Molten Antiferromagnets in Two Dimensions

TL;DR

This paper investigates two-dimensional molten antiferromagnets, revealing that magnetic order can persist in liquid phases due to topological order and fractional vortices, challenging traditional phase transition understanding.

Contribution

It introduces a model for molten antiferromagnets with topological order, showing magnetic order survives in liquid phases via fractional vortices and non-local order parameters.

Findings

Antiferromagnetism persists in hexatic and liquid phases.

Elementary dislocations bind to fractional magnetic vortices.

Molten antiferromagnets exhibit topological order.

Abstract

We study crystal melting in two-dimensional antiferromagnets, by analyzing the statistical mechanics of the six-state clock model on a lattice in which defects (dislocations and disclinations) are allowed to appear. We show that the elementary dislocations bind to fractional magnetic vortices. We compute the phase diagram by mapping the system into a Coulomb gas model. Surprisingly, we find that in the limit of dominant magnetic interactions, antiferromagnetism can survive even in the hexatic and liquid phases. The ensuing molten antiferromagnets are topologically ordered and are characterized by spontaneous symmetry breaking of a non-local order parameter.