The Boson-Hubbard Model on a Kagome Lattice with Sextic Ring-Exchange Terms

TL;DR

This study investigates the effects of sixth order ring-exchange interactions on hard-core bosons in a kagome lattice, revealing phase separation and unique ordered solid phases through exact quantum Monte Carlo simulations.

Contribution

First exact quantum Monte Carlo analysis of a kagome lattice model with sixth order ring-exchange interactions, highlighting system instability and novel ordered phases.

Findings

System becomes unstable at large ring-exchange interactions.

Phase separation occurs at all fillings except 1/3 and 2/3.

Formation of a mixed valence bond and charge density ordered solid at specific fillings.

Abstract

High order ring-exchange interactions are crucial for the study of quantum fluctuations on highly frustrated systems. We present the first exact quantum Monte Carlo study of a model of hard-core bosons with sixth order ring-exchange interactions on a two-dimensional kagome lattice. By using the Stochastic Green Function algorithm, we show that the system becomes unstable in the limit of large ring-exchange interactions. It undergoes a phase separation at all fillings, except at 1/3 and 2/3 fillings for which the superfluid density vanishes and an unusual mixed valence bond and charge density ordered solid is formed.