Novel Mechanism of Supersolid of Ultracold Polar Molecules in Optical Lattices

TL;DR

This paper introduces a new type of supersolid phase in ultracold polar molecules within optical lattices, driven by long-range dipole interactions that enable defect hopping without superflow paths, confirmed by quantum Monte Carlo simulations.

Contribution

It reveals a novel supersolid mechanism where long-range dipole interactions facilitate defect hopping, distinct from previous models, supported by quantum Monte Carlo results.

Findings

Identification of a supersolid phase without superflow paths.

Observation of a double peak in momentum distribution as supersolid evidence.

Demonstration of the role of dipole-dipole interactions in stabilizing the supersolid.

Abstract

We study the checkerboard supersolid of the hard-core Bose-Hubbard model with the dipole-dipole interaction. This supersolid is different from all other supersolids found in lattice models in the sense that superflow paths through which interstitials or vacancies can hop freely are absent in the crystal. By focusing on repulsive interactions between interstitials, we reveal that the long-range tail of the dipole-dipole interaction have the role of increasing the energy cost of domain wall formations. This effect produces the supersolid by the second-order hopping process of defects. We also perform exact quantum Monte Carlo simulations and observe a novel double peak structure in the momentum distribution of bosons, which is a clear evidence for supersolid. This can be measured by the time-of-flight experiment in optical lattice systems.