8,727 research outputs found
Property of \sigma(600) and Chiral Symmetry
The iso-singlet scalar resonance \sigma(600), found in the recent \pi\pi
phase shift analysis, is pointed out to have the properties of the \sigma meson
in the \sigma model. The role of the \lambda\phi^4 interaction as a source of
the ``background phase", which was essential there, is also discussed.Comment: 4pages, Latex with Prog.Theor.Phys. format PTPTEX.sty, no figures, to
be published in Prog.Theor.Phys.96(1996
Functions to map photoelectron distributions in a variety of setups in angle-resolved photoemission spectroscopy
The distribution of photoelectrons acquired in angle-resolved photoemission
spectroscopy can be mapped onto energy-momentum space of the Bloch electrons in
the crystal. The explicit forms of the mapping function depend on the
configuration of the apparatus as well as on the type of the photoelectron
analyzer. We show that the existence of the analytic forms of
is guaranteed in a variety of setups. The variety includes the case when the
analyzer is equipped with a photoelectron deflector. Thereby, we provide a
demonstrative mapping program implemented by an algorithm that utilizes both
and . The mapping methodology is also usable in other
spectroscopic methods such as momentum-resolved electron-energy loss
spectroscopy.Comment: Mapping program is open accessed from publisher's sit
An Analysis of \pi\pi-Scattering Phase Shift and Existence of \sigma(555) particle
In most of the Nambu:Jona-Lasinio(NJL)-type models, realizing the hidden
chiral symmetry, the existence of a scalar particle \sigma is needed with a
mass m_\sigma=2 m_q, as a partner of the Nambu-Goldstone boson \pi. However,
the results of many analyses on \pi\pi phase-shift thus far made have been
negative for its existence. In this paper we re-analyze the phase-shift,
applying a new method, the interfering amplitude method, which treats the
T-matrix directly and describes multi-resonances in conformity with the
unitarity. As a result, the existence of \sigma has been strongly suggested
from the behavior of the \pi\pi-->\pi\pi phase shift between the \pi\pi- and
the KK- thresholds, with mass = 553.3 +- 0.5_{st} MeV and width= 242.6 +-
1.2_{st} MeV. The most crucial point in our analysis is the introduction of a
negative background phase, possibly reflecting a ``repulsive core" in \pi\pi
interactions. The properties of f_0(980) are also investigated from data
including those over the KK threshold. Its mass is obtained as 993.2 +-
6.5_{st} +- 6.9_{sys} MeV. Its width is about a hundred MeV, although this
depends largely on the treatment of the elasticity and the \pi\pi-->KK phase
shift, both of which may have large experimental uncertainties.Comment: 22 pages, Latex with Prog. Theor. Phys. format PTPTEX.sty, 4 EPS
figure
Temperature Dependence of the Chemical Potential in NaxCoO2: Implications for the Large Thermoelectric Power
We have performed a temperature-dependent photoemission study of a NaxCoO2
(x~0.8) epitaxial thin film prepared by the reactive solid-phase epitaxy
method. The chemical potential shift as a function of temperature was derived
from the Co 3d peak shift, and revealed a crossover from the degenerate Fermion
state at low temperatures to the correlated hopping state of Co3+/Co4+
mixed-valence at high temperatures. This suggests that the large thermoelectric
power at high temperatures should be considered in the correlated hopping
picture.Comment: 5 pages, 4 figure
Nonlocality in unambiguous pure-state identification without classical knowledge
For two bipartite pure states, we consider the problem of unambiguous
identification without classical knowledge on the states. The optimal success
probability by means of local operations and classical communication is shown
to be less than the maximum attainable by the global measuring scheme.Comment: 8 pages, no figure
Correlation between Superconducting Transition Temperature and Increase of Nuclear Spin-Lattice Relaxation Rate Devided by Temperature at in the Hydrate Cobaltate NaCoOHO
We have performed Co-nuclear quadrupole resonance (NQR) studies on
NaCoOHO compounds with different Na () and hydrate
() contents. Two samples with different Na contents but nearly the same
values ( = 0.348, = 4.7 K ; = 0.339, = 4.6 K) were
investigated. The spin-lattice relaxation rate in the superconducting
(SC) and normal states is almost the same for the two samples except just above
. NQR measurements were also performed on different-hydrate-content
samples with different values, which were prepared from the same
Na-content ( = 0.348) sample. From measurements of using the
different-hydrate-content samples, it was found that a low- sample with
K has a larger residual density of states (DOS) in the SC state and
a smaller increase of just above than a high- sample with
= 4.7 K. The former behavior is consistent with that observed in
unconventional superconductors, and the latter suggests the relationship
between and the increase in DOS just above . This increase, which is
seemingly associated with the two-dimensionality of the CoO plane, is
considered to be one of the most important factors for the occurrence of
superconductivity.Comment: 5 pages, 5 figures, To be published in J. Phys. Soc. Jp
Doping-dependent energy scale of the low-energy band renormalization in (Bi,Pb)2(Sr,La)2CuO6+d
The nodal band-dispersion in (Bi,Pb)2(Sr,La)2CuO6+d (Bi2201) is investigated
over a wide range of doping by using 7-eV laser-based angle-resolved
photoemission spectroscopy. We find that the low-energy band renormalization
("kink"), recently discovered in Bi2Sr2CaCu2O8+d (Bi2212), also occurs in
Bi2201, but at a binding energy around half that in Bi2212, implying its
scaling to Tc. Surprisingly the coupling-energy dramatically increases with a
decrease of carrier concentration, showing a sharp enhancement across the
optimal doping. This strongly contrasts to other mode-couplings at higher
binding-energies (~20, ~40, and ~70 meV) with almost no doping variation in
energy scale. These nontrivial properties of the low-energy kink (material- and
doping-dependence of the coupling-energy) demonstrate the significant
correlation among the mode-coupling, the Tc, and the strong electron
correlation
Evidence for s-wave superconductivity with antiferromagnetic fluctuations in filled skutterudite LaFeP: La and P-NMR studies
We have performed La,P-NMR studies on a filled skutterudite
superconductor LaFeP with a critical temperature K. In
the normal state, the presence of antiferromagnetic (AFM) fluctuations at
finite wave vectors is suggested from the relation between the nuclear
spin-lattice relaxation rate and the Knight shift. In the
superconducting (SC) state, the distinct coherence peak was observed just below
, and is easily suppressed by the applied field. An exponential decrease
of was observed, suggestive of the isotropic superconducting gap with
. Besides, we observed the decrease of the Knight
shift, indicative of the singlet-pair formation below . These results are
clear evidence that LaFeP is a rare s-wave superconductor with
significant AFM fluctuations.Comment: 5 pages, 6 figures, to be published in Journal of the Physical
Society of Japan, Vol.74 No.1
Potential Profiling of the Nanometer-Scale Charge Depletion Layer in n-ZnO/p-NiO Junction Using Photoemission Spectroscopy
We have performed a depth-profile analysis of an all-oxide p-n junction diode
n-ZnO/p-NiO using photoemission spectroscopy combined with Ar-ion sputtering.
Systematic core-level shifts were observed during the gradual removal of the
ZnO overlayer, and were interpreted using a simple model based on charge
conservation. Spatial profile of the potential around the interface was
deduced, including the charge-depletion width of 2.3 nm extending on the ZnO
side and the built-in potential of 0.54 eV
NMR Study of MnSi under Pressure
The magnetic phase diagram of the weak itinerant helimagnetic
compound MnSi is reviewed upon a Nuclear Magnetic Resonance (NMR) experiment.
We present a systematic study on the evolution of the NMR spin echo signal at
K of the non-magnetic silicone sites, Si, up to 17.8 kbar. The
pressure effect is interpreted as a weak variation of the local electronic spin
polarization and the coexistence of magnetic and non magnetic Mn atoms under
pressure. From the volume dependence of (), we show notably that a
local magnetic order remains above the critical pressure of kbar.Comment: 9 pages, 2 figures. To be published in the Review of High Pressure
Science and Technolog
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