21,119 research outputs found
Observation of an optical non-Fermi-liquid behavior in the heavy fermion state of YbRhSi
We report far-infrared optical properties of YbRhSi for photon
energies down to 2 meV and temperatures 0.4 -- 300 K. In the coherent heavy
quasiparticle state, a linear dependence of the low-energy scattering rate on
both temperature and photon energy was found. We relate this distinct dynamical
behavior different from that of Fermi liquid materials to the non-Fermi liquid
nature of YbRhSi which is due to its close vicinity to an
antiferromagnetic quantum critical point.Comment: 5 pages, 4 figures. submitte
Limitations on the extent of off-center displacements in TbMnO3 from EXAFS measurements
We present EXAFS data at the Mn K and Tb L3 edges that provide upper limits
on the possible displacements of any atoms in TbMnO3. The displacements must be
less than 0.005-0.01A for all atoms which eliminates the possibility of
moderate distortions (0.02A) with a small c-axis component, but for which the
displacements in the ab plane average to zero. Assuming the polarization arises
from a displacement of the O2 atoms along the c-axis, the measured polarization
then leads to an O2 displacement that is at least 6X10^{-4}A, well below our
experimental limit. Thus a combination of the EXAFS and the measured electrical
polarization indicate that the atomic displacements likely lie in the range
6X10^{-4} - 5X10^{-3}A.Comment: submitted to PRB; 11 pages (preprint form) 7 figure
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
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
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
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
Novel in-gap spin state in Zn-doped La_1.85Sr_0.15CuO_4
Low-energy spin excitations of La1.85Sr0.15Cu1-yZnyO4 were studied by neutron
scattering. In y=0.004, the incommensurate magnetic peaks show a well defined
``spin gap'' below Tc. The magnetic signals at omega=3 meV decrease below Tc=27
K for y=0.008, also suggesting the gap opening. At lower temperatures, however,
the signal increases again, implying a novel in-gap spin state. In y=0.017, the
spin gap vanishes and elastic magnetic peaks appear. These results clarify that
doped Zn impurities induce the novel in-gap state, which becomes larger and
more static with increasing Zn.Comment: 4 pages, 4 figure
Electronic structures of CrX (X=S, Te) studied by Cr 2p soft x-ray magnetic circular dichroism
Cr 2p core excited XAS and XMCD spectra of ferromagnetic CrTe
with several concentrations of =0.11-0.33 and ferrimagnetic
CrS have been measured. The observed XMCD lineshapes are found to
very weakly depend on for CrTe. The experimental results
are analyzed by means of a configuration-interaction cluster model calculation
with consideration of hybridization and electron correlation effects. The
obtained values of the spin magnetic moment by the cluster model analyses are
in agreement with the results of the band structure calculation.The calculated
result shows that the doped holes created by the Cr deficiency exist mainly in
the Te 5porbital of CrTe, whereas the holes are likely to be in Cr
3d state for CrS.Comment: 8 pages, 6 figures, accepted for publication in Physical Review
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