Universality in molecular halo clusters

TL;DR

This paper investigates the universality of quantum halo states in weakly bound molecular clusters, demonstrating that diverse systems follow a universal behavior in their size and binding energy relationships.

Contribution

It provides the first detailed analysis of quantum halo states in molecular systems, showing their universal properties and how they differ from nuclear halos.

Findings

Clusters follow a universal line in size and binding energy at high scaled binding energies.

Borromean states separate from tango trimers as scaled binding energy decreases.

Precise calculations of size and binding energy using Monte Carlo methods.

Abstract

Ground state of weakly bound dimers and trimers with a radius extending well into the classically forbidden region is explored, with the goal to test the predicted universality of quantum halo states. The focus of the study are molecules consisting of T$\downarrow$, D$\downarrow$, $^3$He, $^4$He and alkali atoms, where interaction between particles is much better known than in the case of nuclei, which are traditional examples of quantum halos. The study of realistic systems is supplemented by model calculations in order to analyze how low-energy properties depend on the interaction potential. The use of variational and diffusion Monte Carlo methods enabled very precise calculation of both size and binding energy of the trimers. In the quantum halo regime, and for large values of scaled binding energies, all clusters follow almost the same universal line. As the scaled binding energy decreases, Borromean states separate from tango trimers.