共查询到20条相似文献,搜索用时 109 毫秒
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《核聚变与等离子体物理》1987,(4)
第1期一种聚变反应堆装置的新概念··········1········……蔡诗东沈解伍陈雁萍徐民健陈允明宋院旭金山康向东金山郭世宠俞雪华汪诗金康向东王乃彦宋院旭王乃彦李有宜荣福瑞刘万东柯孚久周玉美张淳元强流相对论性电子束在低压中性气体中传输的研究一王效军王淦昌强流相对论性电子束在真空漂移管中的传输·················……王效军HL一1装置长脉冲放电的初步分析KT一5托卡马克装置及其初步实验王淦昌(16)苏远(20)……闻一之万树德 韩申生离子束一等离子体系统的电磁不稳定性··,··……场反向位形中… 相似文献
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《光谱学与光谱分析》1987,(6)
第7卷第1期1957年2月BeA12O4:Cr3+系统中ZE~夺A:跃迁谱线随压力的变化 ..·“·“.”·“·“·“·”·..·”·”·“一刘竟青唐沃明王彦云贾帷义商玉生何寿安(l)激光饱和吸收法研究碰撞速率过程·········“·····”·“············一‘“·“·”·”一‘一黄元网(5)吸附在滤纸上的荧光样品量子效率侧量“·”·“·”·“·”·“一…何永安宋胭王银屏(9)发光光谱在多环芳烃分析中的进展一‘···“·”·”·······一~王连生周爱和江善根(12)用格林函数讨论高分子中杂质的红外吸收···“···… 相似文献
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We consider a gas of noninteracting spinless fermions in a rotating optical lattice and calculate the density profile of the gas in an external confinement potential. The density profile exhibits distinct plateaus, which correspond to gaps in the single particle spectrum known as the Hofstadter butterfly. The plateaus result from insulating behavior whenever the Fermi energy lies within a gap. We discuss the necessary conditions to realize the Hofstadter insulator in a cold atom setup and show how the quantized Hall conductance can be measured from density profiles using the Streda formula. 相似文献
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Graphene with a periodic array of defects in a homogeneous magnetic field is considered. We suggest a solvable model of the system. Three types of defects are studied. The spectra of the Hamiltonians have the Hofstadter butterfly type. The comparison of the spectrum for pure graphene and one for the system having defects of each type is made. 相似文献
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Indubala I. Satija 《The European physical journal. Special topics》2016,225(13-14):2533-2547
This paper unveils a mapping between a quantum fractal that describes a physical phenomena, and an abstract geometrical fractal. The quantum fractal is the Hofstadter butterfly discovered in 1976 in an iconic condensed matter problem of electrons moving in a two-dimensional lattice in a transverse magnetic field. The geometric fractal is the integer Apollonian gasket characterized in terms of a 300 BC problem of mutually tangent circles. Both of these fractals are made up of integers. In the Hofstadter butterfly, these integers encode the topological quantum numbers of quantum Hall conductivity. In the Apollonian gaskets an infinite number of mutually tangent circles are nested inside each other, where each circle has integer curvature. The mapping between these two fractals reveals a hidden D 3 symmetry embedded in the kaleidoscopic images that describe the asymptotic scaling properties of the butterfly. This paper also serves as a mini review of these fractals, emphasizing their hierarchical aspects in terms of Farey fractions. 相似文献
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The Hall conductivity and the localization length are calculated for weakly modulated two-dimensional systems within the lowest Landau level approximation. We find that the fractal character of the Hofstadter butterfly is reflected on the coincidence in the localization and the Hall conductivity among a series of fluxes φ+2n with integers n. 相似文献
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We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes- Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter's butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter's butterfly spectrum. 相似文献
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We demonstrate how to create artificial external non-Abelian gauge potentials acting on cold atoms in optical lattices. The method employs atoms with k internal states, and laser assisted state sensitive tunneling, described by unitary k x k matrices. The single-particle dynamics in the case of intense U2 vector potentials lead to a generalized Hofstadter butterfly spectrum which shows a complex mothlike structure. We discuss the possibility to realize non-Abelian interferometry (Aharonov-Bohm effect) and to study many-body dynamics of ultracold matter in external lattice gauge fields. 相似文献
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We study the effect of Rashba spin-orbit coupling on the Hofstadter spectrum of a two-dimensional tight-binding electron system in a perpendicular magnetic field. We obtain the generalized coupled Harper spin-dependent equations which include the Rashba spin-orbit interaction and solve for the energy spectrum and spin polarization. We investigate the effect of spin-orbit coupling on the fractal energy spectrum and the spin polarization for some characteristic states as a function of the magnetic flux α and the spin-orbit coupling parameter. We characterize the complexity of the fractal geometry of the spin-dependent Hofstadter butterfly with the correlation dimension and show that it grows quadratically with the amplitude of the spin-orbit coupling. We study some ground state properties and the spin polarization shows a fractal-like behavior as a function of α, which is demonstrated with the exponent close to unity of the decaying power spectrum of the spin polarization. Some degree of spin localization or distribution around +1 or -1, for small spin-orbit coupling, is found with the determination of the entropy function as a function of the spin-orbit coupling. The excited states show a more extended (uniform) distribution of spin states. 相似文献
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The electronic properties of a square lattice under an applied perpendicular magnetic field in the presence of impurities or vacancies are investigated by the tight-binding method including up to second nearest neighbor interactions. These imperfections result in new gaps and bands in the Hofstadter butterfly even when the second order interactions break the bipartite symmetry. In addition, the whole spectrum of the Hall conduction is obtained by the Kubo formula for the corresponding cases. The results are in accordance with the Thouless-Kohmoto-Nightingale-den Nijs integers when the Fermi energy lies in an energy gap. We find that the states due to the vacancies or impurities with small hopping constants are highly localized and do not contribute to the Hall conduction. However, the impurities with high hopping constants result in new Hall plateaus with constant conduction of σ(xy)?=±?e(2)/h, since high hopping constants increase the probability of an electron contributing to the conduction. 相似文献
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We study the Landau problem on the -deformed two-torus and use well-known projective modules to obtain perturbed energy spectra. For a strong magnetic field B, the problem can be restricted to one particular Landau level. First we represent generators of the algebra of the noncommutative torus T
2 as finite-dimensional matrices. A second approach leads to a reducible representation with a -dependent center. For a simple periodic potential, the rational part of the Hofstadter butterfly spectrum is obtained. 相似文献