Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single-layer and bilayer graphene superlattices: collimation, additional
  Dirac points and Dirac lines   We review the energy spectrum and transport properties of several types of
one- dimensional superlattices (SLs) on single-layer and bilayer graphene. In
single-layer graphene, for certain SL parameters an electron beam incident on a
SL is highly collimated. On the other hand there are extra Dirac points
generated for other SL parameters. Using rectangular barriers allows us to find
analytic expressions for the location of new Dirac points in the spectrum and
for the renormalization of the electron velocities. The influence of these
extra Dirac points on the conductivity is investigated. In the limit of
{\delta}-function barriers, the transmission T through, conductance G of a
finite number of barriers as well as the energy spectra of SLs are periodic
functions of the dimensionless strength P of the barriers, P{\delta}(x) ~ V
(x). For a Kronig-Penney SL with alternating sign of the height of the barriers
the Dirac point becomes a Dirac line for P = {\pi}/2 + n{\pi} with n an
integer. In bilayer graphene, with an appropriate bias applied to the barriers
and wells, we show that several new types of SLs are produced and two of them
are similar to type I and type II semiconductor SLs. Similar as in single-layer
graphene extra "Dirac" points are found. Non-ballistic transport is also
considered.

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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ph
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The categories of this paper are: physics
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int