24,899 research outputs found
Thermal Conductivity of Pr_{1.3-x}La_{0.7}Ce_xCuO_4 Single Crystals and Signatures of Stripes in an Electron-Doped Cuprate
It was recently demonstrated that the anisotropic phonon heat transport
behavior is a good probe of the stripe formation in La_{2-x}Sr_xCuO_4 (LSCO)
[X. F. Sun {\it et al.}, Phys. Rev. B {\bf 67}, 104503 (2003)]. Using this
probe, we examined an electron-doped cuprate Pr_{1.3-x}La_{0.7}Ce_xCuO_4
(PLCCO) and found that essentially the same features as those in LSCO are
observed. Moreover, the in-plane resistivity \rho_{ab} of lightly-doped PLCCO
shows metallic behavior (d\rho_{ab}/dT > 0) in the N\'eel ordered state with a
mobility comparable to that in LSCO. It is discussed that these peculiar
properties in common with LSCO signify the existence of stripes in
electron-doped cuprates.Comment: 4 pages, 4 figures, revised version accepted for publication in Phys.
Rev. Let
Decoherence of flux qubits due to 1/f flux noise
We have investigated decoherence in Josephson-junction flux qubits. Based on
the measurements of decoherence at various bias conditions, we discriminate
contributions of different noise sources. In particular, we present a Gaussian
decay function of the echo signal as evidence of dephasing due to flux
noise whose spectral density is evaluated to be about /Hz
at 1 Hz. We also demonstrate that at an optimal bias condition where the noise
sources are well decoupled the coherence observed in the echo measurement is
mainly limited by energy relaxation of the qubit.Comment: 4 pages, error in Fig.4 corrected, to appear in PR
Microlensing of collimated Gamma-Ray Burst afterglows
We investigate stellar microlensing of the collimated gamma-ray burst
afterglows. A spherical afterglow appears on the sky as a superluminally
expanding thin ring (``ring-like'' image), which is maximally amplified as it
crosses the lens. We find that the image of the collimated afterglow becomes
quite uniform (``disk-like'' image) after the jet break time (after the Lorentz
factor of the jet drops below the inverse of the jet opening angle).
Consequently, the amplification peak in the light curve after the break time is
lower and broader. Therefore detailed monitoring of the amplification history
will be able to test whether the afterglows are jets or not, i.e.,
``disk-like'' or not, if the lensing occurs after the break time. We also show
that some proper motion and polarization is expected, peaking around the
maximum amplification. The simultaneous detection of the proper motion and the
polarization will strengthen that the brightening of the light curve is due to
microlensing.Comment: 16 pages, 6 figures, accepted for publication in Ap
Results from the Apollo passive seismic experiment
Recent results from the Apollo seismic network suggest that primitive differentiation occurred in the outer shell of the moon to a depth of approximately 300 km; and the central region of the moon is presently molten to a radius of between 200 and 300 km. If early melting to a depth of 300 to 400 km was a consequence of accretional energy, very short accretion times are required. The best model for the zone of original differentiation appears to be a crust 40 to 80 km thick, ranging in composition from anorthositic gabbro to gabbro; overlying an ultramafic cumulate (olivine-pyroxene) about 250 km thick. The best candidate for the molten core appears to be iron or iron sulphide. A new class of seismic signals has recently been identified that may correspond to shallow moonquakes. These are rare, but much more energetic than the more numerous, deep moonquakes
Results from the Apollo passive seismic experiment
Recent results from the Apollo Seismic Network suggest that primitive differentiation occurred in the outer shell of the moon to a depth of approximately 300 km and the central region of the moon is presently molten to a radius of between 200 and 300 km. If early melting to a depth of 300 to 400 km was a consequence of accretional energy, very short accretion times are required. It was shown that the best model for the zone of original differentiation is a crust 40 to 80 km thick, ranging in composition from anorthositic gabbro to gabbro, and overlying an ultramafic cumulate about 250 km thick. The best candidate for the molten core appears to be iron or iron sulphide. A new class of seismic signals recently were identified that may correspond to shallow moonquakes. These are rare, but much more energetic than the more numerous, deep moonquakes
Low-Mass Star Formation, Triggered by Supernova in Primordial Clouds
The evolution of a gas shell, swept by the supernova remnant of a massive
first generation star, is studied with H_2 and HD chemistry taken into account.
When a first-generation star explodes as a supernova, H_2 and HD molecules are
formed in the swept gas shell and effectively cool the gas shell to
temperatures of 32 K - 154 K. If the supernova remnant can sweep to gather the
ambient gas, the gas shell comes to be dominated by its self-gravity, and
hence, is expected to fragment. Our result shows that for a reasonable range of
temperatures (200 K - 1000 K) of interstellar gas, the formation of
second-generation stars can be triggered by a single supernova or hypernova.Comment: 38pages, 10 figures, The Astrophysical Journal, accepted 8 Dec. 200
Coexistence of Superconductivity and Antiferromagnetism in Heavy-Fermion Superconductor CeCu_{2}(Si_{1-x}Ge_{x})_{2} Probed by Cu-NQR --A Test Case for the SO(5) Theory--
We report on the basis of Cu-NQR measurements that superconductivity (SC) and
antiferromagnetism (AF) coexist on a microscopic level in
CeCu_{2}(Si_{1-x}Ge_{x})_{2}, once a tiny amount of 1%Ge (x = 0.01) is
substituted for Si. This coexistence arises because Ge substitution expands the
unit-cell volume in nearly homogeneous CeCu2Si2 where the SC coexists with
slowly fluctuating magnetic waves. We propose that the underlying exotic phases
of SC and AF in either nearly homogeneous or slightly Ge substituted CeCu2Si2
are accountable based on the SO(5) theory that unifies the SC and AF. We
suggest that the mechanism of the SC and AF is common in CeCu2Si2.Comment: 7 pages with 6 figures embedded in the text. To be published in J.
Phys. Condens. Matter, 200
- …