3,209 research outputs found
Evidence against strong correlation in 4d transition metal oxides, CaRuO3 and SrRuO3
We investigate the electronic structure of 4d transition metal oxides, CaRuO3
and SrRuO3. The analysis of the photoemission spectra reveals significantly
weak electron correlation strength (U/W ~ 0.2) as expected in 4d systems and
resolves the long standing issue that arose due to the prediction of large U/W
similar to 3d-systems. It is shown that the bulk spectra, thermodynamic
parameters and optical properties in these systems can consistently be
described using first principle approaches. The observation of different
surface and bulk electronic structures in these weakly correlated 4d systems is
unusual.Comment: 4 pages, 4 figure
Observation of R-Band Variability of L Dwarfs
We report, for the first time, photometric variability of L dwarfs in
band. Out of three L1 dwarfs (2MASS 1300+19, 2MASS 1439+19, and 2MASS 1658+70)
observed, we have detected R band variability in 2MASS 1300+19 and 2MASS
1439+19. The objects exhibit variability of amplitude ranging from 0.01 mag to
0.02 mag. Object 2MASS 1658+70, turns out to be non-variable in both and
band. However, more observations are needed to infer its variability. No
periodic behaviour in the variability is found from the two L1 dwarfs that are
variable. All the three L1 dwarfs have either negligible or no
activity. In the absence of any direct evidence for the presence of
sufficiently strong magnetic field, the detection of polarization at the
optical favors the presence of dust in the atmosphere of L dwarfs. We suggest
that the observed band photometric variability is most likely due to
atmospheric dust activity.Comment: 13 pages (latex, aastex style) including 3 eps figures. Accepted for
publication in The Astrophysical Journal Letter
Micellar Aggregates of Gemini Surfactants: Monte Carlo Simulation of a Microscopic Model
We propose a "microscopic" model of gemini surfactants in aqueous solution.
Carrying out extensive Monte Carlo simulations, we study the variation of the
critical micellar concentration (CMC) of these model gemini surfactants with
the variation of the (a) length of the spacer connecting the two hydrophilic
heads, (b) length of the hydrophobic tail and (c) the bending rigidity of the
hydrocarbon chains forming the spacer and the tail; some of the trends of
variation are counter-intuitive but are in excellent agreement with the
available experimental results. Our simulations also elucidate the dependence
of the shapes of the micellar aggregates and the magnitude of the CMC on the
geometrical shape and size of the surfactant molecules and the electrical
charge on the hydrophilic heads
Evolution of superconductivity in Fe-based systems with doping
We study the symmetry and the structure of the gap in Fe-based
superconductors by decomposing the pairing interaction obtained in the RPA into
s- and d-wave components and into contributions from scattering between
different Fermi surfaces. We show that each interaction is well approximated by
the lowest angular harmonics and use this simplification to analyze the origin
of the attraction in the two channels, the competition between s- and d-wave
solutions, and the origin of superconductivity in heavily doped systems, when
only electron or only hole pockets are present.Comment: 4pp, 2 figures, 2 table
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