20,223 research outputs found
Quasi-particle scattering and protected nature of topological states in a parent topological insulator BiSe
We report on angle resolved photoemission spectroscopic studies on a parent
topological insulator (TI), BiSe. The line width of the spectral
function (inverse of the quasi-particle lifetime) of the topological metallic
(TM) states shows an anomalous behavior. This behavior can be reasonably
accounted for by assuming decay of the quasi-particles predominantly into bulk
electronic states through electron-electron interaction and defect scattering.
Studies on aged surfaces reveal that topological metallic states are very much
unaffected by the potentials created by adsorbed atoms or molecules on the
surface, indicating that topological states could be indeed protected against
weak perturbations.Comment: accepted for publication in Phys. Rev. B(R
Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity
We report temperature-dependent polarized optical conductivity
[] spectra of CeFeAl, which is a reference material
for CeRuAl and CeOsAl with an anomalous magnetic
transition at 28 K. The spectrum along the b-axis differs
greatly from that in the -plane, indicating that this material has an
anisotropic electronic structure. At low temperatures, in all axes, a shoulder
structure due to the optical transition across the hybridization gap between
the conduction band and the localized states, namely -
hybridization, appears at 55 meV. However, the gap opening temperature and the
temperature of appearance of the quasiparticle Drude weight are strongly
anisotropic indicating the anisotropic Kondo temperature. The strong
anisotropic nature in both electronic structure and Kondo temperature is
considered to be relevant the anomalous magnetic phase transition in
CeRuAl and CeOsAl.Comment: 5 pages, 4 figure
Internal magnetic field effect on magnetoelectricity in orthorhombic crystals
We have investigated the role of the 4 moment on the magnetoelectric (ME)
effect of orthorhombic MnO (=rare earth ions). In order to clarify
the role of the 4 moment, we prepared three samples: (Eu,Y)MnO without
the 4 moment, TbMnO with the anisotropic 4 moment, and
(Gd,Y)MnO with the isotropic 4 moment. The ferroelectric behaviors of
these samples are different from each other in a zero magnetic field.
(Eu,Y)MnO and (Gd,Y)MnO show the ferroelectric polarization along
the a axis in the ground state, while TbMnO shows it along the c axis.
Such difference may arise from the influence of the anisotropic Tb 4
moment. The direction of the ferroelectric polarization of MnO is
determined by the internal magnetic field arising from the 4 moment.Comment: 2 pages, 1 figure, the proceeding of International Conference of
Magnetism, to be published in the Journal of Magnetism and Magnetic Material
Low scale Seesaw model and Lepton Flavor Violating Rare B Decays
We study lepton flavor number violating rare B decays, , in a seesaw model with low scale singlet Majorana neutrinos
motivated by the resonant leptogenesis scenario. The branching ratios of
inclusive decays with two almost
degenerate singlet neutrinos at TeV scale are investigated in detail. We find
that there exists a class of seesaw model in which the branching fractions of and can be as large as and
within the reach of Super B factories, respectively, without being in
conflict with neutrino mixings and mass squared difference of neutrinos from
neutrino data, invisible decay width of and the present limit of .Comment: 19 pages, 6 figure
Uniaxial pressure dependencies of the phase transitions in GdMnO
GdMnO shows an incommensurate antiferromagnetic order below
K, transforms into a canted A-type antiferromagnet below K, and for
finite magnetic fields along the b axis ferroelectric order occurs below
K. From high-resolution thermal expansion measurements along all
three principal axes, we determine the uniaxial pressure dependencies of the
various transition temperatures and discuss their correlation to changes of the
magnetic exchange couplings in MnO ().Comment: 2 pages, 3 figures, submitted to JMMM (Proceedings of ICM'06, Kyoto
Magnetodielectric detection of magnetic quadrupole order in Ba(TiO)Cu(PO) with CuO square cupolas
In vortex-like spin arrangements, multiple spins can combine into emergent
multipole moments. Such multipole moments have broken space-inversion and
time-reversal symmetries, and can therefore exhibit linear magnetoelectric (ME)
activity. Three types of such multipole moments are known: toroidal, monopole,
and quadrupole moments. So far, however, the ME-activity of these multipole
moments has only been established experimentally for the toroidal moment. Here,
we propose a magnetic square cupola cluster, in which four corner-sharing
square-coordinated metal-ligand fragments form a noncoplanar buckled structure,
as a promising structural unit that carries an ME-active multipole moment. We
substantiate this idea by observing clear magnetodielectric signals associated
with an antiferroic ME-active magnetic quadrupole order in the real material
Ba(TiO)Cu(PO). The present result serves as a useful guide for
exploring and designing new ME-active materials based on vortex-like spin
arrangements.Comment: 4 figure
Halo models in modified gravity theories with self-accelerated expansion
We investigate the structure of halos in the sDGP (self-accelerating branch
of the Dvali-Gavadadze-Porrati braneworld gravity) model and the galileon
modified gravity model on the basis of the static and spherically symmetric
solutions of the collisionless Boltzmann equation, which reduce to the singular
isothermal sphere model and the King model in the limit of Newtonian gravity.
The common feature of these halos is that the density of a halo in the outer
region is larger (smaller) in the sDGP (galileon) model, respectively, in
comparison with Newtonian gravity. This comes from the suppression
(enhancement) of the effective gravity at large distance in the sDGP (galileon)
model, respectively. However, the difference between these modified gravity
models and Newtonian gravity only appears outside the halo due to the
Vainshtein mechanism, which makes it difficult to distinguish between them. We
also discuss the case in which the halo density profile is fixed independently
of the gravity model for comparison between our results and previous work.Comment: 15pages, 6 figures, maches the version to be published in Int. J.
Mod. Phys. D, typos correcte
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