Superfluid-Insulator transitions of bosons on Kagome lattice at non-integer fillings

TL;DR

This paper investigates superfluid-insulator transitions of bosons on a Kagome lattice at non-integer fillings, revealing superfluid stability at f=1/2 due to vortex localization and a quantum phase transition at f=2/3.

Contribution

It provides a duality analysis of bosonic phases on the Kagome lattice at incommensurate fillings, highlighting the role of lattice symmetry and vortex dynamics in phase transitions.

Findings

Bosons are always superfluid at f=1/2 due to vortex localization.

At f=2/3, a transition occurs between superfluid and Mott insulator phases.

The system maps to a XXZ spin model with specific properties.

Abstract

We study the superfluid-insulator transitions of bosons on the Kagome lattice at incommensurate filling factors f=1/2 and 2/3 using a duality analysis. We find that at f=1/2 the bosons will always be in a superfluid phase and demonstrate that the T_3 symmetry of the dual (dice) lattice, which results in dynamic localization of vortices due to the Aharanov-Bohm caging effect, is at the heart of this phenomenon. In contrast, for f=2/3, we find that the bosons exhibit a quantum phase transition between superfluid and translational symmetry broken Mott insulating phases. We discuss the possible broken symmetries of the Mott phase and elaborate the theory of such a transition. Finally we map the boson system to a XXZ spin model in a magnetic field and discuss the properties of this spin model using the obtained results.