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介观金属双环系统中的持续电流和量子能谱 总被引:8,自引:1,他引:7
崔元顺 《原子与分子物理学报》2006,23(3):527-531
基于电荷的不连续性,对处于外磁场中的介观双环系统进行量子化.假设系统在电荷表象中具有变换的对称性,通过求解电流和Hamilton算符的本征值方程,给出介观金属环互感系统中的量子电流和能谱关系;分析和研究了介观金属环中量子电流和能谱的性质.结果表明,持续电流和量子能谱不仅与外磁场、介观双环参数有关,而且还明显地依赖于电荷的量子化性质. 相似文献
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利用平均场近似理论,研究了一个嵌入T型弱耦合双量子点的介观环系统的基态性质. 结果表明,体系中复杂的基态性质源于Kondo效应与Fano效应相互竞争. 当介观环的尺寸达到足以产生完全Kondo共振时,随双量子点间耦合强度的增强,尖锐的持续电流峰出现了,且越发显著,这说明体系中存在着显著的Fano 效应. 但介观环的Kondo共振持续电流峰值却几乎不发生变化,这为测定Kondo 屏蔽云提供了一个新的可能模型.
关键词:
耦合量子点
持续电流
Kondo效应
Fano 效应 相似文献
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基于电荷具有离散性的事实对介观电路进行量子化,以介观三环为例研究多环耦合系统中的量子电流增强效应.结果表明,量子电流增强效应不仅存在于耦合双环系统中,而且在金属多环系统中也存在.
关键词:
介观电路
耦合系统
量子电流
增强效应 相似文献
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通过正则化变换,研究了耗散介观电容耦合电路的量子化,并讨论了系统中电荷和广义电流 的量子涨落.
关键词:
耗散介观电容耦合电路
量子化
正则化变换 相似文献
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基于电荷量子化的事实,运用最小平移算符Q∧的性质等,计算对应的相干态下介观金属环中电荷、电流及能量的量子涨落,研究影响量子涨落的因素.结果表明:计及电荷的离散性,在相干态下介观金属环中电荷、能量的量子涨落不为零,分别与电荷量子、相干态参量等因素有关;此外,能量的量子涨落还决定于金属环的电感、外磁通及其时间变化率的大小. 相似文献
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We investigate the effects of impurity spin dynamics on quantum coherence in mesoscopic metallic rings. Spin relaxation induces temporal current fluctuations which are closely related to persistent currents in such systems. The persistent current is suppressed in the presence of magnetic impurities. We discuss spin-polarisation effects, spin-glass ordering, and the Kondo effect which are shown to restore the current even in the presence of magnetic scattering. 相似文献
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The idea of nondissipative, persistent currents in mesoscopic metallic or semiconducting rings and cyclinders appears counterintuitive, because it contradicts our experience with currents in macroscopic metals. On the other hand such orbital currents are well known properties of atoms. A comparative study of nondissipative ring currents in different finite quantum systems is therefore of interest. In this paper the properties of atoms, mesoscopic metallic or semiconducting rings and cylinders and elongated molecules called carbon nanotubes are discussed and compared. 相似文献
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We present a study of persistent currents (PC) in mesoscopic two-dimensional metallic cavities. The cavity is simulated with a gate potential that constrains the electrons to be in the regions of the sample. Varying the profile of the gate potential we can change the size and the geometry of the sample. We study non-single connected samples for which the typical current, Ityp, is substantially enhanced at half-filling, due to the existence of electronic border states near the Fermi level for this filling. These states have a large angular momentum and its response to the magnetic external flux is paramagnetic. We discuss the relevance of our results in relation to the, as yet, unexplained discrepancies between measurements of large values of PC in mesoscopic metallic rings and theoretical predictions. 相似文献
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Ying-hua Ji Hai-mei Luo Jie Liu Hua-Ming Wan 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):668-674
We propose a quantum Hamiltonian and obtain the relationship between external magnetic field and currents of three mesoscopic coupling rings. The impact of coupling on quantum current magnification in the system is studied. It is found that the quantum current magnification effect strongly depend on both the external magnetic flux and the coupling factors. As a result, by taking use of coupling rings, we can design some circuits to transfer and communicate signals. 相似文献
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P. Schwab 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):189-192
In a weakly disordered metal electron interactions are responsible for both decoherence of the quasi-particles as well as
for quantum corrections to thermodynamic properties. We consider electrons which are interacting with two-level-systems. We
show that the two-level-systems enhance the average equilibrium (“persistent”) current in an ensemble of mesoscopic rings.
The result supports the recent suggestion that two puzzles in mesoscopic physics may be related: The low temperature saturation
of the dephasing time and the high persistent current in rings.
Received 26 May 2000 相似文献
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M. Henkel D. Karevski 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):787-792
The effect of point defects on persistent currents in mesoscopic rings is studied in a simple tight-binding model. Using an
analogy with the treatment of the critical quantum Ising chain with defects, conformal invariance techniques are employed
to relate the persistent current amplitude to the Hamiltonian spectrum just above the Fermi energy. From this, the dependence
of the current on the magnetic flux is found exactly for a ring with one or two point defects. The effect of an aperiodic
modulation of the ring, generated through a binary substitution sequence, on the persistent current is also studied. The flux-dependence
of the current is found to vary remarkably between the Fibonacci and the Thue-Morse sequences.
Received: 4 March 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998 相似文献