共查询到20条相似文献,搜索用时 62 毫秒
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量子点电子态的尺寸效应和磁场的影响 总被引:5,自引:0,他引:5
在有效质量近似下,使用少体物理的方法,计算了在不同大小约束势情况下二维量子点三电子系统的自旋极化态的能谱.结果显示幻数角动量是否出现,主要取决于量子力学对称性、约束势大小及磁场的强度.关键词: 相似文献
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半导体量子点电子结构理论研究的进展 总被引:3,自引:1,他引:3
半导体量子点材料由其具有重要的理论研究意义和潜在的巨大应用前景而成为当今理论和材料研究的热点,本文综述了半导体量子点材料电子结构的理论研究发展进程。 相似文献
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半导体量子点激光器研究进展 总被引:11,自引:0,他引:11
首先简要地回顾了半导体激光器发展的历史和量子点激光器所特有的优异性能,进而介绍半导体量子点及其三维量子点阵列的制备技术,然后分别讨论了量子点激光器(能带)结构设计思想,实现基态激射时所必须具备的条件和近年来国内外半导体量子点器的研究进展。最后分析讨论了量子点激光器研制中存在的问题和发展趋势。 相似文献
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透射电子显微镜(TEM)研究了CdS0.3,Se0.7掺杂的半导体微晶玻璃的微晶尺寸分布,微晶尺寸由热处理温度和时间来控制。当微晶尺寸接近或小于激子Bohr半径时,吸收光谱出现亚带结构,带隙能向高能移动,证明了量子尺寸效应。非相干光时间延迟的四波混频(TDFWM-IL)技术测试研究了玻璃的快速弛豫过程。 相似文献
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Transport through symmetric parallel coupled quantum dot system has been studied, using non-equilibrium Green function formalism.
The inter-dot tunnelling with on-dot and inter-dot Coulomb repulsion is included. The transmission coefficient and Landaur-Buttiker
like current formula are shown in terms of internal states of quantum dots. The effect of inter-dot tunnelling on transport
properties has been explored. Results, in intermediate inter-dot coupling regime show signatures of merger of two dots to
form a single composite dot and in strong coupling regime the behaviour of the system resembles the two decoupled dots.
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Quantum phase transition and Coulomb blockade effect in triangular quantum dots with interdot capacitive and tunnel couplings
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The quantum phase transition and the electronic transport in a triangular quantum dot system are investigated using the numerical renormalization group method.We concentrate on the interplay between the interdot capacitive coupling V and the interdot tunnel coupling t.For small t,three dots form a local spin doublet.As t increases,due to the competition between V and t,there exist two first-order transitions with phase sequence spin-doublet-magnetic frustration phase-orbital spin singlet.When t is absent,the evolutions of the total charge on the dots and the linear conductance are of the typical Coulomb-blockade features with increasing gate voltage.While for sufficient t,the antiferromagnetic spin correlation between dots is enhanced,and the conductance is strongly suppressed for the bonding state is almost doubly occupied. 相似文献
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Jürgen Knig Teemu Pohjola Herbert Schoeller Gerd Schn 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
We consider electron transport through quantum dots with large level spacing and charging energy. At low temperature and strong coupling to the leads, quantum fluctuations and the Kondo effect become important. They show up, e.g., as zero-bias anomalies in the current–voltage characteristics. We use a recently developed diagrammatic technique as well as a new real-time renormalization-group approach to describe charge and spin fluctuations. The latter gives rise to a Kondo-assisted enhancement of the current through the dot as seen in experiments. 相似文献
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Kamil Walczak 《Central European Journal of Physics》2006,4(1):8-19
The rate-equation approach is used to describe sequential tunneling through a molecular junction in the Coulomb blockade regime.
Such device is composed of molecular quantum dot (with discrete energy levels) coupled with two metallic electrodes via potential
barriers. Based on this model, we calculate nonlinear transport characteristics (conductance-voltage and current-voltage dependences)
and compare them with the results obtained within a self-consistent field approach. It is shown that the shape of transport
characteristics is determined by the combined effect of the electronic structure of molecular quantum dots and by the Coulomb
blockade. In particular, the following phenomena are discussed in detail: the suppression of the current at higher voltages,
the charging-induced rectification effect, the charging-generated changes of conductance gap and the temperature-induced as
well as broadening-generated smoothing of current steps. 相似文献
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U. Banin J.C. Lee A.A. Guzelian A.V. Kadavanich A.P. Alivisatos 《Superlattices and Microstructures》1997,22(4):559-568
The near band-gap level structure in high-quality colloidal InAs nanocrystal quantum dots within the very strong confinement regime is investigated. Size-selective photoluminescence excitation and fluorescence line narrowing measurements reveal a size-dependent splitting between the absorbing and the emitting states. The splitting is assigned to the confinement-enhanced electron–hole exchange interaction. The size dependence of the splitting significantly deviates from the idealized 1/r3scaling law for the exchange splitting. A model incorporating a finite barrier which allows for wavefunction leakage is introduced. The model reproduces the observed 1/r2dependence of the splitting and good agreement with the experimental data is obtained. The smaller barriers for embedded InAs dots grown by molecular-beam epitaxy, are predicted to result in smaller exchange splitting as compared with colloidal dots with a similar number of atoms. 相似文献
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We study the eigenstates in quantum dots in which electrons are confined by the application of an inhomogeneous perpendicular magnetic field, focusing on the effect that the specific details of the shape of confining field has on determining these states. In contrast to the edge state picture established in studies on circular dots, we find that dots with more irregular geometries show a more complicated behavior in the interior of the dot. In particular, we find that certain states show indications of having their amplitude enhanced along particular classical periodic orbits in the interior, a phenomenon known as ‘scarring’. 相似文献
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The Coulomb blockade (CB) in quantum dots (QDs) is by now well documented. It has been used to guide the fabrication of single
electron transistors. Even the most sophisticated techniques for synthesizing QDs (e.g. MOCVD/MBE) result in an assembly in
which a certain amount of disorder is inevitable. On the other hand, theoretical approaches to CB limit themselves to an analysis
of a single QD. In the present work we consider two types of disorders: (i) size disorder; e.g. QDs have a distribution of
sizes which could be unimodal or bimodal in nature. (ii) Potential disorder with the confining potential assuming a variety
of shapes depending on growth condition and external fields. We assume a Gaussian distribution in disorder in both size and
potential and employ a simplified mean field theory. To do this we rely on the scaling laws for the CB (also termed as Hubbard
U) obtained for an isolated QD [1]. We analyze the distribution in the Hubbard U as a consequence of disorder and observe that Coulomb blockade is partially suppressed by the disorder. Further, the distribution
in U is a skewed Gaussian with enhanced broadening.
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K. Ishibashi S. Moriyama T. Fuse T. Yamaguchi 《Physica E: Low-dimensional Systems and Nanostructures》2006,35(2):338
Quantum dots have been fabricated with single-wall carbon nanotubes (SWCNTs), and their transport properties have been measured at low temperatures. The single-electron transport measurements revealed the artificial atom characteristics with a shell structure and the Zeeman splitting of single particle states. They have been observed with the metallic SWCNT that includes many electrons, in striking contrast to the case of semiconductor artificial atoms that have a few electrons. The unique features in the SWCNT artificial atom are discussed in terms of the energy scales associated with the quantum dot. 相似文献
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We consider the Maxwell equations for an electromagnetic field propagating in a solid with a three-dimensional superlattice
of quantum dots linked by strong tunneling along one axis, where electrons with different spin projections are affected by
the strong Coulomb repulsion at a single site. We obtain a phenomenological equation in the form of the classical 1+1-dimensional
sine-Gordon equation. Electrons are considered within the framework of quantum formalism taking into account the changes in
the dispersion law provided by the presence of Coulomb interactions. The phenomenological equation is solved numerically,
and the influence of Coulomb repulsion and the degree of band population on the propagation of ultra-short optical pulses
is analyzed. 相似文献