We measure the frequency spectra of random spin fluctuations, or "spin noise", in ensembles of (In,Ga)As/GaAs quantum dots (QDs) at low temperatures. We employ a spin noise spectrometer based on a sensitive optical Faraday rotation magnetometer that is coupled to a digitizer and field-programmable gate array, to measure and average noise spectra from 0-1 GHz continuously in real time with sub-nanoradian/root-Hz sensitivity. Both electron and hole spin fluctuations generate distinct noise peaks, whose shift and broadening with magnetic field directly reveal their g-factors and dephasing rates within the ensemble. A large, energy-dependent anisotropy of the in-plane hole g-factor is clearly exposed, reflecting systematic variations in the average QD confinement potential.
@article{arxiv.0909.1592,
title = {Spin noise of electrons and holes in self-assembled quantum dots},
author = {S. A. Crooker and J. Brandt and C. Sandfort and A. Greilich and D. R. Yakovlev and D. Reuter and A. D. Wieck and M. Bayer},
journal= {arXiv preprint arXiv:0909.1592},
year = {2010}
}