Excitonic States in Medium-Size Quantum Dots

TL;DR

This paper investigates excitonic states in medium-sized quantum dots, revealing how Coulomb interactions influence energy spectra and absorption features, with implications for understanding quantum dot optical properties.

Contribution

It introduces an approximation beyond Tamm-Dankoff for constructing excitonic states in quantum dots with dozens of electrons, highlighting spectral and absorption characteristics.

Findings

Excitonic states show renormalized excitation gaps due to Coulomb interactions.

Energy level density increases exponentially at higher energies.

Interband absorption exhibits a linear background with distinct resonance peaks.

Abstract

In a quantum dot with dozens of electrons, an approximation beyond Tamm-Dankoff is used to construct the quantum states with an additional electron-hole pair, i.e. the "excitonic" states. The lowest states mimic the non-interacting spectrum, but with excitation gaps renormalized by Coulomb interactions. At higher excitation energies, the computed density of energy levels shows an exponential increase with energy. In the interband absorption, we found a background level in the quasicontinuum of states rising linearly with the excitation energy. Above this background, there are distinct peaks related to single resonances or to groups of many states with small interband dipole moments.