Z2 spin liquid and chiral antiferromagnetic phase in the Hubbard model on a honeycomb lattice

Yuan-Ming Lu and Ying Ran
Phys. Rev. B 84, 024420 – Published 15 July 2011

Abstract

In a Schwinger-fermion representation we classify all 128 possible spin liquids that preserves SU(2) spin-rotational symmetry, honeycomb lattice group symmetry, and time-reversal symmetry. Among them we identify a Z2 spin liquid called the sublattice-pairing state (SPS) as the spin liquid phase discovered in recent numerical study on a honeycomb lattice [Meng et al., Nature (London) 464, 847 (2010)]. Our method provides a systematic way to identify spin liquids close to Mott transition. We also show that the SPS is identical to the zero-flux Z2 spin liquid in Schwinger-boson representation [Wang, Phys. Rev. B 82, 024419 (2010)]. through an explicit duality transformation. SPS is connected to an unusual antiferromagnetic ordered phase, which we term the chiral-antiferromagnetic (CAF) phase, by an O(4) critical point. The CAF phase breaks the SU(2) spin rotational symmetry completely and has three Goldstone modes. Our results indicate that there is likely a hidden phase transition between the CAF phase and the simple antiferromagnetic phase at large U/t. We also propose numerical measurements to reveal the CAF phase and the hidden phase transition.

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  • Received 5 December 2010

DOI:https://doi.org/10.1103/PhysRevB.84.024420

©2011 American Physical Society

Authors & Affiliations

Yuan-Ming Lu and Ying Ran

  • Department of Physics, Boston College, Chestnut Hill, MA 02467, USA

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Issue

Vol. 84, Iss. 2 — 1 July 2011

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