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GaxIn1-xAs/GaInAsP应变量子阱结构能带的计算 总被引:1,自引:0,他引:1
对含有Luttinger-Kohn哈密顿量的有效质量方程,利用S.L.Chuang提出的传递矩阵法,计算了量子阱中不同Ga组分的GaxIn1-xAs/GaInAsP应变量子阱结构的能带,该结构可被选作980nm光通信泵浦激光器的有源层,研究还得到了GaxIn1-xAs/GaInAsP双应变量子阱结构中电子和空穴的能级以及能级的色散关系。 相似文献
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调制掺杂Al0.27Ga0.73As/GaAs多量子阱结构的光致发光 总被引:2,自引:0,他引:2
在调制掺杂(Si)Al0.27Ga0.73As/GaAs多量子阱结构的光致发光谱中,观测到一个强发光峰及多个低能弱发光峰.强发光峰是量子阱中基态电子与重空穴复合,即激子复合形成的,其低温发光线形可用Voigt函数拟合.低能弱峰是势垒层Al0.27Ga0.73As中DX中心能级上的电子跃迁到SiAs原子而引起,由此确定DX中心有四个能级,其激活能分别为0.35、037、0.39、0.41eV 相似文献
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采用密度泛函理论研究了氧等离子体改性前后的(8,0)碳纳米管的性能,比较了改性前后结合能、能带结构及态密度之间的差异,结果表明改性后碳管的结合能变小,其表面的分散性提高,从而可以稳定存在。另外,尽管碳管的能隙Eg非常小,但其价带顶和导带底均未穿过费米能级,验证了(8,0)碳纳米管是半导体管的理论。改性后碳纳米管的几何结构受到羟基和羧基的影响很大,横截面C-C间距增大,比表面积增加;同时,羟基和羧基使得费米能Ef以及费米能级上的态密度明显增大,而且羧基的作用更显著,这表明氧等离子体增强了碳纳米管的化学活性,是一种有效的改性方法。 相似文献
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介绍了采用金属有机化学气相沉积方法制备的单结GaAs量子阱太阳能电池.X射线双晶衍射表明电池中的材料缺陷较少,具有良好结晶质量与周期性.光谱响应实验表明量子阱结构的引入可以扩展吸收光谱.与无量子阱结构的电池相比,量子阱电池增加了输出电流,但同时也带来了开路电压的下降.量子阱电池在长波范围内短路电流明显增加,使得量子阱电池可以代替三结电池中的中间电池,优化电池结构设计,提高三结电池的转换效率. 相似文献
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文章在费米子平均占据数受限的情况下 ,利用费米型量子高斯加性噪声的球谐函数展开方法 ,给出单模费米子在一般费米量子加性信道上传输经典信息的经典容量 相似文献
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Xiu F He L Wang Y Cheng L Chang LT Lang M Huang G Kou X Zhou Y Jiang X Chen Z Zou J Shailos A Wang KL 《Nature nanotechnology》2011,6(4):216-221
Topological insulators display unique properties, such as the quantum spin Hall effect, because time-reversal symmetry allows charges and spins to propagate along the edge or surface of the topological insulator without scattering. However, the direct manipulation of these edge/surface states is difficult because they are significantly outnumbered by bulk carriers. Here, we report experimental evidence for the modulation of these surface states by using a gate voltage to control quantum oscillations in Bi(2)Te(3) nanoribbons. Surface conduction can be significantly enhanced by the gate voltage, with the mobility and Fermi velocity reaching values as high as ~5,800?cm(2)?V(-1)?s(-1) and ~3.7?×?10(5)?m?s(-1), respectively, with up to ~51% of the total conductance being due to the surface states. We also report the first observation of h/2e periodic oscillations, suggesting the presence of time-reversed paths with the same relative zero phase at the interference point. The high surface conduction and ability to manipulate the surface states demonstrated here could lead to new applications in nanoelectronics and spintronics. 相似文献
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We report density functional theory analysis of the electronic and quantum transport properties of Bi(2)Se(3) topological insulator, focusing on the helical surface states at the Fermi level E(F). The calculated Dirac point and the tilt angle of the electron spin in the helical states are compared quantitatively with the experimental data. The calculated conductance near E(F) shows a V-shaped spectrum, consistent with STM measurements. The spins in the helical states at E(F) not only tilts out of the two-dimensional plane, they also oscillate with a 3-fold symmetry going around the two-dimensional Brillouin zone. The helical states penetrate into the material bulk, where the first quintuple layer contributes 70% of the helical wave functions. 相似文献
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J. P. F. LeBlanc J. P. Carbotte 《Journal of Superconductivity and Novel Magnetism》2011,24(7):2053-2063
The phenomenological Green’s function developed in the works of Yang, Rice, and Zhang has been very successful in understanding
many of the anomalous superconducting properties of the deeply underdoped cuprates. It is based on considerations of the resonating
valence bond spin liquid approximation and is designed to describe the underdoped regime of the cuprates. Here, we emphasize
the region of doping, x, just below the quantum critical point at which the pseudogap develops. In addition to Luttinger hole pockets centered around
the nodal direction, there are electron pockets near the antinodes which are connected to the hole pockets by gapped bridging
contours. We determine the contours of nearest approach as would be measured in angular resolved photoemission experiments
and emphasize signatures of the Fermi surface reconstruction from the large Fermi contour of Fermi liquid theory (which contains
1+x hole states) to the Luttinger pocket (which contains x hole states). We find that the quasiparticle effective mass renormalization increases strongly toward the edge of the Luttinger
pockets beyond which it diverges. 相似文献
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I.V Altukhov M.S Kagan V.P Sinis S.G Thomas K.L Wang A Blom M.O Odnoblyudov 《Thin solid films》2000,380(1-2):218-220
Lateral conductivity and magnetotransport measurements were performed with SiGe single quantum well (QW) structures doped with boron in the QW. The conductivity at low temperatures (T) is shown to be due to hopping over B centers while at higher T, it is due to two-stage excitation: thermal activation of holes from the ground to strain-split B states are followed by hole tunneling into the valence band. The tunneling is due to a potential drop across the QW which is due to hole capture at surface states of the Si cap layer making the surface charged. The external potential applied across the QW essentially changes the lateral conductivity as well as the activation energy. The calculations of band profile, free carrier concentration in the QW and acceptor population, as well as an effect on the transverse electric field were carried out taking into account the charging of surface states. 相似文献
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Galanakis D Khatami E Mikelsons K Macridin A Moreno J Browne DA Jarrell M 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1941):1670-1686
Transport measurements on the cuprates suggest the presence of a quantum critical point (QCP) hiding underneath the superconducting dome near optimal hole doping. We provide numerical evidence in support of this scenario via a dynamical cluster quantum Monte Carlo study of the extended two-dimensional Hubbard model. Single-particle quantities, such as the spectral function, the quasi-particle weight and the entropy, display a crossover between two distinct ground states: a Fermi liquid at low filling and a non-Fermi liquid with a pseudo-gap at high filling. Both states are found to cross over to a marginal Fermi-liquid state at higher temperatures. For finite next-nearest-neighbour hopping t', we find a classical critical point at temperature T(c). This classical critical point is found to be associated with a phase-separation transition between a compressible Mott gas and an incompressible Mott liquid corresponding to the Fermi liquid and the pseudo-gap state, respectively. Since the critical temperature T(c) extrapolates to zero as t' vanishes, we conclude that a QCP connects the Fermi liquid to the pseudo-gap region, and that the marginal Fermi-liquid behaviour in its vicinity is the analogue of the supercritical region in the liquid-gas transition. 相似文献
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We investigated the conducting properties of functionalized single wall nanotubes (SWNTs) with a finite addend concentration. Robust differences are found between monovalent and divalent additions. For the former a small number of addends can significantly disrupt the ballistic conductance of nanotubes near the Fermi level. As the concentration increases the conductance decreases rapidly and approaches zero at addend to C ratio around 25%. In contrast, divalent functionalizations have weak effects, and the nanotube quantum conductance remains above 50% of that of a perfect tube even for an addend concentration as large as 25%. These differences can be attributed to the formation of impurity states near the Fermi level for monovalent additions, while divalent addends create impurity states far away from the Fermi level. 相似文献
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Sebastian SE Harrison N Lonzarich GG 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1941):1687-1711
We review recent progress in the study of quantum oscillations as a tool for uniquely probing low-energy electronic excitations in high-T(c) cuprate superconductors. Quantum oscillations in the underdoped cuprates reveal that a close correspondence with Landau Fermi-liquid behaviour persists in the accessed regions of the phase diagram, where small pockets are observed. Quantum oscillation results are viewed in the context of momentum-resolved probes such as photoemission, and evidence examined from complementary experiments for potential explanations for the transformation from a large Fermi surface into small sections. Indications from quantum oscillation measurements of a low-energy Fermi surface instability at low dopings under the superconducting dome at the metal-insulator transition are reviewed, and potential implications for enhanced superconducting temperatures are discussed. 相似文献
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We present a theoretical study of the spectral and the spin-dependent transport properties of a few electron semiconductor parallel double quantum dot (DQD) in the presence of local induced Zeeman splittings at the quantum dots. Working in an extended Hubbard model and treating the coupled QD as a single coherent system, the linear response spin-dependent conductance is calculated at low temperatures. We analyze the conditions such that the device would operate as a bipolar spin filter by only varying the incident electron Fermi energy from non-magnetic leads. 相似文献
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Yoshiyuki Shirakawa Naoto Ii Mikio Yoshida Ryusuke Takashima Atsuko Shimosaka Jusuke Hidaka 《Advanced Powder Technology》2010,21(4):500-505
Calculation of contact charging at metal/polymer interfaces were performed by a quantum chemical method (DV-Xa). In the calculation, model clusters with dangling bonds were used. The model clusters showed surface states in the density of states (DOS), the electron transfer occurred at the contact interfaces between polymer and Al. Then, 0.3 nm was a reasonable value as the contact distance in the present simulation.Contact electrifications between PTFE and six metals, such as Pt, Au, Cu, Al, Pb and Ca were simulated. The charge transferred from the metal to PTFE depended on the work function of the metals, and had a gap in range of 4.25–4.28 eV. According to the gap of metals were classified into two groups. If Fermi level of a metal is lower than the lowest unoccupied molecular orbital (LUMO) level of PTFE, the electrons of the metal transfer to the surface state (interface state). Electrons in the other metals with a higher Fermi level move into the conduction band of PTFE. 相似文献