Interaction of a hydrogenlike ion with a planar topological insulator

TL;DR

This paper investigates how hydrogenlike ions interact with a topological insulator surface, revealing distance-dependent spectral shifts and magnetic effects due to image monopoles, with implications for Casimir-Polder forces and atomic energy structures.

Contribution

It introduces a detailed analysis of atomic spectra near topological insulators considering magnetic monopole effects, highlighting new distance-dependent energy shifts and potential modifications.

Findings

Hyperfine structure is affected by image magnetic monopoles.

Circular Rydberg ions amplify energy shifts.

Magnetic interactions create a repulsive Casimir-Polder tail.

Abstract

An electric charge near the surface of a topological insulator (TI) induces an image magnetic monopole. Here we study the spectra of hydrogenlike ions near the surface of a planar TI, taking into account the modifications which arise due to the presence of the image monopole magnetic fields. In fact, the atom-TI interaction provides additional contributions to the Casimir-Polder potential while the ion-TI interaction modifies the energy shifts in the spectrum, which now became distance dependent. We show that the hyperfine structure is sensitive to the image magnetic monopole fields in states with nonzero angular momentum, and that circular Rydberg ions can enhance the maximal energy shifts. We discuss in detail the energy splitting of the $n$P$_{1/2}$ and $n$P$_{3/2}$ states in hydrogen. We also analyze the Casimir-Polder potential and find that this magnetic interaction produces a large distance repulsive tail for some particular atomic states. A sizable value of the maximum of the potential requires TIs with very low values of the permittivity together with high values of the topological magnetoelectric polarization.