Quantum phase transition, O(3) universality class, and phase diagram of the spin- 1 2 Heisenberg antiferromagnet on a distorted honeycomb lattice: A tensor renormalization-group study

Wei Li, Shou-Shu Gong, Yang Zhao, and Gang Su *
College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049, China
(Received 3 January 2010; revised manuscript received 4 March 2010; published 21 May 2010)



The spin - 1/2 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 αc0.54, where the quantum critical exponents ν≈0.69(2) and γ≈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.