5,809 research outputs found
Comment on "Absence of Compressible Edge Channel Rings in Quantum Antidots"
In a recent article, Karakurt et al. [I. Karakurt et al., Phys. Rev. Lett.
89, 226803 (2002)] reported the absence of compressible regions around antidots
in the quantum Hall regime. We wish to point out a significant flaw in their
analysis, which invalidates their claim.Comment: 1 page 1 figure, to be published in Phys. Rev. Let
Experimental Pulmonary Granuloma Mimicking Sarcoidosis Induced by Propionibacterium acnes in Mice
Propionibacterium acnes has been implicated as an etiologic agent of sarcoidosis since the isolation of this bacterium from sarcoid lesions. We experimentally produced a murine pulmonary granuloma model using P. acnes with several features that simulate sarcoidosis. Mice were sensitized with heat-killed P. acnes and complete Freund's adjuvant and were subsequently challenged with heat-killed P. acnes at 2-week intervals. P. acnes-challenged mice developed epitheloid cell granulomas in the lungs. These mice showed a pulmonary immune response characterized by an increased number of T-lymphocytes, especially CD4 cells, and the ratio of CD4/CD8 in bronchoalveolar lavage (BAL) fluid also increased. Furthermore, significant elevations in both angiotensin-converting enzyme (ACE) serum levels and antibody titers against P. acnes were observed. Mice sensitized with P. acnes without complete Freund's adjuvant were capable of forming pulmonary granulomas, which appeared to be caused by indigenous P. acnes. The genome of P. acnes was found in the lungs, BAL cells, hilar lymph nodes, liver, and spleen in non-sensitized mice, which were thought to be germ-free. These results suggest that the immune response against indigenous P. acnes may play an important role in the pathogenesis of granuloma formation in a murine model.</p
Scanning Gate Spectroscopy of transport across a Quantum Hall Nano-Island
We explore transport across an ultra-small Quantum Hall Island (QHI) formed
by closed quan- tum Hall edge states and connected to propagating edge channels
through tunnel barriers. Scanning gate microscopy and scanning gate
spectroscopy are used to first localize and then study a single QHI near a
quantum point contact. The presence of Coulomb diamonds in the spectroscopy
con- firms that Coulomb blockade governs transport across the QHI. Varying the
microscope tip bias as well as current bias across the device, we uncover the
QHI discrete energy spectrum arising from electronic confinement and we extract
estimates of the gradient of the confining potential and of the edge state
velocity.Comment: 13 pages, 3 figure
Non-adiabatically driven electron in quantum wire with spin-orbit interaction
An exact solution is derived for the wave function of an electron in a
semiconductor quantum wire with spin-orbit interaction and driven by external
time dependent harmonic confining potential. The formalism allows analytical
expressions for various quantities to be derived, such as spin and pseudo-spin
rotations, energy and occupation probabilities for excited states. It is
demonstrated how perfect spin and pseudo-spin flips can be achieved at high
frequencies of order \omega, the confining potential level spacing. By an
appropriately chosen driving term, spin manipulation can be exactly performed
far into the non-adiabatic regime. Implications for spin-polarised emission and
spin-dependent transport are also discussed.Comment: 11 pages, 3 figure
Picosecond coherent electron motion in a silicon single-electron source
Understanding ultrafast coherent electron dynamics is necessary for
application of a single-electron source to metrological standards, quantum
information processing, including electron quantum optics, and quantum sensing.
While the dynamics of an electron emitted from the source has been extensively
studied, there is as yet no study of the dynamics inside the source. This is
because the speed of the internal dynamics is typically higher than 100 GHz,
beyond state-of-the-art experimental bandwidth. Here, we theoretically and
experimentally demonstrate that the internal dynamics in a silicon
singleelectron source comprising a dynamic quantum dot can be detected,
utilising a resonant level with which the dynamics is read out as
gate-dependent current oscillations. Our experimental observation and
simulation with realistic parameters show that an electron wave packet
spatially oscillates quantum-coherently at 200 GHz inside the source.
Our results will lead to a protocol for detecting such fast dynamics in a
cavity and offer a means of engineering electron wave packets. This could allow
high-accuracy current sources, high-resolution and high-speed
electromagnetic-field sensing, and high-fidelity initialisation of flying
qubits
Charge dynamics in two-electron quantum dots
We investigate charge dynamics in a two-electron double quantum dot. The
quantum dot is manipulated by using a time-dependent external voltage that
induces charge oscillations between the dots. We study the dependence of the
charge dynamics on the external magnetic field and on the periodicity of the
external potential. We find that for suitable parameter values, it is possible
to induce both one-electron and two-electron oscillations between the dots.Comment: 4 pages, 7 figures, proceedings of the Quantum Dot 2010 conferenc
Phonon emission and arrival times of electrons from a single-electron source
In recent charge-pump experiments, single electrons are injected into quantum Hall edge channels at energies significantly above the Fermi level. We consider here the relaxation of these hot edge-channel electrons through longitudinal-optical-phonon emission. Our results show that the probability for an electron in the outermost edge channel to emit one or more phonons en route to a detector some microns distant along the edge channel suffers a double-exponential suppression with increasing magnetic field. This explains recent experimental observations. We also describe how the shape of the arrival-time distribution of electrons at the detector reflects the velocities of the electronic states post phonon emission. We show how this can give rise to pronounced oscillations in the arrival-time-distribution width as a function of magnetic field or electron energy
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