12 research outputs found
Measuring the effective phonon density of states of a quantum dot
We employ detuning-dependent decay-rate measurements of a quantum dot in a
photonic-crystal cavity to study the influence of phonon dephasing in a
solid-state quantum-electrodynamics experiment. The experimental data agree
with a microscopic non-Markovian model accounting for dephasing from
longitudinal acoustic phonons, and identifies the reason for the hitherto
unexplained difference between non-resonant cavity feeding in different
nanocavities. From the comparison between experiment and theory we extract the
effective phonon density of states experienced by the quantum dot. This
quantity determines all phonon dephasing properties of the system and is found
to be described well by a theory of bulk phonons.Comment: 5 pages, 3 figures, submitte
Quenching of phonon-induced processes in quantum dots due to electron-hole asymmetries
Differences in the confinement of electrons and holes in quantum dots are
shown to profoundly impact the magnitude of scattering with acoustic phonons in
materials where crystal deformation shifts the conduction and valence band in
the same direction. Using an extensive model that includes the non-Markovian
nature of the phonon reservoir, we show how the effect may be addressed by
photoluminescence excitation spectroscopy of a single quantum dot. We also
investigate the implications for cavity QED, i.e. a coupled quantum dot-cavity
system, and demonstrate that the phonon scattering may be strongly quenched.
The quenching is explained by a balancing between the deformation potential
interaction strengths and the carrier confinement and depends on the quantum
dot shape. Numerical examples suggest a route towards engineering the phonon
scattering.Comment: 5 pages, 5 figures, submitted for peer review, comments are welcom
Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics:Paper
We present detuning-dependent spectral and decay-rate measurements to study
the difference between spectral and dynamical properties of single quantum dots
embedded in micropillar and photonic-crystal cavities. For the micropillar
cavity, the dynamics is well described by the dissipative Jaynes-Cummings
model, while systematic deviations are observed for the emission spectra. The
discrepancy for the spectra is attributed to coupling of other exciton lines to
the cavity and interference of different propagation paths towards the detector
of the fields emitted by the quantum dot. In contrast, quantitative information
about the system can readily be extracted from the dynamical measurements. In
the case of photonic crystal cavities we observe an anti crossing in the
spectra when detuning a single quantum dot through resonance, which is the
spectral signature of strong coupling. However, time-resolved measurements
reveal that the actual coupling strength is significantly smaller than
anticipated from the spectral measurements and that the quantum dot is rather
weakly coupled to the cavity. We suggest that the observed Rabi splitting is
due to cavity feeding by other quantum dots and/or multiexcition complexes
giving rise to collective emission effects.Comment: 14 pages, 5 figures, submitte