The Experts below are selected from a list of 29196 Experts worldwide ranked by ideXlab platform
Hongkang Zhao - One of the best experts on this subject based on the ideXlab platform.
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photon and phonon assisted Shot Noise in a molecular quantum dot ferromagnetic system in the coulomb blockade regime
European Physical Journal B, 2015Co-Authors: Weike Zou, Hongkang ZhaoAbstract:The dynamic Shot Noise in a molecular quantum dot connected to two non-collinear ferromagnetic terminals under the perturbation of ac fields has been investigated by the nonequilibrium Green’s function approach. The formulas of current, current correlation, and Shot Noise have been presented in the weak electron-phonon (el-ph) interaction regime to address the cooperated behaviors generated by the photon and phonon perturbation. The photon and phonon perturbations induce quite different current correlations, and the Noise suppression occurs unambiguously by increasing the phonon energy in the valley regime. The suppression of Shot Noise comes from drawing the unbalanced current correlation towards the balanced one, where coherent current correlation takes major role. The suppression of photon-assisted Shot Noise can be completed mainly by rotating polarization angle of the terminals, and increasing the phonon energy ħω 0. The Fano factor is enhanced considerably by the el-ph interaction, and it is also enhanced by increasing the polarization angle from θ = 0 to θ = π.
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photon assisted Shot Noise of the double quantum dot interferometer in weak kondo regime
Physics Letters A, 2012Co-Authors: Lili Zhao, Hongkang Zhao, Jian WangAbstract:Abstract The Shot Noise of a parallel double quantum dot (DQD) system under the perturbation of microwave fields is investigated in the weak Kondo regime. Peak-valley structures exhibit in the differential conductance and Shot Noise, and side resonant peaks emerge around the Kondo peak due to the absorption and emission of photons. The Shot Noise is sensitively dependent on the adjusting approach through changing the gate voltages. Large resonant Fano factor accompanying photon-induced side peaks appear by simultaneously varying the two gate voltages. The photon suppression and enhancement of Shot Noise have been evaluated corresponding to the coherent and incoherent current correlation. The destructive interference causes the suppression of Shot Noise by changing the Aharonov–Bohm phase.
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photon assisted Shot Noise due to the charging effect in a quantum dot device
European Physical Journal B, 2008Co-Authors: Q Chen, Hongkang ZhaoAbstract:We have investigated the spectral density of Shot Noise for an ultra-small quantum dot(QD) system in the Coulomb blockade regime when irradiated with microwave fields (MWFs) by employing a nonequilibrium Green’s function technique. The Shot Noise is sensitive to Coulomb interaction, and the photon-assisted Coulomb blockade behaviour strongly modifies the mesoscopic transport. We have calculated the first and second derivatives of Shot Noise in the strong and weak coupling regimes to compare the theoretical results with existing experimental results. In the strong coupling regime, the first and second derivatives of Shot Noise display Fano type peak-valley structures around the charging channel 2E c due to Coulomb interaction. When the magnitudes of the MWFs are sufficiently large, the system displays channel blockade due to photon irradiation. The photon-assisted and Coulomb blockade steps in the Noise — as well as the resonant behaviour in the differential Noise — are smeared by increasing temperature. The Coulomb interaction suppresses the Shot Noise, but the ac fields can either suppress the Shot Noise(balanced case) or enhance the Shot Noise(unbalanced case). The suppression of Shot Noise caused by ac fields in the balanced case is greater than that caused by Coulomb interaction in our system. Super-Poissonian Shot Noise may be induced due to the compound effects of strong Coulomb interaction and photon absorption-emission processes.
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multi photon behaviors of Shot Noise in a quantum dot system under the perturbation of two microwave fields
European Physical Journal B, 2007Co-Authors: Hongkang Zhao, Jian WangAbstract:We have investigated the Shot Noise affected by the perturbation of two microwave fields (MWFs) with frequencies ω1 and ω2, which can be classified as the commensurate and incommensurate external ac fields. The time-dependent current correlation function and the spectral density of Shot Noise have been obtained. They are very different compared with the single-field applied system in the nonlinear regime of the ac potentials. The different photon absorption and emission processes induce different kinds of Noise spectral density. We have performed the numerical calculations for both commensurate balanced and unbalanced photon absorptions and emissions. The multi-photon procedure can be seen clearly from the resonance of Shot Noise. Different commensurate number q = ω2/ω1 contributes to different photon absorption and emission behaviors. It is found that the asymmetric configuration of Shot Noise is intimately associated with the commensurate number q. The differential conductance appears symmetric and asymmetric behaviors, and the channel blockade exhibits. The Shot Noise is large enough to surpass its saturated value for the unbalanced photon absorption case. The sensitive behaviors of Fano factor associated with different commensurate numbers and amplitudes of ac fields signify that the Shot Noise can be controlled by external MWFs significantly.
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photon assisted Shot Noise in the mesoscopic system with a toroidal carbon nanotube coupled to normal metal leads perturbed by ac fields
Physical Review B, 2006Co-Authors: Hongkang Zhao, Jian WangAbstract:We have investigated the Shot Noise of a system with a toroidal carbon nanotube (TCN) coupled to two metal leads with applied microwave fields. The tunneling current operator is derived by determining the electron operators in different parts of the system. The Landauer-B\"uttiker-like current operator is also obtained, from which we obtain the time-dependent current fluctuation correlations, and consequently the spectral density of Shot Noise. The photon-assisted Shot Noise exhibits interesting behaviors due to the special properties of the TCN and the transport behaviors of electrons in multichannel mesoscopic systems. The quantum steps of the Shot Noise with respect to the source-drain bias reflect the quantum nature of the TCN, as well as the applied microwave field. The saturated value of the Shot Noise is suppressed by the applied microwave fields, and the suppression is strongly associated with the structure of the TCN. The obtained Shot Noises are sub-Poissonian when the source-drain bias increases to a definite value, and super-Poissonian Shot Noise appears below this value.
Jian Wang - One of the best experts on this subject based on the ideXlab platform.
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photon assisted Shot Noise of the double quantum dot interferometer in weak kondo regime
Physics Letters A, 2012Co-Authors: Lili Zhao, Hongkang Zhao, Jian WangAbstract:Abstract The Shot Noise of a parallel double quantum dot (DQD) system under the perturbation of microwave fields is investigated in the weak Kondo regime. Peak-valley structures exhibit in the differential conductance and Shot Noise, and side resonant peaks emerge around the Kondo peak due to the absorption and emission of photons. The Shot Noise is sensitively dependent on the adjusting approach through changing the gate voltages. Large resonant Fano factor accompanying photon-induced side peaks appear by simultaneously varying the two gate voltages. The photon suppression and enhancement of Shot Noise have been evaluated corresponding to the coherent and incoherent current correlation. The destructive interference causes the suppression of Shot Noise by changing the Aharonov–Bohm phase.
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enhancement of Shot Noise due to the fluctuation of coulomb interaction
Bulletin of the American Physical Society, 2012Co-Authors: Lei Zhang, Jian WangAbstract:We have developed a theoretical formalism to investigate the contribution of fluctuation of Coulomb interaction to the Shot Noise based on Keldysh non-equilibrium Green's function method. We have applied our theory to study the behavior of dc Shot Noise of atomic junctions using the method of nonequilibrium Green's function combined with the density functional theory (NEGF-DFT). In particular, for atomic carbon wire consisting 4 carbon atoms in contact with two Al(100) electrodes, first principles calculation within NEGF-DFT formalism shows a negative differential resistance (NDR) region in I-V curve at finite bias due to the effective band bottom of the Al lead. We have calculated the Shot Noise spectrum using the conventional gauge invariant transport theory with Coulomb interaction considered explicitly on the Hartree level along with exchange and correlation effect. Although the Fano factor is enhanced from 0.6 to 0.8 in the NDR region, the expected super-Poissonian behavior in the NDR regionis not observed. When the fluctuation of Coulomb interaction is included in the Shot Noise, our numerical results show that the Fano factor is greater than one in the NDR region indicating a super-Poissonian behavior.
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multi photon behaviors of Shot Noise in a quantum dot system under the perturbation of two microwave fields
European Physical Journal B, 2007Co-Authors: Hongkang Zhao, Jian WangAbstract:We have investigated the Shot Noise affected by the perturbation of two microwave fields (MWFs) with frequencies ω1 and ω2, which can be classified as the commensurate and incommensurate external ac fields. The time-dependent current correlation function and the spectral density of Shot Noise have been obtained. They are very different compared with the single-field applied system in the nonlinear regime of the ac potentials. The different photon absorption and emission processes induce different kinds of Noise spectral density. We have performed the numerical calculations for both commensurate balanced and unbalanced photon absorptions and emissions. The multi-photon procedure can be seen clearly from the resonance of Shot Noise. Different commensurate number q = ω2/ω1 contributes to different photon absorption and emission behaviors. It is found that the asymmetric configuration of Shot Noise is intimately associated with the commensurate number q. The differential conductance appears symmetric and asymmetric behaviors, and the channel blockade exhibits. The Shot Noise is large enough to surpass its saturated value for the unbalanced photon absorption case. The sensitive behaviors of Fano factor associated with different commensurate numbers and amplitudes of ac fields signify that the Shot Noise can be controlled by external MWFs significantly.
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photon assisted Shot Noise in the mesoscopic system with a toroidal carbon nanotube coupled to normal metal leads perturbed by ac fields
Physical Review B, 2006Co-Authors: Hongkang Zhao, Jian WangAbstract:We have investigated the Shot Noise of a system with a toroidal carbon nanotube (TCN) coupled to two metal leads with applied microwave fields. The tunneling current operator is derived by determining the electron operators in different parts of the system. The Landauer-B\"uttiker-like current operator is also obtained, from which we obtain the time-dependent current fluctuation correlations, and consequently the spectral density of Shot Noise. The photon-assisted Shot Noise exhibits interesting behaviors due to the special properties of the TCN and the transport behaviors of electrons in multichannel mesoscopic systems. The quantum steps of the Shot Noise with respect to the source-drain bias reflect the quantum nature of the TCN, as well as the applied microwave field. The saturated value of the Shot Noise is suppressed by the applied microwave fields, and the suppression is strongly associated with the structure of the TCN. The obtained Shot Noises are sub-Poissonian when the source-drain bias increases to a definite value, and super-Poissonian Shot Noise appears below this value.
Zhongmin Yang - One of the best experts on this subject based on the ideXlab platform.
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broad bandwidth near Shot Noise limited intensity Noise suppression of a single frequency fiber laser
Optics Letters, 2016Co-Authors: Qilai Zhao, Kaijun Zhou, Changsheng Yang, Zhouming Feng, Mingying Peng, Huaqiu Deng, Zhongmin YangAbstract:A significant broad-bandwidth near-Shot-Noise-limited intensity Noise suppression of a single-frequency fiber laser is demonstrated based on a semiconductor optical amplifier (SOA) with optoelectronic feedback. By exploiting the gain saturation effect of the SOA and the intensity feedback loop, a maximum Noise suppression of over 50 dB around the relaxation oscillation frequencies and a suppression bandwidth of up to 50 MHz are obtained. The relative intensity Noise of −150 dB/Hz in the frequency range from 0.8 kHz to 50 MHz is achieved, which approaches the Shot-Noise limit. The obtained optical signal-to-Noise ratio is more than 70 dB. This near-Shot-Noise-limited laser source shows important implications for the advanced fields of high-precision frequency stabilization, quantum key distribution, and gravitational wave detection.
Aleksander M Iksanov - One of the best experts on this subject based on the ideXlab platform.
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new explicit examples of fixed points of poisson Shot Noise transforms
Australian & New Zealand Journal of Statistics, 2004Co-Authors: Aleksander M Iksanov, Che Soong KimAbstract:AbstractWe show that gamma distributions, generalized positive Linnik distri-butions, S2 distributions are fixed points of Poisson Shot Noise transforms.The corresponding response functions are identified via their inverse func-tions except for some special cases when those can be obtained explicitly.As a by-product, it is proven that log-convexity of the response function isnot necessary for selfdecomposability of non-negative Poisson Shot Noisedistribution. Some attention is given to perpetuities of a rather specialtype which are closely related to our model. In particular, we study theproblem of their existence and uniqueness.Key words: Poisson Shot Noise transform · Shot Noise distribution ·fixed points · perpetuity · infinite divisibility · selfdecomposability 1 Introduction. 1 Let P + be the set of all probability distributions on the Borel subsets ofR + = [0,∞) and h : R + → R + be a Borel measurable function which in whatfollows we call response function . Fix a probability space (Ω,F,P). It will beassumed throughout the paper that all random variables (r.v.’s) involved aredefined there, and this space is rich enough to accumulate independent copiesof some r.v.’s. Also from now on notation µ = L(ξ) means that µ ∈ P
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on fixed points of poisson Shot Noise transforms
Advances in Applied Probability, 2002Co-Authors: Aleksander M Iksanov, Zbigniew J JurekAbstract:Distributional flxed points of a Poisson Shot Noise transform (for nonnegative, non-increasing and bounded by 1, response functions) are characterized. The tail behavior of flxed points is described. Typically they have either exponential moments or their tails are proportional to a power function, with exponent greater than minus one. The uniqueness of flxed points is also discussed. Finally it is proved that in most cases flxed points are absolutely continuous, apart from the possible atom at zero.
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on fixed points of poisson Shot Noise transforms
arXiv: Probability, 2002Co-Authors: Aleksander M Iksanov, Zbigniew J JurekAbstract:Distributional fixed points of a Poisson Shot Noise transform (for nonnegative, nonincreasing response functions bounded by 1) are characterized. The tail behavior of fixed points is described. Typically they have either exponential moments or their tails are proportional to a power function, with exponent greater than -1. The uniqueness of fixed points is also discussed. Finally, it is proved that in most cases fixed points are absolutely continuous, apart from the possible atom at zero.
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new explicit examples of fixed points of poisson Shot Noise transforms
arXiv: Probability, 2002Co-Authors: Aleksander M Iksanov, Che Soong KimAbstract:We show that gamma distributions, generalized positive Linnik distributions, S2 distributions are fixed points of Poisson Shot Noise transforms. The corresponding response functions are identified via their inverse functions except for some special cases when those can be obtained explicitly. As a by-product, it is proven that log-convexity of the response function is not necessary for selfdecomposability of non-negative Poisson Shot Noise distribution. Some attention is given to perpetuities of a rather special type which are closely related to our model. In particular, we study the problem of their existence and uniqueness.
Zbigniew J Jurek - One of the best experts on this subject based on the ideXlab platform.
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on fixed points of poisson Shot Noise transforms
Advances in Applied Probability, 2002Co-Authors: Aleksander M Iksanov, Zbigniew J JurekAbstract:Distributional flxed points of a Poisson Shot Noise transform (for nonnegative, non-increasing and bounded by 1, response functions) are characterized. The tail behavior of flxed points is described. Typically they have either exponential moments or their tails are proportional to a power function, with exponent greater than minus one. The uniqueness of flxed points is also discussed. Finally it is proved that in most cases flxed points are absolutely continuous, apart from the possible atom at zero.
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on fixed points of poisson Shot Noise transforms
arXiv: Probability, 2002Co-Authors: Aleksander M Iksanov, Zbigniew J JurekAbstract:Distributional fixed points of a Poisson Shot Noise transform (for nonnegative, nonincreasing response functions bounded by 1) are characterized. The tail behavior of fixed points is described. Typically they have either exponential moments or their tails are proportional to a power function, with exponent greater than -1. The uniqueness of fixed points is also discussed. Finally, it is proved that in most cases fixed points are absolutely continuous, apart from the possible atom at zero.
