Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of unconventional charge density wave at the surface of
  K0.9Mo6O17   We use Angle Resolved Photoemission Spectroscopy (ARPES), Raman spectroscopy,
Low Energy Electron Diffraction (LEED) and x-ray scattering to reveal an
unusual electronically mediated charge density wave (CDW) in K0.9Mo6O17. Not
only does K0.9Mo6O17 lack signatures of electron-phonon coupling, but it also
hosts an extraordinary surface CDW, with TS CDW =220 K nearly twice that of the
bulk CDW, TB CDW =115 K. While the bulk CDW has a BCS-like gap of 12 meV, the
surface gap is ten times larger and well in the strong coupling regime. Strong
coupling behavior combined with the absence of signatures of strong
electron-phonon coupling indicates that the CDW is likely mediated by
electronic interactions enhanced by low dimensionality.

27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc