Abstract
The two spin stiffnesses (ρ∥,ρ⊥) of the quantum Heisenberg antiferromagnet on the triangular lattice are investigated by a first-order spin-wave theory. At the thermodynamic limit, spin-wave calculations predict a large reduction of the spin stiffnesses by quantum fluctuations: relative to their classical values, the reduction is 68% for , 12% for , and 40% for the average spin stiffness . In this approach quantum fluctuations, not large enough to destroy the rigidity of Néel order, are nevertheless changing the sign of the anisotropy of the spin stiffnesses tensor. A method using exact diagonalizations on finite lattices is used to countercheck the importance of quantum fluctuations on small sizes. These last results confirm qualitatively the conclusions of the first-order spin-wave calculation.
- Received 28 February 1995
DOI:https://doi.org/10.1103/PhysRevB.52.9162
©1995 American Physical Society