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

Max Hering,Francesco Ferrari,Aleksandar Razpopov,Roser Valentí,Johannes Reuther,Igor I Mazin,Harald O Jeschke

doi:10.1038/s41524-021-00689-0

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 J⬡, J, and J^{prime}, and uncover a rich ground state phase diagram even at the classical level. Using analytical arguments and numerical techniques we identify a collinear overrightarrow{Q}=0 magnetic phase, two unusual non-collinear coplanar overrightarrow{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 overrightarrow{Q}=(1/3,1/3) order, which remains stable even after the 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.

Highlights

The kagome lattice is arguably one of the most important twodimensional (2D) lattices for the study of magnetic frustration
Analyzing the corresponding Heisenberg model as a function of its two coupling ratios, using analytical arguments and numerical techniques, we find a surprisingly rich ground state phase diagram, even at the classical level
We can distinguish two inequivalent sets of sites inside the unit cell, which are not functional renormalization group (PFFRG) we argue that quantum fluctuations are not sufficiently strong to suppress the long-range magnetic order

Summary

INTRODUCTION

The kagome lattice is arguably one of the most important twodimensional (2D) lattices for the study of magnetic frustration. !Q 1⁄4 ð1=3; 1=3Þ order extends for a finite region along the J0=J⬡ axis (red area in Fig. 2), which is bounded by the onset of the classical spin-liquid phase. Within this region, the numerical minimization of the classical energy shows that the spin pattern is unchanged with respect to of couplings for Y-kapellasite. In the strong hexagon limit, where the system is made of weakly coupled hexagons forming a triangular pattern, the excitation spectrum at low energies resembles that of the triangular lattice antiferromagnet

DISCUSSION

METHODS

Findings

CODE AVAILABILITY