Long-range orientational order in a two-dimensional degenerate system of dipoles on a square lattice

It is shown that in a planar degenerate system on a square lattice with dipole-dipole interactions of electric or magnetic moments the thermodynamic fluctuations destroy the Goldstone mode in the spectrum of orientational oscillations. This gives rise to layered antiferroelectric structures characterized by a nonzero long-range orientational order parameter, which in the low-temperature limit is proportional to exp(−T|lnT|). Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 623–627 (25 April 1996)