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Cross-Polarized Single Photon Emission from Single semiconductor quantum dots with V-Type Level Driven by Pulse Field

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Communications in Theoretical Physics 2008年第12期50卷 1417-1421页

作者： LIU Wen-Juan LI Yao-Yi School of Science Hunan University of Technology Zhuzhou 412008 China Department of Physics Wuhan University Wuhan 430072 China State Key Laboratory for Surface Physics Institute of Physics the Chinese Academy of Sciences Beijing 100080 China

The statistic properties of photon emissions from single semiconductor quantum dots with V-type leveldriven by pulses are investigated *** on quantum regression theorem and master equations,the dynamicequations of the second-order correlation function of the photon emissions are *** calculated results reveal thatthe efficiency of single photon emissions from two orthogonal polarization eigenstates(|x〉and |y〉)reaches the maximumwhen the input pulses area is about π,and the probability of the cross-polarized single photon emission from |x〉and |y〉decreases with increasing of pulse width.

关键词： semiconductor quantum dots cross-polarized single photon emission V-type system

Influence of temperature and LO phonon on the effective mass of bipolarons in polar semiconductor quantum dots

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Optoelectronics Letters 2012年第6期8卷 477-480页

作者：辛伟高忠明韩超额尔敦朝鲁 Institute of Condensed Matter Physics Hebei Normal University of Science&Technology

The temperature and LO phonon effects of the bipolaron in polar semiconductor quantum dots （QDs） are studied by using the Tokuda modified linear-combination operator method and the Lee-Low-Pines variational method. The expressions for the mean number ofLO phonons and the effective mass of the bipolaron are derived. Numerical results show that the mean number of LO phonons of the bipolaron decreases with increasing the temperature and the relative distance r between two electrons, but increases with increasing the electron-phonon coupling strength a The effective mass of the bipolaron M＊ increases rapidly with increasing the relative distance r between two electrons when r is smaller, and it reaches a maximum at r ≈ 4.05rp, while after that, 34＊ decreases slowly with increasing r. The effective mass of the bipolaron M＇ decreases with increasing the temperature. The electron-phonon coupling strength a markedly influences the changes of mean number of LO phonons and the effective mass M＊ with the relative distance r and the temperature parameter y.

关键词： Electron correlations Electron phonon interactions semiconductor quantum dots

Size-dependent optical properties and carriers dynamics in CdSe/ZnS quantum dots

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Chinese Physics B 2008年第4期17卷 1280-1285页

作者：马红马国宏王文军高学喜马洪良 Department of Physics Shanghai University Shanghai 200444 China School of Physics Science and Information Engineering Liaocheng University Liaocheng 252059 China Instrumental Analysis and Research Center Shanghai University Shanghai 200444 China

Size-dependence of optical properties and energy relaxation in CdSe/ZnS quantum dots （QDs） were investigated by two-colour femtosecond （fs） pump-probe （400/800 nm） and picosecond time-resolved photoluminescence （ps TRPL） experiments. Pump-probe measurement results show that there are two components for the excited carriers relaxation, the fast one with a time constant of several ps arises from the Auger-type recombination, which shows almost particle sizeindependence. The slow relaxation component with a time constant of several decades of ns can be clearly determined with ps TRPL spectroscopy in which the slow relaxation process shows strong particle size-dependence. The decay time constants increase from 21 to 34 ns with the decrease of particle size from 3.2 to 2.1 nm. The room-temperature decay lifetime is due to the thermal mixing of bright and dark excitons, and the size-dependence of slow relaxation process can be explained very well in terms of simple three-level model.

关键词： semiconductor quantum dots Auger-type recombination time-resolved spectroscopy

Effects of Magnetic Field on the Valence Bond Property of the Double—quantum—Dot Molecule

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Chinese Physics Letters 2002年第4期19卷 546-549页

作者：王立民罗莹等 DepartmentofPhysicsandInstituterofTheoreticalPhysics BeijingNormalUniversityBeijing100875

The effects of the magnetic field on the valence bond property of the double-quantum-dot molecule are numerically studied by the finite element method and perturbation approach because of the absence of cylindrical symmetry in the horizontally coupled dots. The calculation results show that the energy value of the ground state changes differently from that of the first excited state with increasing magnetic field strength, and they cross under a certain magnetic field. The increasing magnetic field makes the covalent bond state change into an ionic bond state, which agrees qualitatively with experimental results and makes ionic bond states remain. The oscillator strength of transition between covalent bond states decreases distinctly with the increasing magnetic field strength, when the molecule is irradiated by polarized light. Such a phenomenon is possibly useful for actual applications.

关键词： semiconductor quantum dots

Dynamic Localization of a One—Dimensional quantum Dot Array in an ac Electric Field

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Chinese Physics Letters 2002年第7期19卷 981-984页

作者：罗莹范文斌等 DepartmentofPhysicsandInstituteofTheoreticalPhysics BeijingNormalUniversityBeijing100875 InstituteofAppliedPhysicsandComputationalMathematics POBox8009Beijing100088

We investigate the dynamics of two interaction electrons confined to one-dimensional quantum dot array in an ac electric field. We find that initially localized electrons will remain localized in the absence of Coulomb interaction if the ratio of the ac field magnitude to the frequency is a root of the ordinary zero-order Bessel function. In contrast to the case without Coulomb interaction, no matter what the value is, the electrons are delocalized and the delocalization effect depends on the ratio U/ω and eaE/ω, where U is the strength of Coulomb interaction, a is the lattice constant, and E and ω are the ac field amplitude and frequency, respectively.

关键词： semiconductor quantum dots

Local Heating in a Normal-Metal-quantum-Dot-Superconductor System without Electric Voltage Bias

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Chinese Physics Letters 2017年第6期34卷 79-83页

作者：周利玲周雪云程融侯翠岭沈红 Department of Physics Jiujiang University Jiujiang 332005

We investigate the heat generation Q in a quantum dot （QD）, coupled to a normal metal and a superconduc- tor, without electric bias voltage. It is found that Q is quite sensitive to the lead temperatures TL,R and the superconductor gap magnitude △. At TL,R 〈〈 ω0 （ω0 is the phonon frequency）, the superconductor affects Q only at △ 〈ω0, and the maximum magnitude of negative Q appears at some △ slightly smaller than ω0. At elevated lead temperature, contribution to O from the superconductor arises at △, ranging from less than to much larger than wo. However, the peak value of Q is several times smaller than that in the case of TL,R 〈〈ω0. Interchanging lead temperatures TL and TR leads to quite different Q behaviors, while this makes no difference for a normal-metal quantum-dot-normal-metal system, and the QD can be cooled much more efficiently when the superconductor is colder.

关键词： semiconductor quantum dots

Dynamical Localization in a Two—Electron quantum Dot Molecule Biased by a dc Voltage

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Chinese Physics Letters 2003年第8期20卷 1340-1343页

作者：王立民段素青赵宪庚刘承师 InstituteofAppliedPhysicsandComputationalMathematics POBox8009(26)Beijing100088 DepartmentofPhysics HebeiNormalUniversityShijiazhuang050091 InstituteofAppliedPhysicsandComputationalMathematics POBox8009(26)Beijing100088 DepartmentofPhysicsandInstituteofTheoreticalPhysics BeltingNormalUniversityBeijing100875

We study the dynamics of two interacting electrons in a coupled-quantum-dot system with a time-dependent external electric field. The numerical results of the two-particle states reveal that the dynamical localization still exists under appropriate dc and ac voltage amplitudes. Such localization is different from the stationary localization phenomenon. Our conclusion is instructive for the field of quantum function devices.

关键词： semiconductor quantum dots

Dynamic Localization Condition of Two Electrons in a Strong dc-ac Biased quantum Dot Molecule

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Chinese Physics Letters 2004年第2期21卷 370-373页

作者：王立民段素青赵宪庚刘承师 InstituteofAppliedPhysicsandComputationalMathematics POBox8009(26)Beijing100088 DepartmentofPhysics HebeiNormalUniversityShijiazhuang050091 InterdisciplinaryCenterofTheoreticalStudies ChineseAcademyofSciencesBeijing100080

We present a perturbation investigation of dynamic localization condition of two electrons in a strong dc–ac biased quantum dot molecule. By reducing the system to an Hubbard-type effective two-site model and by applying Floquet theory, we find that the dynamical localization phenomenon occurs under certain values of the large strength of the dc and ac field. This demonstrates the possibility of using appropriate dc–ac fields to manipulate dynamical localized states in mesoscopic devices, which is an essential component of practical schemes for quantum information processing. Our conclusion is instructive to the field of quantum function devices.

关键词： semiconductor quantum dots

Magnetoabsorption spectra of magnetoexciton transitions in GaAs/Ga_(0.7)Al_(0.3)As quantum wells

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Chinese Optics Letters 2009年第4期7卷 335-338页

作者：米贤武李德俊孟凡斌赵鹤平 College of Physics Science and Information Engineering Jishou University

The internal transitions and absorption spectra of confined magnetoexcitons in GaAs/*** quan- tum wells have been theoretically investigated under magnetic fields along the growth direction of the semiconductor heterostructure. The magnetoexciton states are obtained within the effective-mass ap- proximation by using a variational procedure. The trial exciton-envelope wavefunctions are described as hydrogeniclike polynomial functions. The internal transition energies are investigated by studying the allowed magnetoexcitonic transitions using terahertz radiation circularly polarized in the plane of the quantum well. The intraexcitonic magnetoabsorption to 2p^± like magnetoexciton states as functions of the coefficients are obtained for transitions from 1s-like applied magnetic field.

关键词： Aluminum Magnetic fields semiconductor growth semiconductor quantum dots