magnetic field is too small, the switching effect will disappear. The precessions of mx and my are the best for the tilt angle of the external magnetic field θt=0°, i.e., the field is perpendicular to the sample plane.

Transition intensity calculation of Yb: YAG

Hong-Bo Zhang, Qing-Li Zhang, Xing Wang, Gui-Hua Sun, Xiao-Fei Wang, De-Ming Zhang, Dun-Lu Sun
Chin. Phys. B 2018, 27 (6): 067801;  doi: 10.1088/1674-1056/27/6/067801
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The Yb:YAG is an excellent high-average power and ultra-short pulse laser crystal. Transition intensity parameters Atpk and Huang-Rhys factors are fitted to its emission spectrum by the full-profile fitting method. Calculated results indicate that the emission spectrum of Yb:YAG at cryogenic temperature consists of three pure electron state transitions and two phonon-assisted transitions, one vibronic transition releases one-phonon of 3 cm-1, and the other vibronic transition absorbs one-phonon of 22 cm-1. At 300 K, the phonon assisted transition of 3 cm-1 turns into two-or more-phonon assisted transitions. The procedure absorbing phonon can reduce the thermal load of Yb:YAG and improve the laser efficiency, which may be one of the reasons why Yb:YAG has excellent performance. The emission bands of Yb:YAG are broadened thermally, and the peak values decrease by several times. The emission cross sections of Yb:YAG determined by Fuchtbauer-Ladenburg (F-L) formula are remarkably different from those calculated with Atpk, which indicates that it is necessary for a laser material to determine its transition intensity parameters Atpk in order to reasonably evaluate the laser performance.

Variable angle spectroscopic ellipsometry and its applications in determining optical constants of chalcogenide glasses in infrared

Ning-Ning Wei, Zhen Yang, Hong-Bo Pan, Fan Zhang, Yong-Xing Liu, Rong-Ping Wang, Xiang Shen, Shi-Xun Dai, Qiu-Hua Nie
Chin. Phys. B 2018, 27 (6): 067802;  doi: 10.1088/1674-1056/27/6/067802
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The principle of variable angle spectroscopic ellipsometry (VASE) and the data analysis models, as well as the applications of VASE in the characterization of chalcogenide bulk glasses and thin films are reviewed. By going through the literature and summarizing the application scopes of various analysis models, it is found that a combination of various models, rather than any single data analysis model, is ideal to characterize the optical constants of the chalcogenide bulk glasses and thin films over a wider wavelength range. While the reliable optical data in the mid-and far-infrared region are limited, the VASE is flexible and reliable to solve the issues, making it promising to characterize the optical properties of chalcogenide glasses.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

Free-standing, curled and partially reduced graphene oxide network as sulfur host for high-performance lithium-sulfur batteries

Hui-Liang Chen, Zhuo-Jian Xiao, Nan Zhang, Shi-Qi Xiao, Xiao-Gang Xia, Wei Xi, Yan-Chun Wang, Wei-Ya Zhou, Si-Shen Xie
Chin. Phys. B 2018, 27 (6): 068101;  doi: 10.1088/1674-1056/27/6/068101
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Lithium-sulfur (Li-S) batteries have received more and more attention because of higher specific capacity and energy density of sulfur than current lithium-ion batteries. However, the low electrical conductivity of sulfur and its discharge product, and also the high dissolution of polysulfides restrict the Li-S battery practical applications. To improve their performances, in this work, we fabricate a novel free-standing, curled and partially reduced graphene oxide (CPrGO for short) network and combine it with sulfur to form a CPrGO-S composite as a cathode for Li-S battery. With sulfur content of 60 wt%, the free-standing CPrGO-S composite network delievers an initial capacity of 988.9 mAh·g-1. After 200 cycles, it shows a stable capacity of 841.4 mAh·g-1 at 0.2 C, retaining about 85% of the initial value. The high electrochemical performance demonstrates that the CPrGO-S network has great potential applications in energy storage system. Such improved properties can be ascribed to the unique free-standing and continous CPrGO-S network which has high specific surface area and good electrical conductivity. In addition, oxygen-containing groups on the partially reduced graphene oxide are beneficial to preventing the polysulfides from dissolving into electrolyte and can mitigate the “shuttle effect”.

Wider frequency domain for negative refraction index in a quantized composite right-left handed transmission line

Qi-Xuan Wu, Shun-Cai Zhao
Chin. Phys. B 2018, 27 (6): 068102;  doi: 10.1088/1674-1056/27/6/068102
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The refraction index of the quantized lossy composite right-left handed transmission line (CRLH-TL) is deduced in the thermal coherence state. The results show that the negative refraction index (herein the left-handedness) can be implemented by the electric circuit dissipative factors(i.e., the resistances R and conductances G) in a higher frequency band (1.446 GHz ≤ ω ≤ 15 GHz), and flexibly adjusted by the left-handed circuit components (Cl, Ll) and the right-handed circuit components (Cr, Lr) at a lower frequency (ω=0.995 GHz). The flexible adjustment for left-handedness in a wider bandwidth will be significant for the microscale circuit design of the CRLH-TL and may make the theoretical preparation for its compact applications.

In situ growth of different numbers of gold nanoparticles on MoS2 with enhanced electrocatalytic activity for hydrogen evolution reaction

Xuan Zhao, Da-Wei He, Yong-Sheng Wang, Chen Fu
Chin. Phys. B 2018, 27 (6): 068103;  doi: 10.1088/1674-1056/27/6/068103
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Producing hydrogen through a hydrogen evolution reaction (HER) by splitting water at the suitable overpotential is a great alternative to solving the problems of environmental pollution and the energy crisis. Molybdenum sulfide (MoS2) has attracted extensive attention as one of the most promising catalytic materials for HER. In this work, we design a facile method to in situ grow gold nanoparticles (AuNPs) on MoS2. Different numbers of AuNPs with MoS2 are used to find the best catalytic activity. Due to the larger active surface area and higher conductivity of the Au-MoS2 composites, all the Au-MoS2 composites exhibit more enhanced HER electroactivity than pure MoS2. In brief, the new material architecture exhibits optimized HER activity with a low onset overpotential of 0.12 V, low Tafel slope of 0.163 V·dec-1, and an excellent stability in acidic solution.

Effect of substrate curvature on thickness distribution of polydimethylsiloxane thin film in spin coating process

Ying Yan, Ping Zhou, Shang-Xiong Zhang, Xiao-Guang Guo, Dong-Ming Guo
Chin. Phys. B 2018, 27 (6): 068104;  doi: 10.1088/1674-1056/27/6/068104
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The polymer spin coating is critical in flexible electronic manufaction and micro-electro-mechanical system (MEMS) devices due to its simple operation, and uniformly coated layers. Some researchers focus on the effects of spin coating parameters such as wafer rotating speed, the viscosity of the coating liquid and solvent evaporation on final film thickness. In this work, the influence of substrate curvature on film thickness distribution is considered. A new parameter which represents the edge bead effect ratio (re) is proposed to investigate the influence factor of edge bead effect. Several operation parameters including the curvature of the substrate and the wafer-spin speed are taken into account to study the effects on the film thickness uniformity and edge-bead ratio. The morphologies and film thickness values of the spin-coated PDMS films under various substrate curvatures and coating speeds are measured with laser confocal microscopy. According to the results, both the convex and concave substrate will help to reduce the edge-bead effect significantly and thin film with better surface morphology can be obtained at high spin speed. Additionally, the relationship between the edge-bead ratio and the thin film thickness is like parabolic curve instead of linear dependence. This work may contribute to the mass production of flexible electronic devices.

Tuning hybrid liquid/solid electrolytes by lowering Li salt concentration for lithium batteries Hot!

Wei Yang, Qi-Di Wang, Yu Lei, Zi-Pei Wan, Lei Qin, Wei Yu, Ru-Liang Liu, Deng-Yun Zhai, Hong Li, Bao-Hua Li, Fei-Yu Kang
Chin. Phys. B 2018, 27 (6): 068201;  doi: 10.1088/1674-1056/27/6/068201
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Hybrid liquid/solid electrolytes (HLSEs) consisting of conventional organic liquid electrolyte (LE), polyacrylonitrile (PAN), and ceramic lithium ion conductor Li1.5Al0.5Ge1.5(PO4)3 (LAGP) are proposed and investigated. The HLSE has a high ionic conductivity of over 2.25×10-3 S/cm at 25℃, and an extended electrochemical window of up to 4.8 V versus Li/Li+. The Li|HLSE|Li symmetric cells and Li|HLSE|LiFePO4 cells exhibit small interfacial area specific resistances (ASRs) comparable to that of LE while much smaller than that of ceramic LAGP electrolyte, and excellent performance at room temperature. Bis(trifluoromethane sulfonimide) salt in HLSE significantly affects the properties and electrochemical behaviors. Side reactions can be effectively suppressed by lowering the concentration of Li salt. It is a feasible strategy for pursuing the high energy density batteries with higher safety.

Electrical field-driven ripening profiles of colloidal suspensions

Zi-Rui Wang, Wei-Jia Wen, Li-Yu Liu
Chin. Phys. B 2018, 27 (6): 068301;  doi: 10.1088/1674-1056/27/6/068301
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Electrorheological (ER) fluid is a type of smart fluid whose shear yield stress relies on the external electrical field strength. The transition of ER fluid microstructure driven by the electrical field is the reason why viscosity changes. Experimentally, the transparent electrodes are used to investigate the column size distribution where an external electric field is applied to a colloidal suspension, i.e., ER fluid is increased. The coarsening profile of ER suspensions is strongly related to electrical field strength, but it is insensitive to particle size. In addition, in a low field range the shear stress corresponding to the mean column diameter is studied and they are found to satisfy a power law. However, this dependence is invalid when the field strength surpasses a threshold value.

Tunable circularly-polarized turnstile-junction mode converter for high-power microwave applications

Xiao-Yu Wang, Yu-Wei Fan, Ting Shu, Cheng-Wei Yuan, Qiang Zhang
Chin. Phys. B 2018, 27 (6): 068401;  doi: 10.1088/1674-1056/27/6/068401
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Frequency tunability has become a subject of concern in the field of high-power microwave (HPM) source research. However, little information about the corresponding mode converter is available. A tunable circularly-polarized turnstile-junction mode converter (TCTMC) for high-power microwave applications is presented in this paper. The input coaxial TEM mode is transformed into TE10 mode with different phase delays in four rectangular waveguides and then converted into a circularly-polarized TE11 circular waveguide mode. Besides, the rods are added to reduce or even eliminate the reflection. The innovations in this study are as follows. The tunning mechanism is added to the mode converter, which can change the effective length of rectangular waveguide and the distance between the rods installed upstream and the closest edge of the rectangular waveguide, thus improving the conversion efficiency and bandwidth. The conversion efficiency of TCTMC can reach above 98% over the frequency range of 1.42 GHz-2.29 GHz, and the frequency tunning bandwidth is about 47%. Significantly, TCTMC can obtain continuous high conversion efficiency of different frequency points with the change of tuning mechanism.

Characterization of barrier-tunable radio-frequency-SQUID for Maxwell's demon experiment

Gang Li, Suman Dhamala, Hao Li, Jian-She Liu, Wei Chen
Chin. Phys. B 2018, 27 (6): 068501;  doi: 10.1088/1674-1056/27/6/068501
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We present the design, fabrication, and characterization of a barrier-tunable superconducting quantum interference device (SQUID) qubit for the study of Maxwell's demon experiment. In this work, a compound Josephson junction (CJJ) radio-frequency (RF)-SQUID qubit with an overdamped resistively shunted direct-current (DC)-SQUID magnetometer is used to continuously monitor the state of the qubit. The circuit is successfully fabricated with the standard Nb/Al-AlOx/Nb trilayer process of our laboratory and characterized in a low noise measurement system, which is capable of measuring coherent dynamics of superconducting qubits, in an Oxford dilution refrigerator. All circuit parameters are determined accurately by fitting experimental data to theoretical analysis and simulation, which allows us to make a quantitative comparison between the results of the experiment and theory.

Compact wide stopband superconducting bandpass filter using modified spiral resonators with interdigital structure

Di Wu, Bin Wei, Bo Li, Xu-Bo Guo, Xin-Xiang Lu, Bi-Song Cao
Chin. Phys. B 2018, 27 (6): 068502;  doi: 10.1088/1674-1056/27/6/068502
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In this study, we propose a novel resonator that is composed of a modified spiral with an embedded interdigital capacitor. A large ratio of the first spurious frequency to the fundamental resonant frequency is obtained, which is suitable for the design of filters with wide stopbands, and the circuit size is considerably reduced by embedding the interdigital structure in the spiral. For demonstration, a compact four-pole high temperature superconducting (HTS) filter with a center frequency of 568 MHz is designed and fabricated on double-sided YBCO film with a size of 11.4 mm×8.0 mm. The filter measurement shows excellent performance with an out-of-band rejection level better than 60.9 dB up to 3863 MHz.

Compact high-order quint-band superconducting band-pass filter

Di Wu, Bin Wei, Xi-Long Lu, Xin-Xiang Lu, Xu-Bo Guo, Bi-Song Cao
Chin. Phys. B 2018, 27 (6): 068503;  doi: 10.1088/1674-1056/27/6/068503
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In this paper, we present a compact quint-band superconducting filter operating at 2.4, 3.5, 4.7, 5.3, and 5.9 GHz. Matching junctions with different impedance branch lines are used to connect a dual-band sub-filter with a tri-band sub-filter and to reduce the channel interactions. The quint-band filter design is divided into two sections to determine the controllable frequencies and bandwidths, while ensuring compact size and reducing design complexity. The filter is fabricated on double-sided YBCO film deposited on an MgO substrate with a size of 26 mm×19 mm. The measured results match well with the simulations.

Degradation of current-voltage and low frequency noise characteristics under negative bias illumination stress in InZnO thin film transistors

Li Wang, Yuan Liu, Kui-Wei Geng, Ya-Yi Chen, Yun-Fei En
Chin. Phys. B 2018, 27 (6): 068504;  doi: 10.1088/1674-1056/27/6/068504
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The instabilities of indium-zinc oxide thin film transistors under bias and/or illumination stress are studied in this paper. Firstly, illumination experiments are performed, which indicates the variations of current-voltage characteristics and electrical parameters (such as threshold voltage and sub-threshold swing) are dominated by the stress-induced ionized oxygen vacancies and acceptor-like states. The dependence of degradation on light wavelength is also investigated. More negative shift of threshold voltage and greater sub-threshold swing are observed with the decrease of light wavelength. Subsequently, a negative bias illumination stress experiment is carried out. The degradation of the device is aggravated due to the decrease of recombination effects between ionized oxygen vacancies and free carriers. Moreover, the contributions of ionized oxygen vacancies and acceptor-like states are separated by using the mid-gap method. In addition, ionized oxygen vacancies are partially recombined at room temperature and fully recombined at high temperature. Finally, low-frequency noise is measured before and after negative bias illumination stress. Experimental results show few variations of the oxide trapped charges are generated during stress, which is consistent with the proposed mechanism.

Physics-based analysis and simulation model of electromagnetic interference induced soft logic upset in CMOS inverter

Yu-Qian Liu, Chang-Chun Chai, Yu-Hang Zhang, Chun-Lei Shi, Yang Liu, Qing-Yang Fan, Yin-Tang Yang
Chin. Phys. B 2018, 27 (6): 068505;  doi: 10.1088/1674-1056/27/6/068505
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The instantaneous reversible soft logic upset induced by the electromagnetic interference (EMI) severely affects the performances and reliabilities of complementary metal-oxide-semiconductor (CMOS) inverters. This kind of soft logic upset is investigated in theory and simulation. Physics-based analysis is performed, and the result shows that the upset is caused by the non-equilibrium carrier accumulation in channels, which can ultimately lead to an abnormal turn-on of specific metal-oxide-semiconductor field-effect transistor (MOSFET) in CMOS inverter. Then a soft logic upset simulation model is introduced. Using this model, analysis of upset characteristic reveals an increasing susceptibility under higher injection powers, which accords well with experimental results, and the influences of EMI frequency and device size are studied respectively using the same model. The research indicates that in a range from L waveband to C waveband, lower interference frequency and smaller device size are more likely to be affected by the soft logic upset.

Integration of a field-effect-transistor terahertz detector with a diagonal horn antenna

Xiang Li, Jian-dong Sun, Zhi-peng Zhang, V V Popov, Hua Qin
Chin. Phys. B 2018, 27 (6): 068506;  doi: 10.1088/1674-1056/27/6/068506
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Efficient coupling of terahertz electromagnetic wave with the active region in a terahertz detector is required to enhance the optical sensitivity. In this work, we demonstrate direct integration of a field-effect-transistor (FET) terahertz detector chip at the waveguide port of a horn antenna. Although the integration without a proper backshot is rather preliminary, the noise-equivalent power is greatly reduced from 2.7 nW/Hz1/2 for the bare detector chip to 76 pW/Hz1/2 at 340 GHz. The enhancement factor of about 30 is confirmed by simulations revealing the effective increase in the energy flux density seen by the detector. The simulation further confirms the frequency response of the horn antenna and the on-chip antennas. A design with the detector chip fully embedded within a waveguide cavity could be made to further enhance the coupling efficiency.

Interaction between human telomeric G-quadruplexes characterized by single molecule magnetic tweezers

Yi-Zhou Wang, Xi-Miao Hou, Hai-Peng Ju, Xue Xiao, Xu-Guang Xi, Shuo-Xing Dou, Peng-Ye Wang, Wei Li
Chin. Phys. B 2018, 27 (6): 068701;  doi: 10.1088/1674-1056/27/6/068701
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Human telomeric G-quadruplex plays a crucial role in regulating the genome stability. Despite extensive studies on structures and kinetics of monomeric G-quadruplex, the interaction between G-quadruplexes is still in debate. In this work, we employ magnetic tweezers to investigate the folding and unfolding kinetics of two contiguous G-quadruplexes in 100-mM K+ buffer. The interaction between G-quadruplexes and the consequent effect on the kinetics of G-quadruplex are revealed. The linker sequence between G-quadruplexes is further found to play an important role in the interaction between two G-quadruplexes. Our results provide a high-resolution insight into kinetics of multimeric G-quadruplexes and genome stability.

Detection of finger interruptions in silicon solar cells using photoluminescence imaging

Lei Zhang, Peng Liang, Hui-Shi Zhu, Pei-De Han
Chin. Phys. B 2018, 27 (6): 068801;  doi: 10.1088/1674-1056/27/6/068801
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Since publication, it has been brought to the attention of the Editorial Office of Chinese Physics B that parts of this paper showed strong similarities to the following article (including one equation, some analyses, the motivation and the conclusion) without citation: “Detection of Finger Interruptions in Silicon Solar Cells Using Line Scan Photoluminescence Imaging,” IEEE Journal of Photovoltaics, 2017, vol. 7, No. 6, pp. 1496-1502. Following our investigation, this article has been retracted by the Editorial Office of Chinese Physics B.


Finger interruptions are common problems in screen printed solar cells, resulting in poor performance in efficiency because of high effective series resistance. Electroluminescence (EL) imaging is typically used to identify interrupted fingers. In this paper, we demonstrate an alternative method based on photoluminescence (PL) imaging to identify local series resistance defects, with a particular focus on finger interruptions. Ability to detect finger interruptions by using PL imaging under current extraction is analyzed and verified. The influences of external bias control and illumination intensity on PL images are then studied in detail. Finally, in comparison with EL imaging, the using of PL imaging to identify finger interruptions possesses the prominent advantages:in PL images, regions affected by interrupted fingers show higher luminescence intensity, while regions affected by recombination defects show lower luminescence intensity. This inverse signal contrast allows PL imaging to more accurately identify the defect types.

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