Phonon-Induced Dephasing of Optically Driven Exciton States in Quantum Dots: Spectral Interpretation

Abstract

In recent years it has become possible to control the charge state of a single quantum dot (QD) far beyond the linear absorption regime. A convincing example of this experimental progress are pulse area-dependent Rabi oscillations of the exciton occupation, i.e., coherent transitions from the ground crystal state to the singleor bi-exciton state and back, driven by optical pulses of variable intensity [1]. These achievements show that the atomic-like properties of charge systems confined in a QD may allow one to transfer quantum control schemes developed in the quantum-optical context to the semiconductor systems. However, charges in QDs, unlike those in natural atoms, undergo strong interactions with their solid-state environment resulting in strong decoherence of their quantum states. In self-assembled dots, an important contribution to decoherence is that of pure dephasing due to carrier-phonon interactions [2, 3]. These phonon-related effects may be analyzed for arbitrary driving pulses within the theoretical approach developed recently [4, 5], which allows one to treat phonon effects perturbatively, while unperturbed system evolution, including external driving, is included exactly.