  In a recent Letter, Hassan and S\'en\'echal [1] discussed the existence of a
spin-liquid phase of the half-filled Hubbard model on the honeycomb lattice.
Using schemes, such as the variational cluster approximation (VCA) and the
cluster dynamical mean field theory (CDMFT) in combination with exact
diagonalization (ED), they argued that a single bath orbital per site of the
six-atom unit cell is insufficient and leads to the erroneous conclusion that
the system is gapped for all nonzero values of the onsite Coulomb interaction
$U$. In contrast, we point out here that, in the case of the honeycomb lattice,
six bath levels per six-site unit cell are perfectly adequate for the
description of short-range correlations. Instead, we demonstrate that it is the
violation of long-range translation symmetry inherent in CDMFT-like schemes
which opens a gap at Dirac points. The gap found at small $U$ therefore does
not correspond to a Mott gap. As a result, present CDMFT schemes are not
suitable for the identification of a spin-liquid phase on the honeycomb
lattice. [1] S.R. Hassan and D. S\'en\'echal, Phys. Rev. Lett. 110, 096402
(2013).

Strongly Correlated Electrons