6,864 research outputs found
Possible hard X-ray shortages in bursts from KS 1731-260 and 4U 1705-44
Aims: A hard X-ray shortage, implying the cooling of the corona, was observed
during bursts of IGR J17473-272, 4U 1636-536, Aql X-1, and GS 1826-238. Apart
from these four sources, we investigate here an atoll sample, in which the
number of bursts for each source is larger than 5, to explore the possible
additional hard X-ray shortage during {\it Rossi X-ray timing explorer (RXTE)}
era. Methods: According to the source catalog that shows type-I bursts, we
analyzed all the available pointing observations of these sources carried out
by the {\it RXTE} proportional counter array (PCA). We grouped and combined the
bursts according to their outburst states and searched for the possible hard
X-ray shortage while bursting. Results: We found that the island states of KS
1731-260 and 4U 1705-44 show a hard X-ray shortage at significant levels of 4.5
and 4.7 and a systematic time lag of s and
s with respect to the soft X-rays, respectively. While in their banana branches
and other sources, we did not find any consistent shortage.Comment: 5 pages, 4 figures, accepted by A&A as a research not
Spectral and optical properties in the antiphase stripe phase of the cuprate superconductors
We investigate the superconducting order parameter, the spectral and optical
properties in a stripe model with spin (charge) domain-derived scattering
potential (). We show that the charge domain-derived scattering
is less effective than the spin scattering on the suppression of
superconductivity. For , the spectral weight concentrates on
the () antinodal region, and a finite energy peak appears in the optical
conductivity with the disappearance of the Drude peak. But for , the spectral weight concentrates on the () nodal region,
and a residual Drude peak exists in the optical conductivity without the finite
energy peak. These results consistently account for the divergent observations
in the ARPES and optical conductivity experiments in several high-
cuprates, and suggest that the "insulating" and "metallic" properties are
intrinsic to the stripe state, depending on the relative strength of the spin
and charge domain-derived scattering potentials.Comment: 7 pages, 4 figure
Coexistence of the antiferromagnetic and superconducting order and its effect on spin dynamics in electron-doped high- cuprates
In the framework of the slave-boson approach to the model, it is
found that for electron-doped high- cuprates, the staggered
antiferromagnetic (AF) order coexists with superconducting (SC) order in a wide
doping level ranged from underdoped to nearly optimal doping at the mean-field
level. In the coexisting phase, it is revealed that the spin response is
commensurate in a substantial frequency range below a crossover frequency
for all dopings considered, and it switches to the incommensurate
structure when the frequency is higher than . This result is in
agreement with the experimental measurements. Comparison of the spin response
between the coexisting phase and the pure SC phase with a
-wave pairing plus a higher harmonics term (DP+HH) suggests
that the inclusion of the two-band effect is important to consistently account
for both the dispersion of the spin response and the non-monotonic gap behavior
in the electron-doped cuprates.Comment: 6 pages, 5 figure
- β¦