Efimovian states of three charged particles

TL;DR

This paper demonstrates the existence of Efimov-like states in systems of three charged particles across different dimensions, using the Born-Oppenheimer approximation, and discusses their potential experimental observation.

Contribution

It reveals that Efimov states can form in charged particle systems without fine-tuning, extending the concept beyond neutral particles and specific dimensions.

Findings

Efimov states occur in three charged particles with two equal and one opposite charge.

These states can be quasibound or genuine bound states depending on the system and dimension.

Potential experimental realization in hydrogen molecular ions, trions, and quantum vortices.

Abstract

When three particles in three dimensions interact with a short-range potential fine-tuned to an infinite scattering length, they form an infinite sequence of loosely bound states obeying discrete scale invariance known as Efimov states. Here we show that analogous states are formed by three charged particles carrying two equal charges and one opposite charge in one, two, and three dimensions without any fine-tuning. Our finding is based on the Born-Oppenheimer approximation, where an effective inverse-square attraction is induced as a consequence of the dipole-charge interaction between a hydrogenlike heavy-light atom and a far-separated heavy particle. Because the resulting Efimovian states emerge toward the second or higher dissociation threshold, they are to be realized as quasibound states and may be observed by exciting hydrogen molecular ions and trions in excitonic systems. We also consider the same system but with a logarithmic Coulomb potential relevant to quantum vortices in two-dimensional superfluids, where the Efimovian states are shown to emerge as genuine bound states toward the first dissociation threshold.