Z2 spin liquid and chiral antiferromagnetic phase in Hubbard model on the honeycomb lattice: duality between Schwinger-fermion and Schwinger-boson representations

Note: 2 PM
Speaker: Ying Ran, Boston College

When: April 20, 2011 (Wed), 02:00PM to 03:00PM (add to my calendar)
Location: SCI 328

This event is part of the Condensed Matter Theory Seminar Series.

Abstract:
In a recent remarkable quantum Monte Carlo simulation of the hubbard model on honeycomb lattice, a spin disordered Mott insulator phase is discovered in the intermediate correlation regime. Using Projective Symmetry Group classification and physical arguments, we identify this spin liquid phase as the Sublattice-Pairing State (SPS) in the
Schwinger-fermion representation. In addition, we show that SPS is identical to the zero-flux Z2 spin liquid in Schwinger-boson representation found by Wang via an explicit duality transformation. SPS is connected to an unusual antiferromagnetic ordered phase, which we term as chiral-antiferromagnetic (CAF) phase, by an O(4) critical point.  CAF phase breaks the SU(2) spin rotation symmetry completely and has three Goldstone modes. Our results indicate that there is likely a hidden phase transition between CAF phase and simple AF phase at large U/t. We propose numerical measurements to reveal the CAF phase and the hidden phase transition.