Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bulk and surface low-energy excitations in YBa2Cu3O7-d studied by
  high-resolution angle-resolved photoemission spectroscopy   We have performed high-resolution angle-resolved photoemission spectroscopy
on YBa2Cu3O7-delta (Y123; delta = 0.06; Tc = 92 K). By accurately determining
the Fermi surface and energy band dispersion, we solve long-standing
controversial issues as to the anomalous electronic states of Y-based high-Tc
cuprates. We unambiguously identified surface-bilayer-derived bonding and
antibonding bands, together with their bulk counterparts. The surface bands are
highly overdoped (hole concentration x = 0.29), showing no evidence for the gap
opening or the dispersion anomaly in the antinodal region, while the bulk bands
show a clear dx2-y2-wave superconducting gap and the Bogoliubov
quasiparticle-like behavior with a characteristic energy scale of 50-60 meV
indicative of a strong electron-boson coupling in the superconducting state.
All these results suggest that the metallic and superconducting states coexist
at the adjacent bilayer of Y123 surface.

31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin