A hidden Goldstone mechanism in the Kagomé lattice antiferromagnet

Abstract

In this paper, we study the phases of the Heisenberg model on the \kagome lattice with antiferromagnetic nearest neighbour coupling $J_1$ and ferromagnetic next neighbour coupling $J_2$. Analysing the long wavelength, low energy effective action that describes this model, we arrive at the phase diagram as a function of $χ= \frac{J_2}{J_1} $. The interesting part of this phase diagram is that for small $χ$, which includes $χ=0$, there is a phase with no long range spin order and with gapless and spin zero low lying excitations. We discuss our results in the context of earlier, numerical and experimental work.

21 pages, latex file with 5 figures