Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: N\'eel and Valence-Bond Crystal phases of the Two-Dimensional Heisenberg
  Model on the Checkerboard Lattice   I use an improved version of the two-step density matrix renormalization
group method to study ground-state properties of the 2D Heisenberg model on the
checkerboard lattice. In this version the Hamiltonian is projected on a tensor
product of two-leg ladders instead of chains. This allows investigations of 2D
isotropic models. I show that this method can describe both the magnetically
disordered and ordered phases. The ground-state phases of the checkerboard
model as $J_2$ increases are: (i) N\'eel with $Q=(\pi,\pi)$, (ii) a valence
bond crystal (VBC) of plaquettes, (iii) N\'eel with $Q=(\pi/2,\pi)$, and (iv) a
VBC of crossed dimers. In agreement with previous results, I find that at the
isotropic point $J_2=J_1$, the ground state is made of weakly interacting
plaquettes with a large gap $\Delta \approx 0.67 J_1$ to triplet excitations.

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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-th
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn