388 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
Influence of Pure Dephasing on Emission Spectra from Single Photon Sources
We investigate the light-matter interaction of a quantum dot with the
electromagnetic field in a lossy microcavity and calculate emission spectra for
non-zero detuning and dephasing. It is found that dephasing shifts the
intensity of the emission peaks for non-zero detuning. We investigate the
characteristics of this intensity shifting effect and offer it as an
explanation for the non-vanishing emission peaks at the cavity frequency found
in recent experimental work.Comment: Published version, minor change
Intercalibration of Boreal and Tethyan timescales: the magneto-biostratigraphy of the Middle Triassic and the latest Early Triassic from Spitsbergen, Arctic Norway
An integrated bio-magnetostratigraphic study of the latest Early Triassic to the upper parts of the Middle Triassic, at Milne Edwardsfjellet in central Spitsbergen, Svalbard, allows a detailed correlation of Boreal and Tethyan biostratigraphies. The biostratigraphy consists of ammonoid and palynomorph zonations, supported by conodonts, through some 234 m of succession in two adjacent sections. The magnetostratigraphy consists of ten substantive normal–reverse polarity chrons defined by sampling at 150 stratigraphic levels. The magnetization is carried by magnetite and an unidentified magnetic sulphide, and is difficult to fully separate from a strong present-day like magnetization. The bio-magnetostratigraphy from the late Olenekian (Vendomdalen Member) is supplemented by data from nearby Vikinghøgda. The early and mid-Anisian has a high sedimentation rate, comprising over half the ca. 140-m thickness of the Botneheia Formation, whereas the late Anisian and lower Ladinian is condensed into about 20 m. The two latest Boreal Ladinian ammonoid zones are absent due to erosional truncation below the Tschermakfjellet Formation. Correlation to Tethyan bio-magnetostratigraphies shows the traditional base of the Boreal Anisian (base of G. taimyrensis Zone) precedes the base Anisian (using here definitions based on the Desli Caira section in Romania). The Boreal upper Anisian G. rotelliforme and F. nevadanus ammonoid zones correlate to most of the Tethyan Pelsonian and Illyrian substages. The base Ladinian defined in the Tethyan global boundary stratotype and point (GSSP) is closely equivalent to the traditional base of the Boreal Ladinian at the I. oleshkoi Zone. The latest Olenekian to early Anisian magnetic polarity timescale is refined using the Spitsbergen data
Comparison of EIT schemes in semiconductor quantum dot structures: Impact of many-body interactions
We investigate the impact of many-body interactions on group-velocity
slowdown achieved via electromagnetically induced transparency in quantum dots
using three different coupling-probe schemes (ladder, V, and Lambda,
respectively). We find that for all schemes many-body interactions have an
important impact on the slow light properties. In the case of the Lambda and V
schemes, the minimum required coupling power to achieve slow light is
significantly reduced by many-body interactions. V type schemes are found to be
generally preferable due to a favorable redistribution of carriers in energy
space
Microscopic theory of phonon-induced effects on semiconductor quantum dot decay dynamics in cavity QED
We investigate the influence of the electron-phonon interaction on the decay
dynamics of a quantum dot coupled to an optical microcavity. We show that the
electron-phonon interaction has important consequences on the dynamics,
especially when the quantum dot and cavity are tuned out of resonance, in which
case the phonons may add or remove energy leading to an effective non-resonant
coupling between quantum dot and cavity. The system is investigated using two
different theoretical approaches: (i) a second-order expansion in the bare
phonon coupling constant, and (ii) an expansion in a polaron-photon coupling
constant, arising from the polaron transformation which allows an accurate
description at high temperatures. In the low temperature regime we find
excellent agreement between the two approaches. An extensive study of the
quantum dot decay dynamics is performed, where important parameter dependencies
are covered. We find that in general the electron-phonon interaction gives rise
to a greatly increased bandwidth of the coupling between quantum dot and
cavity. At low temperature an asymmetry in the quantum dot decay rate is
observed, leading to a faster decay when the quantum dot has a larger energy
than to the cavity. We explain this as due to the absence of phonon absorption
processes. Furthermore, we derive approximate analytical expressions for the
quantum dot decay rate, applicable when the cavity can be adiabatically
eliminated. The expressions lead to a clear interpretation of the physics and
emphasizes the important role played by the effective phonon density,
describing the availability of phonons for scattering, in quantum dot decay
dynamics. Based on the analytical expressions we present the parameter regimes
where phonon effects are expected to be important. Also, we include all
technical developments in appendices.Comment: published PRB version, comments are very welcom
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