562 research outputs found
Circularly Polarized Resonant Rayleigh Scattering and Skyrmions in the = 1 Quantum Hall Ferromagnet
We use the circularly polarized resonant Rayleigh scattering (RRS) to study
the quantum Hall ferromagnet at = 1. At this filling factor we observe a
right handed copolarized RRS which probes the Skyrmion spin texture of the
electrons in the photoexcited grounds state. The resonant scattering is not
present in the left handed copolarization, and this can be related to the
correlation between Skymionic effects, screening and spin wave excitations.
These results evidence that RRS is a valid method for the study of the spin
texture of the quantum Hall states
Resonant Raman scattering by collective modes of the one-dimensional electron gas
We show that the low-energy peak in the polarized resonant Raman spectra of
quantum wires, which is commonly associated with ``single particle
excitations'', can be interpreted as signature of intra-band collective spin
excitations. A broad maximum in the resonant depolarized spectra is predicted
to exist above the frequency of the spin density excitation, due to
simultaneous but independent propagation of spin- and charge-density modes.Comment: 4 pages, accepted for publication in Phys. Rev. Let
High resolution temperature and density profiles during the energy quench of density limit disruptions in Rijnhuizen tokamak project
Measurements of the electron temperature, Te, and density, ne, during the energy quench of a major disruption showed that the onset of Te erosion in the neighborhood of the m/n = 2/1 O point at the low field side (LFS) accelerates the well-known m/n = 1/1 erosion of the core temperature. During this phase Te(r) is only partially flat in the region between the q = 2 and the q = 1 surfaces and ne(r) decreases in the core and increases inside the m/n = 2/1 island. Immediately after the flattening of Te(r) a large peak in Te and to a lesser extent in ne has been observed. This peak is radially localized at the q = 2 radius at the LFS, is very short lived and is poloidally asymmetric. Te profiles measured by the heterodyne radiometer and the Thomson scattering agree very well up to the time Te(r) flattens but afterwards can be a factor of two different
Magnetization of noncircular quantum dots
We calculate the magnetization of quantum dots deviating from circular
symmetry for noninteracting electrons or electrons interacting according to the
Hartree approximation. For few electrons the magnetization is found to depend
on their number, and the shape of the dot. The magnetization is an ideal probe
into the many-electron state of a quantum dot.Comment: 11 RevTeX pages with 6 included Postscript figure
Spin and orbital mechanisms of the magneto-gyrotropic photogalvanic effects in GaAs/AlGaAs quantum well structures
We report on the study of the linear and circular magneto-gyrotropic
photogalvanic effect (MPGE) in GaAs/AlGaAs quantum well structures. Using the
fact that in such structures the Land\'e-factor g* depends on the quantum well
(QW) width and has different signs for narrow and wide QWs, we succeeded to
separate spin and orbital contributions to both MPGEs. Our experiments show
that, for most quantum well widths, the PGEs are mainly driven by spin-related
mechanisms, which results in a photocurrent proportional to the g* factor. In
structures with a vanishingly small g* factor, however, linear and circular
MPGE are also detected, proving the existence of orbital mechanisms.Comment: 10 pages, 10 figure
Tomonaga-Luttinger features in the resonant Raman spectra of quantum wires
The differential cross section for resonant Raman scattering from the
collective modes in a one dimensional system of interacting electrons is
calculated non-perturbatively using the bosonization method. The results
indicate that resonant Raman spectroscopy is a powerful tool for studying
Tomonaga-Luttinger liquid behaviour in quasi-one dimensional electron systems.Comment: 4 pages, no figur
AC-conductance of a quantum wire with electron-electron interaction
The complex ac-response of a quasi-one dimensional electron system in the
one-band approximation with an interaction potential of finite range is
investigated. It is shown that linear response is exact for this model. The
influence of the screening of the electric field is discussed. The complex
absorptive conductance is analyzed in terms of resistive, capacitive and
inductive behaviors.Comment: 13 pages, REVTeX, 7 eps figures, to appear in Phys. Rev.
Commissioning of inline ECE system within waveguide based ECRH transmission systems on ASDEX upgrade
A CW capable inline electron cyclotron emission (ECE) separation system for feedback control, featuring oversized corrugated waveguides, is commissioned on ASDEX upgrade (AUG). The system is based on a combination of a polarization independent, non-resonant, Mach-Zehnder diplexer equipped with dielectric plate beam splitters [2, 3] employed as corrugated oversized waveguide filter, and a resonant Fast Directional Switch, FADIS [4, 5, 6, 7] as ECE/ECCD separation system. This paper presents an overview of the system, the low power characterisation tests and first high power commissioning on AUG
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