共查询到20条相似文献,搜索用时 250 毫秒
1.
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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使用双杂质Anderson模型的哈密顿,从理论上研究了一个嵌入并联耦合双量子点介观环系统 , 当处在Kondo区时的基态性质, 并用slave-boson平均场方法求解了哈密顿.研究的结果表 明, 在这个系统中,当两个量子点处于强耦合时,两个量子点可以相干耦合成一个人造分 子,导致一个增强的Kondo效应和超强持续电流的出现.因此,在未来的纳米装置应用中,这 个系统具有潜在的应用价值.
关键词:
并联耦合双量子点
Kondo效应
超强持续电流 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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利用隶玻色子平均场近似理论,并借助于单杂质的Anderson模型的哈密顿量,研究了T型耦合双量子点嵌入正常电极的基态输运性质.结果表明:在体系处于平衡状态时,随着双量子点的耦合强度增加,体系的Kondo 效应被削弱. 当耦合强度足够强时,Kondo量子点态密度的Kondo共振单峰分裂成两个不对等的Kondo共振双峰.在体系处于非平衡状态时,增加两电极的偏压,态密度的Kondo分裂的非对等性明显加强.
关键词:
Kondo效应
态密度
格林函数法
耦合双量子点 相似文献
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使用双杂质的Ansderson模型的哈密顿 ,从理论上研究了一个嵌入并联耦合量子点(DQD)的介观A -B环系统处在Kondo区时的基态性质 ,并用slave boson平均场方法求解了哈密顿。结果表明 ,在这个系统中 ,由磁通诱导而产生的持续电流依赖于系统的宇称效应和尺寸大小 ,并随隧穿耦合强度的增加而变得越来越复杂。在δ >T0 K 时 ,它的电流的峰值是奇宇称的大于偶宇称的 ,并随隧穿耦合强度的增加而增大 ,但Fano共振却被削弱 ,系统始终存在宇称效应 ,这个系统与单 (串联耦合双 )量子点系统相比 ,有许多不同的物理性质。因此 ,在未来的装置设计中 ,是很有潜力的。 相似文献
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我们利用单杂质Anderson模型及运动方程等理论,通过求解格林函数的方法研究了通过T型量子点结构(耦合于铁磁电极和介观环量子点结构)的自旋极化输运过程.研究结果表明,与量子点相耦合的铁磁电极中的极化强度是控制量子点电子输运的重要参数,由此可以达到自旋阀效应.另外我们还发现与量子点相耦合的介观环中的磁通会影响电子自旋向上和自旋向下近藤共振峰的分裂程度,但若加入适当的外磁场,那么这样的分裂将被抵消。 相似文献
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由于一维磁光子晶体能同时展示出很好的光透射率和法拉第旋转,故可用于实现小尺度的磁光隔离器。采用传输矩阵法研究了由磁光膜(Bi∶YIG)和电介质膜(Ta2O5,SiO2)构成的一维磁光子晶体,分别讨论了在垂直入射和斜入射条件下的法拉第效应,并给出了几种可行性结构,对磁光隔离器件的进一步改进设计具有一定的参考价值。 相似文献
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Zhen Li Rui-xin Wu Yin Poo Qing-bo Li Rong-juan Liu Zhi-yuan Li 《Applied Physics A: Materials Science & Processing》2014,117(2):451-454
We studied how the constitution parameters and applied bias magnetic field influence the bandwidth and frequency tunability of the one-way transmission (OWT) caused by magnetic surface plasmon resonance of the magnetic photonic crystals (MPC). We found that wide-band OWT could be obtained using ferrite rods with larger normalized radius and suppressing the bulk modes of MPC in the frequencies where the edge and bulk modes coexist. We verified that bias magnetic field tunes the frequencies of OWT but has little effects on its bandwidth by experiments, and a simple way is proposed to suppress the bulk modes by introducing air defect near the edge of the MPC and experimentally demonstrated its effectiveness. This work provides a way toward practical applications for wide-band tunable one-way devices. 相似文献
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在卤化铜激光器脉冲放电电源系统中,为减轻闸流管的工作负担并同时保证电路的快放电激励,采用了单级磁脉冲压缩器.分析了磁脉冲压缩器的工作机理,介绍了所采用磁脉冲压缩器的设计考虑及参数选用.
关键词:
磁脉冲压缩器
闸流管
CuBr激光器 相似文献
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We have demonstrated an optimization approach in order to obtain desired magnetophotonic crystals (MPCs) composed of a lossy magnetic layer (TbFeCo) placed within a multilayer structure. The approach is an amalgamation between a 4×4 transfer matrix method and a genetic algorithm. Our objective is to enhance the magneto-optic Kerr effect of TbFeCo at short visible wavelength of 405 nm. Through the optimization approach, MPC structures are found meeting definite criteria on the amount of reflectivity and Kerr rotation. The resulting structures are fitted more than 99.9% to optimization criteria. Computation of the internal electric field distribution shows energy localization in the vicinity of the magnetic layer, which is responsible for increased light-matter interaction and consequent enhanced magneto-optic Kerr effect. Versatility of our approach is also exhibited by examining and optimizing several MPC structures. 相似文献
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设计制作了全固态高重复频率磁脉冲压缩发生器,最高重复频率5 kHz,脉宽70 ns,通过调节初始储能电容上的电压可在500 阻性负载上获得4~40 kV连续可调的输出电压。通过分析简化的磁压缩末级回路,分析了预脉冲产生的过程,得出了预脉冲的电压表达式,选取适当的磁芯相对磁导率,经过求解,得出在磁开关未饱和电感一定时预脉冲随负载阻值变化的曲线簇,从曲线中可以看出:随着负载的阻值的增大,预脉冲的峰值绝对值也增大;在负载恒定的情况下,增大磁开关未饱和电感的大小可以显著地减小负载两端预脉冲的峰值绝对值,这要求磁开关磁芯有更高的相对磁导率。 相似文献
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This paper aims to study the general conditions under which omnidirectional band gaps (OBGs) are achieved by using heterostructure magnetic photonic crystals (HMPCs). These structures contain periodic layers with alternative dielectric permittivity and magnetic permeability. The proposed design offers the stacking of two magnetic photonic crystals (MPCs), where one MPC has Brewster’s angle at TE polarization and another has the angle at TM polarization. The propagation of electromagnetic waves is investigated by means of the transfer matrix method. Also, the total reflection frequency range for any incident angle and polarization is discussed in this paper. As a conclusion, although each MPC has no OBG individually, the proposed HMPC may contain an OBG. The main advantage of the proposed design is that the obtained OBG is independent of the ambient media refractive index. Therefore, it can be used in engineering omnireflectors in integrated photonics. 相似文献
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A special kind of one-dimensional (1D) magnetic photonic crystal (MPC) is investigated. The refractive indices of the alternating layers in such a MPC are equal. As a result, the stop-band edges of TE mode coincide with those of TM mode, and the stop-bands for both modes expand as the incident angle increases. Based on the incident angle domain method, the omnidirectional total reflection (ODTR) band determined by the wave impedance ratio between the composites can be enlarged substantially using a heterostructure in which the stop-band edges of the sub-PCs can be completely adjacent at any incident angle. Moreover, the requirement of ODTR of each sub-PC is unnecessary, which extends the range of materials; that is, the wave impedance ratio between the composites and the refractive index ratio between the composites and the incident media can be much lower than that required in a single periodic structure. 相似文献
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分析了传统磁脉冲压缩系统的原理及缺点,对基于省去磁芯复位电路的磁脉冲压缩系统进行了介绍,为了更加深入地分析这种磁脉冲压缩系统,应用Pspice仿真分析软件建立了省去磁芯复位电路的磁脉冲压缩系统模型,计算出各级压缩过程中各元件的电压波形,及饱和变压器和磁开关的磁芯感应强度变化曲线;经测试,当负载为500 Ω纯阻性负载时,系统两端输出的负极性脉冲峰值约-27 kV,半高宽约为70 ns,下降沿约为40 ns。通过分析仿真结果与实验结果,仿真中需考虑测量探头引入的并联电容对电路的影响。 相似文献
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We examine manipulating electromagnetic waves in magnetic photonic crystals (MPCs) with external magnetic fields. We predict new giant magnetoreflectivity and giant magnetorefractivity effects: with an external magnetic field of a magnitude much smaller than the anisotropy field of the ferromagnet, the MPC can be changed from completely reflecting to nonreflecting with corresponding changes in the angle of refraction. Application to the storage of electromagnetic radiation is also discussed. 相似文献
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We theoretically investigate the spin-dependent Seebeck effect in an Aharonov–Bohm mesoscopic ring in the presence of both Rashba and Dresselhaus spin–orbit interactions under magnetic flux perpendicular to the ring. We apply the Green's function method to calculate the spin Seebeck coefficient employing the tight-binding Hamiltonian. It is found that the spin Seebeck coefficient is proportional to the slope of the energy-dependent transmission coefficients. We study the strong dependence of spin Seebeck coefficient on the Fermi energy, magnetic flux, strength of spin–orbit coupling, and temperature. Maximum spin Seebeck coefficients can be obtained when the strengths of Rashba and Dresselhaus spin–orbit couplings are slightly different. The spin Seebeck coefficient can be reduced by increasing temperature and disorder. 相似文献