39,265 research outputs found
Antenna and radome loss measurements for MFMR and PMIS with appendix on MFMR/PMIS computer programs
The NMSU/PSL radiometer antenna calibration facility is described, and the antenna and radome loss measurements made on the passive microwave imaging system and the multifrequency microwave radiometer are summarized. Antenna/radome data reduction techniques, estimation of sky brightness temperatures, and bucket performance tests are presented along with radiometer computer programs
Observation of narrow-band noise accompanying the breakdown of insulating states in high Landau levels
Recent magnetotransport experiments on high mobility two-dimensional electron
systems have revealed many-body electron states unique to high Landau levels.
Among these are re-entrant integer quantum Hall states which undergo sharp
transitions to conduction above some threshold field. Here we report that these
transitions are often accompanied by narrow- and broad-band noise with
frequencies which are strongly dependent on the magnitude of the applied dc
current.Comment: 4 pages, 3 figure
Metastable Resistance Anisotropy Orientation of Two-Dimensional Electrons in High Landau Levels
In half-filled high Landau levels, two-dimensional electron systems possess
collective phases which exhibit a strongly anisotropic resistivity tensor. A
weak, but as yet unknown, rotational symmetry-breaking potential native to the
host semiconductor structure is necessary to orient these phases in macroscopic
samples. Making use of the known external symmetry-breaking effect of an
in-plane magnetic field, we find that the native potential can have two
orthogonal local minima. It is possible to initialize the system in the higher
minimum and then observe its relaxation toward equilibrium.Comment: 5 pages, 3 figures. Figure references corrected. Version accepted for
publication in Physical Review Letter
Corrigendum to "Knot Floer homology detects fibred knots"
We correct a mistake on the citation of JSJ theory in \cite{Ni}. Some
arguments in \cite{Ni} are also slightly modified accordingly.Comment: 3 page
New Physics in High Landau Levels
Recent magneto-transport experiments on ultra-high mobility 2D electron
systems in GaAs/AlGaAs heterostructures have revealed the existence of whole
new classes of correlated many-electron states in highly excited Landau levels.
These new states, which appear only at extremely low temperatures, are
distinctly different from the familiar fractional quantum Hall liquids of the
lowest Landau level. Prominent among the recent findings are the discoveries of
giant anisotropies in the resistivity near half filling of the third and higher
Landau levels and the observation of re- entrant integer quantum Hall states in
the flanks of these same levels. This contribution will survey the present
status of this emerging field.Comment: 8 pages, 9 figures. To be published in the Proceedings of the 13th
International Conference on the Electronic Properties of Two-Dimensional
System
Reply to Simon's Comment on "Evidence for an Anisotropic State of Two-Dimensional Electrons in High Landau Levels"
We recently reported [PRL 82, 394 (1999)] large transport anisotropies in a
two-dimensional electron gas in high Landau levels. These observations were
made utilizing both square and Hall bar sample geometries. Simon recently
commented [cond-mat/9903086] that a classical calculation of the current flow
in the sample shows a magnification of an underlying anisotropy when using a
square sample. In this reply we present more recent data obtained with a very
high mobility sample, and reiterate that, with or without magnification, an
anisotropic state develops in high Landau levels at very low temperatures.Comment: 1 page, 1 figur
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