1,095 research outputs found
Local Energy Gap in Deformed Carbon Nanotubes
The effects of graphite surface geometrical deformation on the dynamics of
conducting electrons are investigated theoretically. The analysis is performed
within the framework of a deformation-induced gauge field and corresponding
deformation-induced magnetic field. It is shown that the latter gives a local
energy gap along the axis of a deformed nanotube. We compare our energy gap
results with experimental data on energy gaps in nanotubes and peapods. We also
discuss the mixing of two Fermi points and construct a general model of low
energy dynamics, including a short-range deformation of the graphite sheet.
This model is equivalent to the Weyl equation in {\it U}(1) Abelian and {\it
SU}(2) non-Abelian deformation-induced gauge fields.Comment: 18 pages, 4 figures, corrected typos, added references, improved
presentation (v4, published version
Role of Interlayer Coupling on the Evolution of Band Edges in Few-Layer Phosphorene
Using first-principles calculations, we have investigated the evolution of
band-edges in few-layer phosphorene as a function of the number of P layers.
Our results predict that monolayer phosphorene is an indirect band gap
semiconductor and its valence band edge is extremely sensitive to strain. Its
band gap could undergo an indirect-to-direct transition under a lattice
expansion as small as 1% along zigzag direction. A semi-empirical interlayer
coupling model is proposed, which can well reproduce the evolution of valence
band-edges obtained by first-principles calculations. We conclude that the
interlayer coupling plays a dominated role in the evolution of the band-edges
via decreasing both band gap and carrier effective masses with the increase of
phosphorene thickness. A scrutiny of the orbital-decomposed band structure
provides a better understanding of the upward shift of valence band maximum
surpassing that of conduction band minimum.Comment: 25 pages, 9 figure
Statics and dynamics of phase segregation in multicomponent fermion gas
We investigate the statics and dynamics of spatial phase segregation process
of a mixture of fermion atoms in a harmonic trap using the density functional
theory. The kinetic energy of the fermion gas is written in terms of the
density and its gradients. Several cases have been studied by neglecting the
gradient terms (the Thomas-Fermi limit) which are then compared with the
Monte-Carlo results using the full gradient corrected kinetic energy. A linear
instability analysis has been performed using the random-phase approximation.
Near the onset of instability, the fastest unstable mode for spinodal
decomposition is found to occur at . However, in the strong coupling
limit, many more modes with decay with comparable time scales.Comment: 14 figure
First-principles study of phenyl ethylene oligomers as current-switch
We use a self-consistent method to study the distinct current-switch of
-amino-4-ethynylphenyl-4'-ethynylphenyl-5'-nitro-1-benzenethiol, from
the first-principles calculations. The numerical results are in accord with the
early experiment [Reed et al., Sci. Am. \textbf{282}, 86 (2000)]. To further
investigate the transport mechanism, we calculate the switching behavior of
p-terphenyl with the rotations of the middle ring as well. We also study the
effect of hydrogen atom substituting one ending sulfur atom on the transport
and find that the asymmetry of I-V curves appears and the switch effect still
lies in both the positive and negative bias range.Comment: 6 pages, 6 figure
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