Spin dynamics and level structure of quantum-dot quantum wells

TL;DR

This study investigates the spin dynamics and energy level structure of CdS/CdSe/CdS quantum-dot quantum wells using time-resolved Faraday rotation, revealing how electron g-factors and spin lifetimes depend on quantum well width and symmetry considerations.

Contribution

It provides the first detailed characterization of spin dynamics in quantum-dot quantum wells and introduces a model accounting for broken spherical symmetry.

Findings

Electron g-factor varies with quantum well width.

Transverse spin lifetime remains several nanoseconds up to room temperature.

Resonances in TRFR signal identify individual exciton transitions.

Abstract

We have characterized CdS/CdSe/CdS quantum-dot quantum wells using time-resolved Faraday rotation (TRFR). The spin dynamics show that the electron g-factor varies as a function of quantum well width and the transverse spin lifetime of several nano-seconds is robust up to room temperature. As a function of probe energy, the amplitude of the TRFR signal shows pronounced resonances, which allow one to identify individual exciton transitions. While the TRFR data are inconsistent with the conduction and valence band level scheme of spherical quantum-dot quantum wells, a model in which broken spherical symmetry is taken into account captures the essential features.