18,579 research outputs found
First Detection of Ar-K Line Emission from the Cygnus Loop
We observed the Cygnus Loop with XMM-Newton (9 pointings) and Suzaku (32
pointings) between 2002 and 2008. The total effective exposure time is 670.2
ks. By using all of the available data, we intended to improve a
signal-to-noise ratio of the spectrum. Accordingly, the accumulated spectra
obtained by the XIS and the EPIC show some line features around 3 keV that are
attributed to the S He and Ar He lines, respectively. Since the
Cygnus Loop is an evolved (10,000 yr) supernova remnant whose temperature
is relatively low (1 keV) compared with other young remnants, its spectrum
is generally faint above 3.0 keV, no emission lines, such as the Ar-K line have
ever been detected. The detection of the Ar-K line is the first time and we
found that its abundance is significantly higher than that of the solar value;
9.0 and 8.4 (in units of solar), estimated from
the XIS and the EPIC spectra, respectively. We conclude that the Ar-K line
originated from the ejecta of the Cygnus Loop. Follow-up X-ray observations to
tightly constrain the abundances of Ar-rich ejecta will be useful to accurately
estimate the progenitor's mass.Comment: 12 pages, 9 figures, accepted for publication in PAS
Temperature dependence of the impurity-induced resonant state in Zn-doped Bi_2Sr_2CaCu_2O by Scanning Tunneling Spectroscopy
We report on the temperature dependence of the impurity-induced resonant
state in Zn-doped Bi_2Sr_2CaCu_2O by scanning tunneling
spectroscopy at 30 mK < T < 52 K. It is known that a Zn impurity induces a
sharp resonant peak in tunnel spectrum at an energy close to the Fermi level.
We observed that the resonant peak survives up to 52 K. The peak broadens with
increasing temperature, which is explained by the thermal effect. This result
provides information to understand the origin of the resonant peak.Comment: 4 pages, 3 figures, to appear in Phys. Rev.
Linear-response theory of the longitudinal spin Seebeck effect
We theoretically investigate the longitudinal spin Seebeck effect, in which
the spin current is injected from a ferromagnet into an attached nonmagnetic
metal in a direction parallel to the temperature gradient. Using the fact that
the phonon heat current flows intensely into the attached nonmagnetic metal in
this particular configuration, we show that the sign of the spin injection
signal in the longitudinal spin Seebeck effect can be opposite to that in the
conventional transverse spin Seebeck effect when the electron-phonon
interaction in the nonmagnetic metal is sufficiently large. Our linear-response
approach can explain the sign reversal of the spin injection signal recently
observed in the longitudinal spin Seebeck effect.Comment: Proc. of ICM 2012 (Accepted for publication in J. Korean Phys. Soc.),
typos correcte
Effect of disorder outside the CuO planes on of copper oxide superconductors
The effect of disorder on the superconducting transition temperature
of cuprate superconductors is examined. Disorder is introduced into the cation
sites in the plane adjacent to the CuO planes of two single-layer
systems, BiSrLnCuO and
LaNdSrCuO. Disorder is controlled by changing
rare earth (Ln) ions with different ionic radius in the former, and by varying
the Nd content in the latter with the doped carrier density kept constant. We
show that this type of disorder works as weak scatterers in contrast to the
in-plane disorder produced by Zn, but remarkably reduces suggesting
novel effects of disorder on high- superconductivity.Comment: 5 pages, 5 figures, to be published in Phys. Rev. Let
Many-Body Theory of Synchronization by Long-Range Interactions
Synchronization of coupled oscillators on a -dimensional lattice with the
power-law coupling and randomly distributed intrinsic
frequency is analyzed. A systematic perturbation theory is developed to
calculate the order parameter profile and correlation functions in powers of
. For , the system exhibits a sharp
synchronization transition as described by the conventional mean-field theory.
For , the transition is smeared by the quenched disorder, and the
macroscopic order parameter \Av\psi decays slowly with as |\Av\psi|
\propto g_0^2.Comment: 4 pages, 2 figure
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