Competing States in the S=1/2 Triangular-Lattice J_{1}-J_{2} Heisenberg Model: A Dynamical Density-Matrix Renormalization Group Study.

Previous studies of the S=1/2 triangular-lattice J_{1}-J_{2} Heisenberg antiferromagnet have inferred the existence of a nonmagnetic ground-state phase for an intermediate range of J_{2}, but disagree concerning whether it is a gapped Z_{2} quantum spin liquid (QSL), a gapless (Dirac) QSL, or a weakly symmetry-broken phase. Using an improved dynamical density-matrix renormalization group method, we investigate the relevant intermediate J_{2} regime for cylinders with circumferences from 6 to 9. Depending on the initial state and boundary conditions, we find two distinct variational states. The higher energy state is consistent with a Dirac QSL. In the lower-energy state, both the static and dynamical properties are qualitatively similar to the magnetically ordered state at J_{2}=0, suggestive of either a weakly magnetically ordered non-QSL or a gapped QSL proximate to a continuous transition to such an ordered state.