Abstract

The study of the spin dynamics in semiconductor quantum wells (QW) is of growing interest in recent years.^1-5. In this paper we use a powerful novel technique, absorption quantum beats, to investigate this process. Controlling the initial spin orientation by the polarization of the pump pulse we excite the system in a superposition of two eigen-states with different energies. We observe two kinds of absorption quantum beats: Beats between Zeeman split levels and between excitons and bi-excitons. The frequency of these beats corresponds to the small energy splitting between the states involved, and the damping rate - to their dephasing. Experiments are performed on several QW samples at 4K and magnetic fields up to 5T, in a standard pump-probe configuration with a time resolution of ~ 1 ps.

© 1992 The Author(s)