Rotational excitations of polar molecules on an optical lattice: from novel exciton physics to quantum simulation of new lattice models

TL;DR

This paper explores the unique properties of rotational excitons in ultracold polar molecules on optical lattices, highlighting their potential for quantum simulation and studying exciton interactions in a highly tunable system.

Contribution

It introduces rotational Frenkel excitons in polar molecules on optical lattices and demonstrates their use for quantum simulation of complex condensed matter models.

Findings

Rotational excitons exhibit unique tunable properties.

External electric fields can control exciton interactions.

Potential to simulate complex lattice models like the Holstein model.

Abstract

Ultracold polar molecules trapped on an optical lattice is a many-body system that, under appropriate conditions, may support collective excitations reminiscent of excitons in solid state crystals. Here, we discuss the rotational excitations of molecules on an optical lattice leading to rotational Frenkel excitons. Apart from solid hydrogen, there is no other natural system that exhibits rotational excitons. The rotational excitons have unique properties that can be exploited for tuning non-linear exciton interactions and exciton-impurity scattering by applying an external electric field. We show that this can be used to explore the competing role of the dynamical and kinematic exciton-exciton interactions in excitonic energy transfer and to study quantum localization in a dynamically tunable disordered potential. The rotational excitons can also be used as a basis for quantum simulation of condensed matter models that cannot be realized with ultracold atoms. As an example, we discuss the possibility of engineering the Holstein model with polar molecules on an optical lattice.