Toward Perfection: Kapellasite, Cu3Zn(OH)6Cl2, a New Model S = 1/2 Kagome Antiferromagnet

TL;DR

This paper introduces Kapellasite as a new S=1/2 kagome antiferromagnet model system, providing experimental evidence that it exhibits properties consistent with a resonating valence bond (RVB) state, a key quantum spin liquid phase.

Contribution

The study presents Kapellasite as a novel experimental realization of the S=1/2 kagome antiferromagnet, supporting its potential as a model for the RVB state.

Findings

Susceptibility data shows a magnetic moment collapse below 25 K.

Crystal structure closely approximates a 2D kagome lattice.

Evidence suggests spins condense into a non-magnetic RVB state.

Abstract

The search for the resonating valence bond (RVB) state continues to underpin many areas of condensed matter research. The RVB is made from the dimerisation of spins on different sites into fluctuating singlets, and was proposed by Anderson to be the reference state from which the transition to BCS superconductivity occurs. Little is known about the state experimentally, due to the scarcity of model materials. Theoretical work has put forward the S = 1/2 kagome antiferromagnet (KAFM) as a good candidate for the realization of the RVB state. In this paper we introduce a new model system, the S = 1/2 KAFM Kapellasite, Cu3Zn(OH)6Cl2. We show that its crystal structure is a good approximation to a 2-dimensional kagome antiferromagnet and that susceptibility data indicate a collapse of the magnetic moment below T = 25 K that is compatible with the spins condensing into the non-magnetic RVB state.