3,168 research outputs found
Low-Temperature Spin Dynamics of Doped Manganites: roles of Mn-t2g and eg and O-2p states
The low-temperature spin dynamics of doped manganites have been analyzed
within a tight-binding model, the parameters of which are estimated by mapping
the results of ab initio density functional calculations onto the model. This
approach is found to provide a good description of the spin dynamics of the
doped manganites, observed earlier within the ab initio calculations. Our
analysis not only provides some insight into the roles of the eg and the t2g
states but also indicates that the oxygen p states play an important role in
the spin dynamics. This may cast doubt on the adaptability of the conventional
model Hamiltonian approaches to the analysis of spin dynamics of doped
manganites.Comment: 12 pages; Includes 5 figure
Composite Polarons in Ferromagnetic Narrow-band Metallic Manganese Oxides
A new mechanism is proposed to explain the colossal magnetoresistance and
related phenomena. Moving electrons accompanied by Jahn-Teller phonon and
spin-wave clouds may form composite polarons in ferromagnetic narrow-band
manganites. The ground-state and finite-temperature properties of such
composite polarons are studied in the present paper. By using a variational
method, it is shown that the energy of the system at zero temperature decreases
with the formation of composite polaron; the energy spectrum and effective mass
of the composite polaron at finite temperature is found to be strongly
renormalized by the temperature and the magnetic field. It is suggested that
the composite polaron contribute significantly to the transport and the
thermodynamic properties in ferromagnetic narrow-band metallic manganese
oxides.Comment: Latex, no figur
NMR imaging of the soliton lattice profile in the spin-Peierls compound CuGeO_3
In the spin-Peierls compound CuGeO, the commensurate-incommensurate
transition concerning the modulation of atomic position and the local
spin-polarization is fully monitored at T=0 by the application of an external
magnetic field () above a threshold value 13 Tesla. The
solitonic profile of the spin-polarization, as well as its absolute magnitude,
has been precisely imaged from NMR lineshapes obtained for
varying from 0.0015 to 2. This offers a unique possibility
to test quantitatively the various numerical and analytical methods developed
to solve a generic Hamiltonian in 1-D physics, namely strongly interacting
fermions in presence of electron-phonon coupling at arbitrary band filling.Comment: 3 pages, 4 eps figures, RevTeX, submitted to Physical Review Lette
Ogle-2018-blg-0677lb: A super earth near the galactic bulge
We report the analysis of the microlensing event OGLE-2018-BLG-0677. A small
feature in the light curve of the event leads to the discovery that the lens is
a star-planet system. Although there are two degenerate solutions that could
not be distinguished for this event, both lead to a similar planet-host mass
ratio. We perform a Bayesian analysis based on a Galactic model to obtain the
properties of the system and find that the planet corresponds to a
super-Earth/sub-Neptune with a mass . The host star has a mass . The projected
separation for the inner and outer solutions are ~AU
and ~AU respectively. At , this is by far the lowest for any
securely-detected microlensing planet to date, a feature that is closely
connected to the fact that it is detected primarily via a "dip" rather than a
"bump".Comment: 15 page, 12 figures, Published in A
OGLE-2017-BLG-1130: The First Binary Gravitational Microlens Detected From Spitzer Only
We analyze the binary gravitational microlensing event OGLE-2017-BLG-1130
(mass ratio q~0.45), the first published case in which the binary anomaly was
only detected by the Spitzer Space Telescope. This event provides strong
evidence that some binary signals can be missed by observations from the ground
alone but detected by Spitzer. We therefore invert the normal procedure, first
finding the lens parameters by fitting the space-based data and then measuring
the microlensing parallax using ground-based observations. We also show that
the normal four-fold space-based degeneracy in the single-lens case can become
a weak eight-fold degeneracy in binary-lens events. Although this degeneracy is
resolved in event OGLE-2017-BLG-1130, it might persist in other events.Comment: 14 pages, 5 figure
Electron-fluctuation interaction in a non-Fermi superconductor
We studied the influence of the amplitude fluctuations of a non-Fermi
superconductor on the energy spectrum of the 2D Anderson non-Fermi system. The
classical fluctuations give a temperature dependence in the pseudogap induced
in the fermionic excitations.Comment: revtex fil
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