Bound States and Universality in Layers of Cold Polar Molecules

TL;DR

This paper investigates bound states of cold polar molecules in layered optical traps, revealing universal behaviors and the likelihood of complex multi-particle bound states due to long-range dipole interactions.

Contribution

It provides a detailed analysis of two-body bound states in bilayer systems, highlighting universal properties and implications for multi-particle complexes in layered molecular gases.

Findings

At least one bound state exists in bilayer systems.

Zero-energy bound states exhibit universal large-radius behavior.

Bound complexes of more than two particles are likely in multilayer setups.

Abstract

The recent experimental realization of cold polar molecules in the rotational and vibrational ground state opens the door to the study of a wealth of phenomena involving long-range interactions. By applying an optical lattice to a gas of cold polar molecules one can create a layered system of planar traps. Due to the long-range dipole-dipole interaction one expects a rich structure of bound complexes in this geometry. We study the bilayer case and determine the two-body bound state properties as a function of the interaction strength. The results clearly show that a least one bound state will always be present in the system. In addition, bound states at zero energy show universal behavior and extend to very large radii. These results suggest that non-trivial bound complexes of more than two particles are likely in the bilayer and in more complicated chain structures in multi-layer systems.