2,872 research outputs found
Macroscopic quantum tunneling and quasiparticle-tunneling blockade effect in s-wave/d-wave hybrid junctions
We have theoretically investigated macroscopic quantum tunneling (MQT) and
the influence of nodal quasiparticles and zero energy bound states (ZES) on MQT
in s-wave/ d-wave hybrid Josephson junctions. In contrast to d-wave/d-wave
junctions, the low-energy quasiparticle dissipation resulting from nodal
quasiparticles and ZES is suppressed due to a quasiparticle-tunneling blockade
effect in an isotropic s-wave superconductor. Therefore, the inherent
dissipation in these junctions is found to be very weak. We have also
investigated MQT in a realistic s-wave/d-wave (Nb/Au/YBCO) junction in which
Ohmic dissipation in a shunt resistance is stronger than the inherent
dissipation and find that MQT is observable within the current experimental
technology. This result suggests high potential of s-wave/d-wave hybrid
junctions for applications in quantum information devices.Comment: 4 pages, 3 figure
Optical I-band Linear Polarimetry of the Magnetar 4U 0142+61 with Subaru
The magnetar 4U~0142+61 has been well studied at optical and infrared
wavelengths and is known to have a complicated broad-band spectrum over the
wavelength range. Here we report the result from our linear imaging polarimetry
of the magnetar at optical -band. From the polarimetric observation carried
out with the 8.2-m Subaru telescope, we determine the degree of linear
polarization 3.4\%, or 5.6\% (90\% confidence level).
Considering models suggested for optical emission from magnetars, we discuss
the implications of our result. The upper limit measurement indicates that
different from radio pulsars, magnetars probably would not have strongly
polarized optical emission if the emission arises from their magnetosphere as
suggested.Comment: 5 pages, 1 figure, accepted for publication on Ap
Distinct transport behaviors of LaFe1-yCoyAsO1-xFx (x=0.11) between the superconducting and nonsuperconducting metallic y regions divided by y ~ 0.05
Electrical resistivities, Hall coefficients and thermoelectric powers have
been measured for polycrystalline samples of LaFe1-yCoyAsO1-xFx (x=0.11) with
various values of y. The results show that there exists clear distinction of
these transport behaviors between the superconducting and nonsuperconducting
metallic regions of y divided by the boundary value yc~0.05. We have found that
the behaviors in both regions are very similar to those of high-Tc Cu oxides in
the corresponding phases. If they reflect, as in the case of Cu oxides, effects
of strong magnetic fluctuations, the energy scale of the fluctuations is
considered to be smaller than that of the high Cu oxides by a factor of ~1/2.
Arguments on the electronic nature and superconducting symmetry are presented
on the basis of the observed small rate of the Tc suppression rate by the Co
doping.Comment: 8 pages, 4 figures, submitted to J. Phys. Soc. Jp
Magnetic Ordering in V-Layers of the Superconducting System of Sr2VFeAsO3
Results of transport, magnetic, thermal, and 75As-NMR measurements are
presented for superconducting Sr2VFeAsO3 with an alternating stack of FeAs and
perovskite-like block layers. Although apparent anomalies in magnetic and
thermal properties have been observed at ~150 K, no anomaly in transport
behaviors has been observed at around the same temperature. These results
indicate that V ions in the Sr2VO3-block layers have localized magnetic moments
and that V-electrons do not contribute to the Fermi surface. The electronic
characteristics of Sr2VFeAsO3 are considered to be common to those of other
superconducting systems with Fe-pnictogen layers.Comment: 4 pages, 4 figures, To appear in JPSJ 79 (2010) 12371
Critical Temperature Tc and Charging Energy Ec between B-B layers of Superconducting diboride materials MgB2 in 3D JJA model
The diboride materials MB2 (M = Mg, Be, Pb, etc.) are discussed on the basis
of the 3D Josephson junction array (JJA) model due to Kawabata-Shenoy-Bishop,
in terms of the B-B layers in the diborides analogous to the Cu-O ones in the
cuprates.
We propose a possibility of superconducting materials with the MgB2-type
structure which exhibit higher critical temperature Tc over 39K of MgB2.
We point out a role of interstitial ionic atoms (e.g., Mg in MgB2) as
capacitors between the B-B layers, which reduce the charging coupling energy in
JJA.Comment: 3 pages, 1 figure included; to be published in J. Phys. Soc. Jpn. 70,
No.10 (2001
The evolution of the peculiar Type Ia supernova SN 2005hk over 400 days
photometry and medium resolution optical spectroscopy of peculiar
Type Ia supernova SN 2005hk are presented and analysed, covering the
pre-maximum phase to around 400 days after explosion. The supernova is found to
be underluminous compared to "normal" Type Ia supernovae. The photometric and
spectroscopic evolution of SN 2005hk is remarkably similar to the peculiar Type
Ia event SN 2002cx. The expansion velocity of the supernova ejecta is found to
be lower than normal Type Ia events. The spectra obtained \gsim 200 days
since explosion do not show the presence of forbidden [\ion{Fe}{ii}],
[\ion{Fe}{iii}] and [\ion{Co}{iii}] lines, but are dominated by narrow,
permitted \ion{Fe}{ii}, NIR \ion{Ca}{ii} and \ion{Na}{i} lines with P-Cygni
profiles. Thermonuclear explosion model with Chandrasekhar mass ejecta and a
kinetic energy smaller (\KE = 0.3 \times 10^{51} {\rm ergs}) than that of
canonical Type Ia supernovae is found to well explain the observed bolometric
light curve. The mass of \Nifs synthesized in this explosion is 0.18 \Msun.
The early spectra are successfully modeled with this less energetic model with
some modifications of the abundance distribution. The late spectrum is
explained as a combination of a photospheric component and a nebular component.Comment: Accepted for publication in The Astrophysical Journal. Minor
revision, discussion section adde
Production and detection of entangled electron-hole pairs in a degenerate electron gas
We demonstrate theoretically that the shot noise produced by a tunnel barrier
in a two-channel conductor violates a Bell inequality. The non-locality is
shown to originate from entangled electron-hole pairs created by tunneling
events -- without requiring electron-electron interactions. The degree of
entanglement (concurrence) equals 2(T_1 T_2)^1/2 (T_1+T_2)^-1, with T_1,T_2 <<
1 the transmission eigenvalues. A pair of edge channels in the quantum Hall
effect is proposed as experimental realization.Comment: 4 pages including 1 figure; three comments have been added to the
reference list, addressing the entanglement of formation, the Clauser-Horne
inequality, and the dephasing effect of a finite voltag
Microscopic description of the surface dipole plasmon in large Na_N clusters (950 < N < 12050)
Fully microscopic RPA/LDA calculations of the dipole plasmon for very large
neutral and charged sodium clusters, Na_N^Z+, in the size range 950
< N < 12050 are presented for the first time. 60 different sizes are
considered altogether, which allows for an in-depth investigation of the
asymptotic behavior of both the width and the position of the plasmon.Comment: Latex/Revtex, 4 pages with 4 Postscript figures, accepted for
publication in Physical Review
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