Abstract
The spin-12 Heisenberg antiferromagnet on the distorted honeycomb (DHC) lattice is studied by means of the tensor renormalization-group method. It is unveiled that the system has a quantum phase transition of second order between the gapped quantum dimer phase and a collinear Néel phase at the critical point of coupling ratio c0.54, where the quantum critical exponents 0.69(2) and 1.363(8) are obtained. The quantum criticality is found to fall into the O(3) universality class. A ground-state phase diagram in the field-coupling ratio plane is proposed, where the phases such as the dimer, semiclassical Néel, and polarized phases are identified. A link between the present spin system to the boson Hubbard model on the DHC lattice is also discussed.