Pair supersolid of the extended Bose-Hubbard model with atom-pair hopping on the triangular Lattice

TL;DR

This study uses quantum Monte Carlo simulations to explore a complex extended Bose-Hubbard model on a triangular lattice, revealing various superfluid, solid, and supersolid phases driven by atom-pair hopping, on-site, and nearest-neighbor interactions.

Contribution

It provides the first detailed phase diagram of the extended Bose-Hubbard model with atom-pair hopping on a triangular lattice, highlighting the emergence of a stable pair supersolid phase due to three-body constraints.

Findings

Continuous transition between atomic and pair superfluid phases.

First order transitions between Mott insulators and pair superfluid.

Emergence of a stable pair supersolid phase at small on-site repulsion.

Abstract

We systematically study an extended Bose-Hubbard model with atom hopping and atom-pair hopping in the presence of a three-body constraint on the triangular lattice. By means of large-scale Quantum Monte Carlo simulations, the ground-state phase diagram are studied. We find a continuous transition between the atomic superfluid phase and the pair superfluid when the ratio of the atomic hopping and the atom-pair hopping is adapted. We then focus on the interplay among the atom-pair hopping, the on-site repulsion and the nearest-neighbor repulsion. With on-site repulsion present, we observe first order transitions between the Mott Insulators and pair superfluid driven by the pair hopping. With the nearest-neighbor repulsion turning on, three typical solid phases with 2/3, 1 and 4/3-filling emerge at small atom-pair hopping region. A stable pair supersolid phase is found at small on-site repulsion. This is due to the three-body constraint and the pair hopping, which essentially make the model a quasi hardcore boson system. Thus the pair supersolid state emerges basing on the order-by-disorder mechanism, by which hardcore bosons avoid classical frustration on the triangular lattice. The transition between the pair supersolid and the pair superfluid is first order, except for the particle-hole symmetric point. We compare the results with those obtained by means of mean-field analysis.