, whereas approximate results are obtained for larger lattices. As an application of the approach, we analyze the scaling of the ground-state entanglement entropy at the quantum critical point of the model. We confirm the presence of a positive additive constant to the area law for half a torus. We also find a logarithmic additive correction to the entropic area law for a square block. The single copy entanglement for half a torus reveals similar corrections to the area law with a further term proportional to

1/L

DOI: 10.1103/physrevb.80.235127

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L\ifmmode\times\else\texttimes\fi{}L

lattice with the topology of a torus. Accurate results are obtained for

L={4,6,8}

1/L

α<1

Rényi entanglement entropies for single-branch cuts obey an area law, as in ground and low-energy states of certain gapped systems.