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electric-field control of the activity of the graphene-based catalyst

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Science China(Physics,Mechanics & Astronomy) 2011年第5期54卷 804-808页

作者： LU YunHao FENG YuanPing Department of Physics National University of Singapore 2 Science Drive 3 Singapore 117542 Singapore

Effects of an electric field on CO oxidation of Au-embedded graphene are investigated using first-principles method. Results of our calculations show that the initial step of the reaction is more likely to proceed via the Langmuir-Hinshelwood mechanism in the presence of the field, and the reaction barrier can be tuned continuously by the electric field. However, the applied electric field makes it more difficult for the product of the reaction, CO2, to desorb from the reaction site. These two competing effects make an electric field not entirely advantageous in controlling the activity of Au-embedded graphene for CO oxidation reaction. Nevertheless, the findings of our study provide a basis for further investigation on control of chemical reactions by electric fields.

关键词： graphene catalysis electric-field DFT

Accurate reconstruction of electric field of ultrashort laser pulse with complete two-step phase-shifting

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High Power Laser Science and Engineering 2019年第1期7卷 92-98页

作者： Yi Cai Zhenkuan Chen Shuiqin Zheng Qinggang Lin Xuanke Zeng Ying Li Jingzhen Li Shixiang Xu Shenzhen Key Laboratory of Micro-Nano Photonic Information Technology College of Electronic Science and TechnologyShenzhen University International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology Engineering Technology Research Center for 2D Material Information Function Devices and Systems of Guangdong ProvinceShenzhen University

This paper presents a complete two-step phase-shifting(TSPS) spectral phase interferometry for direct electric-field reconstruction(SPIDER) to improve the reconstruction of ultrafast optical fields. Here, complete TSPS acts as a balanced detection that can not only remove the effect of the dc term of the interferogram, but also reduce measurement noises,and thereby improve the capability of SPIDER to measure the pulses with narrow spectra or complex spectral *** prisms are chosen to replace some environment-sensitive optical components, especially reflective optics to improve operating stability and improve signal-to-noise ratio further. Our experiments show that the available shear can be decreased to 1.5% of the spectral width, which is only about 1/3 compared with traditional SPIDER.

关键词： electric-field reconstruction shearing interferometry spectral phase ultrashort laser pulse

Giant modulation of magnetism in(Ga,Mn)As ultrathin films via electric field

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Journal of Semiconductors 2019年第9期40卷 61-65页

作者： Hailong Wang Jialin Ma Jianhua Zhao State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing 100049China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China

Taking the advantages of semiconducting properties and carrier-mediated ferromagnetism in(Ga,Mn)As,a giant modulation of magnetism via electric field in(Ga,Mn)As ultrathin film has been ***,huge interfacial electric field is obtained by using ionic liquid as the gate *** magnetization and transport measurements are employed to characterize the samples,while the transport data are used to analyze the electric filed effect on *** demagnetization of(Ga,Mn)As film is then realized by thinning its thickness down to ~2 nm,during which the degradation of ferromagnetism of(Ga,Mn)As ultrathin film induced by quantum confinement effect is suppressed by inserting a heavily-doped p-type GaAs buffer *** variation of the Curie temperature is more than 100 K,which is nearly 5-times larger than previous *** results provide a new pathway on the efficient electrical control of magnetism.

关键词： (Ga,Mn)As film electric-field effect Curie temperature demagnetization

Excitonic Absorption of Semiconductor Nanorings under Terahertz fields

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Chinese Physics Letters 2005年第10期22卷 2643-2646页

作者：张同意赵卫朱少岚 State Key Laboratory of Transient Optics and Photonics. Xi'an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi'an 710068

The optical absorption of GaAs nanorings （NRs） under adc electric field and a terahertz （THz） ac electric field applied in the plane containing the NRs is investigated theoretically. The NRs may enclose some magnetic flux in the presence of a magnetic field perpendicular to the NRs plane. Numerical calculation shows that the excitonic effects are essential to correctly describe the optical absorption in NRs. The applied lateral THz electric field, as well as the dc field leads to reduction, broadening and splitting of the exciton peak. In contrast to the presence of a dc field, significant optical absorption peak arises below the zero-field bandgap in the presence ofa THz electric field at a certain frequency. The optical absorption spectrum depends evidently on the frequency and amplitude of the applied THz field and on the magnetic flux threading the NRs. This promises potential applications of NRs for magneto-optical and THz electro-optical sensing.

关键词： SIDE-BAND GENERATION GAAS QUANTUM-WELLS OPTICAL-ABSORPTION electric-field SPECTRA RINGS ILLUMINATION IONIZATION RADIATION

All-Optical Photorefractive Effect in Carbazole-Based Azo-Side Group Polymer

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Chinese Physics Letters 2006年第9期23卷 2468-2471页

作者：黄毛毛陈志坚石军曹少魁龚旗煌 School of Physics State Key Laboratory for Mesoscopic Physics Peking University Beijing 100871 College of Materials Engineering Zhengzhou University Zhengzhou 450052

We observe the photorefractivity without bias voltage or prepoling in a bifunctional photorefractive polymer. The maximum two-beam coupling gain is measured to be 126cm^-1 at zero bias voltage. The sample is considered to be poled by the photoinduced longitudinal electric field, which is formed due to the light intensity gradient along the light path. The expression of the electric field was deduced. The energy transfer direction between two writing beams and light intensity dependence of the two-beam coupling gain coefficient is predicted to be consistent with the experimental results. Furthermore, the dependence of the two-beam coupling gain coefficient on external applied electrical field is measured and this experiment verifies the existence of the photoinduced longitudinal electric field.

关键词： electric-field COMPOSITES

Reduced Magneto-Resistivity of a Rare-Earth Crystalline and the Degeneracy Removals of Its Crystal-field Levels

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Chinese Physics Letters 2007年第7期24卷 2052-2055页

作者：刘照森 Faculty of Mathematics and Physics Nanjing University of Information Science and Technology Nanjing 210044

A theoretical approach is generalized and employed to calculate the magneto-resistivity of a rare-earth crystalline （CeAh） with degenerate ground crystal-field （CF） level in the presence of external fields. The calculated results show that when a magnetic field is applied in the c-direction, the magneto-resistivity may be reduced by more than 90% in certain cases in comparison with the pure CF contribution at the same temperature, demonstrating the strong effects of the degeneracy removals of the CF levels on the magnetic resistivity.

关键词： electric-field PRAL2

Spin-Flip of Polaron in Polymers with a Magnetic Impurity

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Chinese Physics Letters 2007年第6期24卷 1690-1692页

作者：陈美娟鄢永红吴长勤 Department of Physics Fhdan University Shanghai 200433

Using a nonadiabatic evolution method, we investigate the spin-flip process of polaron in polymers with a magnetic impurity. Our results show that when the spin orientation of this impurity is fixed to be perpendicular to the spin of polaron （θ = π/2）, the magnetic impurity causes a spin-flip process. The probability of the spin-flip increases with the increase of exchange integral J up to about 0.35 eV and then decreases with the increase of J. In the case J is fixed while the spin orientation is adjustable, we find the probability of the spin-flip varies with the impurity orientation and reaches a maximum value at θ=π/2.

关键词： CONDUCTING POLYMERS electric-field POLYACETYLENE SOLITONS DYNAMICS MOTION

Photodetachment of H^- near a Partially Reflecting Surface-Ⅰ

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Chinese Physics Letters 2008年第2期25卷 475-478页

作者： A. Afaq Department of Physics COMSATS Institute of Information Technology Lahore Pakistan

Theoretical and interpretative study on the subject of photodetachment of H^- near a partially reflecting surface is presented, and the absorption effect of the surface is investigated on the total and differential cross sections using a theoretical imaging method. To understand the absorption effect, a reflection parameter K is introduced as a multiplicative factor to the outgoing detached-electron wave of H^- propagating towards the wall. The reflection parameter measures, how much electron wave would reflect from the surface; K = 0 corresponds to no reflection and K = 1 corresponds to the total reflection.

关键词： electric-field QUANTUM SPECTRA MAGNETIC-field CROSS-SECTION IONIZATION

Spin Filter Effect in Organic Polymers in the Presence of Local Magnetic field

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Chinese Physics Letters 2006年第9期23卷 2549-2552页

作者：鄢永红陈美娟吴长勤 Department of Physics Fhdan University Shanghai 200433

Using a nonadiabatic evolution method, we investigate the spin filter effect in organic polymers in the presence of a local magnetic field. Through a spin-dependent magnetic field, polarons （charge carrier） with different spins will feel repulsive or attractive force determined by their spins. Our simulations show that in a single-site magnetic field （affecting electrons at a single site）, for example V150 = 0.35 eV, or V150 = 0.45 eV, a spin-up polaron accelerated to saturated velocity by an electric field can pass through the field while the spin-down polaron is trapped. When the local field extends over several sites （Vn～ exp[-（n - nc）2/nw^2]）, similar behaviour is also found. Simultaneously we find that it is more likely to realize the spin filter effect in a comparatively large field since the polaron which feels attractive force is easily trapped by a local magnetic field.

关键词： CONDUCTING POLYMERS electric-field POLARON POLYACETYLENE SOLITONS DYNAMICS MOTION