Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rung-singlet charge-ordering in alpha'-NaV2O5   We show that the proposed zig--zag charge--ordering model for alpha'--NaV2O5
is incompatible with a single transition that induces both charge--ordering and
spin gap. We introduce a two--band model for alpha'--NaV2O5 within which the
simultaneous charge--spin order transition is driven principally by
electron-phonon interactions. The spin gap is due to the formation of local
dimers, thus explaining the weak magnetic effect on this transition.

12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga