1,302 research outputs found
Photoemission Spectral Weight Transfer and Mass Renormalization in the Fermi-Liquid System LaSrTiO
We have performed a photoemission study of LaSrTiO near
the filling-control metal-insulator transition (MIT) as a function of hole
doping. Mass renormalization deduced from the spectral weight and the width of
the quasi-particle band around the chemical potential is compared with
that deduced from the electronic specific heat. The result implies that, near
the MIT, band narrowing occurs strongly in the vicinity of . Spectral
weight transfer occurs from the coherent to the incoherent parts upon
antiferromagnetic ordering, which we associate with the partial gap opening at
.Comment: 4 pages, 3 figure
Dynamics of localized spins coupled to the conduction electrons with charge/spin currents
The effects of the charge/spin currents of conduction electrons on the
dynamics of the localized spins are studied in terms of the perturbation in the
exchange coupling between them. The equations of motion for the
localized spins are derived exactly up to , and the equations for
the two-spin system is solved numerically. It is found that the dynamics
depends sensitively upon the relative magnitude of the charge and spin
currents, i.e., it shows steady state, periodic motion, and even chaotic
behavior. Extension to the multi-spin system and its implications including
possible ``spin current detector'' are also discussed.Comment: 5 pages, 4 figures, REVTe
Localization in a quantum spin Hall system
Localization problem of electronic states in a two-dimensional quantum spin
Hall system (QSH - a symplectic model with a non-trivial topological structure)
is studied by the transfer matrix method. The phase diagram in the plane of
energy and disorder strength is exposed, and demonstrates "levitation" and
"pair-annihilation" of the domains of extended states analogous to that of the
integer quantum Hall system. The critical exponent for the divergence of
the localization length is estimated as which is distinct from
both exponents pertaining to the conventional symplectic and the unitary
quantum Hall systems. This strongly suggests a different universality class
related to the non-trivial topology of the QSH system.Comment: 5 pages, 4 figures, REVTe
Quantum Dynamics of Multiferroic Helimagnets: a Schwinger-Boson Approach
We study the quantum dynamics/fluctuation of the cycloidal helical magnet in
terms of the Schwinger boson approach. In sharp contrast to the classical
fluctuation, the quantum fluctuation is collinear in nature which gives rise to
the collinear spin density wave state slightly above the helical cycloidal
state as the temperature is lowered. Physical properties such as the reduced
elliptic ratio of the spiral, the neutron scattering and infrared absorption
spectra are discussed from this viewpoint with the possible relevance to the
quasi-one dimensional LiCuO and LiCuVO.Comment: 5 pages, 4 figure
Effective mass staircase and the Fermi liquid parameters for the fractional quantum Hall composite fermions
Effective mass of the composite fermion in the fractional quantum Hall
system, which is of purely interaction originated, is shown, from a numerical
study, to exhibit a curious nonmonotonic behavior with a staircase correlated
with the number (=2,4,...) of attached flux quanta. This is surprising since
the usual composite-fermion picture predicts a smooth behavior. On top of that,
significant interactions are shown to exist between composite fermions, where
the excitation spectrum is accurately reproduced in terms of Landau's Fermi
liquid picture with negative (i.e., Hund's type) orbital and spin exchange
interactions.Comment: 4 pages, 3 figures, REVTe
The electrokinetic behavior of calcium oxalate monohydrate in macromolecular solutions
Electrophoretic mobilities were measured for calcium oxalate monohydrate (COM) in solutions containing macromolecules. Two mucopolysaccharides (sodium heparin and chrondroitin sulfate) and two proteins (positively charged lysozyme and negatively charged bovine serum albumin) were studied as adsorbates. The effects of pH, calcium oxalate surface charge (varied by calcium or oxalate ion activity), and citrate concentration were investigated. All four macromolecules showed evidence for chemical adsorption. The macromolecule concentrations needed for reversing the surface charge indicated that the mucopopolysacchrides have greater affinity for the COM surface than the proteins. The amount of proteins that can chemically adsorb appears to be limited to approximately one monomolecular layer. When the surface charge is high, an insufficient number of proteins can chemically adsorb to neutralize or reverse the surface charge. The remaining surface charge is balanced by proteins held near the surface by longer range electrostatic forces only. Citrate ions at high concentrations appear to compete effectively with the negative protein for surface sites but show no evidence for competing with the positively charged protein
Effect of mechanical treatment on the powder properties of zinc phosphate white pigments
Temperature dependent magnetotransport around = 1/2 in ZnO heterostructures
The sequence of prominent fractional quantum Hall states up to =5/11
around =1/2 in a high mobility two-dimensional electron system confined at
oxide heterointerface (ZnO) is analyzed in terms of the composite fermion
model. The temperature dependence of \Rxx oscillations around =1/2
yields an estimation of the composite fermion effective mass, which increases
linearly with the magnetic field. This mass is of similar value to an enhanced
electron effective mass, which in itself arises from strong electron
interaction. The energy gaps of fractional states and the temperature
dependence of \Rxx at =1/2 point to large residual interactions between
composite fermions.Comment: 5 pages, 4 Figure
Chirality induced anomalous-Hall effect in helical spin crystals
Under pressure, the itinerant helimagnet MnSi displays unusual magnetic
properties. We have previously discussed a BCC helical spin crystal as a
promising starting point for describing the high pressure phenomenology. This
state has topologically nontrivial configurations of the magnetization field.
Here we note the consequences for magneto-transport that arise generally from
such spin textures. In particular a skyrmion density induced `topological' Hall
effect, with unusual field dependence, is described.Comment: 4 pages, 3 figures, to appear in the proceedings of SCES 07 (the
international conference on strongly correlated electron systems 2007 in
Houston, USA
Universal Scaling Behavior of Anomalous Hall Effect and Anomalous Nernst Effect in Itinerant Ferromagnets
Anomalous Hall effect (AHE) and anomalous Nernst effect (ANE) in a variety of
ferromagnetic metals including pure metals, oxides, and chalcogenides, are
studied to obtain unified understandings of their origins. We show a universal
scaling behavior of anomalous Hall conductivity as a function of
longitudinal conductivity over five orders of magnitude, which is
well explained by a recent theory of the AHE taking into account both the
intrinsic and extrinsic contributions. ANE is closely related with AHE and
provides us with further information about the low-temperature electronic state
of itinerant ferromagnets. Temperature dependence of transverse Peltier
coefficient shows an almost similar behavior among various
ferromagnets, and this behavior is in good agreement quantitatively with that
expected from the Mott rule.Comment: 4pages, 4figures, 1tabl
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