11,135 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
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
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
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
Charge transport in two dimensional electron gas/superconductor junctions with Rashba spin-orbit coupling
We have studied the tunneling conductance in two dimensional electron gas /
insulator / superconductor junctions in the presence of Rashba spin-orbit
coupling (RSOC). It is found that for low insulating barrier the tunneling
conductance is suppressed by the RSOC while for high insulating barrier it is
almost independent of the RSOC. We also find the reentrant behavior of the
conductance at zero voltage as a function of RSOC for intermediate insulating
barrier strength. The results are essentially different from those predicted in
ferromagnet / superconductor junctions. The present derivation of the
conductance is applicable to arbitrary velocity operator with off-diagonal
components.Comment: 8 pages, 6 figure
Correlation Inequalities for Quantum Spin Systems with Quenched Centered Disorder
It is shown that random quantum spin systems with centered disorder satisfy
correlation inequalities previously proved (arXiv:cond-mat/0612371) in the
classical case. Consequences include monotone approach of pressure and ground
state energy to the thermodynamic limit. Signs and bounds on the surface
pressures for different boundary conditions are also derived for finite range
potentials.Comment: 4 page
Perturbation theory for localized solutions of sine-Gordon equation: decay of a breather and pinning by microresistor
We develop a perturbation theory that describes bound states of solitons
localized in a confined area. External forces and influence of inhomogeneities
are taken into account as perturbations to exact solutions of the sine-Gordon
equation. We have investigated two special cases of fluxon trapped by a
microresistor and decay of a breather under dissipation. Also, we have carried
out numerical simulations with dissipative sine-Gordon equation and made
comparison with the McLaughlin-Scott theory. Significant distinction between
the McLaughlin-Scott calculation for a breather decay and our numerical result
indicates that the history dependence of the breather evolution can not be
neglected even for small damping parameter
Extrinsic Entwined with Intrinsic Spin Hall Effect in Disordered Mesoscopic Bars
We show that pure spin Hall current, flowing out of a four-terminal
phase-coherent two-dimensional electron gas (2DEG) within inversion asymmetric
semiconductor heterostructure, contains contributions from both the extrinsic
mechanisms (spin-orbit dependent scattering off impurities) and the intrinsic
ones (due to the Rashba coupling). While the extrinsic contribution vanishes in
the weakly and strongly disordered limits, and the intrinsic one dominates in
the quasiballistic limit, in the crossover transport regime the spin Hall
conductance, exhibiting sample-to-sample large fluctuations and sign change, is
not simply reducible to either of the two mechanisms, which can be relevant for
interpretation of experiments on dirty 2DEGs [V. Sih et al., Nature Phys. 1, 31
(2005)].Comment: 5 pages, 3 color EPS figure
Band-width control in a perovskite-type 3d^1 correlated metal Ca_1-xSr_xVO_3. II. Optical spectroscopy investigation
Optical conductivity spectra of single crystals of Ca_1-xSr_xVO_3 have been
studied to elucidate how the electronic behavior depends on the strength of the
electron correlation without changing the nominal number of electrons per
vanadium atom. The effective mass deduced by the analysis of the Drude-like
contribution do not show critical enhancement, even though the system is close
to the Mott transition. Besides the Drude-like contribution, two anomalous
features were observed in the optical conductivity spectra of the intraband
transition within the 3d band. These features can be assigned to transitions
involving the incoherent and coherent bands near the Fermi level. The large
spectral weight redistribution in this system, however, does not involve a
large mass enhancement.Comment: 12 pages in a Phys. Rev. B camera-ready format with 16 EPS figures
embedded. LaTeX 2.09 source file using "camera.sty" and "prbplug.sty"
provided by N. Shirakawa. For OzTeX (Macintosh), use "ozfig.sty" instead of
"psfig.sty". "ozfig.sty" can be also obtained by e-mail request to N.
Shirakawa: . Submitted to Phys. Rev. B. See "Part I (by
Inoue et al.)" at cond-mat/980107
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