共查询到20条相似文献,搜索用时 46 毫秒
1.
Vram Mughnetsyan Vidar Gudmundsson Nzar Rauf Abdullah Chi-Shung Tang Valeriu Moldoveanu Andrei Manolescu 《Annalen der Physik》2024,536(4):2300274
Quantum electrodynamical density functional theory is applied to obtain the electronic density, spin polarization, as well as orbital and spin magnetizations of square periodic arrays of quantum dots or antidots subjected to the influence of a far-infrared cavity photon field. A gradient-based exchange-correlation functional adapted to a 2D electron gas in a transverse homogeneous magnetic field is used in the theoretical framework and calculations. The obtained results predict a non-trivial effect of the cavity field on the electron distribution in the unit cell of the superlattice, as well as on the orbital and spin magnetizations. The number of electrons per unit cell of the superlattice is shown to play a crucial role in the modification of the magnetization via the electron–photon coupling. The calculations show that cavity photons strengthen the diamagnetic effect in the quantum dot structure, while they weaken the paramagnetic effect in the antidot structure. As the number of electrons per unit cell of the lattice increases, the electron–photon interaction reduces the exchange forces that will otherwise promote strong spin splitting for both the dot and the antidot arrays. 相似文献
2.
S. Bujkiewicz C. R. Tench T. M. Fromhold M. J. Carter F. W. Sheard L. Eaves 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
The semiclassical motion of an electron along the axis of a superlattice may be calculated from the miniband dispersion curve. Under a weak electric field the electron executes Bloch oscillations which confines the motion along the superlattice axis. When a magnetic field, tilted with respect to the superlattice axis, is applied the electron orbits become chaotic. The onset of chaos is characterised by a complex mixed stable-chaotic phase space and an extension of the orbital trajectories along the superlattice axis. This delocalisation of the orbits is also reflected in the quantum eigenstates of the system some of which show well-defined patterns of high probability density whose shapes resemble certain semiclassical orbits. This suggests that the onset of chaos will be manifest in electron transport through a finite superlattice. We also propose that these phenomena may be observable in the motion of trapped ultra-cold atoms in an optically induced superlattice potential and magnetic quadrupole potential whose axis is tilted relative to the superlattice axis. 相似文献
3.
D. V. Dmitriev I. S. Strygin A. A. Bykov S. Dietrich S. A. Vitkalov 《JETP Letters》2012,95(8):420-423
Low-temperature dependences of the transport relaxation time (τtr) and quantum lifetime (τq) on the density of the two-dimensional electron gas (n e ) in GaAs quantum wells with AlAs/GaAs lateral superlattice barriers have been studied. An exponential increase in the quantum lifetime with increasing electron density has been observed. It has been shown that the sharp increase in the quantum lifetime correlates with the appearance of X electrons in the AlAs/GaAs lateral superlattice barriers. It has been established that the ratio of the transport relaxation time to the quantum lifetime in the studied structures nonmonotonically depends on the density: the ratio τtr/τq first increases linearly with n e and then decreases. This behavior is not described by the existing theories. 相似文献
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V. A. Maksimenko V. V. Makarov A. A. Koronovskii A. E. Hramov R. Venckevičius G. Valušis A. G. Balanov F. V. Kusmartsev K. N. Alekseev 《JETP Letters》2016,103(7):465-470
A very simple model describing steady-state electron transport along a quantum superlattice of a finite length taking into account an arbitrary electrical characteristic of the injecting contact is considered. In the singleminiband approximation, exact formulas for the spatial distribution of the electric field in the superlattice are derived for different types of contact. Conditions under which the field is uniform are identified. Analytical expressions for the current–voltage characteristics are obtained. In the context of the developed theory, the possibility of attaining uniform-field conditions in a diode structure with a natural silicon-carbide superlattice is discussed. 相似文献
6.
鉴于“方形”势阱过于简单和理想,引入了反比相关双曲余弦平方势描述超晶格量子阱中的电子运动行为。在量子力学框架内,把电子的Schrodinger方程化为了超几何方程, 并以Ga1-xAlxAs-GaAs- Ga1-xAlxAs量子阱为例计算了电子的带内跃迁和带间跃迁。结果表明,能级数目和跃迁能量与阱深、阱宽等系统参数有关,只需适当调节这些参数就可望实现对超晶格量子阱光电特征的调节与控制。 相似文献
7.
A. K. Bakarov A. A. Bykov N. D. Aksenova D. V. Sheglov A. V. Latyshev A. I. Toropov 《JETP Letters》2003,77(12):662-665
Oscillations of the magnetoresistance commensurate with the spatial modulation period of the growth surfaces were observed in selectively doped GaAs quantum wells with AlAs/GaAs superlattice barriers grown by molecular beam epitaxy. The experimental data obtained are explained by the lateral potential modulation of the two-dimensional electron gas in narrow GaAs quantum wells with corrugated heteroboundaries and agree with the two-dimensional distribution of the local capacitance in such structures. 相似文献
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Diffraction and channeling in nanotubes 总被引:1,自引:0,他引:1
A theory of the interaction of fast charged particles and gamma rays with nanotubes with different helicity is developed. Analytical expressions are obtained for the potential and the electron density of a nanotube taking account of the anisotropic thermal vibrations of the atoms. A system of equations determining the quantum states of the transverse motion of relativistic electrons, positrons, and x-ray photons in a superlattice consisting of nanotubes is formulated, and methods for solving this system are developed. Calculations of the soft x-ray Bragg reflection coefficients of a superlattice are performed in the two-wave approximation of the dynamical theory of diffraction. 相似文献
10.
V. Ya. Demikhovskii A. A. Kayakin E. V. Frolova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(4):596-603
The quantum states of a two-dimensional electron gas with spin-orbit coupling located in the periodic potential of a lateral-surface superlattice are studied. The spin-split energy bands and the distribution of spin projections in the Brillouin zone are constructed. Bloch oscillations accompanied by spin precession in superlattices with spin-orbit coupling located in a constant electric field are studied. 相似文献
11.
We investigate the efficiency of electrical manipulation in a two-dimensional topological insulator by inspecting the electronic states of a lateral electrical potential superlattice in the system. The spatial distribution of the electron density in the system can be tuned by changing the strength of the externally applied lateral electrical superlattice potential. This provides us the information about how efficiently one can manipulate the electron motion inside a two-dimensional topo- logical insulator. Such information is important in designing electronic devices, e.g., an electric field effect transistor made of the topological insulator. The electronic states under various conditions are examined carefully. It is found that the dispersion of the mini-band and the electron distribution in the potential well region both display an oscillatory behavior as the potential strength of the lateral superlattice increases. The probability of finding an electron in the potential well region can be larger or smaller than the average as the potential strength varies. These features can be attributed to the coupled multiple-band nature of the topological insulator. In addition, it is also found that these behaviors are not sensitive to the gap parameter of the two-dimensional topological insulator model. Our study suggests that the electron density manipulation via electrical gating in a two-dimensional topological insulator is less effective and more delicate than that in a traditional single-band semiconductor. 相似文献
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以单轴应力作用下超晶格量子阱应变能带理论为基础,采用电子反射与干涉方法,研究了单轴应力对超晶格能带的影响,推导了单轴应力与超晶格导带子能级的定量关系。以GaAs-AlGaAs-GaAs为例,具体计算了导带中子能级对应力的依赖关系,进而给出了单轴应力对n型AlGaAs-GaAs量子阱红外探测器(QWIP)吸收波长的影响。计算结果表明,随着单轴压应力的增大,量子阱红外探测器的吸收波长表现出较明显的变化。当单轴压力增大到1.3GPa,量子阱红外探测器的吸收峰值移动了将近1.1μm,并且基本与应力呈线性关系。量子阱红外探测器吸收波长连续可调范围5.57~4.46μm。 相似文献
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A quantum superlattice with axial symmetry, a heterostructure in which two semiconductor materials in the form of coaxial
wires with a nanosize cross section are in contact with one another and form a periodic structure in the radial direction,
is studied. It is shown that the electron energy spectrum consists of alternating allowed and forbidden bands. The electron
dispersion law is studied for different values of the period of the potential, thicknesses of the semiconductor layers, and
radius of the inner crystal of the system. It is shown that the coherent electron effective mass of the quantum superlattice
is a tensor: The longitudinal component is close in value to the electron effective mass of the semiconductor material characterizing
the quantum well of the superlattice and the radial component depends strongly on the period of the potential, the thicknesses
of the coaxial semiconductor layers, and the core radius of the heterosystem, taking on positive or negative values in different
allowed bands.
Fiz. Tverd. Tela (St. Petersburg) 40, 557–561 (March 1998) 相似文献
15.
《Superlattices and Microstructures》1987,3(2):147-152
A new superlattice device concept which provides for high energy injection of electrons into a semiconductor layer is presented. The device is based on resonant tunneling of electrons between adjacent aligned quantum well levels in a variably spaced superlattice structure. By a judicial choice of well and barrier widths the energy levels under reverse bias become aligned such that resonant tunneling of electrons through the structure can occur. Thus, electrons are injected into a semiconductor layer at an energy corresponding to the energy of the first subband in the last quantum well. This structure has significant advantages over the conventional method of producing hot electrons in that a nearly monoenergetic high-energy electron distribution is created at low reverse bias and with high efficiency, since energy loss to phonons is inhibited as a consequence of the channeling of electrons through a narrow band of quantum states. Applications of the VSSEF structure to avalanche photodiodes, IMPATT diodes and electroluminescent devices are discussed. 相似文献
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A calculation of relaxation time for (i) electron–electron scattering in a modulation-doped superlattice of type-I and (ii) electron–electron, hole–hole and electron–hole scattering processes in a compositional superlattice of type-II has been performed, using Fermi's golden rule. As compared to a two-dimensional electron gas system, both intralayer and interlayer interactions, between charge carriers in a superlattice, contribute to relaxation time. It is found that scattering processes at all possible value of momentum transfer contribute to relaxation time, for a given value of temperature and carrier density. We further find interlayer interactions in a superlattice make a significant contribution to relaxation time. Relaxation time is found to decrease on increasing temperature, carrier density and single particle energy, in a superlattice. The computed relaxation time for an electron (hole) in a superlattice enhances on increasing the width of layer consisting of electrons (holes). The electron–hole (hole–electron) scattering process in a type-II superlattice yields maximum contribution to the relaxation time when a hole layer lies exactly in between two consecutive electron layers. 相似文献
18.
采用有机金属化学气相沉积技术在Si(111)衬底上生长蓝光多量子阱发光二极管(LED) 结构, 通过在量子阱下方分别插入两组不同厚度的InGaN/GaN超晶格, 比较了超晶格厚度对LED光电性能的影响. 结果显示: 随超晶格厚度增加, 样品的反向漏电流加剧; 300 K下电致发光仪测得随着电流增加, LED发光光谱峰值的蓝移量随超晶格厚度增加而减少, 但不同超晶格厚度的两个样品在300 K下的电致发光强度几乎无差异. 结合高分辨X射线衍射仪、扫描电子显微镜、透射电子显微镜对样品的位错密度和V形坑特征分析, 明确了两样品反向漏电流产生巨大差异的原因是由于超晶格厚度大的样品具有更大的V形坑和V形坑密度, 而V形坑可作为载流子的优先通道, 使超晶格更厚的样品反向漏电流加剧. 通过对样品非对称(105)面附近的X射线衍射倒易空间图分析, 算得超晶格厚度大的样品其InGaN量子阱在GaN上的弛豫度也大, 即超晶格厚度增加有利于减小InGaN量子阱所受的应力. 综合以上影响LED发光效率的消长因素, 导致两样品最终的发光强度相近. 相似文献
19.
Pilkyung Moon J. D. Lee S. K. Ha E. H. Lee W. J. Choi J. D. Song J. S. Kim L. S. Dang 《固体物理学:研究快报》2012,6(11):445-447
We fabricated GaAs/AlGaAs quantum dots by droplet epitaxy, and obtained the geometries of the dots by scanning transmission electron microscopy. Post‐growth thermal annealing is essential for the optical activation of quantum dots grown by droplet epitaxy. We measured the emission energy shifts of the dots and the underlying superlattice by post‐ growth thermal annealing, and specified the emission from dots by selectively etching the structure down to a low layer of quantum dots. We studied the influence of the degree of annealing on the optical properties of the dots from the peak shifts of the superlattice, since the superlattice has a uniform and well‐defined geometry. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献