20,046 research outputs found
Electronic structure of CaSrVO: a tale of two energy-scales
We investigate the electronic structure of CaSrVO using
photoemission spectroscopy. Core level spectra establish an electronic phase
separation at the surface, leading to distinctly different surface electronic
structure compared to the bulk. Analysis of the photoemission spectra of this
system allowed us to separate the surface and bulk contributions. These results
help us to understand properties related to two vastly differing energy-scales,
namely the low energy-scale of thermal excitations (~) and the
high-energy scale related to Coulomb and other electronic interactions.Comment: 4 pages and 3 figures. Europhysics Letters (appearing
Tunnel magnetoresistance and interfacial electronic state
We study the relation between tunnel magnetoresistance (TMR) and interfacial
electronic states modified by magnetic impurities introduced at the interface
of the ferromagnetic tunnel junctions, by making use of the periodic Anderson
model and the linear response theory. It is indicated that the TMR ratio is
strongly reduced depending on the position of the -levels of impurities,
based on reduction in the spin-dependent -electron tunneling in the majority
spin state. The results are compared with experimental results for Cr-dusted
ferromagnetic tunnel junctions, and also with results for metallic multilayers
for which similar reduction in giant magnetoresistance has been reported.Comment: 5 pages, 4 figures, 2 column revtex4 format, ICMFS 2002 (Kyoto
Fermi Surface of 3d^1 Perovskite CaVO3 Near the Mott Transition
We present a detailed de Haas van Alphen effect study of the perovskite
CaVO3, offering an unprecedented test of electronic structure calculations in a
3d transition metal oxide. Our experimental and calculated Fermi surfaces are
in good agreement -- but only if we ignore large orthorhombic distortions of
the cubic perovskite structure. Subtle discrepancies may shed light on an
apparent conflict between the low energy properties of CaVO3, which are those
of a simple metal, and high energy probes which reveal strong correlations that
place CaVO3 on the verge of a metal-insulator transition.Comment: 4 pages, 4 figures (REVTeX
Giant Intrinsic Spin and Orbital Hall Effects in Sr2MO4 (M=Ru,Rh,Mo)
We investigate the intrinsic spin Hall conductivity (SHC) and the d-orbital
Hall conductivity (OHC) in metallic d-electron systems, by focusing on the
t_{2g}-orbital tight-binding model for Sr2MO4 (M=Ru,Rh,Mo). The conductivities
obtained are one or two orders of magnitude larger than predicted values for
p-type semiconductors with 5% hole doping. The origin of these giant Hall
effects is the ``effective Aharonov-Bohm phase'' that is induced by the
d-atomic angular momentum in connection with the spin-orbit interaction and the
inter-orbital hopping integrals. The huge SHC and OHC generated by this
mechanism are expected to be ubiquitous in multiorbital transition metal
complexes, which pens the possibility of realizing spintronics as well as
orbitronics devices.Comment: 5 pages, accepted for publication in PR
Flat-band excitonic states in Kagome lattice on semiconductor surface
Excitonic properties in the Kagome lattice system, which is produced by
quantum wires on semiconductor surfaces, are investigated by using the exact
diagonalization of a tight binding model. It is shown that due to the existence
of flat bands the binding energy of exciton becomes remarkably large in the
two-dimensional Kagome lattice compared to that in one-dimensional lattice, and
the exciton Bohr radius is quite small as large as a lattice constant. We also
discuss the magnetic field effects on the exciton binding energy and the
stability of exciton against the creation of charged exciton and biexciton.Comment: 5 pages, 5 figure
Possible Magnetic Chirality in Optically Chiral Magnet [Cr(CN)][Mn()-pnH(HO)](HO) Probed by Muon Spin Rotation and Relaxation
Local magnetic fields in a molecule-based optically chiral magnet
[Cr(CN)][Mn()-pnH(HO)](HO) (GN-S) and its enantiomer (GN-R) are
studied by means of muon spin rotation and relaxation (muSR). Detailed analysis
of muon precession signals under zero field observed below T_c supports the
average magnetic structure suggested by neutron powder diffraction. Moreover,
comparison of muSR spectra between GN-S and GN-R suggests that they are a pair
of complete optical isomers in terms of both crystallographic and magnetic
structure. Possibility of magnetic chirality in such a pair is discussed.Comment: 5 pages, 5 figures, submitted to J. Phys. Soc. Jp
Variation of the broad X-ray iron line in MCG-6-30-15 during a flare
We report results on the broad iron emission line of the Seyfert galaxy
MCG-6-30-15, obtained from the second long ASCA observation in 1997. The
time-averaged profile of the broad line is very similar to that seen with ASCA
in 1994, so confirming the detailed model fit then obtained. A bright flare is
seen in the light curve, during which the continuum was soft. At that time the
emission line peaks around 5 keV and most of its emission is shifted below 6
keV with no component detected at 6.4 keV (EW<60 eV). This can be interpreted
as the result of an extraordinarily large gravitational redshift due to a
dominant flare occurring very close to the black hole at a radius of <5m.Comment: 5 pages, accepted or publication in MNRAS Letter
A mechanism for unipolar resistance switching in oxide non-volatile memory devices
Building on a recently introduced model for non-volatile resistive switching,
we propose a mechanism for unipolar resistance switching in
metal-insulator-metal sandwich structures. The commutation from the high to low
resistance state and back can be achieved with successive voltage sweeps of the
same polarity. Electronic correlation effects at the metal-insulator interface
are found to play a key role to produce a resistive commutation effect in
qualitative agreement with recent experimental reports on binary transition
metal oxide based sandwich structures.Comment: 4 pages, 2 figure
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