Optical signatures of spin dependent coupling in semimagnetic quantum dot molecules

TL;DR

This study investigates how spin-dependent coupling in semimagnetic quantum dot molecules affects their optical properties, revealing resonant interactions and hybridized states through photoluminescence measurements.

Contribution

It demonstrates the formation of molecular states and spin-dependent optical signatures in coupled quantum dots with variable spacing, supported by a quantitative model.

Findings

Resonant enhancement of electron-Mn exchange interaction observed

Anomalous increase in Zeeman shift at close dot spacing

Transition linewidths show resonant behavior indicating coupling

Abstract

We present photoluminescence studies of CdTe and CdMnTe quantum dots grown in two adjacent layers. We show that when the dots are 8 nm apart, their magnetooptical properties - Zeeman shifts and transition linewidths - are analogous to those of individual CdTe or CdMnTe dots. When the dots are grown closer, at a distance of 4 nm, it becomes possible to tune the electron states to resonance and obtain a formation of a molecular state hybridized over the two dots. As a result of the resonant enhancement of the electron-Mn ion exchange interaction, spectroscopic signatures specific to spin-dependent inter-dot coupling appear. Namely, an anomalous increase of the Zeeman shift and a resonant increase in the transition linewidth are observed. A simple model calculation allows us to quantitatively reproduce the experimental results.