Manipulating and storing spin coherence in semiconductors

Femtosecond-resolved optical experiments reveal a remarkable resistance of quantum spin slates to environmental decoherence in a variety of semiconductors. Optical pulses are used to create a superposition of the basis spin states defined by an applied magnetic field, and to follow the phase, amplitude, and location of the resulting electronic spin precession in bulk semiconductors, heterostructures, and quantum dots. The data show that spin lifetimes can exceed hundreds of nanoseconds and spin packets can be transported over a hundred microns in some of these systems. Spatial imaging and dynamical magnetometry monitors decoherence and dephasing of itinerant spin information as it flows not only through semiconductors, but also across dissimilar material interfaces in engineered structures. Periodic excitation of the electronic spin system can be used to resonantly operate on the nuclear spins of a semiconductor host and to detect associated changes in the nuclear magnetization, thereby demonstrating all-optical nuclear magnetic resonance. (C) 2001 Elsevier Science B.V. All rights reserved.