All-optical tomography of electron spins in (In,Ga)As quantum dots

Abstract

We demonstrate the basic features of an all-optical spin tomography on picosecond time scale. The magnetization vector associated with a mode-locked electron spin ensemble in singly charged quantum dots is traced by ellipticity measurements using picosecond laser pulses. After optical orientation the spins precess about a perpendicular magnetic field. By comparing the dynamics of two interacting ensembles with the dynamics of a single ensemble we find buildup of a spin component along the magnetic field in the two-ensemble case. This component arises from a Heisenberg-like spin-spin interaction.Received 6 December 2013Revised 11 February 2014DOI:https://doi.org/10.1103/PhysRevB.89.081310©2014 American Physical Society