We introduce a two-dimensional frustrated Heisenberg antiferromagnet on interpenetrating honeycomb and triangular lattices. Classically the two sublattices decouple, and "order from disorder" drives them into a coplanar state. Applying Friedan's geometric approach to nonlinear sigma models, we show that the scaling of the spin-stiffnesses corresponds to the Ricci flow of a 4D metric tensor. At low temperatures, the relative phase between the spins on the two sublattices is described by a six-state clock model with an emergent critical phase.
@article{arxiv.1206.5740,
title = {Emergent Critical Phase and Ricci Flow in a 2D Frustrated Heisenberg Model},
author = {Peter P. Orth and Premala Chandra and Piers Coleman and Jörg Schmalian},
journal= {arXiv preprint arXiv:1206.5740},
year = {2015}
}