Spin Dynamics and Dimensionality in Magnetic Semiconductor Quantum Structures

Abstract

Complementary sets of low temperature magneto-optical experiments have been performed on a series of diluted magnetic semiconductor heterostructures in order to explore the effects of quantum confinement and reduced dimensionality on fundamental electronic and magnetic spin dynamics. In the first set, femtosecond time-resolved photoluminescence spectroscopy was used on a series of Zn1-xMnxSe/ZnSe spin superlattice structures to directly probe the spin-dependent dynamics as the carriers’ confining potential was systematically controlled by a magnetic field. Exciton lifetimes and spin relaxation are found to be strongly dependent on both the energy and location of spin states in the heterostructures. In the second set of experiments, a variety of nonmagnetic Zn1-yCdySe/ZnSe double quantum well heterostructures coupled by a thin diluted magnetic semiconductor barrier were studied by magneto-luminescence measurements. Spin splitting of the quantum confined ground state and the resulting large luminescence polarization were observed by tuning the barrier potential with a magnetic field. In the third set of experiments, femtosecond spectroscopic measurements of optically induced magnetization performed on ZnTe/Cd1-xMnxSe heterostructures reveal the formation and evolution of electron-based bound magnetic polarons. The magnetic spin dynamics on ultrashort time scales was found to vary dramatically with the degree of electron confinement. These experiments demonstrate the potential of spin-engineering to explore new carrier dynamics that are highly dependent on confinement and applied magnetic fields as well as the magnetic state of the host.