Valence bond supersolid in a bilayer extended Bose Hubbard model

TL;DR

This paper numerically investigates a bilayer extended Bose Hubbard model, revealing a novel valence bond supersolid phase where valence bond order coexists with superfluidity, with potential experimental realization in cold atom systems.

Contribution

First demonstration of a valence bond supersolid phase in a bilayer Bose Hubbard model through numerical analysis.

Findings

Identification of valence bond checkerboard solid at quarter filling.

Discovery of valence bond supersolid phase with coexisting order and superfluidity.

Phase transitions to dimer solid and Mott insulator at higher fillings.

Abstract

The hardcore extended Bose Hubbard model on a bilayer square lattice with attractive (repulsive) interplane (intraplane) interactions has been investigated numerically. Focusing on the strong interplane hopping parameter regime, triplet valence bonds of dimers are stabilized to form valence bond checkerboard solid at quarter filling. Increasing the particle number we confirm, for the first time, the presence of the exotic valence bond supersolid phase, where the valence bond solid ordering and the boson superfluidity coexist. Rising further the particle number will lead to a checkerboard solid of dimer pair at half filling for strong intraplane repulsion, or a valence bond Mott insulator for weak repulsive interactions. We analyze the rich ground state phase diagrams of this model, which can be experimentally realized in optical lattices of cold atoms.