Photon-Assisted Electron Transport for a λ-shaped Carbon Nanotube Junction

We theoretically study the electron transport properties for two coupled single-walled caxbon nanotube quantum dots connected to metallic electrodes under the irradiation of an external electromagnetic field at low tempera- tures. Using the standaxd nonequilibrium Green＇s function techniques, we examine the time-averaged transmission coefficient and linear conductance. It is shown that by some numerical examples, the photon-assisted inter-dot coupling causes Fano resonance and the conductance of the system is sensitive to the external field parameters. The transport dependence on the external field parameters may be used to detect the high-frequency microwave irradiation.     

Inelastic Electron Transport in Monoatomic Wires

Based on non-equilibrium Green＇s function theory and density functional theory, we investigate the vibrational property and electron-phonon （el-ph） interaction induced inelastic scattering in electron transport through metallic monoatomic wires.     

Effect of Inelastic Scattering on the Electron Transport in a One-Dimensional Electron Interferorneter

Using the Büttiker formalism, we calculated the conductance of a one-dimensional interferometer,which consists of two quantum point contacts (QPC's) and a cavity sandwiched between them, in the presence of a phase randomizing scatterer located at the lower boundary of the cavity. The results show that a little inelastic scattering will completely destroy the formation of discrete zero-dimensional states, but the Aharonov-Bohrn-type oscillations can still take place, which are influenced by the inelastic scatterer.     

First-principles Study of Electron Transport Through Oligoacenes

利用非平衡格林函数和电子密度泛函理论研究了多并苯分子结(多并苯分子末端通过硫原子以串联和并联方式连接在两个Au(111)表面之间)的电子输运特性．在小偏压下,多并苯分子结的电子输运性能主要取决于来自最高占据分子轨道的透射输运峰的尾部在费米能级附近的贡献．随着多并苯分子中苯环个数的增加,串联型多并苯分子的零偏压电导值先减少后变大,它既不遵循指数衰减规律,也没有表现出振荡现象,而并联型分子结的零偏压电导值随苯环个数的增加而单调增加．理论计算结果表明,分子轨道空间分布图、能隙变化以及费米能级所处位置可以用来阐明多并苯分子结的电子输运机     

Transport of Electron Pairs in a Superconducting Junction Device: Underdamped Case

Transport of electron pairs in a superconducting junction device in the underdamped case is investigated. It is shown that the capacitance of the junctions can slow the movement of the electron pairs and reduce the net voltage. It is also shown that, for the underdamped case and the overdamped case, the movement of the electron pairs in this superconducting junctions device has some similar features. By controlling the correlation between the additive and multiplicative noise, the flux can be reversed. In addition, if the additive noise strength (or the temperature T) is large enough, a reversal can also be induced.     

Nonequilibrium Electron Transport Through a Quantum Dot from Kubo Formula

Based on the Kubo formula for an electron tunneling junction, we revisit the nonequilibrium transport properties through a quantum dot. Since the Fermi level of the quantum dot is set by the conduction electrons of the leads, we calculate the electron current from the left side by assuming the quantum dot coupled to the right lead as another side of the tunneling junction, and the other way round is used to calculate the current from the right side. By symmetrizing these two currents, an effective local density states on the dot can be obtained, and is discussed at high and low temperatures, respectively.     

环形碳纳米管-量子点耦合系统的介观输运

应用非平衡格林函数方法研究通过环形碳纳米管-量子点耦合系统的介观输运.相干隧穿与环形碳纳米管和量子点各自的能级结构有强烈的依赖关系,阿哈郎诺夫-玻姆效应使能级周期性变化,隧穿电流则随磁通量作周期性振荡.环形碳纳米管的具体纳米结构显示出金属-半导体相变特性,这种行为也在输出电流中体现出来.子系统量子能级的匹配与失配关系在介观输运过程中起重要作用.     

Electron Transport Through Double-Dot Aharonov-Bohm Interferometer in the Kondo Regime

By applying the slave boson technique, we have studied the electron transport through double-dot Aharonov-Bohm interferometer in the Kondo regime. For the system with symmetric quantum dots, the linear conductance is shown to be enhanced by Kondo effect, but it is suppressed in the deep dot level regime in the presence of nonzero magnetic flux. The Aharonov-Bohm oscillations of the conductance are also investigated.     

N24B24分子结的电子传输

利用GW近似和非平衡格林函数结合的方法 研究了耦合到两个金属触点的N₂₄B₂₄分子的电子传输性. 计算结果表明,在单个和多个原子触点的态密度曲线上分别出现四个和三个谐振隧峰. 在I-V特性曲线上出现断路状态和微分负阻效应. 对于一、四、六、八原子的触点在电压分别在 ∓4.5、∓4、∓4.6、∓4.3 V表现出微分负阻效应行为. I-V特性在以低电压断开状态,呈独立的触点类型. I-V曲线取决于触点类型,并且表明N₂₄B₂₄分子呈现半导体的特性.     

Transport Coefficients for Inelastic Maxwell Mixtures

The Boltzmann equation for inelastic Maxwell models (IMM) is used to determine the Navier–Stokes transport coefficients of a granular binary mixture in d-dimensions. The Chapman–Enskog method is applied to solve the Boltzmann equation for states near the (local) homogeneous cooling state. The mass, heat, and momentum fluxes are obtained to first order in the spatial gradients of the hydrodynamic fields, and the corresponding transport coefficients are identified. There are seven relevant transport coefficients: the mutual diffusion, the pressure diffusion, the thermal diffusion, the shear viscosity, the Dufour coefficient, the pressure energy coefficient, and the thermal conductivity. All these coefficients are exactly obtained in terms of the coefficients of restitution and the ratios of mass, concentration, and particle sizes. The results are compared with known transport coefficients of inelastic hard spheres (IHS) obtained analytically in the leading Sonine approximation and by means of Monte Carlo simulations. The comparison shows a reasonably good agreement between both interaction models for not too strong dissipation, especially in the case of the transport coefficients associated with the mass flux     

Investigation of Terminal Group Effect on Electron Transport Through Open Molecular Structures

The effect of terminal groups on the electron transport through metal-molecule-metal system has been investigated using nonequilibrium Green's function (NEGF) formalism combined with extended Huckel theory (EHT). Au-molecule-Au junctions are constructed with borazine and BCN unit structure as core molecule and sulphur (S), oxygen (O), selenium (Se) and cyano-group (CN) as terminal groups. The electron transport characteristics of the borazine and BCN molecular systems are analyzed through the transmission spectra and the current-voltage curve. The results demonstrate that the terminal groups modifying the transport behaviors of these systems in a controlled way. Our result shows that, selenium is the best linker to couple borazine to Au electrode and oxygen is the best one to couple BCN to Au electrode. Furthermore, the results of borazine systems are compared with that of BCN molecular systems and are discussed. Simulation results show that the conductance through BCN molecular systems is four times larger than the borazine molecular systems. Negative differential resistance behavior is observed with borazine-CN system and the saturation feature appears in BCN systems.     

Appearance of Spatial-Temporal Noise in Super-conducting Junction and Its Effect on Transport of Electron Pairs

Transport of electron pairs in super-conducting junction with spatial-temporal noise is investigated. We show that the spatial-temporal noise can produce the current of the electron pairs, which stems from a symmetry breaking of the system induced by the correlation of the spatial-temporal noise with the phase difference. It is found that there is a positive current for the electron pairs, exhibiting a peak with increasing the values of some parameters of the noises. The results provide a theoretical foundation for the further investigation of the super-conducting junction.     

哑铃型富勒烯化合物的光诱导电子转移反应

DTE-甲亚胺叶立德盐(DTE:二噻吩乙烯基)与C60在甲苯中的1,3-偶极环加成反应被用于合成新型的哑铃型富勒烯化合物1．为了与1作比较,还同时合成了单加成物2.并通过HF-3/21G方法计算确定了这两种化合物分子的几何结构,同时在室温下测定了化合物在不同极性溶剂中的紫外-可见光谱和荧光光谱,证明了化合物内给体和受体间光诱导分子内电子转移过程的存在．     

Schottky Barrier Formation at a Carbon Nanotube-Scandium Junction

Recent experiment shows that scandium （Sc） can make a good performance contact with carbon nanotubes （CNTs） to fabricate n-type field effect transistor （n-FET）. We study the Schottky barrier （SB） of scandium （Sc） and palladium （Pd） with a （8,0） single-wall CNT （SWCNT） using first-principles calculation. It is found that the p-type SB height （SBH） of the Pd-CNT contact is about 0.34 eV, which is in good agreement with the experimental data. For the Sc-CNT contact, an n-type contact is formed and the SBH is about O.08eV in agreement with the experimental observations. Our calculation demonstrates that by contacting CNT with Pd and Sc, p-FET and n-FET can be fabricated, respectively. The dipole effect at the interface is used to explain our result.     

Multichannel Electronic Transport Through a Kondo Dot

Electronic transport through the quantum dot with two energy levels is studied by means of the non-equilibrium Green functions and the slave boson method. Special attention is focused on an interplay between quantum inference of traveling waves and electronic correlations. It is shown that if impurity states are far below the Fermi level the transport is through the highest state only. Interference processes become relevant when the levels are shifted towards the mixed valence regime.     

Scanning Tunneling Electron Transport into a Kondo Lattice

We theoretically present the results for a scanning tunneling transport between a metallic tip and a Kondo lattice.We calculate the density of states(DOS)and the tunneling current and differential conductance(DC)under different conduction-fermion band hybridization and temperature in the Kondo lattice.It is found that the hybridization strength and temperature give asymmetric coherent peaks in the DOS separated by the Fermi energy.The corresponding current and DC intensity depend on the temperature and quantum interference effect among the c-electron and f-electron states in the Kondo lattice.     

Resonant Electron Transfer in Collisions between Two Fullerene Ions

Fullerenes are a direct link between atoms with discrete electronic energy levels and solids with a band structure and a well-defined surface. In this Letter, we report on the first ever experiment on resonant electron transfer in collisions between two fullerene ions. Total cross sections have been measured for the reaction C+60+C2+60-->C2+60+C+60 at center-of-mass energies ranging from 27 to 69 keV. Surprisingly, within the error bars, these cross sections are identical to the respective cross sections for C+60+C60 measured by Rohmund and Campbell [J. Phys. B 30, 5293 (1997)]]. We show that the experimental data for both collision systems are very well reproduced by a quantum mechanical treatment of the reaction based on the concept of hole particles and the polarizability of the fullerene molecule.     

Energy Transport Through Rare Collisions

We study a one-dimensional Hamiltonian chain of masses perturbed by an energy conserving noise. The dynamics is such that, according to its Hamiltonian part, particles move freely in cells and interact with their neighbors through collisions, made possible by a small overlap of size ϵ>0 between near cells. The noise only randomly flips the velocity of the particles. If ϵ→0, and if time is rescaled by a factor 1/ϵ, we show that energy evolves autonomously according to a stochastic equation, which hydrodynamic limit is known in some cases. In particular, if only two different energies are present, the limiting process coincides with the simple symmetric exclusion process.     

金属电极对有机分子非弹性电子隧穿谱的影响

利用第一性原理计算金属电极下1,6-己二硫醇和1,4-二巯基苯分子结的非弹性电子隧穿谱,发现非弹性电子隧穿谱对金属电极的变化十分灵敏,并且非弹性电子隧穿谱的振动峰位置和强度与硫原子和金属电极表面的距离密切相关.结果表明电极材料和分子与金属成键的情况是影响分子结的非弹性电子输运的重要因素.理论分析进一步表明不同金属电极和有机分子的耦合能不同导致了谱峰强弱的调整.     

Nonlinear Transport in Inelastic Maxwell Mixtures Under Simple Shear Flow

The Boltzmann equation for inelastic Maxwell models is used to analyze nonlinear transport in a granular binary mixture in the steady simple shear flow. Two different transport processes are studied. First, the rheological properties (shear and normal stresses) are obtained by solving exactly the velocity moment equations. Second, the diffusion tensor of impurities immersed in a sheared inelastic Maxwell gas is explicitly determined from a perturbation solution through first order in the concentration gradient. The corresponding reference state of this expansion corresponds to the solution derived in the (pure) shear flow problem. All these transport coefficients are given in terms of the restitution coefficients and the parameters of the mixture (ratios of masses, concentration, and sizes). The results are compared with those obtained analytically for inelastic hard spheres in the first Sonine approximation and by means of Monte Carlo simulations. The comparison between the results obtained for both interaction models shows a good agreement over a wide range values of the parameter space.