Optical control of carrier wavefunction in magnetic quantum dots

TL;DR

This study demonstrates optical control of the carrier wavefunction in magnetic quantum dots with Type-II band alignment, revealing how excitation energy influences magnetic interactions via hole wavefunction penetration.

Contribution

It introduces a novel approach to manipulate magnetic interactions in quantum dots through optical excitation, emphasizing the role of hole wavefunction dynamics in Type-II structures.

Findings

Photoluminescence shifts depend on excitation energy.

Multiple hole occupancy enhances wavefunction penetration.

Microscopic calculations confirm the role of Coulomb and exchange interactions.

Abstract

Spatially indirect Type-II band alignment in magnetically-doped quantum dot (QD) structures provides unexplored opportunities to control the magnetic interaction between carrier wavefunction in the QD and magnetic impurities. Unlike the extensively studied, spatially direct, QDs with Type-I band alignment where both electrons and holes are confined in the QD, in ZnTe QDs embedded in a (Zn,Mn)Se matrix only the holes are confined in the QDs. Photoexcitation with photon energy 3.06 eV (2.54 eV) generates electron-hole pairs predominantly in the (Zn,Mn)Se matrix (ZnTe QDs). The photoluminescence (PL) at 7 K in the presence of an external magnetic field exhibits an up to three-fold increase in the saturation red shift with the 2.54 eV excitation compared to the shift observed with 3.06 eV excitation. This unexpected result is attributed to multiple hole occupancy of the QD and the resulting increased penetration of the hole wavefunction tail further into the (Zn,Mn)Se matrix. The proposed model is supported by microscopic calculations which accurately include the role of hole-hole Coulomb interactions as well as the hole-Mn spin exchange interactions.