Triangular-lattice Heisenberg anti-ferromagnets: A Schwinger-boson study

We study, within the Schwinger-boson approach, the ground-state structure of two Heisenberg anti-ferromagnets on the triangular lattice: the J1 – J2 model, which includes a next-nearest-neighbor coupling J2, and the spatially-anisotropic J1 – Jʹ1 model, in which the nearest-neighbor coupling takes a different value Jʹ1 along one of the bond directions. For both models, the inclusion of one-loop corrections to saddle-point results leads to the prediction of nonmagnetic phases for particular values of the parameters J1/J2 and Jʹ1/J1. In the case of the J1 – J2 model we shed light on the existence of such a disordered quantum state, a question which is controversial in the literature. For the J1 – Jʹ1 model our results nicely agree with series-expansions predictions.