Classical spin-liquid on the maximally frustrated honeycomb lattice

TL;DR

This paper demonstrates that a specific classical Heisenberg antiferromagnet on a honeycomb lattice exhibits a spin-liquid state with characteristic pinch points, fractionalization, and nematic order, revealing novel frustrated magnetic phenomena.

Contribution

It identifies a classical spin-liquid phase in the honeycomb Heisenberg model with specific couplings and explores fractionalization and nematic order in related XY models.

Findings

Presence of pinch-point singularities in structure factor

Emergence of fractionalized degrees of freedom upon dilution

Nematic thermal order by disorder in XY model

Abstract

We show that the honeycomb Heisenberg antiferromagnet with $J_1/2=J_2=J_3$, where $J_{1/2/3}$ are first-, second- and third-neighbour couplings respectively, forms a classical spin liquid with pinch-point singularities in the structure factor at the Brillouin zone corners. Upon dilution with non-magnetic ions, fractionalised degrees of freedom carrying $1/3$ of the free moment emerge. Their effective description in the limit of low-temperature is that of spins randomly located on a triangular lattice, with a frustrated interaction of long-ranged logarithmic form. The XY version of this magnet exhibits nematic thermal order by disorder, which comes with a clear experimental diagnostic.