共查询到19条相似文献,搜索用时 62 毫秒
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在紧束缚近似下,利用常量相互作用模型和Landauer-Bütticker公式,计算了扶手椅型和金属锯齿型碳纳米管量子点的电导。发现,根据碳纳米管量子点的长度的不同,扶手椅型碳纳米管量子点的电导可以具有两电子或四电子的壳层结构。而锯齿型碳纳米管量子点的电导却仅有四电子的壳层结构,与长度无关;这些理论结果与之前的实验结果符合的很好。 相似文献
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基于量子点输运理论与B ures角度量的方法,研究了耗散环境下单量子点系统输运过程中的量子速度极限特性.结果表明:由于隧穿过程存在库仑阻塞效应与量子相干效应,系统可加速能力随左侧隧穿概率有微小的变化;然而,系统可加速能力随右侧隧穿概率变化明显,归因于动力学通道阻塞与共隧穿的共同效应.能级差的增大使系统向目标态演化需要更长的时间,从而改变系统的加速潜力以及随时间演化的震荡频率.耗散环境中弛豫速率对系统可加速能力的影响不是单调的,存在一个有趣的转折点,当弛豫速率小于该点时,系统的可加速能力产生震荡变化,当弛豫速率大于该点时,加速潜力的变化受到了弛豫速率的单调抑制,弛豫速率的增大总体上抑制了系统的可加速能力. 相似文献
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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. 相似文献
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This paper investigates Kondo transport properties in a quadruple quantum dot (QD) based on the slave-boson mean field theory and the non-equilibrium Green’s function.In the quadruple QD structure one Kondo-type QD sandwiched between two leads is side coupled to two separate QD structures:a single-QD atom and a double-QD molecule.It shows that the conductance valleys and peaks always appear in pairs and by tuning the energy levels in three side QDs,the one-,two-,or three-valley conductance pattern can be obtained.Furthermore,it finds that whether the valley and the peak can appear is closely dependent on the specific values of the interdot couplings and the energy level difference between the two QDs in the molecule.More interestingly,an extra novel conductance peak can be produced by the coexistence of the two different kinds of side QD structures. 相似文献
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Inelastic transport through double quantum dot systems with coupling between electronic and vibrational degrees of freedom is examined by means of a master equation approach. The current and the conductance are analyzed for both weak and strong interdot couplings. The results show that an asymmetry in the current-voltage characteristic and appearance of negative differential conductance due to electron-phonon interaction. The influence of temperature on the current is studied and found that increasing temperature gives rise to eliminating the current blockade and, thus, removing the Coulomb diamonds in the conductance spectra. 相似文献
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Bo Chang 《Physics letters. A》2010,374(29):2985-2938
We report a theoretical analysis of electron transport through a quantum dot with an embedded biaxial single-molecule magnet (SMM) based on mapping of the many-body interaction-system onto a one-body problem by means of the non-equilibrium Green function technique. It is found that the conducting current exhibits a stepwise behavior and the nonlinear differential conductance displays additional peaks with variation of the sweeping speed and the magnitude of magnetic field. This observation can be interpreted by the interaction of electron-spin with the SMM and the quantum tunneling of magnetization. The inelastic conductance and the corresponding tunneling processes are investigated with normal as well as ferromagnetic electrodes. In the case of ferromagnetic configuration, the coupling to the SMM leads to an asymmetric tunneling magnetoresistance (TMR), which can be enhanced or suppressed greatly in certain regions. Moreover, a sudden TMR-switch with the variation of magnetic field is observed, which is seen to be caused by the inelastic tunneling. 相似文献
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应用非平衡格林函数方法,研究了带有微波调制的侧向耦合量子点的量子线中的光辅助隧穿.在考虑了量子干涉和微波场的情况下,得出并讨论了电子传榆幅度和相位方面的信息.电子传输幅度显示出一系列的反共振峰(对应图中的谷结构).峰值的高度与振荡的微波场的幅度和频率有关,而峰的位置只与微波场的频率有关.在有限温的情况下,反共振峰值的高度随着温度的增加而减小,当温度足够高时,反共振峰会消失,特别地,在一定的温度下,低温下谷的地方会演变成峰. 相似文献
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Quantum-state engineering, i.e. active manipulation over the coherent dynamics of
suitable quantum-mechanical systems, has become a fascinating prospect of modern
physics. Here we discuss the dynamics of two interacting electrons in a coupled
quantum dot driven by an external electric field. The results show that the two
quantum dots can be used to prepare a maximally entangled Bell state by changing
the strength and duration of an oscillatory electric field. Different from the
suggestion made by Loss \textit et al (1998 Phys. Rev. A 57 120, the
present entanglement involves the spatial degree of freedom for the two electrons.
We also find that the coherent tunnelling suppression discussed by Grossmann
\textit et al (1991 Phys. Rev. Lett. 67 516 persists in the
two-particle case: i.e. two electrons initially localized in one dot can remain
dynamically localized, although the strong Coulomb repulsion prevents them from
behaving so. Surprisingly, the interaction enhances the degree of localization to a
large extent compared with that in the non-interacting case. This phenomenon is
referred to as the Coulomb-enhanced dynamical localization. 相似文献
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Using the scattering-matrix method, we investigate the thermal conductance in a two-slit quantum waveguide at low temperature. The results show that the total thermal conductance decreases monotonically with temperature increasing. Moreover, we find that the behaviours of the thermal conductance versus temperature are different for different types of slits. 相似文献
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M. Crisan I. Grosu I. ifrea 《Physica E: Low-dimensional Systems and Nanostructures》2007,39(2):214-218
We analyze the zero temperature conductance of a parallel T-shaped double quantum dot system. We present an analytical expression for the conductance of the system in terms of the total number of electrons in both quantum dots. Our results confirm that the system's conductance is strongly influenced by the dot which is not directly connected to the leads. We discuss our results in connection with similar results reported in the literature. 相似文献
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S. K. Jung S. W. Hwang D. Ahn J. H. Park Yong Kim E. K. Kim 《Physica E: Low-dimensional Systems and Nanostructures》2000,7(3-4)
We report on the fabrication and the characterization of quantum dot transistors incorporating a single self-assembled quantum dot. The current–voltage characteristics exhibit clear staircase structures at room temperature. They are attributed to electron tunneling through the quantized energy levels of a single quantum dot. 相似文献
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Dynamic localization of two electrons in AC-driven triple quantum dots and quantum dot shuttles 下载免费PDF全文
We analyze the dynamic localization of two interacting electrons induced by alternating current electric fields in triple quantum dots and triple quantum dot shuttles. The calculation of the long-time averaged occupation probability shows that both the intra-and inter-dot Coulomb interaction can increase the localization of electrons even when the AC field is not very large. The mechanical oscillation of the quantum dot shuttles may keep the localization of electrons at a high level within a range if its frequency is quite a bit smaller than the AC field. However, the localization may be depressed if the frequency of the mechanical oscillation is the integer times of the frequency of the AC field. We also derive the analytical condition of two-electron localization both for triple quantum dots and quantum dot shuttles within the Floquet formalism. 相似文献