Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Scanning Tunneling Microscopy of Defect States in the Semiconductor
  Bi$_2$Se$_3$   Scanning tunneling spectroscopy images of Bi$_2$Se$_3$ doped with excess Bi
reveal electronic defect states with a striking shape resembling clover leaves.
With a simple tight-binding model we show that the geometry of the defect
states in Bi$_2$Se$_3$ can be directly related to the position of the
originating impurities. Only the Bi defects at the Se sites five atomic layers
below the surface are experimentally observed. We show that this effect can be
explained by the interplay of defect and surface electronic structure.

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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn