共查询到20条相似文献,搜索用时 0 毫秒
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R.H. Blick D.W. van der Weide R.J. Haug K. von Klitzing K. Eberl 《Superlattices and Microstructures》1998,23(6):1265-1271
We investigate the photoconductance through a double quantum dot or ‘artificial molecule’ induced by a broadband millimeter wave source. This source functions as a heterodyne interferometer, consisting of two nonlinear transmission lines generating harmonic output in the range of 2–400 GHz, and, being coherent, allows tracking of the induced current of the sample in both magnitude and phase. This enables us to monitor effects related to coherent electronic transport through these ‘artificial molecules’. 相似文献
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D. Pfannkuche R.H. Blick R.J. Haug K. von Klitzing K. Eberl 《Superlattices and Microstructures》1998,23(6):1255-1265
Transport spectroscopy reveals the microscopic features of few-electron quantum dots which justify the nameartificial atoms. New physics evolve when two quantum dots are coupled by a tunneling barrier. We study, both theoretically and experimentally, the tunneling spectroscopy on a double quantum dot. A detailed lineshape analysis of the conductance resonances proves that off-resonant coherent interdot tunneling governs transport through this system, while tunneling into the double quantum dot occurs resonantly. This coherent interdot tunneling witnesses the evolution of a delocalized electronic state which can be compared to a valence electron of thisartificial molecule. 相似文献
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Hui Pan Li-Na Zhao Rong Lü 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2988-2994
The time-dependent electron transport through an Aharonov–Bohm ring embedded with two quantum dots in the presence of external microwave (MW) fields are investigated theoretically by using the nonequilibrium Green's function method. Whether the MW field can induce or suppress the Fano resonance depends on the part to which the field is applied. When the MW field is applied only to the two quantum dots, the photon-assisted Fano peaks appear at the sidebands of the original Fano peak. The existence of the original Fano peak or the photon-assisted ones can be controlled by the field strength. When the MW field is applied only to one lead, the original Fano peak is suppressed by the MW field, and the negative current caused by the electron–photon pump effects is found. 相似文献
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Maxim S. Gaponenko Oleg V. Buganov Alexei A. Onushchenko Stephen G. Hickey Alexander M. Malyarevich Sergei A. Tikhomirov Konstantin V. Yumashev 《固体物理学:研究快报》2010,4(12):341-343
Exciton relaxation in PbS quantum dots (QDs) in glass and tetrachloroethylene have been investigated and the radiative and non‐radiative relaxation rates of the lowest 1S–1S state have been measured. An estimate of the carrier intra‐band transition rates and their transfer efficiency is calculated. The dependence of the exciton dynamics on the QD surface properties is presented and discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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本文以三个不同粒径(1#:2.3 nm, 2#:2.8 nm和3#:3.5 nm)的巯基乙酸包覆的CdTe量子点(thioglycolic acid capped CdTe quantum dots, TGA-CdTe QDs)样品为研究对象, 其时间相关单光子计数(time-correlated single photon counting, TCSPC)实验得到的时间分辨光谱显示, 三个量子点的荧光平均寿命依次是~6 ns, ~10 ns和~12 ns, 其动力学过程包括慢过程和快过程两部分. 随其粒径尺寸的增加, 其慢过程延长, 快过程在变短. 然后, 通过瞬态吸收和荧光上转换两种基于飞秒的时间分辨光谱技术, 对TGA-CdTe量子点的带间弛豫过程做了探究. 实验结果显示, 三个TGA-CdTe量子点样品, 随其粒径增大, 最高激发态和最低激发态填充速率减慢, 其中, 最高激发态从0.33 ps增加至0.79 ps; 最低激发态从0.53 ps增至~1 ps. 另外, 由瞬态吸收和荧光上转换两种时间分辨手段相结合, 可得到CdTe量子点带间弛豫的完整图像, 结果显示了TGA-CdTe 量子点的一个本征特征:即在基态漂白恢复过程中的初始上升阶段, 荧光上转换信号要慢于瞬态吸收信号. 这可以为量子点在光电转换应用上提供帮助. 相似文献
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We analyze the transport through asymmetric double quantum dots with an inhomogeneous Zeeman splitting in the presence of crossed dc and ac magnetic fields.A strong spin-polarized current can be obtained by changing the dc magnetic field.It is mainly due to the resonant tunnelling.But for the ferromagnetic right electrode,the electron spin resonance also plays an important role in transport.We show that the double quantum dots with three-level mixing under crossed dc and ac magnetic fields can act not only as a bipolar spin filter but also as a spin inverter under suitable conditions. 相似文献
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《中国物理 B》2021,30(5):53201-053201
The exciton Stark shift and polarization in hemispherical quantum dots(HQDs) each as a function of strength and orientation of applied electric field are theoretically investigated by an exact diagonalization method. A highly anisotropic Stark redshift of exciton energy is found. As the electric field is rotated from Voigt to Faraday geometry, the redshift of exciton energy monotonically decreases. This is because the asymmetric geometric shape of the hemispherical quantum dot restrains the displacement of the wave function to the higher orbital state in response to electric field along Faraday geometry. A redshift of hole energy is found all the time while a transition of electron energy from this redshift to a blueshift is found as the field is rotated from Voigt to Faraday geometry. Taking advantage of the diminishing of Stark effect along Faraday geometry, the hemispherical shapes can be used to improve significantly the radiative recombination efficiency of the polar optoelectronic devices if the strong internal polarized electric field is along Faraday geometry. 相似文献
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文章主要研究了CdSe量子点微腔结构,微腔结构包括上下分布式布拉格反射镜(DBR),中间的有源层为溶解在聚甲基丙烯酸甲酯(PMMA)中的CdSe胶体量子点.采用传递矩阵法模拟微腔的反射光谱,对实验测试曲线进行较好的拟合.通过测试微腔结构的光致荧光(PL)光谱,其半峰宽(FWHM)由未加入微腔的CdSe量子点样品的27.9 nm,减小到微腔结构的7.5 nm,在微腔中的量子点,由于腔模式的出现,其发光谱的品质因数增加了3.6倍,达到了荧光增强的效果.
关键词:
CdSe量子点
微腔效应
荧光增强 相似文献
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考虑铁基超导中能带间的相互作用和界面对每一个能带的散射作用, 利用推广的Blonder-Tinkham-Klapwijk模型, 并通过求解Bogoliubov-de Gennes 方程研究了具有不同类型双能隙系统的量子线/铁基超导隧道结中准粒子的输运系数和隧道谱. 研究表明: 1)在弹道极限时, 随着带间相互作用的增大, s± 波隧道谱中零偏压附近的平台演变成电导峰; s++ 波的平台演变成凹陷; p波的零偏压电导峰被压低. 2)界面对两个能带的散射作用不为零时, 随着带间相互作用的增大, s± 波和s++ 波两能隙处的峰值将降低, 而两峰间的凹陷值将变大; p波的零偏压电导峰被压低, 非零偏压电导增大. 3)界面对每个能带的散射, 可使其产生的电导峰变得更加尖锐, 但可压低和抹平另一个带产生的电导峰值. 这些结果对于澄清铁基超导体的能隙结构和区别不同类型铁基超导体有所帮助. 相似文献
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T. S. Shamirzaev A. M. Gilinsky A. I. Toropov A. K. Bakarov D. A. Tenne K. S. Zhuravlev C. von Borczyskowski D. R. T. Zahn 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):282
The temperature dependence of steady-state and time-resolved photoluminescence from self-assembled InAs quantum dots embedded in AlAs has been studied. Millisecond-long nonexponential photoluminescence decay is observed in the temperature range of 4.2–50 K. At higher temperatures, the decay time decreases to a few nanoseconds. The experimental results are interpreted using a model of singlet–triplet splitting of exciton levels in small dots in a dense quantum dot system with local carrier transfer between dots. 相似文献
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Current transport mechanism in Schottky diode containing InAs quantum dots (QDs) is investigated using temperature-varying current-voltage characteristics. We found that the tunnelling emission has obvious effects on the I-V characteristics. The I-V-T measurements revealed clear effects of QDs on the overall current flow. Field emission (FE, pure tunnelling effect) was observed at low temperature and low voltages bias region. The zero-bias barrier height decreases and the ideality factor increases with decreasing temperature, and the ideality factor was found to follow the T0-effect. When the reverse bias is varied, the ideality factors of Schottky barriers exhibit oscillations due to the tunnelling of electrons through discrete levels in quantum dots. The traps distributed within InAlAs layer can also act as a transition step for reverse bias defect-assisted tunnelling current which can phenomenologically explain the decrease of the effective barrier height with measurement temperature. 相似文献
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本文研究了在两个耦合的量子点和腔QED系统中的双模激子的压缩性质.讨论了不同的初始光场对双模激子的正常压缩与和压缩的影响.计算表明,当初始态光场制备在相干态时,双模激子既不存在正常压缩,也不存在和压缩,这说明双模激子振辐的两个正交分量具有相同的量子涨落;然而,当初始腔场处于压缩真空态时,无论是正常压缩还是和压缩,双模激子振辐的两个正交分量总有一个存在压缩.这意味着量子噪声能被有效的得到抑制.此外,两种情形下的最大压缩都由初始腔场的压缩因子r决定.经过比较,我们还发现双模激子的正常压缩比和压缩大. 相似文献
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Karel Kral 《Czechoslovak Journal of Physics》2006,56(1):33-40
Longitudinal optical phonons have been used to interpret the electronic energy relaxation in quantum dots and at the same
time they served as a reservoir, with which the electronic subsystem is in contact. Such a phonon subsystem is expected to
be passive, namely, in a long-time limit the whole system should be able to achieve such a stationary state, in which statistical
distributions of both subsystems do not change in time. We pay attention to this property of the LO phonon bath. We show the
passivity property of the so far used approximations to electronic transport in quantum dots. Also we show a way how to improve
the passivity of LO phonon bath using canonical Lang-Firsov transformation.
Presented at the X-th Symposium on Suface Physics, Prague, Czech Republic, July 11–15, 2005. 相似文献
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We design a double quantum-dot (QD) shuttle (DQDS) model including two rigidly connected QDs that are softly linked to two leads via deformable organic materiaJs. Based on the full quantum mechanical approaches we explore the influences on the electron transport induced by the electrical and mechanical degrees of freedom. First of a/l the modified rate equations of the DQDS are derived theoretically and then a numerical investigation on the quantum transport through the DQDS is performed. For the classical DQDS, the time-dependent evolutions of the electron- occupation probabilities and the currents flowing through the DQDS show the periodic oscillations with their periods determined by the oscillation period of the DQDS. Both the mechanical oscillation amplitude and the interdot coupling can play crucial roles in adjusting the peak shapes of the currents and the probabilities. For the quantum DQDS, the current and electron-occupation probabilities of the DQDS evolve into a stationary state as time goes on, with no periodical oscillations observed. As a consequence, the sharp differences of the time-dependent properties between the c/assica/ and quantum DQDS systems are clearly demonstrated, which should be greatly helpful in designing new nanoelectromechanical devices. Also, this work is of great significance to understanding the kind of rigidly connected QD shuttle systems that have more than two QDs. 相似文献
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Single electron transistors with wire channels are fabricated by a nanoelectrode-pair technique. Their characteristics strongly depend on the channel widths and the voltages on the in-plane gates. A few dips in the Coulomb blockade oscillations were observed at the less positive gate voltages for a device with a 70nm-wide wire due to Coulomb blockade between the coupled dots. By applying negative voltages to the in-plane gates, the oscillations became periodic, which indicated the formation of a single dot in the conducting channel. These gates facilitate fabricating single-electron transistors with single dot structures, which have potential applications on its integration. 相似文献
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Temperature dependence of the electron distribution in a GaAs matrix with embedded InAs quantum dots
Adenilson J. Chiquito Marcelo G. de Souza 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):912
We report on the effect of the Debye averaging process on the CV characteristics of a sample containing four coupled planes of InAs self-assembled quantum dots. The observed electron distribution presented a dynamical dependence of the temperature during the C–V measurements which was explained in terms of the screening length dependence on the temperature. In addition, using the C–V data, we calculated the electron density at the planes containing the InAs dots and we have observed a high-temperature stability: the electron density at the quantum dots remained constant over a large range of temperature. 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