Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unveiling the Atomic and Electronic Structure at the Surface of the
  Parent Pnictide SrFe2As2   The parent compounds of the recently discovered iron-arsenic (pnictide) high
temperature superconductors transition into an intriguing spin density wave
(SDW) phase at low temperatures. Progress in understanding this SDW state has
been complicated by a complex band structure and by the fact that the spin,
electronic, and structural degrees of freedom are closely intertwined in these
compounds. Scanning tunneling microscopy (STM) measurements have added to this
complexity by revealing different topographies with no consensus on the surface
structure. In this paper, we use a combination of high-resolution STM imaging
and spectroscopy, and low energy electron diffraction (LEED) to determine the
atomic and electronic structure of the parent pnictide SrFe2As2. Our data
present a compelling picture of the existence of two coexisting homotopic
structures on the surface. Based on this, we construct a simple model for the
surface, which offers an explanation of the two classes of topographies seen by
STM. STM spectroscopy shows that while the high energy density of states (DOS)
profile is consistent with the Fe 3d and As 4p-electrons predicted by LDA it is
in better agreement with calculations that include electron correlations beyond
LDA. Importantly, we find a gap of ~15 meV in the low energy density of states
on both structures which may be linked with the SDW or the observed surface
reconstruction.

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The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph