114 research outputs found
Glass Transition in a Two-Dimensional Electron System in Silicon in a Parallel Magnetic Field
Studies of low-frequency resistance noise show that the glassy freezing of
the two-dimensional electron system (2DES) in Si in the vicinity of the
metal-insulator transition (MIT) persists in parallel magnetic fields B of up
to 9 T. At low B, both the glass transition density and , the
critical density for the MIT, increase with B such that the width of the
metallic glass phase () increases with B. At higher B, where the
2DES is spin polarized, and no longer depend on B. Our results
demonstrate that charge, as opposed to spin, degrees of freedom are responsible
for glassy ordering of the 2DES near the MIT.Comment: 4 pages, 5 figure
Effect of Local Magnetic Moments on the Metallic Behavior in Two Dimensions
The temperature dependence of conductivity in the metallic phase
of a two-dimensional electron system in silicon has been studied for different
concentrations of local magnetic moments. The local moments have been induced
by disorder, and their number was varied using substrate bias. The data suggest
that in the limit of the metallic behavior, as characterized by
, is suppressed by an arbitrarily small amount of scattering by
local magnetic moments.Comment: 4 pages, revtex, plus four encapsulated postscript figure
Fantastic Fits with fantasy of Active Galactic Nuclei Spectra -- Exploring the Fe II emission near the H line
In this study, a refined approach for multicomponent fitting of active
galactic nuclei (AGN) spectra is presented utilizing the newly developed Python
code (fully automated python tool for AGN spectra analysis). AGN
spectra are modeled by simultaneously considering the underlying broken
power-law continuum, predefined emission line lists, and an Fe II model, which
is here extended to cover the wavelength range 3700 - 11000 A. The Fe II model,
founded solely on atomic data, effectively describes the extensive emission of
the complex iron ion in the vicinity of the H and H lines, as
well as near the H line, which was previously rarely studied. The
proposed spectral fitting approach is tested on a sample of high-quality AGN
spectra from the Sloan Digital Sky Survey (SDSS) Data Release 17. The results
indicate that when Fe II emission is present near H, it is also detected
redward from H, potentially contaminating the broad H line
wings and thus affecting the measurements of its flux and width. The production
of Fe II emission is found to be strongly correlated with Eddington luminosity
and appears to be controlled by the similar mechanism as the hydrogen Balmer
lines. The study highlights the benefits of fitting AGN type 1 spectra with the
code, pointing that it may be used as a robust tool for analyzing a
large number of AGN spectra in the coming spectral surveys.Comment: Accepted in ApJ
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