Exciton spectra in vertical stacks of triple and quadruple quantum dots in an electric field

TL;DR

This paper investigates exciton energy levels in stacked quantum dots under electric fields, revealing how their spectra and recombination probabilities are affected by dot configuration and external influences.

Contribution

It introduces a detailed analysis of exciton spectra in multi-quantum-dot stacks, highlighting the effects of electric fields and dot depth variations on energy levels and tunneling behaviors.

Findings

Bright energy levels form families linked to hole localization.

Electric fields cause avoided crossings with distinct patterns for each family.

Adding dots modifies the exciton spectrum and energy level interactions.

Abstract

We study an electron-hole pair in a stack of multiple quantum dots in the presence of an external electric field using the configuration interaction approach. We find that the bright energy levels can be grouped into families which are associated with the hole localized in a specific dot of the stack. The exciton energy levels undergo avoided crossings as function of the external electric field with different pattern for each family. We show that the variation of the depths of the dots along the stack can be deduced from the exciton spectrum. In the strong confinement limit the families are mixed by a weak electric field due to hole tunneling. This results in a characteristic multiple avoided crossing of energy levels belonging to different families with an accompanying modulation of the recombination probabilities and an appearance of a single particularly bright state. We discuss the modification of the spectrum when dots are added to the stack.