# Controlled Coulomb effects in core-shell quantum rings

## TL;DR

This paper theoretically explores how external electric and magnetic fields can control in-gap corner-localized two-electron states in a triangular quantum ring, revealing tunable energy levels and absorption properties.

## Contribution

It introduces a contactless method to manipulate in-gap states in quantum rings by external fields, highlighting the effects of geometry and field orientation.

## Key findings

- External fields alter energy levels and degeneracy of in-gap states.
- Absorption spectra are sensitive to electric and magnetic field presence.
- Control of electron states is achievable without contact-based methods.

## Abstract

We analyse theoretically the possibilities of contactless control of in-gap states formed by a pair of electrons confined in a triangular quantum ring. The in-gap states are corner-localized states associated with two electrons occupying the same corner area, and thus shifted to much higher energies than other corner states, but still they are below the energies of corner-side-localized states. We show how the energies, degeneracy and splittings between consecutive levels change with the orientation of an external electric field relatively to the polygonal cross section. We also show how absorption changes in the presence of external electric and magnetic fields.