排序方式: 共有74条查询结果,搜索用时 31 毫秒
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将无反射势阱的Schr?dinger方程作自变量双曲函数变换,可使其转化为associated-Legendre方程。从而得到分别用associated-Legendre多项式和函数表示的束缚态和散射态本征函数,并讨论了散射态的归一化和这种精确本征函数的应用问题。本文给出的解较文献中已有的渐近解或特殊值的解具有一般性。
关键词: 相似文献
43.
Using the equation of motion, we investigate theoretically the dynamical ac conductance of a clean Luttingerliquid quantum wire adiabatically coupled to Fermi liquid electron reservoirs in the presence of short-ranged electron-electron interactions. For a perfect single mode quantum wire, in the limit of zero-ranged interaction we conclude that the static dc conductance of ω → 0 is e^2 /h, which is independent of the electron interactions. While in the dynamical case of ω≠0, the ac conductance oscillates with the amplitude e^2/h and the period which depends on the interaction strength and the driving frequency as well as the position in the wire. 相似文献
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Confined states and spin polarization on a topological insulator thin film modulated by an electric potential
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We study the electronic structure and spin polarization of the surface states of a three-dimensional topological insulator thin film modulated by an electrical potential well. By routinely solving the low-energy surface Dirac equation for the system, we demonstrate that confined surface states exist, in which the electron density is almost localized inside the well and exponentially decayed outside in real space, and that their subband dispersions are quasilinear with respect to the propagating wavevector. Interestingly, the top and bottom surface confined states with the same density distribution have opposite spin polarizations due to the hybridization between the two surfaces. Along with the mathematical analysis, we provide an intuitive, topological understanding of the effect. 相似文献
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Electronic states and spin-filter effect in three-dimensional topological insulator Bi_2Se_3 nanoribbons
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We study the electronic band structure, density distribution, and transport of a Bi_2Se_3 nanoribbon. We find that the density distribution of the surface states is dependent on not only the shape and size of the transverse cross section of the nanoribbon, but also the energy of the electron. We demonstrate that a transverse electric field can eliminate the coupling between surface states on the walls of the nanoribbon, remove the gap of the surface states, and restore the quantum spin Hall effects. In addition, we study the spin-dependent transport property of the surface states transmitting from top and bottom surfaces(x-y plane) to the side surfaces(z-x plane) of a Bi_2Se_3 nanoribbon. We find that transverse electric fields can open two surface channels for spin-up and-down Dirac electrons, and then switch off one channel for the spin-up Dirac electron. Our results may provide a simple way for the design of a spin filter based on topological insulator nanostructures. 相似文献
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The spin-dependent conductance and magnetoresistance ratio
(MRR) for a semiconductor heterostructures consisting of two
magnetic barriers with different height and space have been
investigated by the transfer-matrix method. It is shown that the
splitting of the conductance for parallel and antiparallel
magnetization configurations results in tremendous spin-dependent
MRR, and the maximal MRRs reach 5300\% and 3800\% for the magnetic
barrier spaces W=81.3 and 243.9~nm, respectively. The obtained
spin-filtering transport property of nanostructures with magnetic
barriers may be useful to magnetic-barrier-based spintronics. 相似文献
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提出了一种新型椭圆形百叶窗翅片,采用CFD方法对其阻力特性及传热特性进行了模拟研究,并与传统矩形百叶窗翅片进行比较,分析了雷诺数对两种结构内流体的流动与传热性能的影响,同时对两种结构内流场与温度场的协同性也进行了研究。结果表明:新提出的椭圆形百叶窗翅片与矩形百叶窗翅片相比,阻力因子f降低了16%~20%,传热因子j提高了5%~7%,且雷诺数Re在225.7~451.3范围内,椭圆形翅片综合评价因子j/f1/3比矩形百叶窗翅片的提高了11%~15%,且椭圆形百叶窗翅片的速度与温度场的协同性优于矩形百叶窗翅片,椭圆形百叶窗翅片的综合换热性能高于矩形百叶窗翅片。 相似文献
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采用周期性模型对L型混沌流道内流体流动与传热性能进行数值模拟,并与普通平直流道相对比,分析得到了两种流道内流体流场与温度场分布的细观信息,同时还讨论了不同Re数对混沌流道内流体传热与流动的影响。设计制作了测试流体流动性能的冷模试验装置,采用激光多普勒测速仪对L型混沌流道中流道内特殊点的速度进行测量,并将试验测量结果与数值模拟计算结果进行对比。结果标明:试验测量结果与数值模拟计算结果总体变化趋势基本一致,主流方向上速度相对误差最大为13.8%,在工程允许的误差范围之内,由此验证了数值模拟计算的可靠性。 相似文献
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