Spin-Exchange Interaction in ZnO-based Quantum Wells

TL;DR

This study explores how quantum confinement and electric fields in ZnO/(Zn,Mg)O quantum wells influence the spin exchange interaction, revealing tunability based on well width and internal electric effects.

Contribution

It demonstrates the ability to control the short-range spin exchange interaction in ZnO quantum wells through well width and electric field effects, a novel insight for spintronic applications.

Findings

Exchange interaction increases in wells under 3 nm.

Internal electric fields suppress exchange energy in wider wells.

Oscillator strength redistribution correlates with well width.

Abstract

Wurtzitic ZnO/(Zn,Mg)O quantum wells grown along the (0001) direction permit unprecedented tunability of the short-range spin exchange interaction. In the context of large exciton binding energies and electron-hole exchange interaction in ZnO, this tunability results from the competition between quantum confinement and giant quantum confined Stark effect. By using time-resolved photoluminescence we identify, for well widths under 3 nm, the redistribution of oscillator strengths between the A and B excitonic transitions, due to the enhancement of the exchange interaction. Conversely, for wider wells, the redistribution is cancelled by the dominant effect of internal electric fields, which dramatically reduce the exchange energy.