1,152 research outputs found
Voltage-controlled electron-hole interaction in a single quantum dot
The ground state of neutral and negatively charged excitons confined to a
single self-assembled InGaAs quantum dot is probed in a direct absorption
experiment by high resolution laser spectroscopy. We show how the anisotropic
electron-hole exchange interaction depends on the exciton charge and
demonstrate how the interaction can be switched on and off with a small dc
voltage. Furthermore, we report polarization sensitive analysis of the
excitonic interband transition in a single quantum dot as a function of charge
with and without magnetic field.Comment: Conference Proceedings, Physics and Applications of Spin-Related
Phenomena in Semiconductors, Santa Barbara (CA), 2004. 4 pages, 4 figures;
content as publishe
Facial train-of-four monitoring as an evaluation of neuromuscular blockade in a patient with ICU-acquired weakness
Facial train-of-four monitoring as an evaluation of neuromuscular blockade in a patient with ICU-acquired weakness
Facial train-of-four monitoring as an evaluation of neuromuscular blockade in a patient with ICU-acquired weakness
Neuromuscular blocking agents are used in the ICU for various reasons, such as during status asthmaticus and patient-ventilator dyssynchrony. We report a 76-year-old man with adenocarcinoma of the oesophagus treated with laparoscopic transthoracic oesophagectomy, which was complicated by a fistula between the gastric reconstruction and the right main bronchus. He developed extensive ICU-acquired weakness and was treated with differential lung ventilation followed by continuous rocuronium infusion. Evaluation of neuromuscular blockade by train-of-four (TOF) stimulation showed a discrepancy in facial and ulnar TOF monitoring. The different number of neuromuscular junctions at each muscle group could be an explanation for this. Therefore, it is suggested to use facial TOF monitoring in ICU patients instead of ulnar TOF monitoring to differentiate between an intoxication of neuromuscular blockade and ICU-acquired weakness
Dynamic nuclear spin polarization in resonant laser spectroscopy of a quantum dot
Resonant optical excitation of lowest-energy excitonic transitions in
self-assembled quantum dots lead to nuclear spin polarization that is
qualitatively different from the well known optical orientation phenomena. By
carrying out a comprehensive set of experiments, we demonstrate that nuclear
spin polarization manifests itself in quantum dots subjected to finite external
magnetic field as locking of the higher energy Zeeman transition to the driving
laser field, as well as the avoidance of the resonance condition for the lower
energy Zeeman branch. We interpret our findings on the basis of dynamic nuclear
spin polarization originating from non-collinear hyperfine interaction and find
an excellent agreement between the experimental results and the theoretical
model
Absorption and photoluminescence spectroscopy on a single self-assembled charge-tunable quantum dot
We have performed detailed photoluminescence (PL) and absorption spectroscopy
on the same single self-assembled quantum dot in a charge-tunable device. The
transition from neutral to charged exciton in the PL occurs at a more negative
voltage than the corresponding transition in absorption. We have developed a
model of the Coulomb blockade to account for this observation. At large
negative bias, the absorption broadens as a result of electron and hole
tunneling. We observe resonant features in this regime whenever the quantum dot
hole level is resonant with two-dimensional hole states located at the capping
layer-blocking barrier interface in our structure.Comment: 6 pages, 6 figure
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