Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Beyond the quantum spin liquid concept in frustrated two dimensional
  organic superconductors   The occurrence of antiferromagnetism in kappa-(ET)_2X can be understood
within an effective 1/2-filled band with dimers of ET molecules containing one
hole each. We argue that while this effective model can describe the presence
of antiferromagnetism, a complete description for these materials requires the
correct carrier density of one-half per molecule. For dimerized and strongly
frustrated 1/4-filled lattices we show that a singlet-paired state coexisting
with charge ordering occurs that we have termed the Paired Electron Crystal
(PEC). Here we investigate the 1/4-filled model on a dimerized lattice, showing
regions where AFM, PEC, and the Wigner-crystal occur. We point out the need to
go beyond quantum spin liquid concepts for highly frustrated materials such as
kappa-(ET)_2Cu_2(CN)_3 and beta'-EtMe_3Sb[Pd(dmit)_2]_2 which we believe are
PECs at low temperatures.

22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics