[an error occurred while processing this directive]
[an error occurred while processing this directive]
Chin. Phys. B  
  Chin. Phys. B--2019, Vol.28, No.12
Select | Export to EndNote
SPECIAL TOPIC—Recent advances in thermoelectric materials and devices
TOPICAL REVIEW—Strong-field atomic and molecular physics
SPECIAL TOPIC—Strong-field atomic and molecular physics

Electrically tunable spin diode effect in a tunneling junction of quantum dot

Xukai Peng, Zhengzhong Zhang
Chin. Phys. B 2019, 28 (12): 127202 ;  doi: 10.1088/1674-1056/ab53d0
Full Text: PDF (720KB) ( 112 ) RICH HTML
Show Abstract
Control over the tunneling current in spintronic devices by electrical methods is an interesting topic, which is experiencing a burst of activity. In this paper, we theoretically investigate the transport property of electrons in a spin-diode structure consisting of a single quantum dot (QD) weakly coupled to one nonmagnetic (NM) and one half-metallic ferromagnet (HFM) leads, in which the QD has an artificial atomic nature. By modulating the gate voltage applied on the dot, we observe a pronounced decrease in the current for one bias direction. We show that this rectification is spin-dependent, which stems from the interplay between the spin accumulation and the Coulomb blockade on the quantum dot. The degree of such spin diode behavior is fully and precisely tunable using the gate and bias voltages. The present device can be realized within current technologies and has potential application in molecular spintronics and quantum information processing.

Coulomb-dominated oscillations in a graphene quantum Hall Fabry-Pérot interferometer Hot!

Guan-Qun Zhang, Li Lin, Hailin Peng, Zhongfan Liu, Ning Kang, Hong-Qi Xu
Chin. Phys. B 2019, 28 (12): 127203 ;  doi: 10.1088/1674-1056/ab55d3
Full Text: PDF (2132KB) ( 185 ) RICH HTML
Show Abstract

The electronic Fabry-Pérot interferometer operating in the quantum Hall regime may be a promising tool for probing edge state interferences and studying the non-Abelian statistics of fractionally charged quasiparticles. Here we report on realizing a quantum Hall Fabry-Pérot interferometer based on monolayer graphene. We observe resistance oscillations as a function of perpendicular magnetic field and gate voltage both on the electron and hole sides. Their Coulomb-dominated origin is revealed by the positive (negative) slope of the constant phase lines in the plane of magnetic field and gate voltage on the electron (hole) side. Our work demonstrates that the graphene interferometer is feasible and paves the way for the studies of edge state interferences since high-Landau-level and even denominator fractional quantum Hall states have been found in graphene.

Different behavior of upper critical field in Fe1-xSe single crystals Hot!

Shunli Ni, Wei Hu, Peipei Shen, Zhongxu Wei, Shaobo Liu, Dong Li, Jie Yuan, Li Yu, Kui Jin, Fang Zhou, Xiaoli Dong, Zhongxian Zhao
Chin. Phys. B 2019, 28 (12): 127401 ;  doi: 10.1088/1674-1056/ab50b4
Full Text: PDF (884KB) ( 179 ) RICH HTML
Show Abstract
The temperature dependences of upper critical field (Hc2) for a series of iron-deficient Fe1-xSe single crystals are obtained from the measurements of in-plane resistivity in magnetic fields up to 9 T and perpendicular to the ab plane. For the samples with lower superconducting transition temperature Tc (<7.2 K), the temperature dependence of Hc2 is appropriately described by an effective two-band model. For the samples with higher Tc (≥7.2 K), the temperature dependence can also be fitted by a single-band Werthamer-Helfand-Hohenberg formula, besides the two-band model. Such a Tc-dependent change in Hc2(T) behavior is discussed in connection with recent related experimental results, showing an inherent link between the changes of intrinsic superconducting and normal state properties in the FeSe system.

Probing the minigap in topological insulator-based Josephson junctions under radio frequency irradiation

Guang Yang, Zhaozheng Lyu, Xiang Zhang, Fanming Qu, Li Lu
Chin. Phys. B 2019, 28 (12): 127402 ;  doi: 10.1088/1674-1056/ab5211
Full Text: PDF (2362KB) ( 98 ) RICH HTML
Show Abstract
Recently, a contact-resistance-measurement method was developed to detect the minigap, hence the Andreev bound states (ABSs), in Josephson junctions constructed on the surface of three-dimensional topological insulators (3D TIs). In this work, we further generalize that method to the circumstance with radio frequency (rf) irradiation. We find that with the increase of the rf power, the measured minigap becomes broadened and extends to higher energies in a way similar to the rf power dependence of the outer border of the Shapiro step region. We show that the corresponding data of contact resistance under rf irradiation can be well interpreted by using the resistively shunted Josephson junction (RSJ) model and the Blonder-Tinkham-Klapwijk (BTK) theory. Our findings could be useful when using the contact-resistance-measurement method to study the Majorana-related physics in topological insulator-based Josephson junctions under rf irradiation.

Optical phonon behavior and magnetism of columbite Zn0.8Co0.2Nb2O6

Liang Li, Xiaohan Wang, Ying Liu, Fangfei Li, Qiang Zhou, Tian Cui
Chin. Phys. B 2019, 28 (12): 128104 ;  doi: 10.1088/1674-1056/ab5438
Full Text: PDF (751KB) ( 78 ) RICH HTML
Show Abstract
Columbite Zn0.8Co0.2Nb2O6 crystals were grown by optical floating zone methods. The x-ray diffraction (XRD) was used to check the structure information of the grown Zn0.8Co0.2Nb2O6 crystal. The room temperature and temperature-dependent Raman spectra were tested to investigate the optical phonon behaviors of columbite Zn0.8Co0.2Nb2O6, which exhibited a temperature stable property. The magnetics properties of Zn0.8Co0.2Nb2O6, measured by a physical property measurement system (PPMS), were also presented in this work.

Dark and multi-dark solitons in the three-component nonlinear Schrödinger equations on the general nonzero background

Zhi-Jin Xiong, Qing Xu, Liming Ling
Chin. Phys. B 2019, 28 (12): 120201 ;  doi: 10.1088/1674-1056/ab50fc
Full Text: PDF (11521KB) ( 121 ) RICH HTML
Show Abstract
We exhibit some new dark soliton phenomena on the general nonzero background for a defocusing three-component nonlinear Schrödinger equation. As the plane wave background undergoes unitary transformation SU(3), we obtain the general nonzero background and study its modulational instability by the linear stability analysis. On the basis of this background, we study the dynamics of one-dark soliton and two-dark-soliton phenomena, which are different from the dark solitons studied before. Furthermore, we use the numerical method for checking the stability of the one-dark-soliton solution. These results further enrich the content in nonlinear Schrödinger systems, and require more in-depth studies in the future.

Quantum search for unknown number of target items by hybridizing fixed-point method with trail-and-error method

Tan Li, Shuo Zhang, Xiang-Qun Fu, Xiang Wang, Yang Wang, Jie Lin, Wan-Su Bao
Chin. Phys. B 2019, 28 (12): 120301 ;  doi: 10.1088/1674-1056/ab4e88
Full Text: PDF (1241KB) ( 77 ) RICH HTML
Show Abstract
For the unsorted database quantum search with the unknown fraction λ of target items, there are mainly two kinds of methods, i.e., fixed-point and trail-and-error. (i) In terms of the fixed-point method, Yoder et al.[Phys. Rev. Lett. 113 210501 (2014)] claimed that the quadratic speedup over classical algorithms has been achieved. However, in this paper, we point out that this is not the case, because the query complexity of Yoder's algorithm is actually in O(1/√λ0) rather than O(1/√λ), where λ0 is a known lower bound of λ. (ii) In terms of the trail-and-error method, currently the algorithm without randomness has to take more than 1 times queries or iterations than the algorithm with randomly selected parameters. For the above problems, we provide the first hybrid quantum search algorithm based on the fixed-point and trail-and-error methods, where the matched multiphase Grover operations are trialed multiple times and the number of iterations increases exponentially along with the number of trials. The upper bound of expected queries as well as the optimal parameters are derived. Compared with Yoder's algorithm, the query complexity of our algorithm indeed achieves the optimal scaling in λ for quantum search, which reconfirms the practicality of the fixed-point method. In addition, our algorithm also does not contain randomness, and compared with the existing deterministic algorithm, the query complexity can be reduced by about 1/3. Our work provides a new idea for the research on fixed-point and trial-and-error quantum search.

Quantum discord of two-qutrit system under quantum-jump-based feedback control

Chang Wang, Mao-Fa Fang
Chin. Phys. B 2019, 28 (12): 120302 ;  doi: 10.1088/1674-1056/ab4e83
Full Text: PDF (892KB) ( 109 ) RICH HTML
Show Abstract
This paper studies quantum discord of two qutrits coupled to their own environments independently and coupled to the same environment simultaneously under quantum-jump-based feedback control. Our results show that spontaneous emission, quantum feedback parameters, classical driving, initial state, and detection efficiency all affect the evolution of quantum discord in a two-qutrit system. We find that under the condition of designing proper quantum-jump-based feedback parameters, quantum discord can be protected and prepared. In the case where two qutrits are independently coupled to their own environments, classical driving, spontaneous emission, and low detection efficiency have negative effect on the protection of quantum discord. For different initial states, it is found that the evolution of quantum discord under the control of appropriate parameters is similar. In the case where two qutrits are simultaneously coupled to the same environment, the classical driving plays a positive role in the generation of quantum discord, but spontaneous emission and low detection efficiency have negative impact on the generation of quantum discord. Most importantly, we find that the steady discord depends on feedback parameters, classical driving, and detection efficiency, but not on the initial state.

Optimal phase estimation with photon-number difference measurement using twin-Fock states of light Hot!

J H Xu, J Z Wang, A X Chen, Y Li, G R Jin
Chin. Phys. B 2019, 28 (12): 120303 ;  doi: 10.1088/1674-1056/ab4e7f
Full Text: PDF (720KB) ( 131 ) RICH HTML
Show Abstract
Quantum phase measurement with multiphoton twin-Fock states has been shown to be optimal for detecting equal numbers of photons at the output ports of a Mach-Zehnder interferometer (i.e., the so-called single-fringe detection), since the phase sensitivity can saturate the quantum Cramér-Rao lower bound at certain values of phase shift. Here we report a further step to achieve a global phase estimation at the Heisenberg limit by detecting the particle-number difference (i.e., the Ĵz measurement). We show the role of experimental imperfections on the ultimate estimation precision with the six-photon twin-Fock state of light. Our results show that both the precision and the sensing region of the Ĵz measurement are better than those of the single-fringe detection, due to combined contributions of the measurement outcomes. We numerically simulate the phase estimation protocol using an asymptotically unbiased maximum likelihood estimator.

Relations between tangle and I concurrence for even n-qubit states

Xin-Wei Zha, Ning Miao, Ke Li
Chin. Phys. B 2019, 28 (12): 120304 ;  doi: 10.1088/1674-1056/ab4e7d
Full Text: PDF (321KB) ( 77 ) RICH HTML
Show Abstract
Gilad Gour and Nolan R Wallach[J. Math. Phys. 51 112201 (2010)] have proposed the 4-tangle and the square of the I concurrence. They also gave the relationship between the 4-tangle and the square of the I concurrence. In this paper, we give the expression of the square of the I concurrence and the n-tangle for six-qubit and eight-qubit by some local unitary transformation invariant. We prove that in six-qubit and eight-qubit states there exist strict monogamy laws for quantum correlations. We elucidate the relations between the square of the I concurrence and the n-tangle for six-qubit and eight-qubits. Especially, using this conclusion, we can show that 4-uniform states do not exist for eight-qubit states.

Improving entanglement of assistance bylocal parity-time symmetric operation

Zhi He, Zun-Yan Nie, Qiong Wang
Chin. Phys. B 2019, 28 (12): 120305 ;  doi: 10.1088/1674-1056/ab50fb
Full Text: PDF (619KB) ( 71 ) RICH HTML
Show Abstract
We investigate entanglement of assistance without and with decoherence using a local non-Hermitian operation, i.e., parity-time (PT) symmetric operation. First we give the explicit expressions of entanglement of assistance for a general W-like state of a three-qubit system under a local parity-time symmetric operation. Then for a famous W state without decoherence, we find that entanglement of assistance shared by two parties can be obviously enhanced with the assistance of the third party by a local parity-time symmetric operation. For the decoherence case, we provide two schemes to show the effects of local parity-time symmetric operation on improvement of entanglement of assistance against amplitude damping noise. We find that for the larger amplitude damping case the scheme of PT symmetric operation performed on one of two parties with the influence of noise is superior to that of PT symmetric operation performed on the third party without the influence of noise in suppressing amplitude damping noise. However, for the smaller amplitude damping case the opposite result is given. The obtained results imply that the local PT symmetric operation method may have potential applications in quantum decoherence control.

Generalized Hardy-type tests for hierarchy of multipartite non-locality

Fei Yang, Yu Yuan, Wen-Lu Lin, Shu-Ao Liao, Cheng-Jie Zhang, Qing Chen
Chin. Phys. B 2019, 28 (12): 120306 ;  doi: 10.1088/1674-1056/ab54b8
Full Text: PDF (459KB) ( 57 ) RICH HTML
Show Abstract
We propose a family of Hardy-type tests for an arbitrary n-partite system, which can detect different degrees of non-locality ranging from standard to genuine multipartite non-locality. For any non-signaling m-local hidden variable model, the corresponding tests fail, whereas a pass of this type of test indicates that this state is m non-local. We show that any entangled generalized GHZ state exhibits Hardy's non-locality for each rank of multipartite non-locality. Furthermore, for the detection of m non-localities, a family of Bell-type inequalities based on our test is constructed. Numerical results show that it is more efficient than the inequalities proposed in[Phys. Rev. A 94 022110 (2016)].

Entanglement teleportation via a couple of quantum channels in Ising-Heisenberg spin chain model of a heterotrimetallic Fe-Mn-Cu coordination polymer

Yi-Dan Zheng, Zhu Mao, Bin Zhou
Chin. Phys. B 2019, 28 (12): 120307 ;  doi: 10.1088/1674-1056/ab53cc
Full Text: PDF (2576KB) ( 89 ) RICH HTML
Show Abstract
We investigate the teleportation of an entangled state via a couple of quantum channels, which are composed of a spin-1/2 Heisenberg dimer in two infinite Ising-Heisenberg chains. The heterotrimetallic coordination polymer CuMn(L1)] [Fe(bpb)(CN)2]·ClO4·H2O (abbreviated as Fe-Mn-Cu) can be regarded as an actual material for this chain. We apply the transfer-matrix approach to obtain the density operator for the Heisenberg dimer and use the standard teleportation protocol to derive the analytical expression of the density matrix of the output state and the average fidelity of the entanglement teleportation. We study the effects of the temperature T, anisotropy coupling parameter , Heisenberg coupling parameter J2 and external magnetic field h on the quantum channels. The results show that anisotropy coupling and Heisenberg coupling J2 can favor the generation of the output concurrence and expand the scope of the successful average fidelity.

Thermal properties of regular black hole with electric charge in Einstein gravity coupled to nonlinear electrodynamics

Yi-Huan Wei
Chin. Phys. B 2019, 28 (12): 120401 ;  doi: 10.1088/1674-1056/ab4e80
Full Text: PDF (401KB) ( 80 ) RICH HTML
Show Abstract
We propose a regular spherically symmetric spacetime solution with three parameters in Einstein gravity coupled to nonlinear electrodynamics (NED), which describes the NED black hole with electric charge. It is found that the system enclosed by the horizon of NED spacetime satisfies the first law of thermodynamics. In order to obtain the NED spacetime with only electric charge, the case of two parameters taking the same value is considered. In this case, we express the mass of the NED spacetime as a function of the entropy and electric charge of the NED black hole, give the Smarr-like formula and the approximate Smarr formula for the mass of NED spacetime.

A new type of adiabatic invariants for disturbednon-conservative nonholonomic system

Xin-Xin Xu, Yi Zhang
Chin. Phys. B 2019, 28 (12): 120402 ;  doi: 10.1088/1674-1056/ab5210
Full Text: PDF (367KB) ( 62 ) RICH HTML
Show Abstract
According to the Herglotz variational principle and differential variational principle of Herglotz type, we study the adiabatic invariants for a non-conservative nonholonomic system. Firstly, the differential equations of motion of the non-conservative nonholonomic system based upon the generalized variational principle of Herglotz type are given, and the exact invariant for the non-conservative nonholonomic system is introduced. Secondly, a new type of adiabatic invariant for the system under the action of a small perturbation is obtained. Thirdly, the inverse theorem of the adiabatic invariant is given. Finally, an example is given.

Controllable laning phase for oppositely driven disk systems

Lin Liu, Ke Li, Xiao-Lin Zhou, Lin-Li He, Lin-Xi Zhang
Chin. Phys. B 2019, 28 (12): 120501 ;  doi: 10.1088/1674-1056/ab4e86
Full Text: PDF (4996KB) ( 90 ) RICH HTML
Show Abstract
A two-dimensional binary driven disk system embedded by impermeable tilted plates is investigated through nonequilibrium computer simulations. It is well known that a binary disk system in which two particle species are driven in opposite directions exhibits jammed, phase separated, disordered, and laning states. The presence of tilted plates can not only advance the formation of laning phase, but also effectively stabilize laning phase by suppressing massively drifting behavior perpendicular to the driving force. The lane width distribution can be controlled easily by the interplate distance. The collective behavior of driven particles in laning phase is guided by the funnel-shaped confinements constituted by the neighboring tilted plates. Our results provide the important clues for investigating the mechanism of laning formation in driven system.

Soliton excitations and interaction in alpha helical protein with interspine coupling in modified nonlinear Schrödinger equation

Ming-Ming Li, Cheng-Lai Hu, Jun Wu, Xian-Jing Lai, Yue-Yue Wang
Chin. Phys. B 2019, 28 (12): 120502 ;  doi: 10.1088/1674-1056/ab5188
Full Text: PDF (1671KB) ( 86 ) RICH HTML
Show Abstract
The three-coupling modified nonlinear Schrödinger (MNLS) equation with variable-coefficients is used to describe the dynamics of soliton in alpha helical protein. This MNLS equation with variable-coefficients is firstly transformed to the MNLS equation with constant-coefficients by similarity transformation. And then the one-soliton and two-soliton solutions of the variable-coefficient-MNLS equation are obtained by solving the constant-coefficient-MNLS equation with Hirota method. The effects of different parameter conditions on the soliton solutions are discussed in detail. The interaction between two solitons is also discussed. Our results are helpful to understand the soliton dynamics in alpha helical protein.

Relaxation dynamics of Kuramoto model with heterogeneous coupling

Tianwen Pan, Xia Huang, Can Xu, Huaping Lü
Chin. Phys. B 2019, 28 (12): 120503 ;  doi: 10.1088/1674-1056/ab55d0
Full Text: PDF (478KB) ( 73 ) RICH HTML
Show Abstract
The Landau damping which reveals the characteristic of relaxation dynamics for an equilibrium state is a universal concept in the area of complex system. In this paper, we study the Landau damping in the phase oscillator system by considering two types of coupling heterogeneity in the Kuramoto model. We show that the critical coupling strength for phase transition, which can be obtained analytically through the balanced integral equation, has the same formula for both cases. The Landau damping effects are further explained in the framework of Laplace transform, where the order parameters decay to zero in the long time limit.

Dynamics of the Au+H2 reaction by time-dependent wave packet and quasi-classical trajectory methods

Yong Zhang, Chengguo Jiang
Chin. Phys. B 2019, 28 (12): 123101 ;  doi: 10.1088/1674-1056/ab52f2
Full Text: PDF (1907KB) ( 61 ) RICH HTML
Show Abstract
Dynamics of the Au+H2 reaction are studied using time-dependent wave packet (TDWP) and quasi-classical trajectory (QCT) methods based on a new potential energy surface[Int. J. Quantum Chem. 118 e25493 (2018)]. The dynamic properties such as reaction probability, integral cross section, differential cross section and the distribution of product are studied at state-to-state level of theory. Furthermore, the present results are compared with the theoretical studies available. The results indicate that the complex-forming reaction mechanism is dominated in the reaction in the low collision energy region and the abstract reaction mechanism plays a dominant role at high collision energies. Different from previous theoretical calculations, the side-ways scattering signals are found in the present work and become more and more apparent with increasing collision energy.

Electromagnetically induced transparency at optical nanofiber-cesium vapor interface

Rui-Juan Liu, Dian-Qiang Su, Zi-Xuan Song, Zhong-Hua Ji, Yan-Ting Zhao
Chin. Phys. B 2019, 28 (12): 124201 ;  doi: 10.1088/1674-1056/ab4d44
Full Text: PDF (523KB) ( 87 ) RICH HTML
Show Abstract
Optical nanofiber (ONF) is a special tool for effectively controlling coupling of light and atoms. In this paper, we study the ladder-type electromagnetically induced transparent (EIT) under ultralow power level in a warm cesium vapor by observing the transmission of ONF that couples the 6S→6P Cs atoms in the presence of a 6P→8S control beam through the same fiber. The linewidth and transmission of the EIT signal are investigated at different intensities of the control laser. In addition, we theoretically study the nonlinear interaction at the ONF interface using the multi-level density matrix equations, and obtain good agreements between theory and experiments. The results may have great significance for further study of optical nonlinear effect at low power level.

Design and optimization of microstructure optical fiber sensor based on bimetal plasmon mode interaction

Meng Wu, Xin-Yu Liu, Gui-Yao Zhou, Chang-Ming Xia, Bo-Yao Li, Zhi-Yun Hou
Chin. Phys. B 2019, 28 (12): 124202 ;  doi: 10.1088/1674-1056/ab4d48
Full Text: PDF (923KB) ( 106 ) RICH HTML
Show Abstract
A surface plasmon resonance (SPR) sensor with two orthogonal open loops based on microstructured optical fibers (MOFs) is introduced. The interaction between core mode and surface plasmon polariton (SPP) mode produced by two different metal films is studied. Full vector finite element method is used to analyze the coupling and sensing characteristics. The results show that there are three loss peaks near the Au/Ag film, and multi-peak calibration is achieved. Because of the positive and negative sensitivity of the amplitude, the sensor has strong anti-interference capability when the external environment changes. The sensor can detect the refractive index between 1.37 and 1.40, and the working wavelength is between 1600 nm and 2400 nm. Because the sensor has some excellent characteristics, it can be used in biochemical sensing, environmental detection, and other related fields.

Self-starting all-fiber PM Er: laser mode locked by a biased nonlinear amplifying loop mirror

Ke Yin, Yi-Ming Li, Yan-Bin Wang, Xin Zheng, Tian Jiang
Chin. Phys. B 2019, 28 (12): 124203 ;  doi: 10.1088/1674-1056/ab4d42
Full Text: PDF (2586KB) ( 126 ) RICH HTML
Show Abstract
A compact all-fiber polarization-maintaining Er:laser using a nonlinear amplifying loop mirror is reported. Fundamental single-pulse mode-locking operation can always self start, with a cavity round-trip decreased from~4.7 m to~1.7 m. When the pulse repetition rate is 121.0328 MHz, output pulse is measured to have a center wavelength/3-dB spectral bandwidth/radio frequency signal to noise ratio (SNR)/pulse width of 1571.65 nm/18.70 nm/80 dB/477 fs, respectively. Besides, three states including the exponential growth, damping state, and steady state are investigated through the build-up process both experimentally and numerically. Excellent stability of this compact Er:laser is further evaluated, demonstrating that it can be an easy-fabrication maintenance-free ultrafast candidate for the scientific area of this kind.

Selective synthesis of three-dimensional ZnO@Ag/SiO2@Ag nanorod arrays as surface-enhanced Raman scattering substrates with tunable interior dielectric layer

Jia-Jia Mu, Chang-Yi He, Wei-Jie Sun, Yue Guan
Chin. Phys. B 2019, 28 (12): 124204 ;  doi: 10.1088/1674-1056/ab4d45
Full Text: PDF (1735KB) ( 50 ) RICH HTML
Show Abstract
We describe the synthesis of three-dimensional (3D) multilayer ZnO@Ag/SiO2@Ag nanorod arrays by the physico-chemical method. The surface-enhanced Raman scattering (SERS) performance of the 3D multilayer ZnO@Ag/SiO2@Ag nanorod arrays is studied by varying the thickness of dielectric layer SiO2 and outer-layer noble Ag. The 3D ZnO@Ag/SiO2@Ag nanorod arrays create a huge number of SERS “hot spots” that mainly contribute to the high SERS sensitivity. The great enhancement of SERS results from the electron transfer between ZnO and Ag and different electromagnetic enhancements of Ag nanoparticles (NPs) with different thicknesses. Through the finite-difference time-domain (FDTD) theoretical simulation, the enhancement of SERS signal can be ascribed to a strong electric field enhancement produced in the 3D framework. The simplicity and generality of our method offer great advantages for further understanding the SERS mechanism induced by the surface plasmon resonance (SPR) effect.

One-dimensional structure made of periodic slabs of SiO2/InSb offering tunable wide band gap at terahertz frequency range

Sepehr Razi, Fatemeh Ghasemi
Chin. Phys. B 2019, 28 (12): 124205 ;  doi: 10.1088/1674-1056/ab4d46
Full Text: PDF (5450KB) ( 86 ) RICH HTML
Show Abstract
Optical features of a semiconductor-dielectric photonic crystal are studied theoretically. Alternating layers of micrometer sized SiO2/InSb slabs are considered as building blocks of the proposed ideal crystal. By inserting additional layers and disrupting the regularity, two more defective crystals are also proposed. Photonic band structure of the ideal crystal and its dependence on the structural parameters are explored at the first step. Transmittance of the defective crystals and its changes with the thicknesses of the layers are studied. After extracting the optimum values for the thicknesses of the unit cells of the crystals, the optical response of the proposed structures at different temperatures and incident angles are investigated. Changes of the defect layers' induced mode(s) are discussed by taking into consideration of the temperature dependence of the InSb layer permittivity. The results clearly reflect the high potential of the proposed crystals to be used at high temperature terahertz technology as a promising alternative to their electronic counterparts.

Finite-dimensional pair coherent state engendered via the nonlinear Bose operator realization and its Wigner phase-space distributions

Jianming Liu, Xiangguo Meng
Chin. Phys. B 2019, 28 (12): 124206 ;  doi: 10.1088/1674-1056/ab4f5f
Full Text: PDF (561KB) ( 57 ) RICH HTML
Show Abstract
We theoretically analyze the photon number distribution, entanglement entropy, and Wigner phase-space distribution, considering the finite-dimensional pair coherent state (FDPCS) generated in the nonlinear Bose operator realization. Our results show that the photon number distribution is governed by the two-mode photon number sum q of the FDPCS, the entanglement of the FDPCS always increases quickly at first and then decreases slowly for any q, and the nonclassicality of the FDPCS for odd q is more stronger than that for even q.

Interlayer distance effects on absorption coefficient and refraction index change in p-type double-δ-doped GaAs quantum wells

H Noverola-Gamas, L M Gaggero-Sager, O Oubram
Chin. Phys. B 2019, 28 (12): 124207 ;  doi: 10.1088/1674-1056/ab5278
Full Text: PDF (506KB) ( 95 ) RICH HTML
Show Abstract
In the framework of the Thomas-Fermi (TF) approach, a model for the p-type double-δ-doped (DDD) system in GaAs is presented. This model, unlike other works in the literature, takes into account that the Poisson equation associated with the system is nonlinear. The electronic structure is calculated for heavy and light holes. The changes in the electronic structure result of the distance d between the doped layers are studied. In particular, the relative absorption coefficient as well as the relative refractive index change is calculated as a function of the incident photon energy for heavy holes. The effect of the interlayer distance exhibits, in the absorption coefficient, a red shift of the peak position and a decrease in amplitude when the distance increases. In addition, the relative refractive index change node has a red shift as well as the interlayer distance increases. The calculations show that the effect of the separation between layers has a greater influence on the linear terms. These results are very important for theoretical calculations and engineering of optical and electronic devices based in δ-doped GaAs.

Wide color gamut switchable autostereoscopic 3D display based on directional quantum-dot backlight

Bin Xu, Xue-Ling Li, Yuan-Qing Wang
Chin. Phys. B 2019, 28 (12): 124208 ;  doi: 10.1088/1674-1056/ab53d1
Full Text: PDF (7444KB) ( 64 ) RICH HTML
Show Abstract
A switchable autostereoscopic 3-dimensional (3D) display device with wide color gamut is introduced in this paper. In conjunction with a novel directional quantum-dot (QD) backlight, the precise scanning control strategy, and the eye-tracking system, this spatial-sequential solution enables our autostereoscopic display to combine all the advantages of full resolution, wide color gamut, low crosstalk, and switchable 2D/3D. And also, we fabricated an autostereoscopic display prototype and demonstrated its performances effectively. The results indicate that our system can both break the limitation of viewing position and provide high-quality 3D images. We present two working modes in this system. In the spatial-sequential mode, the crosstalk is about 6%. In the time-multiplexed mode, the viewer should wear auxiliary and the crosstalk is about 1%, just next to that of a commercial 3D display (BENQ XL2707-B and View Sonic VX2268WM). Additionally, our system is also completely compatible with active shutter glasses and its 3D resolution is same as its 2D resolution. Because of the excellent properties of the QD material, the color gamut can be widely extended to 77.98% according to the ITU-R recommendation BT.2020 (Rec.2020).

Underwater acoustic metamaterial based on double Dirac cone characteristics in rectangular phononic crystals

Dong-Liang Pei, Tao Yang, Meng Chen, Heng Jiang
Chin. Phys. B 2019, 28 (12): 124301 ;  doi: 10.1088/1674-1056/ab55d2
Full Text: PDF (4354KB) ( 95 ) RICH HTML
Show Abstract
We theoretically construct a rectangular phononic crystal (PC) structure surrounded by water with C2v symmetry, and then place a steel rectangular scatterer at each quarter position inside each cell. The final complex crystal has two forms:the vertical type, in which the distance s between the center of the scatterer and its right-angle point is greater than 0.5a, and the transverse type, in which s is smaller than 0.5a (where a is the crystal constant in the x direction). Each rectangular scatterer has three variables:length L, width D, and rotation angle θ around its centroid. We find that, when L and D change and θ is kept at zero, there is always a linear quadruply degenerate state at the corner of the irreducible Brillouin zone. Then, we vary θ and find that the quadruply degenerate point splits into two doubly-degenerate states with odd and even parities. At the same time, the band structure reverses and undergoes a phase change from topologically non-trivial to topologically trivial. Then we construct an acoustic system consisting of a trivial and a non-trivial PC with equal numbers of layers, and calculate the projected band structure. A helical one-way transmission edge state is found in the frequency range of the body band gap. Then, we use the finite-element software Comsol to simulate the unidirectional transmission of this edge state and the backscattering suppression of right-angle, disorder, and cavity defects. This acoustic wave system with rectangular phononic crystal form broadens the scope of acoustic wave topology and provides a platform for easy acoustic operation.

Polarization resolved analysis of phonon transport in a multi-terminal system

Yun-Feng Gu, Liu-Tong Zhu, Xiao-Li Wu
Chin. Phys. B 2019, 28 (12): 124401 ;  doi: 10.1088/1674-1056/ab4d3e
Full Text: PDF (3279KB) ( 53 ) RICH HTML
Show Abstract
The atomistic Green's function method is improved to compute the polarization resolved phonon transport in a multi-terminal system. Based on the recent developments in literature, the algorithm is simplified. The complex phonon band structure of a semi-infinite periodic terminal is obtained by the generalized eigenvalue equation. Then both the surface Green's function and phonon group velocity in the terminal are determined from the wave modes propagating away from the scattering region along the terminal. With these key ingredients, the individual phonon mode transmittance between the terminals can be calculated. The feasibility and validity of the method are demonstrated by the chain example compared with the wave packet method, and an example of graphene nanojunction with three terminals.

A nonlinear Schrödinger equation for gravity waves slowly modulated by linear shear flow

Shaofeng Li, Juan Chen, Anzhou Cao, Jinbao Song
Chin. Phys. B 2019, 28 (12): 124701 ;  doi: 10.1088/1674-1056/ab53cf
Full Text: PDF (1983KB) ( 101 ) RICH HTML
Show Abstract
Assume that a fluid is inviscid, incompressible, and irrotational. A nonlinear Schrödinger equation (NLSE) describing the evolution of gravity waves in finite water depth is derived using the multiple-scale analysis method. The gravity waves are influenced by a linear shear flow, which is composed of a uniform flow and a shear flow with constant vorticity. The modulational instability (MI) of the NLSE is analyzed, and the region of the MI for gravity waves (the necessary condition for existence of freak waves) is identified. In this work, the uniform background flows along or against wave propagation are referred to as down-flow and up-flow, respectively. Uniform up-flow enhances the MI, whereas uniform down-flow reduces it. Positive vorticity enhances the MI, while negative vorticity reduces it. Hence, the influence of positive (negative) vorticity on MI can be balanced out by that of uniform down (up) flow. Furthermore, the Peregrine breather solution of the NLSE is applied to freak waves. Uniform up-flow increases the steepness of the free surface elevation, while uniform down-flow decreases it. Positive vorticity increases the steepness of the free surface elevation, whereas negative vorticity decreases it.

Estimation of tungsten production from the upper divertor in EAST during edge localized modes

Jing Ou, Nong Xiang, Zong-Zheng Men, Ling Zhang, Ji-Chan Xu, Wei Gao
Chin. Phys. B 2019, 28 (12): 125201 ;  doi: 10.1088/1674-1056/ab5279
Full Text: PDF (845KB) ( 53 ) RICH HTML
Show Abstract
During edge localized modes (ELMs), the sheath evolution in front of the Experimental Advanced Superconducting Tokamak (EAST) upper divertor is studied to estimate the sputtered tungsten (W) atoms from the divertor target. A large potential drop across the sheath is formed during ELMs by compared with inter-ELMs, and the maximum of sheath potential drop can exceed one thousand of eV in current EAST operation. Due to the enhancement of the sheath potential drop during ELMs, the W physical sputtering yield from the deuterium (D) ions and the impurity ions on the upper divertor target is found to be significant. It is established that the sputtered W yield during ELMs is at least higher by an order of magnitude than inter-ELMs, and D ions and carbon (C) ions are the main ions governing the W production for the current H-mode with ELMs discharges. With increase in the pedestal electron temperature, the maximum of the D and C ion impact energy during ELMs shows a nearly linear increase, and the D ions have sufficient impact energy to cause the strong W physical sputtering. As a consequence, the D ions may dominate the sputtered W flux from the divertor target when the C concentration is controlled less than one percent for the higher heating power H-mode with ELM discharges in near future.

Observation of deuterium molecule emission spectra under an active feedback control of H-mod plasma divertor detachment experiment on the EAST tokamak

Wei Gao, Juan Huang, Jichan Xu, Liang Wang, Jing Zhang, Jianxun Su, Yingjie Chen, Wei Gao, Zhenwei Wu, EAST Team
Chin. Phys. B 2019, 28 (12): 125202 ;  doi: 10.1088/1674-1056/ab54b2
Full Text: PDF (1103KB) ( 51 ) RICH HTML
Show Abstract

Based on neon gas puffing, an active feedback control of H-mod plasma divertor detachment experiment was successfully operated on the EAST tokamak. During the feedback control discharge, the plasma was detached by puffing neon gas and the strike point splitting phenomenon on divertor target was also clearly observed by divertor probes diagnostic. In boundary region, many neutral particle processes (atom and molecule) were happened and accompanied by their emission spectra under the detachment discharge. By studying these emission spectra, it is helpful for us to understand the role of atoms and molecules in boundary recycling, which is important for studying the physical mechanism of divertor detachment. For the Fulcher-α system (d(3p)3Πu±→a(2s)3Σg+), D2 emission spectra in the range from 601 nm to 606 nm were observed, identified and fitted in the detachment experiment for the first time on the EAST, and the spectra in the Q(0-0) band (d3Πu-→a(2s)3Σg+) in the Q branch of the Fulcher-α system were used for detailed analysis to acquire the boundary region temperature Te (below 5 eV), which could not be provided very well by other diagnostics on the EAST. An electronic version deuterium molecular spectral line database was established to identify the spectral lines and a multi-peak fitting program was developed to fit and analyze the observed spectra.

Basic features of the multiscale interaction between tearing modes and slab ion-temperature-gradient modes

L Wei, Z X Wang, J Q Li, Z Q Hu, Y Kishimoto
Chin. Phys. B 2019, 28 (12): 125203 ;  doi: 10.1088/1674-1056/ab5437
Full Text: PDF (4022KB) ( 198 ) RICH HTML
Show Abstract
Nonlinear interaction between tearing modes (TM) and slab ion-temperature-gradient (ITG) modes is numerically investigated by using a Landau fluid model. It is observed that the energy spectra with respect to wavenumbers become broader during the transition phase from the ITG-dominated stage to TM-dominated stage. Accompanied with the fast growth of the magnetic island, the frequency of TM/ITG with long/short wavelength fluctuations in the electron/ion diamagnetic direction decreases/increases respectively. The decrease of TM frequency is identified to result from the effect of the profile flattening in the vicinity of the magnetic island, while the increase of the frequencies of ITG fluctuations is due to the eigenmode transition of ITG induced by the large scale zonal flow and zonal current related to TM. Roles of zonal current induced by the ITG fluctuations in the instability of TM are also analyzed. Finally, the electromagnetic transport features in the vicinity of the magnetic island are discussed.

Estimation of plasma equilibrium parameters via a neural network approach

Zi-Jian Zhu, Yong Guo, Fei Yang, Bing-Jia Xiao, Jian-Gang Li
Chin. Phys. B 2019, 28 (12): 125204 ;  doi: 10.1088/1674-1056/ab55d1
Full Text: PDF (2102KB) ( 61 ) RICH HTML
Show Abstract
Plasma equilibrium parameters such as position, X-point, internal inductance, and poloidal beta are essential information for efficient and safe operation of tokamak. In this work, the artificial neural network is used to establish a non-linear relationship between the measured diagnostic signals and selected equilibrium parameters. The estimation process is split into a preliminary classification of the kind of equilibrium (limiter or divertor) and subsequent inference of the equilibrium parameters. The training and testing datasets are generated by the tokamak simulation code (TSC), which has been benchmarked with the EAST experimental data. The noise immunity of the inference model is tested. Adding noise to model inputs during training process is proved to have a certain ability for maintaining performance.

Characteristics of non-thermal AC arcs in multi-arc generator

Qifu Lin, Yanjun Zhao, Wenxue Duan, Guohua Ni, Xinyue Jin, Siyuan Sui, Hongbing Xie, Yuedong Meng
Chin. Phys. B 2019, 28 (12): 125205 ;  doi: 10.1088/1674-1056/ab55ce
Full Text: PDF (6263KB) ( 55 ) RICH HTML
Show Abstract
To obtain large-volume non-thermal arc plasma (NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and rotation velocity in the discharge zone, were investigated by high speed photograph and image processing methods. The results showed that the dynamic behaviors and spatial distribution of the arc plasma were strongly related to the electrode configuration. A swirl flow of multi-arc plasma was formed by adjusting the electrode configuration, and a steady luminance area was clearly observed in the center of the discharge zone. Moreover, the size of the luminance area increased by decreasing the gas flow rate. The electrical connection in series could be formed between/among these arc columns with their respective driving power supplies in the multi-arc dynamic evolution process. An approximately periodical process of acceleration and deceleration of the arc rotation velocity was observed in the multi-arc generator with swirl flow configuration. In general, the mean velocity of arc rotation was higher in the multi-arc generator with swirl flow configuration when a pair of electrodes driven by a power supply were opposite to each other rather than adjacent.

Metabasin dynamics of supercooled polymer melt

Jian Li, Bo-Kai Zhang
Chin. Phys. B 2019, 28 (12): 126101 ;  doi: 10.1088/1674-1056/ab4e82
Full Text: PDF (485KB) ( 60 ) RICH HTML
Show Abstract
We employ molecular dynamic simulation to investigate metabasin dynamics for supercooled polymer melt. We find that, in a small system, the α-relaxation process is composed of a few crossing events that the monomers hops from one metabasin to another. Each crossing event is very rapid and involves a democratic movement of many particles, whereas such collective motion is not string-like. Evaluation on the contributions of metabasin exploration and democratic movement shows that the structural relaxation is mostly governed by the latter. Our calculated results show that the metabasin-metabasin transitions are not the main reason of spatially dynamical heterogeneity. It is different from the binary Lennard-Jones mixture model in which the metabasin-metabasin transitions are relevant for the spatially dynamical heterogeneity.

Shock-induced migration of asymmetry tilt grain boundary in iron bicrystal: A case study of Σ3 [110]

Xueyang Zhang, Kun Wang, Jun Chen, Wangyu Hu, Wenjun Zhu, Shifang Xiao, Huiqiu Deng, Mengqiu Cai
Chin. Phys. B 2019, 28 (12): 126201 ;  doi: 10.1088/1674-1056/ab4f61
Full Text: PDF (1871KB) ( 74 ) RICH HTML
Show Abstract
Many of our previous studies have discussed the shock response of symmetrical grain boundaries in iron bicrystals. In this paper, the molecular dynamics simulation of an iron bicrystal containing Σ3[110] asymmetry tilt grain boundary (ATGB) under shock-loading is performed. We find that the shock response of asymmetric grain boundaries is quite different from that of symmetric grain boundaries. Especially, our simulation proves that shock can induce migration of asymmetric grain boundary in iron. We also find that the shape and local structure of grain boundary (GB) would not be changed during shock-induced migration of Σ3[110] ATGB, while the phase transformation near the GB could affect migration of GB. The most important discovery is that the shock-induced shear stress difference between two sides of GB is the key factor leading to GB migration. Our simulation involves a variety of piston velocities, and the migration of GB seems to be less sensitive to the piston velocity. Finally, the kinetics of GB migration at lattice level is discussed. Our work firstly reports the simulation of shock-induced grain boundary migration in iron. It is of great significance to the theory of GB migration and material engineering.

Structural and electrical transport properties of Dirac-like semimetal PdSn4 under high pressure

Bowen Zhang, Chao An, Yonghui Zhou, Xuliang Chen, Ying Zhou, Chunhua Chen, Yifang Yuan, Zhaorong Yang
Chin. Phys. B 2019, 28 (12): 126202 ;  doi: 10.1088/1674-1056/ab50b3
Full Text: PDF (3323KB) ( 97 ) RICH HTML
Show Abstract
We conducted in-situ high-pressure synchrotron x-ray diffraction (XRD) and electrical transport measurements on Dirac-like semimetal PdSn4 in diamond anvil cells with quasi-hydrostatic pressure condition up to 44.5 GPa-52.0 GPa. The XRD data show that the ambient orthorhombic phase (Ccca) is stable with pressures to 44.5 GPa, and the lattice parameters and unit-cell volume decrease monotonously upon compression. The temperature dependence of the resistance exhibits a metallic conduction and follows a Fermi-liquid behavior below 50 K, both of which keep unchanged upon compression to 52.0 GPa. The magnetoresistance curve at 5 K maintains a linear feature in a magnetic field range of 2.5 T-7 T with increasing pressure to 20.0 GPa. Our results may provide pressure-transport constraints on the robustness of the Dirac fermions.

Accelerate Bose-Einstein condensate by interaction

Jie-Li Qin
Chin. Phys. B 2019, 28 (12): 126701 ;  doi: 10.1088/1674-1056/ab4e8a
Full Text: PDF (769KB) ( 70 ) RICH HTML
Show Abstract
In recent years, accelerating waves have attracted great research interests both due to their unique properties and tempting applications. Here we investigate the effect of the inter-particle interaction on accelerating of Bose-Einstein condensate (BEC). We show that spatially homogeneous interactions will have no accelerating effect on BEC regardless of the interaction form (contact, dipole-dipole, or any others). But spatially inhomogeneous interactions may lead to an accelerating motion of the condensate. As an example, the accelerating dynamic of BEC under a spatially linear modulated contact interaction is studied in detail. It is found that such an interaction will accelerate the condensate with a time varying acceleration. Furthermore, an interaction engineering scheme to achieve constantly accelerating BEC is proposed and studied numerically. Numerical results suggest that this engineering scheme can also suppress profile changing of the condensate during its evolution, thus realize an accelerating profile-keeping matter wave packet. Our analysis also applies to optical waves with Kerr nonlinearity.

Electro-optical dual modulation on resistive switching behavior in BaTiO3/BiFeO3/TiO2 heterojunction

Jia-Jia Zhao, Jin-Shuai Zhang, Feng Zhang, Wei Wang, Hai-Rong He, Wang-Yang Cai, Jin Wang
Chin. Phys. B 2019, 28 (12): 126801 ;  doi: 10.1088/1674-1056/ab54b4
Full Text: PDF (935KB) ( 83 ) RICH HTML
Show Abstract
The novel BaTiO3/BiFeO3/TiO2 multilayer heterojunction is prepared on a fluorine-doped tinoxide (FTO) substrate by the sol-gel method. The results indicate that the Pt/BaTiO3/BiFeO3/TiO2/FTO heterojunction exhibits stable bipolar resistive switching characteristic, good retention performance, and reversal characteristic. Under different pulse voltages and light fields, four stable resistance states can also be realized. The analysis shows that the main conduction mechanism of the resistive switching characteristic of the heterojunction is space charge limited current (SCLC) effect. After the comprehensive analysis of the band diagram and the P-E ferroelectric property of the multilayer heterojunction, we can deduce that the SCLC is formed by the effect of the oxygen vacancy which is controlled by ferroelectric polarization-modulated change of interfacial barrier. And the effective photo-generated carrier also plays a regulatory role in resistance state (RS), which is formed by the double ferroelectric layer BaTiO3/BiFeO3 under different light fields. This research is of potential application values for developing the multi-state non-volatile resistance random access memory (RRAM) devices based on ferroelectric materials.

Segregation behavior and embrittling effect of lanthanide La, Ce, Pr, and Nd at Σ3(111) tilt symmetric grain boundary in α-Fe

Jinli Cao, Wen Yang, Xinfu He
Chin. Phys. B 2019, 28 (12): 126802 ;  doi: 10.1088/1674-1056/ab5277
Full Text: PDF (979KB) ( 57 ) RICH HTML
Show Abstract
The migration of lanthanide fission products to cladding materials is recognized as one of the key causes of fuel-cladding chemical interaction (FCCI) in metallic fuels during operation. We have performed first-principles density functional theory calculations to investigate the segregation behavior of lanthanide fission products (La, Ce, Pr, and Nd) and their effects on the intergranular embrittlement at Σ3(111) tilt symmetric grain boundary (GB) in α-Fe. It is found that La and Ce atoms tend to reside at the first layer near the GB with segregation energies of -2.55 eV and -1.60 eV, respectively, while Pr and Nd atoms prefer to the core mirror plane of the GB with respective segregation energies of -1.41 eV and -1.50 eV. Our calculations also show that La, Ce, Pr, and Nd atoms all act as strong embrittlers with positive strengthening energies of 2.05 eV, 1.52 eV, 1.50 eV, and 1.64 eV, respectively, when located at their most stable sites. The embrittlement capability of four lanthanide elements can be determined by the atomic size and their magnetism characters. The present calculations are helpful for understanding the behavior of fission products La, Ce, Pr, and Nd in α-Fe.

Ultra-high voltage 4H-SiC gate turn-off thyristor forlow switching time

Qing Liu, Hong-Bin Pu, Xi Wang
Chin. Phys. B 2019, 28 (12): 127201 ;  doi: 10.1088/1674-1056/ab4e89
Full Text: PDF (1162KB) ( 79 ) RICH HTML
Show Abstract
An ultra-high voltage 4H-silicon carbide (SiC) gate turn-off (GTO) thyristor for low switching time is proposed and analyzed by numerical simulation. It features a double epitaxial p-base in which an extra electrical field is induced to enhance the transportation of the electrons in the thin p-base and reduce recombination. As a result, the turn-on characteristics are improved. What is more, to obtain a low turn-off loss, an alternating p+/n+ region formed in the backside acts as the anode in the GTO thyristor. Consequently, another path formed by the reverse-biased n+-p junction accelerates the fast removal of excess electrons during turn-off. This work demonstrates that the turn-on time and turn-off time of the new structure are reduced to 37 ns and 783.1 ns, respectively, under a bus voltage of 8000 V and load current of 100 A/cm2.

Strong coupling in silver-molecular J-aggregates-silver structure sandwiched between two dielectric media

Kunwei Pang, Haihong Li, Gang Song, Li Yu
Chin. Phys. B 2019, 28 (12): 127301 ;  doi: 10.1088/1674-1056/ab4fda
Full Text: PDF (415KB) ( 82 ) RICH HTML
Show Abstract
We theoretically investigate the strong coupling in silver-molecular J-aggregates-silver structure sandwiched between two dielectric media by using classical methods. Fresnel equations are employed to solve our proposed structure. The results show that both the reflection and transmission spectra show a Rabi splitting-like line shape, revealing the strong coupling phenomenon. Furthermore, the radiative angle versus incident wavelength exhibits a Fano line shape. The strong coupling phenomenon can be well tuned by controlling the surface plasmon excitation, such as the incident angle and the thickness of the silver films. Our structure has potential applications in quantum networks, optical switches, and so on.

Single-electron transport through single and coupling dopant atoms in silicon junctionless nanowire transistor

Xiao-Di Zhang, Wei-Hua Han, Wen Liu, Xiao-Song Zhao, Yang-Yan Guo, Chong Yang, Jun-Dong Chen, Fu-Hua Yang
Chin. Phys. B 2019, 28 (12): 127302 ;  doi: 10.1088/1674-1056/ab527a
Full Text: PDF (1850KB) ( 75 ) RICH HTML
Show Abstract
We investigated single-electron tunneling through single and coupling dopant-induced quantum dots (QDs) in silicon junctionless nanowire transistor (JNT) by varying temperatures and bias voltages. We observed that two possible charge states of the isolated QD confined in the axis of the initial narrowest channel are successively occupied as the temperature increases above 30 K. The resonance states of the double single-electron peaks emerge below the Hubbard band, at which several subpeaks are clearly observed respectively in the double oscillated current peaks due to the coupling of the QDs in the atomic scale channel. The electric field of bias voltage between the source and the drain could remarkably enhance the tunneling possibility of the single-electron current and the coupling strength of several dopant atoms. This finding demonstrates that silicon JNTs are the promising potential candidates to realize the single dopant atom transistors operating at room temperature.

Optical-induced dielectric tunability properties of DAST crystal in THz range

De-Gang Xu, Xian-Li Zhu, Yu-Ye Wang, Ji-Ning Li, Yi-Xin He, Zi-Bo Pang, Hong-Juan Cheng, Jian-Quan Yao
Chin. Phys. B 2019, 28 (12): 127701 ;  doi: 10.1088/1674-1056/ab4e81
Full Text: PDF (840KB) ( 70 ) RICH HTML
Show Abstract
The optical-induced dielectric tunability properties of DAST crystal in THz range were experimentally demonstrated. The DAST crystal was grown by the spontaneous nucleation method (SNM) and characterized by infrared spectrum. With the optimum wavelength of the exciting optical field, the transmission spectra of the DAST crystal excited by 532 nm laser under different power were measured by terahertz time-domain spectroscopy (THz-TDS) at room temperature. The transmitted THz intensity reduction of 26% was obtained at 0.68 THz when the optical field was up to 80 mW. Meanwhile, the variation of refractive index showed an approximate quadratic behavior with the exciting optical field, which was related to the internal space charge field of photorefractive phenomenon in the DAST crystal caused by the photogenerated carrier. A significant enhancement of 13.7% for THz absorption coefficient occurred at 0.68 THz due to the photogenerated carrier absorption effect in the DAST crystal.

Depolarization field in relaxor-based ferroelectric single crystals under one-cycle bipolar pulse drive

Chuan-Wen Chen, Yang Xiang, Li-Guo Tang, Lian Cui, Bao-Qing Lin, Wei-Dong Du, Wen-Wu Cao
Chin. Phys. B 2019, 28 (12): 127702 ;  doi: 10.1088/1674-1056/ab4e85
Full Text: PDF (497KB) ( 64 ) RICH HTML
Show Abstract
The[001]c-polarized (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystals are widely used in ultrasonic detection transducers and underwater acoustic sensors. However, the relatively small coercive field (~2 kV/cm) of such crystals restricts their application at high frequencies because the driving field will exceed the coercive field. The depolarization field can be considerably larger in an antiparallel direction than in a parallel direction with respect to polarization when the bipolar driving cycle starts. Thus, if the direction of the sine wave signal in the first half cycle is opposite to the polarization direction, then the depolarized domains can be repolarized in the second half of the sine cycle. However, if the direction of the sine wave signal in the first half of the cycle is along the polarization direction, then the change is negligible, and the domains switched in the second half of the sine cycle cannot be recovered. The design of electric driving method needs to allow the use of a large applied field to emit strong enough signals and produce good images. This phenomenon combined with the coercive field increases with the driving frequency, thereby making the PMN-PT single crystals usable for high-frequency applications. As such, the applied field can be considerably larger than the conventionally defined coercive field.

Improved interfacial properties of HfGdON gate dielectric Ge MOS capacitor by optimizing Gd content

Lin Zhou, Lu Liu, Yu-Heng Deng, Chun-Xia Li, Jing-Ping Xu
Chin. Phys. B 2019, 28 (12): 127703 ;  doi: 10.1088/1674-1056/ab4e7e
Full Text: PDF (1950KB) ( 48 ) RICH HTML
Show Abstract
High-quality dielectric/Ge interface and low gate leakage current are crucial issues for high-performance nanoscaled Ge-based complementary metal-oxide-semiconductor (CMOS) device. In this paper, the interfacial and electrical properties of high-k HfGdON/LaTaON stacked gate dielectric Ge metal-oxide-semiconductor (MOS) capacitors with different gadolinium (Gd) contents are investigated. Experimental results show that when the controlling Gd content is a suitable value (e.g.,~13.16%), excellent device performances can be achieved:low interface-state density (6.93×1011 cm-2·eV-1), small flatband voltage (0.25 V), good capacitance-voltage behavior, small frequency dispersion, and low gate leakage current (2.29×10-6 A/cm2 at Vg=Vfb + 1 V). These could be attributed to the repair of oxygen vacancies, the increase of conduction band offset, and the suppression of germanate and suboxide GeOx at/near the high k/Ge interface by doping suitable Gd into HfON.

Improved performance of back-gate MoS2 transistors by NH3-plasma treating high-k gate dielectrics Hot!

Jian-Ying Chen, Xin-Yuan Zhao, Lu Liu, Jing-Ping Xu
Chin. Phys. B 2019, 28 (12): 128101 ;  doi: 10.1088/1674-1056/ab50fe
Full Text: PDF (1778KB) ( 115 ) RICH HTML
Show Abstract
NH3-plasma treatment is used to improve the quality of the gate dielectric and interface. Al2O3 is adopted as a buffer layer between HfO2 and MoS2 to decrease the interface-state density. Four groups of MOS capacitors and back-gate transistors with different gate dielectrics are fabricated and their C-V and I-V characteristics are compared. It is found that the Al2O3/HfO2 back-gate transistor with NH3-plasma treatment shows the best electrical performance:high on-off current ratio of 1.53×107, higher field-effect mobility of 26.51 cm2/V…, and lower subthreshold swing of 145 mV/dec. These are attributed to the improvements of the gate dielectric and interface qualities by the NH3-plasma treatment and the addition of Al2O3 as a buffer layer.

A new sulfur-doped source and synergistic effect with nitrogen for carbon dots produced from glucose

Lige Fu, Yuehong Yin, Guohua Cao, Pingping Wu, Jian Wang, Lingling Yan, Baoqing Zhang, Ming Li
Chin. Phys. B 2019, 28 (12): 128102 ;  doi: 10.1088/1674-1056/ab5213
Full Text: PDF (1355KB) ( 49 ) RICH HTML
Show Abstract
The nitrogen and sulfur co-doped carbon dots (N, S-CDs) with increased luminescence were synthesized by a hydrothermal process in one green pot by using glucose, and a new sulfur-doping source of sodium sulfite was developed. The synergistic effect of the N and S groups was well discussed through the structure analysis of Fourier transform infrared spectra and x-ray photoelectron spectra. The surface states of N, S-CDs embody more complicated functional groups, and S element exists as -SSO3, -C-SO3, and SO42- groups due to the introduction of sodium sulfite. The sulfur-containing groups passivate the surface of the CDs, and the relatively high sulfur groups may reduce the non-radiation centers. The fluorescence is affected by the hydroxyl group of the solvent. The quenching of Fe3+ ion to fluorescence and the sensitivity of fluorescence to pH were also investigated.

Multiple enlarged growth of single crystal diamond by MPCVD with PCD-rimless top surface

Ze-Yang Ren, Jun Liu, Kai Su, Jin-Feng Zhang, Jin-Cheng Zhang, Sheng-Rui Xu, Yue Hao
Chin. Phys. B 2019, 28 (12): 128103 ;  doi: 10.1088/1674-1056/ab53cd
Full Text: PDF (3371KB) ( 85 ) RICH HTML
Show Abstract
We report the simultaneous enlarged growth of seven single crystal diamond (SCD) plates free from polycrystalline diamond (PCD) rim by using a microwave plasma chemical vapor deposition (MPCVD) system. Optical microscope and atomic force microscope (AFM) show the typical step-bunching SCD morphology at the center, edge, and corner of the samples. The most aggressively expanding sample shows a top surface area three times of that of the substrate. The effective surface expanding is attributed to the utilization of the diamond substrates with (001) side surfaces, the spacial isolation of them to allow the sample surface expanding, and the adoption of the reported pocket holder. Nearly constant temperature of the diamond surfaces is maintained during growth by only decreasing the sample height, and thus all the other growth parameters can be kept unchanged to achieve high quality SCDs. The SCDs have little stress as shown by the Raman spectra. The full width at half maximum (FWHM) data of both the Raman characteristic peak and (004) x-ray rocking curve of the samples are at the same level as those of the standard CVD SCD from Element Six Ltd. The nonuniformity of the sample thickness or growth rate is observed, and photoluminescence spectra show that the nitrogen impurity increases with increasing growth rate. It is found that the reduction of the methane ratio in the sources gas flow from 5% to 3% leads to decrease of the vertical growth rate and increase of the lateral growth rate. This is beneficial to expand the top surface and improve the thickness uniformity of the samples. At last, the convenience of the growth method transferring to massive production has also been demonstrated by the successful simultaneous enlarged growth of 14 SCD samples.

High performance silicon-based GeSn p-i-n photodetectors for short-wave infrared application Hot!

Yue Zhao, Nan Wang, Kai Yu, Xiaoming Zhang, Xiuli Li, Jun Zheng, Chunlai Xue, Buwen Cheng, Chuanbo Li
Chin. Phys. B 2019, 28 (12): 128501 ;  doi: 10.1088/1674-1056/ab4e84
Full Text: PDF (774KB) ( 97 ) RICH HTML
Show Abstract
An investigation of germanium-tin (GeSn) on silicon p-i-n photodetectors with a high-quality Ge0.94Sn0.06 absorbing layer is reported. The GeSn photodetector reached a responsivity as high as 0.45 A/W at the wavelength of 1550 nm and 0.12 A/W at the wavelength of 2 μm. A cycle annealing technology was applied to improve the quality of the epitaxial layer during the growth process by molecular beam epitaxy. A low dark-current density under 1 V reverse bias about 0.078 A/cm2 was achieved at room temperature. Furthermore, the GeSn photodetector could detect a wide spectrum region and the cutoff wavelength reached to about 2.3 μm. This work has great importance in silicon-based short-wave infrared detection.

Thickness-modulated in-plane Bi2O2Se homojunctions for ultrafast high-performance photodetectors

Cheng-Yun Hong, Gang-Feng Huang, Wen-Wen Yao, Jia-Jun Deng, Xiao-Long Liu
Chin. Phys. B 2019, 28 (12): 128502 ;  doi: 10.1088/1674-1056/ab4e87
Full Text: PDF (1538KB) ( 112 ) RICH HTML
Show Abstract
Bi2O2Se thin film could be one of the promising material candidates for the next-generation electronic and optoelectronic applications. However, the performance of Bi2O2Se thin film-based device is not fully explored in the photodetecting area. Considering the fact that the electrical properties such as carrier mobility, work function, and energy band structure of Bi2O2Se are thickness-dependent, the in-plane Bi2O2Se homojunctions consisting of layers with different thicknesses are successfully synthesized by the chemical vapor deposition (CVD) method across the terraces on the mica substrates, where terraces are created in the mica surface layer peeling off process. In this way, effective internal electrical fields are built up along the Bi2O2Se homojunctions, exhibiting diode-like rectification behavior with an on/off ratio of 102, what is more, thus obtained photodetectors possess highly sensitive and ultrafast features, with a maximum photoresponsivity of 2.5 A/W and a lifetime of 4.8 \upmus. Comparing with the Bi2O2Se uniform thin films, the photo-electric conversion efficiency is greatly improved for the in-plane homojunctions.

Simulation of a-Si: H/c-Si heterojunction solar cells: From planar junction to local junction

Haibin Huang, Lang Zhou, Jiren Yuan, Zhijue Quan
Chin. Phys. B 2019, 28 (12): 128503 ;  doi: 10.1088/1674-1056/ab5212
Full Text: PDF (1339KB) ( 88 ) RICH HTML
Show Abstract
In order to obtain higher conversion efficiency and to reduce production cost for hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) based heterojunction solar cells, an a-Si:H/c-Si heterojunction with localized p-n structure (HACL) is designed. A numerical simulation is performed with the ATLAS program. The effect of the a-Si:H layer on the performance of the HIT (heterojunction with intrinsic thin film) solar cell is investigated. The performance improvement mechanism for the HACL cell is explored. The potential performance of the HACL solar cell is compared with those of the HIT and HACD (heterojunction of amorphous silicon and crystalline silicon with diffused junction) solar cells. The simulated results indicate that the a-Si:H layer can bring about much absorption loss. The conversion efficiency and the short-circuit current density of the HACL cell can reach 28.18% and 43.06 mA/cm2, respectively, and are higher than those of the HIT and HACD solar cells. The great improvement are attributed to (1) decrease of optical absorption loss of a-Si:H and (2) decrease of photocarrier recombination for the HACL cell. The double-side local junction is very suitable for the bifacial solar cells. For an HACL cell with n-type or p-type c-Si base, all n-type or p-type c-Si passivating layers are feasible for convenience of the double-side diffusion process. Moreover, the HACL structure can reduce the consumption of rare materials since the transparent conductive oxide (TCO) can be free in this structure. It is concluded that the HACL solar cell is a promising structure for high efficiency and low cost.

Effects of refractory period on dynamical range inexcitable networks

Ya-Qin Dong, Fan Wang, Sheng-Jun Wang, Zi-Gang Huang
Chin. Phys. B 2019, 28 (12): 128701 ;  doi: 10.1088/1674-1056/ab4f60
Full Text: PDF (713KB) ( 68 ) RICH HTML
Show Abstract
Effects of refractory period on the dynamical range in excitable networks are studied by computer simulations and theoretical analysis. The first effect is that the maximum or peak of the dynamical range appears when the largest eigenvalue of adjacent matrix is larger than one. We present a modification of the theory of the critical point by considering the correlation between excited nodes and their neighbors, which is brought by the refractory period. Our analysis provides the interpretation for the shift of the peak of the dynamical range. The effect is negligible when the average degree of the network is large. The second effect is that the dynamical range increases as the length of refractory period increases, and it is independent of the average degree. We present the mechanism of the second effect. As the refractory period increases, the saturated response decreases. This makes the bottom boundary of the dynamical range smaller and the dynamical range extend.

Non-thermal effects of 0.1 THz radiation on intestinal alkaline phosphatase activity and conformation

Xin-Xin Zhang, Ming-Xia He, Yu Chen, Cheng Li, Jin-Wu Zhao, Peng-Fei Wang, Xin Peng
Chin. Phys. B 2019, 28 (12): 128702 ;  doi: 10.1088/1674-1056/ab50fd
Full Text: PDF (1032KB) ( 48 ) RICH HTML
Show Abstract
Alkaline phosphatase (ALP) plays an integral role in the metabolism of liver and development of the skeleton in humans. To date, the interactions between different-duration terahertz (THz) radiation and ALP activities, as well as the influence mechanism are still unclear. In this study, using the para-nitro-phenyl-phosphate (pNPP) method, we detect changes in ALP activities during 40-minute THz radiation (0.1 THz, 13 mW/cm2). It is found that the activity of ALP decreases in the first 25 min, and subsequently increases in the later 15 min. Compared with the activity of ALP being heated, the results suggest that short-term terahertz radiation induces a decrease in enzyme activity through the non-thermal mechanism. In order to explore the non-thermal effects of THz radiation on ALP, we focus on the impacts of 0.1 THz radiation for 20 min on the activity of ALP in different concentrations. The results reveal that the activity of ALP decreases significantly after exposure to THz radiation. In addition, it could be deduced from fluorescence, ultraviolet-visible (UV-vis), and THz spectra results that THz radiation has induced changes in ALP structures. Our study unlocks non-thermal interactions between THz radiation and ALP, as well as suggests that THz spectroscopy is a promising technique to distinguish ALP structures.

High efficiency hydrogen purification through P2C3 membrane: A theoretical study

Zhao-Qin Chu, Xiao Gu, Xiang-Mei Duan
Chin. Phys. B 2019, 28 (12): 128703 ;  doi: 10.1088/1674-1056/ab55cf
Full Text: PDF (898KB) ( 64 ) RICH HTML
Show Abstract
It is critical to design an effective two-dimensional membrane for hydrogen purification from the mixed gas, due to its wide range of scientific and industrial applications. In this work, we investigate the hydrogen separation performance of P2C3 membranes by density functional theory and molecular dynamics simulations. The results show that the energy barrier of the H2 molecule through the P2C3 film is only 0.18 eV, while the energy barriers of the CO, N2, CO2, and CH4 molecules are 0.77 eV, 0.87 eV, 0.52 eV, and 1.75 eV, respectively. In addition, the P2C3 film has high H2 selectivity toward other gas molecules and high H2 permeability at room temperature. Under 6% tensile strain, 82% hydrogen molecules pass through the film with a H2 permeance of 2.22×107 gas permeance unit (GPU), while other molecules cannot across the membrane at all. Therefore, the P2C3 membrane is an excellent material for hydrogen purification.

Analysis of highly efficient perovskite solar cells with inorganic hole transport material

I Kabir, S A Mahmood
Chin. Phys. B 2019, 28 (12): 128801 ;  doi: 10.1088/1674-1056/ab520f
Full Text: PDF (461KB) ( 138 ) RICH HTML
Show Abstract
Organo-halide perovskites in planar heterojunction architecture have shown considerable promise as efficient light harvesters in solar cells. We carry out a numerical modeling of a planar lead based perovskite solar cell (PSC) with Cu2ZnSnS4 (CZTS) as the hole transporting material (HTM) using the one-dimensional solar cell capacitance simulator (SCAPS-1D). The effects of numerous parameters such as defect density, thickness, and doping density of the absorber layer on the device performance are investigated. The doping densities and electron affinities of the electron transporting material (ETM) and the HTM are also varied to optimize the PSC performance. It has been observed that a thinner absorber layer of~220 nm with a defect density of 1014 cm-3 compared to the reference structure improves the device performance. When doping density of the absorber layer increases beyond 2×1016 cm-3, the power conversion efficiency (PCE) reduces due to enhanced recombination rate. The defect density at the absorber/ETM interface reduces the PCE as well. Considering a series resistance of 5 Ω·cm2 and all the optimum parameters of absorber, ETM and HTM layers simultaneously, the overall PCE of the device increases significantly. In comparison with the reference structure, the PCE of the optimized device has been increased from 12.76% to 22.7%, and hence the optimized CZTS based PSC is highly efficient.

Dynamics and control strategies of infectious disease under different scenarios on hierarchical geographical networks

Xun Ma, Ya-Peng Cui, Xiao-Li Yan, Shun-Jiang Ni, Shi-Fei Shen
Chin. Phys. B 2019, 28 (12): 128901 ;  doi: 10.1088/1674-1056/ab53ce
Full Text: PDF (780KB) ( 67 ) RICH HTML
Show Abstract
Human settlements are embedded in traffic networks with hierarchical structures. In order to understand the spreading mechanism of infectious diseases and deploy control measures, the susceptible-infected-removed spreading process is studied with agents moving globally on the hierarchical geographic network, taking into account agents' preference for node layers and memory of initial nodes. We investigate the spreading behavior in the case of global infection under different scenarios, including different directions of human flow, different locations of infection source, and different moving behaviors of agents between layers. Based on the above-mentioned analysis, we propose screening strategies based on layer rank and moving distance, and compare their effects on delaying epidemic spreading. We find that in the case of global infection, infection spreads faster in high layers than in low layers, and early infection in high layers and moving to high layers both accelerate epidemic spreading. Travels of high-layer and low-layer residents have different effects on accelerating epidemic spreading, and moving between high and low layers increases the peak value of new infected cases more than moving in the same layer or between adjacent layers. Infection in intermediate nodes enhances the effects of moving of low-layer residents more than the moving of high-layer residents on accelerating epidemic spreading. For screening measures, improving the success rate is more effective on delaying epidemic spreading than expanding the screening range. With the same number of moves screened, screening moves into or out of high-layer nodes combined with screening moves between subnetworks has better results than only screening moves into or out of high-layer nodes, and screening long-distance moves has the worst results when the screening range is small, but it achieves the best results in reducing the peak value of new infected cases when the screening range is large enough. This study probes into the spreading process and control measures under different scenarios on the hierarchical geographical network, and is of great significance for epidemic control in the real world.
[an error occurred while processing this directive]