Order by disorder in the classical Heisenberg kagomé antiferromagnet

Antiferromagnetic ordering on a kagome$iaa— net is frustrated by the geometry of the lattice. The infinite number of classical ground states suggests that the system might not order at zero temperature, even for Heisenberg spins. However, high-temperature series expansions and earlier simulations indicate that this degeneracy is resolved by thermal fluctuations (i.e., order by disorder), suggesting a nine-sublattice coplanar Néel-like ordering …