Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Edge modes in zigzag and armchair ribbons of monolayer MoS$_2$   We explore the electronic structure, orbital character and topological aspect
of a monolayer MoS$_2$ nanoribbon using tight-binding (TB) and low-energy
(${\bm k}\cdot{\bm p} $) models. We obtain a mid-gap edge mode in the zigzag
ribbon of monolayer MoS$_2$, which can be traced back to the topological
properties of the bulk band structure. Monolayer MoS$_2$ can be considered as a
valley Hall insulator. The boundary conditions at armchair edges mix the
valleys on the edges, and a gap is induced in the edge modes. The spin-orbit
coupling in the valence band reduces the hybridization of the bulk states.

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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: physics
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The categories of this paper are: supr-con
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The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org