220 research outputs found
Dynamics of Charge Leakage From Self-assembled CdTe Quantum Dots
We study the leakage dynamics of charge stored in an ensemble of CdTe quantum
dots embedded in a field-effect structure. Optically excited electrons are
stored and read out by a proper time sequence of bias pulses. We monitor the
dynamics of electron loss and find that the rate of the leakage is strongly
dependent on time, which we attribute to an optically generated electric field
related to the stored charge. A rate equation model quantitatively reproduces
the results.Comment: 4 pages, submitted to Applied Physics Letter
Quantum interference in exciton-Mn spin interactions in a CdTe semiconductor quantum dot
We show theoretically and experimentally the existence of a new quantum
interference(QI) effect between the electron-hole interactions and the
scattering by a single Mn impurity. Theoretical model, including
electron-valence hole correlations, the short and long range exchange
interaction of Mn ion with the heavy hole and with electron and anisotropy of
the quantum dot, is compared with photoluminescence spectroscopy of CdTe dots
with single magnetic ions. We show how design of the electronic levels of a
quantum dot enable the design of an exciton, control of the quantum
interference and hence engineering of light-Mn interaction.Comment: 11 pages, 4 figures, submitted to PR
Optical manipulation of a single Mn spin in a CdTe-based quantum dot
A system of two coupled CdTe quantum dots, one of them containing a single Mn
ion, was studied in continuous wave and modulated photoluminescence,
photoluminescence excitation, and photon correlation experiments. Optical
writing of information in the spin state of the Mn ion has been demonstrated,
using orientation of the Mn spin by spin-polarized carriers transferred from
the neighbor quantum dot. Mn spin orientation time values from 20 ns to 100 ns
were measured, depending on the excitation power. Storage time of the
information in the Mn spin was found to be enhanced by application of a static
magnetic field of 1 T, reaching hundreds of microseconds in the dark. Simple
rate equation models were found to describe correctly static and dynamical
properties of the system.Comment: 4 pages, 3 figure
A micro-magneto-Raman scattering study of graphene on a bulk graphite substrate
We report on a magneto-Raman scattering study of graphene flakes located on
the surface of a bulk graphite substrate. By spatially mapping the Raman
scattering response of the surface of bulk graphite with an applied magnetic
field, we pinpoint specific locations which show the electronic excitation
spectrum of graphene. We present the characteristic Raman scattering signatures
of these specific locations. We show that such flakes can be superimposed with
another flake and still exhibit a graphene-like excitation spectrum.
Two different excitation laser energies (514.5 and 720 nm) are used to
investigate the excitation wavelength dependence of the electronic Raman
scattering signal.Comment: 6 pages, 5 figure
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