Abstract
We study the S=1/2 Heisenberg antiferromagnet on a triangular lattice with both nearest-neighbor () and next-to-nearest-neighbor () couplings. We have performed a spin-wave analysis around the classical ground state. At large (/) the Néel state is destabilized and the system exhibits the ‘‘order from disorder’’ phenomenon with a threefold-degenerate ground state that spontaneously breaks the lattice rotational invariance. These results are in agreement with a Lanczos study of a 12-site lattice. For even larger values of / the spin-wave calculation shows the existence of a second transition to an incommensurate spiral. Thus, the previously suggested existence of chiral order in this model should be reanalyzed.
- Received 2 May 1990
DOI:https://doi.org/10.1103/PhysRevB.42.4800
©1990 American Physical Society