Neel and Valence Bond Crystal Order on a Distorted Kagome Lattice: Implications For Zn-Paratacamite

TL;DR

This study uses quantum Monte Carlo methods to investigate magnetic order in Zn-Paratacamite, revealing Neel order in distorted phases and valence bond crystal states near the ideal kagome lattice, with implications for understanding quantum phase transitions.

Contribution

It provides numerical evidence for Neel and valence bond crystal orders in Zn-Paratacamite, supporting recent theoretical models and clarifying the nature of magnetic phases in distorted kagome lattices.

Findings

Neel order in strongly distorted Zn-Paratacamite

Valence bond crystal state near the ideal kagome limit

Possible deconfined quantum critical point between phases

Abstract

Zn-Paratacamite is a rare spin 1/2 antiferromagnetic insulator with an ideal kagome lattice structure in part of its phase diagram. As a function of Zn doping, this material undergoes a structural distortion which relieves the frustration and introduces magnetic order in the ground state, though the precise nature of the order is not clear at this point. In this paper, we present strong evidence for Neel ordering in the strongly distorted phase of Zn-Paratacamite through the application of quantum Monte-Carlo techniques. These numerical results support a recent Schwinger-boson mean field theory of Zn-Paratacamite. For weak distortion, close to the ideal kagome limit, our results indicate a regime with no Neel order but with a broken glide-plane symmetry. For this model the glide-plane symmetry is broken by any valence bond crystal. Hence, our results lend support to recent proposals of a valence bond crystal ground state for the undistorted lattice. The phase transition between the two phases could be in the deconfined universality class if it is not a first order transition.