Symmetry fractionalization in the topological phase of the   spin-$\frac{1}{2}$ $J_1$-$J_2$ triangular Heisenberg model
  Using density-matrix renormalization-group calculations for infinite cylinders, we elucidate the properties of the spin-liquid phase of the spin-$\frac{1}{2}$ $J_1$-$J_2$ Heisenberg model on the triangular lattice. We find four distinct ground-states characteristic of a non-chiral, $Z_2$ topologically ordered state with vison and spinon excitations. We shed light on the interplay of topological ordering and global symmetries in the model by detecting fractionalization of time-reversal and space-group dihedral symmetries in the anyonic sectors, which leads to coexistence of symmetry protected and intrinsic topological order. The anyonic sectors, and information on the particle statistics, can be characterized by degeneracy patterns and symmetries of the entanglement spectrum. We demonstrate the ground-states on finite-width cylinders are short-range correlated and gapped; however some features in the entanglement spectrum suggest that the system develops gapless spinon-like edge excitations in the large-width limit. 
S. N. Saadatmand and I. P. McCulloch
cond-mat.str-el