Phase diagram of a distorted kagome antiferromagnet and application to Y-kapellasite

TL;DR

This paper explores the complex magnetic phases of a distorted kagome antiferromagnet model, identifies various ground states, and applies findings to the real material Y-kapellasite, revealing its likely magnetic order.

Contribution

It introduces a new distorted kagome model with multiple magnetic phases and demonstrates its relevance to the synthesized compound Y-kapellasite.

Findings

Identification of multiple magnetic phases including a classical spin liquid.

Y-kapellasite is a realization of the model with a predicted Q = (1/3,1/3) order.

The Q = (1/3,1/3) phase remains stable under quantum fluctuations.

Abstract

We investigate the magnetism of a previously unexplored distorted spin-1/2 kagome model consisting of three symmetry-inequivalent nearest-neighbor antiferromagnetic Heisenberg couplings Jhexagon, J and J', and uncover a rich ground state phase diagram even at the classical level. Using analytical arguments and numerical techniques we identify a collinear Q = 0 magnetic phase, two unusual non-collinear coplanar Q = (1/3,1/3) phases and a classical spin liquid phase with a degenerate manifold of non-coplanar ground states, resembling the jammed spin liquid phase found in the context of a bond-disordered kagome antiferromagnet. We further show with density functional theory calculations that the recently synthesized Y-kapellasite Y3Cu9(OH)19Cl8 is a realization of this model and predict its ground state to lie in the region of Q = (1/3,1/3) order, which remains stable even after inclusion of quantum fluctuation effects within variational Monte Carlo and pseudofermion functional renormalization group. The presented model opens a new direction in the study of kagome antiferromagnets.