The Heisenberg antiferromagnet on the kagome lattice with arbitrary spin: A high-order coupled cluster treatment

TL;DR

This paper uses high-order coupled cluster calculations to study the ground state of the Heisenberg antiferromagnet on the kagome lattice across various spins, revealing how quantum fluctuations influence magnetic order and state selection.

Contribution

It applies a high-order coupled cluster method to analyze the kagome lattice for multiple spins, providing new insights into ground state energies and magnetic order dependence on spin quantum number.

Findings

Ground state energy agrees with DMRG and exact diagonalization for s=1/2.

Quantum fluctuations suppress magnetic order, especially for low spins.

State selection depends on spin: q=0 for s=1/2, sqrt{3} x sqrt{3} for s>1/2.

Abstract

Starting with the sqrt{3} x sqrt{3} and the q=0 states as reference states we use the coupled cluster method to high orders of approximation to investigate the ground state of the Heisenberg antiferromagnet on the kagome lattice for spin quantum numbers s=1/2,1,3/2,2,5/2, and 3. Our data for the ground-state energy for s=1/2 are in good agreement with recent large-scale density-matrix renormalization group and exact diagonalization data. We find that the ground-state selection depends on the spin quantum number s. While for the extreme quantum case, s=1/2, the q=0 state is energetically favored by quantum fluctuations, for any s>1/2 the sqrt{3} x sqrt{3} state is selected. For both the sqrt{3} x sqrt{3} and the q=0 states the magnetic order is strongly suppressed by quantum fluctuations. Within our coupled cluster method we get vanishing values for the order parameter (sublattice magnetization) M for s=1/2 and s=1, but (small) nonzero values for M for s>1. Using the data for the ground-state energy and the order parameter for s=3/2,2,5/2, and 3 we also estimate the leading quantum corrections to the classical values.