Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metal-insulator transition in quarter-filled Hubbard model on triangular
  lattice and its implication for the physics of $Na_{0.5}CoO_{2}$   The metal-insulator transition of the quarter-filled Hubbard model on
triangular lattice is studied at the mean field level. We find a quasi-one
dimensional metallic state with a collinear magnetic order competes closely
with an insulating state with a non-coplanar magnetic order for both signs of
the hopping integral $t$. In the strong correlation regime($U/|t|\gg1$), it is
found that the metal-insulator transition of the system occurs in a two-step
manner. The quasi-one dimensional metallic state with collinear magnetic order
is found to be stable in an intermediate temperature region between the
paramagnetic metallic phase and the non-coplanar insulating phase. Possible
relevance of these results to the physics of metal-insulator transition in
$Na_{0.5}CoO_{2}$ is discussed.

15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess