Coulomb interaction effects on the electronic structure of radial polarized excitons in nanorings

TL;DR

This paper investigates how Coulomb interactions influence the electronic structure of radially polarized excitons in nanorings, revealing different regimes with distinct Aharonov-Bohm oscillation behaviors based on ring size and interaction strength.

Contribution

It provides a rigorous numerical analysis of Coulomb effects on exciton states in nanorings, including analytical approximations for different regimes.

Findings

Small rings show AB oscillations due to individual particle orbits.

Large rings exhibit AB oscillations linked to flux between electron and hole.

Coulomb interaction determines whether exciton states are extended or localized.

Abstract

The electronic structure of radially polarized excitons in structured nanorings is analyzed, with emphasis in the ground-state properties and their dependence under applied magnetic fields perpendicular to the ring plane. The electron-hole Coulomb attraction has been treated rigorously, through numerical diagonalization of the full exciton Hamiltonian in the non-interacting electron-hole pairs basis. Depending on the relative weight of the kinetic energy and Coulomb contributions, the ground-state of polarized excitons has "extended" or "localized" features. In the first case, corresponding to small rings dominated by the kinetic energy, the ground-state shows Aharonov-Bohm (AB) oscillations due to the individual orbits of the building particles of the exciton. In the localized regime, corresponding to large rings dominated by the Coulomb interaction, the only remaining AB oscillations are due to the magnetic flux trapped between the electron and hole orbits. This dependence of the exciton, a neutral excitation, on the flux difference confirms this feature as a signature of Coulomb dominated polarized excitons. Analytical approximations are provided in both regimens, which accurate reproduce the numerical results.