2,164 research outputs found
Electric-field-induced lifting of the valley degeneracy in alpha-(BEDT-TTF)_2I_3 Dirac-like Landau levels
The relativistic Landau levels in the layered organic material
alpha-(BEDT-TTF)_2I_3 [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene] are
sensitive to the tilt of the Dirac cones, which, as in the case of graphene,
determine the low-energy electronic properties under appropriate pressure. We
show that an applied inplane electric field, which happens to be in competition
with the tilt of the cones, lifts the twofold valley degeneracy due to a
different level spacing. The scenario may be tested in infrared transmission
spectroscopy.Comment: 4 pages, 1 figure; version with minor corrections published in EP
Multiband superconductivity in the heavy fermion compound PrOs4Sb12
The thermal conductivity of the heavy fermion superconductor PrOs4Sb12 was
measured down to Tc/40 throughout the vortex state. At lowest temperatures and
for magnetic fields H ~ 0.07Hc2, already 40% of the normal state thermal
conductivity is restored. This behaviour (similar to that observed in MgB2) is
a clear signature of multiband superconductivity in this compound.Comment: 12pages, version #1 20\_06\_200
Non-factorizable long distance contributions in color suppressed decays of B mesons
, , and decays are
studied. Their amplitude is given by a sum of factorized and non-factorizable
ones. The latter which is estimated by using a hard pion approximation is
rather small in color favored and decays but still
can efficiently interfere with the main amplitude given by the factorization.
In the color suppressed and decays, the
non-factorizable contribution is very important. The sum of the factorized and
non-factorizable amplitudes can reproduce well the existing experimental data
on the branching ratios for the color favored and
and the color suppressed and decays by
taking reasonable values of unknown parameters involved.Comment: 19 pages, Revte
Electron Spin Resonance of the ferromagnetic Kondo lattice CeRuPO
The spin dynamics of the ferromagnetic Kondo lattice CeRuPO is investigated
by Electron Spin Resonance (ESR) at microwave frequencies of 1, 9.4, and
34~GHz. The measured resonance can be ascribed to a rarely observed bulk Ce3+
resonance in a metallic Ce compound and can be followed below the ferromagnetic
transition temperature Tc=14 K. At T>Tc the interplay between the RKKY-exchange
interaction and the crystal electric field anisotropy determines the ESR
parameters. Near Tc the spin relaxation rate is influenced by the critical
fluctuations of the order parameter.Comment: This is an article accepted for publication in Journal of Physics:
Condensed Matte
Nuclear g-Factor of the 2972 keV Isomer in 130Xe
開始ページ、終了ページ: 冊子体のページ付
Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
The recent discovery of superconductivity in iron-arsenic compounds below a
transition temperature (Tc) as high as 55K ended the monopoly of copper oxides
(cuprates) in the family of high-Tc superconductors. A critical issue in
understanding this new superconductor, as in the case of cuprates, is the
nature, in particular the symmetry and orbital dependence, of the
superconducting gap. There are conflicting experimental results, mostly from
indirect measurements of the low energy excitation gap, ranging from one gap to
two gaps, from line nodes to nodeless gap function in momentum space. Here we
report a direct observation of the superconducting gap, including its momentum,
temperature, and Fermi surface (FS) dependence in Ba0.6K0.4Fe2As2 (Tc = 37 K)
using angle-resolved photoelectron spectroscopy. We find two superconducting
gaps with different values: a large gap (~ 12 meV) on the two small hole-like
and electron-like FS sheets, and a small gap (~ 6 meV) on the large hole-like
FS. Both gaps, closing simultaneously at the bulk Tc, are nodeless and nearly
isotropic around their respective FS sheets. The isotropic pairing interactions
are strongly orbital dependent, as the ratio 2Delta/kBTc switches from weak to
strong coupling on different bands. The same and surprisingly large
superconducting gap due to strong pairing on the two small FS, which are
connected by the (pi, 0) spin-density-wave vector in the parent compound,
strongly suggests that the pairing mechanism originates from the inter-band
interactions between these two nested FS sheets.Comment: 4 figure
D1-D5 on ALE Space
We construct a two-dimensional N=(0,4) quiver gauge theory on D1-brane
probing D5-branes on ALE space, and study its IR behavior. This can be thought
of as a gauged linear sigma model for the NS5-branes on ALE space.Comment: 17 pages, 1 figure, lanlmac; v2: reference adde
Spectroscopic Study of As and La NMR on Layered Structure Ferromagnet LaCoAsO
As and La field-swept NMR spectra were obtained for the novel
weakly itinerant ferromagnet LaCoAsO with 2D layered structure above the Curie
temperature of 55 K. By analyzing NMR spectra, temperature dependences of
Knight shift and nuclear quadrupole resonance frequency were
obtained successfully for each nucleus. We confirmed from the so-called
- plots that the macroscopic magnetization of our {LaCoAsO} powder
sample is intrinsic and does not contain the contribution from impurity phases.
We estimated hyperfine coupling constants from the slope of - plots
and compared to that of iron-arsenide superconductor.Comment: 5 pages, 5 figures, published on J. Phys. Soc. Jpn. at Vol.79,
pp.054703 (2010)
The effect of uniaxial pressure on the magnetic anomalies of the heavy-fermion metamagnet CeRu2Si2
The effect of uniaxial pressure (P_u) on the magnetic susceptibility (X),
magnetization (M), and magnetoresistance (MR) of the heavy-fermion metamagnet
CeRu2Si2 has been investigated. For the magnetic field along the tetragonal c
axis, it is found that characteristic physical quantities, i.e., the
temperature of the susceptibility maximum (T_max), the pagamagnetic Weiss
temperature (Q_p), 1/X at 2 K, and the magnetic field of the metamagnetic
anomaly (H_M), scale approximately linearly with P_u, indicating that all the
quantities are related to the same energy scale, probably of the Kondo
temperature. The increase (decrease) of the quantities for P_u || c axis (P_u
|| a axis) can be attributed to a decrease (increase) in the nearest Ce-Ru
distance. Consistently in MR and X, we observed a sign that the anisotropic
nature of the hybridization, which is believed to play an important role in the
metamagnetic anomaly, can be controlled by applying the uniaxial pressure.
PACS numbers: 75.20.Hr, 71.27.+a, 74.62.FjComment: 7 pages, ReVTeX, 6 EPS figures : Will appear in Phys. Rev.
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