Sneng, Donna2015-05-212015-05-212015-05https://hdl.handle.net/11299/172323We study the spin-1/2 Heisenberg model on the triangular lattice with the antiferromagnetic first- (J1 ) and second-neighbor (J2 ) interactions by means of density matrix renormalization group (DMRG). Beside the three sublattice ordered Neel phase and a stripe antiferromagnetic phase at smaller (~0.07) and larger J2 (~0.16) sides, we find a quantum spin liquid in the intermediate range of the J2. We show that there are two topological sectors. The odd sector (by pinning spinons at cylinder boundaries) is very robust, while the even topological sector has higher energy for smaller systems possibly due to a competing chiral state. We demonstrate the stabilization of the possible Z2 spin liquid in both sectors with the increase of the system width. We analyze the quantum numbers of different near degenerating states, and discuss the possible characterization of the Z2 spin liquid.enFTPISymmetriesPresentation