Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct observation of charge order in triangular metallic AgNiO2 by
  single-crystal resonant X-ray scattering   We report resonant X-ray scattering measurements on the orbitally-degenerate
triangular metallic antiferromagnet 2H-AgNiO2 to probe the spontaneous
transition to a triple-cell superstructure at temperatures below 365 K. We
observe a strong resonant enhancement of the supercell reflections through the
Ni K-edge. The empirically extracted K-edge shift between the
crystallographically-distinct Ni sites of 2.5(3) eV is much larger than the
value expected from the shift in final states, and implies a core-level shift
of ~1 eV, thus providing direct evidence for the onset of spontaneous honeycomb
charge order in the triangular Ni layers. We also provide band-structure
calculations that explain quantitatively the observed edge shifts in terms of
changes in the Ni electronic energy levels due to charge order and
hybridization with the surrounding oxygens.

15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph