arXiv:cond-mat/9807216 · Physical review. B, Condensed matter
Coherent control for a two-level system coupled to phonons
H. Castella, R. Zimmermann
Abstract
The interband polarization induced by two phase-locked pulses in a semiconductor shows strong interference effects depending on the time, ${\ensuremath{\tau}}_{1},$ separating the pulses. The four-wave mixing signal diffracted from a third pulse delayed by $\ensuremath{\tau}$ is coherently controlled by tuning ${\ensuremath{\tau}}_{1}.$ The four-wave mixing response is evaluated exactly for a two-level system coupled to a single LO phonon. In the weak coupling regime it shows oscillations with the phonon frequency which turn into sharp peaks at multiples of the phonon period for a larger coupling strength. Destructive interferences between the two phase-locked pulses produce a splitting of the phonon peaks into a doublet. For fixed $\ensuremath{\tau}$ but varying ${\ensuremath{\tau}}_{1},$ the signal shows rapid oscillations at the interband transition frequency, whose amplitude exhibits bursts at multiples of the phonon period.