Correlated phases of bosons in the flat lowest band of the dice lattice

TL;DR

This paper explores exotic correlated phases of bosons in the flat lowest band of the dice lattice, revealing vortex lattices, supersolids, and Mott insulators through theoretical modeling and numerical analysis.

Contribution

It introduces a detailed model of bosons in the dice lattice's flat band, analyzing novel phases at various densities and fractional fillings.

Findings

Identification of vortex lattice phases at high density

Discovery of supersolid and Mott insulator phases at fractional fillings

Development of a Hubbard-Hamiltonian with interaction-assisted hopping for the dice lattice

Abstract

We study correlated phases occurring in the flat lowest band of the dice lattice model at flux density one half. We discuss how to realize the dice lattice model, also referred to as the T_3 lattice, in cold atomic gases. We construct the projection of the model to the lowest dice band, which yields a Hubbard-Hamiltonian with interaction-assisted hopping processes. We solve this model for bosons in two limits. In the limit of large density, we use Gross-Pitaevskii mean-field theory to reveal time-reversal symmetry breaking vortex lattice phases. At low density, we use exact diagonalization to identify three stable phases at fractional filling factors \nu of the lowest band, including a classical crystal at \nu=1/3, a supersolid state at \nu=1/2 and a Mott insulator at \nu=1.