Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sweeping Plasma Frequency of Terahertz Surface Plasmon Polaritons with
  Graphene   Plasma frequency is the spectral boundary for low-loss propagation and
evanescent decay of surface plasmon polariton (SPP) waves, which corresponds to
a high cut-off phenomenon and is typically utilized for identifying SPPs. At
terahertz (THz) frequencies, a metal line with periodic metallic grooves can
mimic the conventional optical SPPs, which is referred to as designer SPPs.
Theoretically, the plasma frequency of THz SPPs decreases as the groove depth
increases. Here, by replacing the metallic grooves with graphene sheets,
dynamically sweeping SPP plasma frequency is demonstrated for the first time.
The metal-graphene hybrid structure comprises a metal line with periodic
graphene grooves, a thin-layer ion gel for gating graphene, and metallic tips
for uniforming gate field. As the chemical potential changes, the average
conductivity of graphene is modulated so that the effective depth of the
graphene grooves changes, which sweeps the plasma frequency of THz SPPs
consequently. Both simulated and experimental data demonstrate a red shift of
plasma frequency from 195 to 180 GHz at a low bias from -0.5 to 0.5 V. The
proposed structure reveals a novel approach to control the on/off status of SPP
propagation in the THz range.

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The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin