Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Flat bands in Weaire-Thorpe model and silicene   In order to analytically capture and identify peculiarities in the electronic
structure of silicene, Weaire-Thorpe(WT) model, a standard model for treating
three-dimensional (3D) silicon, is applied to silicene with the buckled 2D
structure. In the original WT model for four hybridized $sp^3$ orbitals on each
atom along with inter-atom hopping, the band structure can be systematically
examined in 3D, where flat (dispersionless) bands exist as well. For examining
silicene, here we re-formulate the WT model in terms of the overlapping
molecular-orbital (MO) method which enables us to describe flat bands away from
the electron-holesymmetric point. The overlapping MO formalism indeed enables
us to reveal an important difference: while in 3D the dipersive bands with
cones are sandwiched by doubly-degenerate flat bands, in 2D the dipersive bands
with cones are sandwiched by triply-degenerate and non-degenerate (nearly) flat
bands, which is consistent with the original band calculation by Takeda and
Shiraishi. Thus emerges a picture for why the whole band structure of silicene
comprises a pair of dispersive bands with Dirac cones with each of the band
touching a nearly flat (narrow) band at $\Gamma$. We can also recognize that,
for band engineering, the bonds perpendicular to the atomic plane are crucial,
and that a ferromagnetism or structural instabilities are expected if we can
shift the chemical potential close to the flat bands.

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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio