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1.
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  
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   

2.
存在自旋轨道耦合的介观小环中的持续自旋流   总被引:1,自引:0,他引:1  
孙庆丰  谢心澄  王健 《物理》2007,36(11):813-816
文章作者研究了存在自旋轨道耦合的介观小环的平衡态性质.此前人们已经知道,在有磁通穿过的介观小环中,绕环运动的电子会产生一附加的Berry相位而导致持续电流;同样地,在仅有自旋轨道耦合的体系中,电子绕环运动也应当会产生附加的自旋Berry相位,进而驱动持续自旋流.文章作者通过对一个有正常区和自旋轨道耦合区的复合小环的计算,结果表明,无电流伴随的纯持续自旋流的确存在.文章作者指出,这持续自旋流描述真实的自旋运动,并且它能被实验观测.  相似文献   

3.
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   

4.
介观多环耦合系统中的量子电流增强效应   总被引:18,自引:0,他引:18       下载免费PDF全文
崔元顺 《物理学报》2005,54(4):1799-1803
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   

5.
嵌入量子点的介观Aharonov-Bohm环的基态与持续电流   总被引:4,自引:0,他引:4       下载免费PDF全文
叶剑斐  叶飞  丁国辉 《物理学报》2003,52(2):468-472
对嵌入量子点的介观金属环进行了研究.在二级微扰变分近似下得出了其基态能量表达式和基态持续电流表达式,并在库仑排斥势趋于无穷大的假设下,得到了系统Kondo温度及持续电流的数值计算结果.并且将它们与一级微扰变分近似所得结果进行了对比,指出了它们之间存在的差异,对于这一系统二级微扰变分近似将给出更好的数值计算结果. 关键词: Kondo效应 持续电流 变分法  相似文献   

6.
介观LC电路中的量子隧道效应   总被引:12,自引:0,他引:12       下载免费PDF全文
考虑到电子在纳米电容器中的运动是一个单电子隧穿过程,因而将电容器作为一个隧道结,应用隧道模型的稳态法,研究了介观LC电路中的电流电压特性.结果表明:由于库仑力的作用,介观LC电路中存在着阈值电压.当外加电压小于阈值电压时,隧穿电流为零,显示出库仑阻塞现象;当外加电压远大于阈值电压时,隧穿电流与电压成正比. 关键词: 介观LC电路 库仑阻塞 单电子隧道过程  相似文献   

7.
耗散介观电容耦合电路的量子化   总被引:7,自引:0,他引:7       下载免费PDF全文
宋同强 《物理学报》2004,53(5):1352-1356
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   

8.
利用格林函数并借助于双杂质Anderson模型的哈密顿量,研究了嵌入平行耦合量子点的非平衡介观环路的磁极化电流性质. 结果表明:在零温环境中,随着双量子点耦合强度的增加,系统的Kondo效应被削弱.在低温环境中,人为控制和调节一定的电路参数,极化电流会发生方向的反转,从而可实现对介观环路的极化. 关键词: 极化电流 耦合量子点 Kondo效应 温度效应  相似文献   

9.
崔元顺 《光子学报》2007,36(8):1530-1533
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   

10.
平移压缩Fock态下介观电容耦合电路的量子涨落   总被引:33,自引:2,他引:31       下载免费PDF全文
王继锁  刘堂昆  詹明生 《物理学报》2000,49(11):2271-2275
从经典电容耦合电路的运动方程出发,研究了在平移压缩Fock态下介观电容耦合电路中每个回路的电荷和电流的量子涨落.结果表明,每个回路中电荷、电流的量子涨落只依赖于两个回路的器件参数和压缩参量,而与平移参量无关. 关键词: 介观电路 电容耦合 平移压缩Fock态 量子涨落  相似文献   

11.
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   

12.
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   

13.
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   

14.
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   

15.
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   

16.
张颖  肖景林 《发光学报》2007,28(3):321-324
利用量子波导理论研究三臂环中的持续电流.结果表明,输运电流存在时,不含磁场且上、下臂等长的三臂环中仍可以有持续电流出现,而且上臂和下臂中的持续电流是相同的.三臂环的各臂长不等时,三个臂中的持续电流各不相同.我们还发现,即使三臂环和单环的上、下臂比值一样,两个环中的持续电流也明显不同.  相似文献   

17.
李鸿明  肖景林 《发光学报》2007,28(4):489-492
采用量子波导理论,研究了介观结构中杂质对透射几率和持续电流的影响。结果发现持续电流的大小不仅依赖于结构中环的尺度,而且也受到杂质的影响,杂质势既可以产生电流放大也可压制持续电流的放大。通过调节杂质的势来控制持续电流。  相似文献   

18.
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   

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