排序方式: 共有49条查询结果,搜索用时 15 毫秒
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In terms of a single-π orbital model, an analytical expression of the lowest-lying conduction-band and the highestlying valence-band is derived for single wall carbon nanotubes under both the uniaxial and torsional strains. We observe not only semiconductor-metal transitions in primary metallic tubes, but also insulator-metal transitions 相似文献
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Yandong Guo 《中国物理 B》2022,31(12):127201-127201
Controlling the spin transport at the single-molecule level, especially without the use of ferromagnetic contacts, becomes a focus of research in spintronics. Inspired by the progress on atomic-level molecular synthesis, through first-principles calculations, we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups, contacted by atomic carbon chain electrodes. It is found that, by rotating the functional group, the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states. Moreover, the transition between spin-up and spin-down polarized states can also be achieved, operating as a dual-spin filter. Further analysis shows that, it is the spin-dependent shift of density of states, caused by the rotation, that triggers the shift of transmission peaks, and then results in the variation of spin polarization. Such a feature is found to be robust to the length of the nanoflake and the electrode material, showing great application potential. Those findings may throw light on the development of spintronic devices. 相似文献
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基于二阶矩近似反应力场方法构建的全维度势能面研究了氢分子及其同位素分子在钯表面的分解过程.在构建势能面的过程中数据库中只包含了氢分子与钯(111)表面相互作用的相关信息,该势能面在研究氢分子在钯(100)表面上的分解过程中表现出了非常好的可转移性.结果表明,氢分子及其同位素分子在钯(111)与钯(100)表面上的分解系数S0均随着入射能量的增加呈现非单调变化,并且通过固定分子取向的方法发现同核分子(H2、D2和T2)最有利分解取向角为90°,而异核分子(HD、HT和DT)受质心偏移的影响,其最有利分解取向角向大角度偏移. 相似文献
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Magnetotransport in a dual waveguide coupled by a finite barrier: Energy filter and directional coupler
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We propose in this paper that a dual waveguide coupled by a finite
barrier be able to serve as an energy filter under a perpendicular
magnetic field. In the waveguide direction, the conductance exhibits
a periodic square-wave pattern in which the miniband is controlled
by the magnetic and potential modulation. The electrons with
energies in the miniband can completely transfer along one waveguide
while the other electrons undergo filtration. Compared with the
coupled waveguide without magnetic modulation, the structure under
magnetic field is found to be a good directional coupler. By
adjusting the potential barrier and magnetic field, the electrons
input from one port of waveguide can transfer to any other ports. 相似文献
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Ground state properties of a Bose-Einstein condensate confined in an anharmonic external potential
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In light of the interference experiment of Bose-Einstein condensates, we present an anharmonic external potential model to study ground state properties of Bose-Einstein condensates. The ground state energy and the chemical potential have been analytically obtained, which are lower than those in harmonic trap. Additionally, it is found that the anharmonic strength of the external potential has an important effect on density and velocity distributions of the ground state for the Thomas-Fermi model. 相似文献
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Based on a force constant model, we investigated the phonon spectrum and then specific heat of single-walled boron nitride nanotubes. The results show that the frequencies of Raman and infrared active modes decrease with increasing diameter in the low frequency, which is consistent with the results calculated by density functional theory. The fitting formulae for diameter and chirality dependence of specific heat at 300K are given. 相似文献
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