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Thermal Entanglement in the Pure Dzyaloshinskii–Moriya Model with Magnetic Field
LI Da-Chuang, LI Xiao-Man, LI Hu, TAO Rui, YANG Ming, CAO Zhuo-Liang
Chin. Phys. Lett. 2015, 32 (5):
050302
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DOI: 10.1088/0256-307X/32/5/050302
We investigate the effects of the directions of Dzyaloshinskii–Moriya (DM) interaction and magnetic field on the thermal entanglement in the pure DM model. It is found that when the Hamiltonian is H1= D⋅(σ1⊗σ2)+B⋅σ1, the entanglement can reach its maximum if the directions of the magnetic field and the DM vector are parallel. In addition, when the Hamiltonian is H2=D⋅(σ1⊗σ2)+B⋅(σ1+σ2), if the directions of the magnetic field and the DM vector are perpendicular in a high magnetic field, or their directions are parallel in a weak magnetic field, the entanglement can also reach its maximum. Thus the entanglement can be enhanced by adjusting the direction of the external magnetic field, and this is feasible within the current experimental technology.
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An Ideal Experiment to Determine the 'Past of a Particle' in the Nested Mach–Zehnder Interferometer
LI Fu, Hashmi F. A., ZHANG Jun-Xiang, ZHU Shi-Yao
Chin. Phys. Lett. 2015, 32 (5):
050303
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DOI: 10.1088/0256-307X/32/5/050303
An ideal experiment is designed to determine the past of a particle in the nested Mach–Zehnder interferometer (MZI) by using standard quantum mechanics with quantum non-demolition measurements. We find that when the photon reaches the detector, it only follows one arm of the outer interferometer and leaves no trace in the inner MZI. When it goes through the inner MZI, it cannot reach the detector. Our result obtained from the standard quantum mechanics contradicts the statement based on two-state vector formulism, 'the photon did not enter the (inner) interferometer, the photon never left the interferometer, but it was there'. Therefore, the statement and also the overlapping claim are incorrect.
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The Recent Development of the EAST Neutral Beam Injector
HU Chun-Dong, XU Yong-Jian, XIE Yuan-Lai, LIU Sheng, LIU Zhi-Min, SHENG Peng, XIE Ya-Hong, LIANG Li-Zhen, NBI Team
Chin. Phys. Lett. 2015, 32 (5):
052901
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DOI: 10.1088/0256-307X/32/5/052901
Neutral beam injection has been recognized as one of the most effective means for plasma heating. According to the research plan of the EAST physics experiment, two sets of neutral beam injectors (4–8 MW, 10–100 s) were built and operated in 2014. We present the development of the EAST neutral beam injector (NBI) and the latest experiment results obtained on the test-stand about operation of ion source, beam extraction, and measurement of key parameters. Those results show that all targets reach or almost reach the design targets. All these lay a solid foundation for the achievement of plasma heating and current drive for EAST in 2014.
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Empirical Scaling Laws of Neutral Beam Injection Power in HL-2A Tokamak
CAO Jian-Yong, WEI Hui-Ling, LIU He, YANG Xian-Fu, ZOU Gui-Qing, YU Li-Ming, LI Qing, LUO Cui-Wen, PAN Yu-Dong, JIANG Shao-Feng, LEI Guang-Jiu, LI Bo, RAO Jun, DUAN Xu-Ru
Chin. Phys. Lett. 2015, 32 (5):
052902
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DOI: 10.1088/0256-307X/32/5/052902
We present an experimental method to obtain neutral beam injection (NBI) power scaling laws with operating parameters of the NBI system on HL-2A, including the beam divergence angle, the beam power transmission efficiency, the neutralization efficiency and so on. With the empirical scaling laws, the estimating power can be obtained in every shot of experiment on time, therefore the important parameters such as the energy confinement time can be obtained precisely. The simulation results by the tokamak simulation code (TSC) show that the evolution of the plasma parameters is in good agreement with the experimental results by using the NBI power from the empirical scaling law.
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Design of a Solid-Core Large-Mode-Area Bragg Fiber
LI Lu, PANG Li-Hui, ZHOU Zhi-Guang, ZHANG Ai-Dong, HE Jian-Li, SI Jin-Hai, LIN Ao-Xiang
Chin. Phys. Lett. 2015, 32 (5):
054201
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DOI: 10.1088/0256-307X/32/5/054201
We report the design and simulation results of a solid-core Bragg fiber with 3-bilayer periodic cladding. The simulation results present single mode bandgap guidance, a large effective area of ~400 μm2 around 1.08 μm, a very low bend loss of 0.038 dB/m at 1.08 μm even under tight bend radius (R=4 cm), and excellent beam quality. The results indicate that the proposed fiber could be a competitive solution for high-power fiber laser applications.
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Fabrication of 32 Gb/s Electroabsorption Modulated Distributed Feedback Lasers by Selective Area Growth Technology
ZHOU Dai-Bing, WANG Hui-Tao, ZHANG Rui-Kang, WANG Bao-Jun, BIAN Jing, AN Xin, LU Dan, ZHAO Ling-Juan, ZHU Hong-Liang, JI Chen, WANG Wei
Chin. Phys. Lett. 2015, 32 (5):
054205
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DOI: 10.1088/0256-307X/32/5/054205
A 32 Gb/s monolithically integrated electroabsorption modulated laser is fabricated by selective area growth technology. The threshold current of the device is below 13 mA. The output power exceeds 10 mW at 0 V bias when the injection current of the distributed feedback laser is 100 mA at 25°C. The side mode suppression ratio is over 50 dB. A 32Gb/s eye diagram is measured with a 3.5Vpp nonreturn-to-zero pseudorandom modulation signal at -2.3 V bias. A clearly opening eyediagram with a dynamic extinction ratio of 8.01 dB is obtained.
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The Line Shape of Double-Sided Tooth-Disk Waveguide Filters Based on Plasmon-Induced Transparency
ZHANG Xin-Yuan, WANG Lu-Lu, CHEN Zhao, CUI Lu-Na, SHANG Ce, ZHAO Yu-Fang, DUAN Gao-Yan, LIU Jian-Bin, YU Li
Chin. Phys. Lett. 2015, 32 (5):
054209
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DOI: 10.1088/0256-307X/32/5/054209
We numerically investigate a coupled-resonator structure consisting of a stub resonator and a nanodisk resonator using a two-dimensional finite element method. Simulation results show that plasmon-induced transparency (PIT) occurs in the transmission spectra, and the sharp asymmetric Fano lines increase the sensitivity to 1.4×103 nm/RIU. We also analyze the properties of the structure with different radii of the nanodisk and the length of the tooth cavity. Moreover, we find that the PIT only happens when the staggered system is around a fixed location with different separate distances, which is not similar to the previous researches. Our model may be important to photonic-integrated circuits and the sensitivity in sensors.
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Temperature-Dependent Fluorescence Properties and Diode-Pumped Deep Red Laser Performance of Pr:LiGdF4 Crystal
ZHANG Yu-Xia, WANG Shu-Xian, Alberto Di Lieto, YU Guo-Lei, YU Hao-Hai, ZHANG Huai-Jin, Mauro Tonelli, XU Xian-Gang, WANG Ji-Yang
Chin. Phys. Lett. 2015, 32 (5):
054210
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DOI: 10.1088/0256-307X/32/5/054210
We demonstrate the temperature-dependent fluorescence properties of Pr:LiGdF4 crystal for the first time, to the best of our knowledge, and its blue diode pumped cw red laser at 720 nm at room temperature. The fluorescence lifetime and polarized emission cross sections in the visible range are measured and calculated in a temperature range from 77 K to 300 K, and the variations of the fluorescence lifetime and spectra are discovered. The reasons for these changes are explained accordingly. The output wavelength of the 720 nm laser is first reported on the laser performance by using a fiber-coupled laser diode at the wavelength of 442 nm as the pump source, and the maximum cw output power is about 303 mW.
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Effect of Crystallinity of Fullerene Derivatives on Doping Density in the Organic Bulk Heterojunction Layer in Polymer Solar Cells
LIU Qian, HE Zhi-Qun, LIANG Chun-Jun, ZHAO Yong, XIAO Wei-Kang, LI Dan
Chin. Phys. Lett. 2015, 32 (5):
056801
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DOI: 10.1088/0256-307X/32/5/056801
Polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are fabricated by using 1,8-diiodooctane (DIO) as a solvent additive to control the doping density of the PSCs. It is shown that the processing of DIO does not change the doping density of the P3HT phase, while it causes a dramatic reduction of the doping density of the PCBM phase, which decreases the doping density of the whole blend layer from 3.7×1016 cm?3 to 1.2×1016 cm?3. The reduction of the doping density in the PCBM phase originates from the increasing crystallinity of PCBM with DIO addition, and it leads to a decreasing doping density in the blend film and improves the short circuit current of the PSCs.
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Electrical Conduction in Deuterated Ammonium Dihydrogen Phosphate Crystals with Different Degrees of Deuteration
ZHU Li-Li, GAN Xiao-Yu, ZHANG Qing-Hua, LIU Bao-An, XU Ming-Xia, ZHANG Li-Song, XU Xin-Guang, GU Qing-Tian, SUN Xun
Chin. Phys. Lett. 2015, 32 (5):
057201
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DOI: 10.1088/0256-307X/32/5/057201
Conductivity measurements of deuterated ammonium dihydrogen phosphate (DADP) crystals with different deuterated degrees are described. The conductivities increase with the deuterium content, and the value of the a-direction is larger than that of the c-direction. Compared with DKDP crystals, DADP crystals have larger conductivities, which is partly due to the existence of A defects. The ac conductivity over the temperature range 25–170°C has shown a knee in the curve of ln(σT) versus T?1. The conductivity activation energy calculated by the slope of the high temperature region decreases with the deuterium content. The previously reported phase transition is not seen.
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GaNAs/InGaAs Superlattice Solar Cells with High N Content in the Barrier Grown by All Solid-State Molecular Beam Epitaxy
LU Jian-Ya, ZHENG Xin-He, WANG Nai-Ming, CHEN Xi, LI Bao-Ji, LU Shu-Long, YANG Hui
Chin. Phys. Lett. 2015, 32 (5):
057301
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DOI: 10.1088/0256-307X/32/5/057301
We demonstrate nearly 1 eV GaN0.03As0.97/In0.09Ga0.91As strain-compensated short-period superlattice solar cells by all solid-state molecular beam epitaxy. The optimal period thickness for the superlattice growth is achieved to realize high structural quality. Meanwhile, the annealing conditions are optimized to realize a photoluminescence (PL) at a low temperature. However, no PL signal is detected at room temperature, which could be reflected by a lower open-circuit voltage of the fabricated devices. The GaN0.03As0.97/In0.09Ga0.91As superlattice solar cells show a reasonably-high short-circuit current density (Jsc) of over 10 mA/cm2. Furthermore, a concentration behavior is measured, which shows a linear relationship between Jsc and concentration ratios. The extrapolated ideality factor and saturated current density by the concentration action are in good agreement with that extracted by the dark case of the p-i-n diodes.
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Magnetism in Quasi-One-Dimensional A2Cr3As3 (A=K,Rb) Superconductors
WU Xian-Xin, LE Cong-Cong, YUAN Jing, FAN Heng, HU Jiang-Ping
Chin. Phys. Lett. 2015, 32 (5):
057401
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DOI: 10.1088/0256-307X/32/5/057401
We predict that the recently discovered quasi-one-dimensional superconductors, A2Cr3As3 (A=K,Rb), possess strong frustrated magnetic fluctuations and are nearby a novel in-out co-planar magnetic ground state. The frustrated magnetism is very sensitive to the c-axis lattice constant and can thus be suppressed by increasing pressure. Our results qualitatively explain strong non-Fermi liquid behaviors observed in the normal state of the superconductors as the intertwining between the magnetism and superconductivity can create a large quantum critical region in quasi-one-dimensional systems and also suggest that the materials share similar phase diagrams and superconducting mechanism with other unconventional superconductors, such as cuprates and iron-based superconductors.
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Tuning the Electronic Structure of Sr2IrO4 Thin Films by Bulk Electronic Doping Using Molecular Beam Epitaxy
LI Ming-Ying, LIU Zheng-Tai, YANG Hai-Feng, ZHAO Jia-Lin, YAO Qi, FAN Cong-Cong, LIU Ji-Shan, GAO Bo, SHEN Da-Wei, XIE Xiao-Ming
Chin. Phys. Lett. 2015, 32 (5):
057402
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DOI: 10.1088/0256-307X/32/5/057402
By means of oxide molecular beam epitaxy with shutter-growth mode, we fabricate a series of electron-doped (Sr1?xLax)2IrO4 (001) (x=0, 0.05, 0.1 and 0.15) single crystalline thin films and then investigate the doping dependence of the electronic structure utilizing in-situ angle-resolved photoemission spectroscopy. It is found that with the increasing doping content, the Fermi levels of samples progressively shift upward. Prominently, an extra electron pocket crossing the Fermi level around the M point is evidently observed in the 15% nominal doping sample. Moreover, bulk-sensitive transport measurements confirm that the doping effectively suppresses the insulating state with respect to the as-grown Sr2IrO4, though the doped samples still remain insulating at low temperatures due to the localization effect possibly stemming from disorders including oxygen deficiencies. Our work provides another feasible doping method to tune electronic structure of Sr2IrO4.
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Structural and Magnetic Properties of Co2MnSi Thin Film with a Low Damping Constant
QIAO Shi-Zhu, ZHANG Jie, QIN Yu-Feng, HAO Run-Run, ZHONG Hai, ZHU Da-Peng, KANG Yun, KANG Shi-Shou, YU Shu-Yun, HAN Guang-Bing, YAN Shi-Shen, MEI Liang-Mo
Chin. Phys. Lett. 2015, 32 (5):
057601
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DOI: 10.1088/0256-307X/32/5/057601
Co2MnSi thin films are made by magnetron sputtering onto MgO (001) substrates. The crystalline quality is improved by increasing depositing temperature and/or annealing temperature. The sample deposited at 550°C and subsequently annealed at 550°C (sample I) exhibits a pseudo-epitaxial growth with partially ordered L21 phase. Sample I shows a four-fold magnetic anisotropy, in addition to a relatively weak uniaxial anisotropy. The Gilbert damping factor of sample I is smaller than 0.001, much smaller than reported ones. The possible reasons responsible for the small Gilbert damping factor are discussed, including weak spin-orbit coupling, small density of states at Fermi level, and so on.
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Dynamic Investigations of Pressure-Induced Abnormal Phase Transitions in PbTiO3
WU Hong-Bo, DUAN Yi-Feng, LIU Kun, LV Dong, QIN Li-Xia, SHI Li-Wei, TANG Gang
Chin. Phys. Lett. 2015, 32 (5):
057701
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DOI: 10.1088/0256-307X/32/5/057701
The effects of pressure on phonon modes of ferroelectric tetragonal P4mm and paraelectric cubic Pm3m PbTiO3 are systematically investigated by using first-principles simulations. The pressure-induced tetragonal-to-cubic and subsequent cubic-to-tetragonal phase transitions are the second-order transitions, which are different from the phase transitions induced by temperature [Phys. Rev. Lett. 25 (1970) 167]. As pressure increases, the lowest A1 and E modes of the tetragonal phase become softer and converge to the F1u mode of the cubic phase. As pressure further increases, the lowest F1u mode first hardens and then softens again, and finally diverges into A1 and E modes. The behaviors of optical phonon modes confirm the ferroelectric-to-paraelectric-to-ferroelectric phase transitions.
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Structure and Strain Properties of GaN Films Grown on Si (111) Substrates with AlxGa1?xN/AlyGa1?yN Superlattices
PAN Lei, NI Jin-Yu, YU Xin-Xin, DONG Xun, PENG Da-Qing, LI Chuan-Hao, LI Zhong-Hui, CHEN Tang-Sheng
Chin. Phys. Lett. 2015, 32 (5):
058103
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DOI: 10.1088/0256-307X/32/5/058103
GaN films with an AlxGa1?xN/AlyGa1?yN superlattice (SL) buffer layer are grown on Si(111) substrates by metal-organic chemical vapor deposition (MOCVD). The structure and strain properties of the samples are studied by optical microscopy, Raman spectroscopy, x-ray diffractometry and atomic force microscopy. The results show that the strain status and crystalline quality of the GaN layers are strongly dependent on the difference of the Al composition between AlxGa1?xN barriers and AlyGa1?yN wells in the SLs. With a large Al composition difference, the GaN film tends to generate cracks on the surface due to the severe relaxation of the SLs. Otherwise, when using a small Al composition difference, the crystalline quality of the GaN layer degrades due to the poor function of the SLs in filtering dislocations. Under an optimized condition that the Al composition difference equals 0.1, the crack-free and compressive strained GaN film with an improved crystalline quality is achieved. Therefore, the AlxGa1?xN/AlyGa1?yN SL buffer layer is a promising buffer structure for growing thick GaN films on Si substrates without crack generation.
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Effects of Thermal Annealing on the Solvent Additive P3HT PC61BM Bulk Heterojunction Solar Cells
FAN Xing, ZHAO Su-Ling, CHEN Yu, ZHANG Jie, YANG Qian-Qian, GONG Wei, XU Zheng, XU Xu-Rong
Chin. Phys. Lett. 2015, 32 (5):
058401
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DOI: 10.1088/0256-307X/32/5/058401
Effects of thermal annealing on the optical, electrical and structural properties of 3 vol% 1,8-diiodoctane added P3HT:PC61BM active layers are investigated, concerning the performance of the bulk heterojunction polymer solar cells by changing the heat temperature. The structure information of the active layer is analyzed by using the grazing incidence wide angle scattering diffraction combined with the optical microscope, light absorption, photoluminescence and the external quantum efficiency spectra. The relationship between the detail of morphology and the optical, electrical properties is investigated.
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A Novel Multi-Finger Gate Structure of AlGaN/GaN High Electron Mobility Transistor
CUI Lei, WANG Quan, WANG Xiao-Liang, XIAO Hong-Ling, WANG Cui-Mei, JIANG Li-Juan, FENG Chun, YIN Hai-Bo, GONG Jia-Min, LI Bai-Quan, WANG Zhan-Guo
Chin. Phys. Lett. 2015, 32 (5):
058501
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DOI: 10.1088/0256-307X/32/5/058501
A novel multi-finger gate high electron mobility transistor (HEMT) is designed to reduce the peak electric field value at the drain-side gate edge when the device is at off-state. The effective gate length (Leff) of the multi-finger gate device is smaller than that of the field plate gate device. In this work, field plate gate, five-finger gate and ten-finger gate devices are simulated. The results of the simulation indicate that the multi-finger gate device has a lower peak value than the device with the gate field plate. Moreover, this value would be further reduced when the number of gate fingers is increased. In addition, it has the potential to make the HEMT work in a higher frequency since it has a lower effective length of gate.
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Effects of Gravitational Correction on Neutrino Emission from Neutron Stars
DING Wen-Bo, E Shan-Shan, YU Zi, ZHANG Qi, QI Zhan-Qiang
Chin. Phys. Lett. 2015, 32 (5):
059701
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DOI: 10.1088/0256-307X/32/5/059701
Considering the gravitational correction through introduction of weakly interacting light vector U bosons, not only the equation of state (EoS) of the neutron star matter, but also the cooling properties of neutron stars may be changed. In this work, effects of gravitational correction on neutrino emission and cooling of neutron stars in the matter with neutrons, protons, electrons, muons, Δ? and Δ0 are studied by the relativistic mean field theory and the related cooling theory. The results show that the effects are sensitive to the ratio of coupling strength to mass squared of U bosons, defined as gU. With increasing gU, the radial region where direct Urca process of nucleons can be allowed in a neutron star with the fixed mass becomes narrower, while the neutrino emissivity is somewhat higher. Moreover, the gravitational correction suppresses the effects of Δ? on neutrino emission. The gravitational correction leads the star to cool faster, and the higher the gU is, the faster the star cools.
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45 articles
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