Spin dynamics of the planar kagome lattice ferromagnet with four-site ring exchange processes

TL;DR

This study uses quantum Monte Carlo simulations to explore the spin dynamics and potential spin fractionalization in a kagome lattice ferromagnet with four-site ring exchange, revealing insights into quantum criticality and spin liquid phases.

Contribution

It provides the first detailed analysis of the dynamical spin structure factor in this model, highlighting signatures of spin fractionalization and comparing excitation gaps with related quantum spin liquid models.

Findings

Identification of spin fractionalization signatures in the non-magnetic regime

Observation of magnon mode softening near the quantum critical point

Comparison of excitation gaps with the Balents-Fisher-Girvin model

Abstract

By means of quantum Monte Carlo simulations, combined with a stochastic analytic continuation, we examine the spin dynamics of the spin-1/2 planar (XY) ferromagnet on the kagome lattice with additional four-site ring exchange terms. Such exchange processes were previously considered to lead into an extended $Z_2$ quantum spin liquid phase beyond a quantum critical point from the XY-ferromagnet. We examine the dynamical spin structure factor in the non-magnetic regime and probe for signatures of spin fractionalization. Furthermore, we contrast our findings and the corresponding energy scales of the excitation gaps in the ring exchange model to those emerging in a related Balents-Fisher-Girvin model with a $Z_2$ quantum spin liquid phase, and monitor the softening of the magnon mode upon approaching the quantum critical point from the XY-ferromagnetic regime.