Near-threshold bound states of the dipole-dipole interaction

TL;DR

This paper investigates the bound states arising from dipole-dipole interactions in ultracold molecules and magnetic atoms, revealing universal patterns and the influence of short-range potentials on these states.

Contribution

It provides a detailed analysis of two-body bound states with realistic short-range interactions, extending understanding beyond idealized models.

Findings

Universal pattern of dipole-dipole bound states with avoided crossings.

Suppression of dipole-dipole effects in magnetic atoms due to Lennard-Jones potential.

Dense manifold of states in polar molecules observable spectroscopically.

Abstract

We study the two-body bound states of a model Hamiltonian that describes the interaction between two field-oriented dipole moments. This model has been used extensively in many-body physics of ultracold polar molecules and magnetic atoms, but its few-body physics has been explored less fully. With a hard-wall short-range boundary condition, the dipole-dipole bound states are universal and exhibit a complicated pattern of avoided crossings between states of different character. For more realistic Lennard-Jones short-range interactions, we consider parameters representative of magnetic atoms and polar molecules. For magnetic atoms, the bound states are dominated by the Lennard-Jones potential, and the perturbative dipole-dipole interaction is suppressed by the special structure of van der Waals bound states. For polar molecules, we find a dense manifold of dipole-dipole bound states with many avoided crossings as a function of induced dipole or applied field, similar to those for hard-wall boundary conditions. This universal pattern of states may be observable spectroscopically for pairs of ultracold polar molecules.