Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electronic States and Excitation Spectra of Copper Oxides with Ladder
  and/or Chain   Recently the superconductivity has been reported in the copper oxides
(Sr,Ca)$_{14}$Cu$_{24}$O$_{41}$ with ladders and edge-sharing chains under
pressure. In order to understand the mechanism of the superconductivity, it is
crucial to clarify the distribution of self-doped holes. From the analysis of
the optical conductivity by ionic model and exact diagonalization method, we
confirm that with substituting Ca for Sr, the self-doped holes are transferred
from the chains to the ladders. We also examine the electronic states of
edge-sharing chain in a variety of copper oxides, and derive the effective
Hamiltonian. The dependences of the magnetic interactions between Cu ions and
of the hopping energies of the Zhang-Rice singlet on the bond angle of Cu-O-Cu
are discussed.

26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an