Ground state and low-lying excitations of the spin-1/2 XXZ model on the kagome lattice at magnetization 1/3

TL;DR

This paper investigates the ground state and low-energy excitations of the spin-1/2 XXZ model on the kagome lattice at 1/3 magnetization, revealing a valence-bond crystal order and a complex spectrum of magnetic and non-magnetic states.

Contribution

It provides new insights into the nature of the ground state and excitations of the XXZ kagome antiferromagnet at fractional magnetization, highlighting valence-bond crystal order and excitation gaps.

Findings

Presence of many non-magnetic states below the magnetic gap

Non-magnetic excitations have a smaller gap than magnetic ones

Evidence of valence-bond crystal order with short-range spin correlations

Abstract

We study the ground state and low-lying excitations of the S=1/2 XXZ antiferromagnet on the kagome lattice at magnetization one third of the saturation. An exponential number of non-magnetic states is found below a magnetic gap. The non-magnetic excitations also have a gap above the ground state, but it is much smaller than the magnetic gap. This ground state corresponds to an ordered pattern with resonances in one third of the hexagons. The spin-spin correlation function is short ranged, but there is long-range order of valence-bond crystal type.