Supersolid Polar Molecules beyond Pairwise Interactions

TL;DR

This paper investigates the phase diagram of ultracold polar molecules in a triangular lattice, revealing extended supersolid phases influenced by tunable two- and three-body interactions, including novel phase transitions and structural properties.

Contribution

It demonstrates the persistence of supersolid phases beyond pairwise interactions and explores the effects of three-body forces on particle-hole symmetry and phase transitions.

Findings

Extended supersolid phase persists with three-body interactions.

A supersolid-supersolid transition indicates symmetry restoration.

Certain complex supersolid structures are excluded at finite temperature.

Abstract

We explore the phase diagram of ultracold bosonic polar molecules confined to a planar optical lattice of triangular geometry. External static electric and microwave fields can be employed to tune the effective interactions between the polar molecules into a regime of extended two- and three-body repulsions of comparable strength, leading to a rich quantum phase diagram. In addition to various solid phases, an extended supersolid phase is found to persist deep into the three-body dominated regime. While three-body interactions break particle-hole symmetry explicitly, a characteristic supersolid-supersolid quantum phase transition is observed, which indicates the restoration of particle-hole symmetry at half-filling. We revisit the spatial structure of the supersolid at this filling, regarding the existence of a further supersolid phase with three inequivalent sublattices, and provide evidence that this state is excluded also at finite temperatures.