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Shot noise of the spin inelastic tunneling through a quantum dot with single molecule-magnet

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Chinese physics B 2011年第1期20卷 601-608页

作者：常博梁九卿 institute of Theoretical physics and department of physics Shanxi University

We have studied the quantum fluctuations of inelastic spin-electron scattering in quantum dot with an embedded biaxial single molecule-magnet and particularly investigated the zero-frequency shot noise and Fano factor in different magnetic fields. It is found that the shot noise and Fano factor exhibit a stepwise behaviour as bias increases in the presence of interaction between the electron and molecule-magnet for a weak magnetic field. As magnetic field becomes strong, a dip is displayed in the shot-noise-bias curve due to the suppression of inelastic shot noise caused by the quantum tunneling of magnetisation. Because of the spontaneous inelastic tunneling at zero bias, a small shot noise occurs, which results in the case of Fano factor F ≥ 1. Moreover, our results show that the sweeping speed can also influence the shot noise and Fano factor obviously.

关键词： quantum dot shot noise molecular magnet quantum tunneling of spin

Luminescence properties of dysprosium doped YVO_4 phosphor

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Journal of Rare Earths 2018年第12期36卷 1245-1249页

作者： H.J.Rajendra C.PANDurangappa D.L.Monika department of physics RNS Institute of TechnologyChannasandra department of physics SJB Institute of Technology

Trivalent dysprosium(Dy) activated nanocrystalline yttrium vanadate(YVO) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), optical absorption and photo luminescence(PL) techniques. The XRD patterns reveal the tetragonal crystalline phase. SEM images reveal that Dy doped YVOnanocrystals are agglomerated. EDAX confirms the formation of YVO:Dy. FTIR spectrum shows two strong absorption bands at 459 and 761 cm. Optical absorption spectrum showed the surface defects in the as-prepared samples. The PL emission spectrum shows two characteristic emission bands at 485 and 575 nm. The strong yellow emission peak at 575 nm is assigned to ~4 F→~6 Hhyper sensitive transition of Dyions, Study of CIE chromaticity diagram indicates the suitability of the phosphor for the development of yellow-green LEDs.

关键词： Precipitation Yttrium vanadate Dysprosium X-ray diffraction Photoluminescence Rare earths

Excitation of defect modes from the extended photonic band-gap structures of 1D photonic lattices

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Chinese physics B 2010年第1期19卷 284-288页

作者：周可雅郭忠义 Muhammad Ashfaq Ahmad 刘树田 department of physics Harbin Institute of Technology COMSATS institute of Information Technology Department of Physics

This paper stuides numerically the model equation in a one dimensional defective photonic lattice by modifying the potential function to a periodic function. It is found that defect modes （DMs） can be regarded as Bloch modes which are excited from the extended photonie band-gap structure at Bloch wave-numbers with kx = 0. The DMs for both positive and negative defects are considered in this method.

关键词： optical-induced photonic lattices photonic band-gaps defect modes

Entanglement dynamics of two atoms successively passing a cavity

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Chinese Optics Letters 2010年第12期8卷 1191-1194页

作者：廖庆洪方光宇王月媛 M.A.Ahmad 刘树田 department of physics Harbin Institute of Technology department of physics COMSATS Institute of Information Technology

By means of concurrence, we investigate the dynamics of entanglement between two initially separate atoms in succession passing through a cavity and their interaction with a Fock state field. We then analyze the effects of the atomic coherence, photon number, and atomic motion on the time evolution of atom-atom entanglement. The results show that there can be entanglement between two separate atoms, and that the threshold time for the creation of the entanglement is controllable by the photon number, atomic motion, and field-mode structure.

关键词： Photons

Quantum phases of Bose gases on a lattice with pair-tunneling

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Chinese physics B 2012年第6期21卷 48-56页

作者：王月明梁九卿 department of physics Institute of Theoretical PhysicsShanxi University

We investigate the strongly interacting lattice Bose gases on a lattice with two-body interaction of nearest neighbors characterized by pair tunneling. The excitation spectrum and the depletion of the condensate of lattice Bose gases are investigated using the Bogoliubov transformation method and the results show that there is a pair condensate as well as a single particle condensate. The various possible quantum phases, such as the Mott-insulator phase （MI）, the superfluid phase （SF） of an individual atom, the charge density wave phase （CDW）, the supersolid phase （SS）, the pair-superfluid （PSF） phase, and the pair-supersolid phase （PSS） are discussed in different parametric regions within our extended Bose-Hubbard model using perturbation theory.

关键词： Bose-Einstein condensate quantum phase optical lattice superfluidity

Information diffusion on adaptive network

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Chinese physics B 2008年第10期17卷 3536-3541页

作者：胡柯唐翌 department of physics and institute of Modern physics Xiangtan University

Based on the adaptive network, the feedback mechanism and interplay between the network topology and the diffusive process of information are studied. The results reveal that the adaptation of network topology can drive systems into the scale-free one with the assortative or disassortative degree correlations, and the hierarchical clustering. Meanwhile, the processes of the information diffusion are extremely speeded up by the adaptive changes of network topology.

关键词： adaptive network information diffusion degree correlation hierarchical clustering

Model for cascading failures with adaptive defense in complex networks

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Chinese physics B 2010年第8期19卷 65-71页

作者：胡柯胡涛唐翌 department of physics and institute of Modern physics Xiangtan University

This paper investigates cascading failures in networks by considering interplay between the flow dynamic and the network topology, where the fluxes exchanged between a pair of nodes can be adaptively adjusted depending on the changes of the shortest path lengths between them. The simulations on both an artificially created scale-free network and the real network structure of the power grid reveal that the adaptive adjustment of the fluxes can drastically enhance the robustness of complex networks against cascading failures. Particularly, there exists an optimal region where the propagation of the cascade is significantly suppressed and the fluxes supported by the network are maximal. With this understanding, a costless strategy of defense for preventing cascade breakdown is proposed. It is shown to be more effective for suppressing the propagation of the cascade than the recent proposed strategy of defense based on the intentional removal of nodes.

关键词： cascading failure adaptive defense complex network

Growth of linear matter perturbations and current observational constraints

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Chinese physics B 2010年第7期19卷 624-629页

作者：付响云吴普训余洪伟 department of physics and institute of physics Hunan Normal University

We discuss, using a recently proposed parametrization for the growth index of linear matter perturbations, the observational constraints on the wCDM model and the Dvali Gabadadze-Porrati （DGP） model with all current growth factor data. We find that the wCDM model is allowed by the observations at the 1σ confidence level, while the DCP model is only consistent with observations at 2σ confidence level.

关键词： dark energy DGP model matter perturbations

Interactions between optical bullets with different velocities in the three-dimensional cubic-quintic complex Ginzburg-Landau equation

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Chinese physics B 2010年第4期19卷 298-303页

作者：郑浪唐翌 department of physics and institute of Modern physics Xiangtan University

By using the three-dimensional complex Ginzburg--Landau equation with cubic--quintic nonlinearity, this paper numerically investigates the interactions between optical bullets with different velocities in a dissipative system. The results reveal an abundance of interesting behaviours relating to the velocities of bullets： merging of the optical bullets into a single one at small velocities; periodic collisions at large velocities and disappearance of two bullets after several collisions in an intermediate region of velocity. Finally, it also reports that an extra bullet derives from the collision of optical bullets when optical bullets are at small velocities but with high energies.

关键词： optical bullet dissipative soliton complex Ginzburg Landau equation