1,757,786 research outputs found
Mossbauer-effect data-collection system
Automated data collection system which uses a small, general-purpose digital computer provides data acquisition from, and minor control of, four Mossbauer-effect experiments. This system is economical with no loss of versatility to the experimenter and is useful in handling large volumes of data from research experiments
Collective Modes of Quantum Hall Stripes
The collective modes of striped phases in a quantum Hall system are computed
using the time-dependent Hartree-Fock approximation. Uniform stripe phases are
shown to be unstable to the formation of modulations along the stripes, so that
within the Hartree-Fock approximation the groundstate is a stripe crystal. Such
crystalline states are generically gapped at any finite wavevector; however, in
the quantum Hall system the interactions of modulations among different stripes
is found to be remarkably weak, leading to an infinite collection of collective
modes with immeasurably small gaps. The resulting long wavelength behavior is
derivable from an elastic theory for smectic liquid crystals. Collective modes
for the phonon branch are computed throughout the Brillouin zone, as are spin
wave and magnetoplasmon modes. A soft mode in the phonon spectrum is identified
for partial filling factors sufficiently far from 1/2, indicating a second
order phase transition. The modes contain several other signatures that should
be experimentally observable.Comment: 36 pages LaTex with 11 postscript figures. Short animations of the
collective modes can be found at
http://www.physique.usherb.ca/~rcote/stripes/stripes.ht
On deformation of electron holes in phase space
This Letter shows that for particularly shaped background particle
distributions momentum exchange between phase space holes and the distribution
causes acceleration of the holes along the magnetic field. In the particular
case of a non-symmetric ring distribution (ring with loss cone) this
acceleration is nonuniform in phase space being weaker at larger perpendicular
velocities thus causing deformation of the hole in phase space.Comment: Original MS in EPL style, 1 Figur
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