Biomedical Engineering Reference
In-Depth Information
Chapter 9
Phonon-Assisted Processes and Spontaneous
Emission in Double Quantum Dots
Paweł Karwat, Krzysztof Gawarecki, Katarzyna Roszak, Anna Sitek,
and Paweł Machnikowski
Abstract
We describe, from a theoretical point of view, phonon-induced dephasing
and relaxation processes in double quantum dots, the specific features of the
spontaneous emission in these systems, and the interplay of these two classes of
physical processes. First, we discuss the phonon-assisted transfer of electron, hole
and exciton occupation in coupled dots, the dephasing of spatially delocalized
superpositions, and the phonon-induced decay of entanglement. Second, we study
the signatures of collective emission in the linear absorption and the four-wave
mixing optical response of these systems, as well as in time-resolved luminescence,
where collective effects are manifested by long-living tails in the emission due to
the vacuum-induced coherence effect. Finally, we analyze the interplay of phonon-
related processes and spontaneous emission. We show that occupation transfer
between bright and dark states in the ground state doublet of a double-dot structure
can lead to a temperature dependence of the spontaneous emission rate, which may
result in a non-monotonic temperature dependence of the luminescence decay rate.
9.1
Introduction
Nanostructures composed of two closely spaced semiconductor quantum dots (QDs)
have attracted much attention in recent years. This is because they not only open
the path for new applications but also provide ways of controlling the states and
dynamics of confined carriers. For example, double quantum dot (DQD) systems
provide the basis for an implementation of excitonic qubits (quantum bits—the
building blocks of quantum information processing) with extended lifetimes [
1
],
allow conditional quantum control of carrier states [
2
], and have been proposed as a
P. Karwat K. Gawarecki K. Roszak A. Sitek P. Machnikowski (
)
Institute of Physics, Wrocław University of Technology, 50-370 Wrocław, Poland
