190,416 research outputs found
Transport phenomenology for a holon-spinon fluid
We propose that the normal-state transport in the cuprate superconductors can
be understood in terms of a two-fluid model of spinons and holons. In our
scenario, the resistivity is determined by the properties of the holons while
magnetotransport involves the recombination of holons and spinons to form
physical electrons. Our model implies that the Hall transport time is a measure
of the electron lifetime, which is shorter than the longitudinal transport
time. This agrees with our analysis of the normal-state data. We predict a
strong increase in linewidth with increasing temperature in photoemission. Our
model also suggests that the AC Hall effect is controlled by the transport
time.Comment: 4 pages, 1 postscript figure. Uses RevTeX, epsf, multico
Evidence for an incommensurate magnetic resonance in La(2-x)Sr(x)CuO(4)
We study the effect of a magnetic field (applied along the c-axis) on the
low-energy, incommensurate magnetic fluctuations in superconducting
La(1.82)Sr(0.18)CuO(4). The incommensurate peaks at 9 meV, which in zero-field
were previously shown to sharpen in q on cooling below T_c [T. E. Mason et al.,
Phys. Rev. Lett. 77, 1604 (1996)], are found to broaden in q when a field of 10
T is applied. The applied field also causes scattered intensity to shift into
the spin gap. We point out that the response at 9 meV, though occurring at
incommensurate wave vectors, is comparable to the commensurate magnetic
resonance observed at higher energies in other cuprate superconductors.Comment: 8 pages, including 4 figure
Wavelength- and material-dependent absorption in GaAs and AlGaAs microcavities
The quality factors of modes in nearly identical GaAs and
Al_{0.18}Ga_{0.82}As microdisks are tracked over three wavelength ranges
centered at 980 nm, 1460 nm, and 1600 nm, with quality factors measured as high
as 6.62x10^5 in the 1600-nm band. After accounting for surface scattering, the
remaining loss is due to sub-bandgap absorption in the bulk and on the
surfaces. We observe the absorption is, on average, 80 percent greater in
AlGaAs than in GaAs and in both materials is 540 percent higher at 980 nm than
at 1600nm.Comment: 4 pages, 2 figures, 1 table, minor changes to disucssion of Qrad and
Urbach tai
Scaling regimes and critical dimensions in the Kardar-Parisi-Zhang problem
We study the scaling regimes for the Kardar-Parisi-Zhang equation with noise
correlator R(q) ~ (1 + w q^{-2 \rho}) in Fourier space, as a function of \rho
and the spatial dimension d. By means of a stochastic Cole-Hopf transformation,
the critical and correction-to-scaling exponents at the roughening transition
are determined to all orders in a (d - d_c) expansion. We also argue that there
is a intriguing possibility that the rough phases above and below the lower
critical dimension d_c = 2 (1 + \rho) are genuinely different which could lead
to a re-interpretation of results in the literature.Comment: Latex, 7 pages, eps files for two figures as well as Europhys. Lett.
style files included; slightly expanded reincarnatio
Self-dual Maxwell Chern-Simons Solitons In 1+1 Dimensions
We study the domain wall soliton solutions in the relativistic self-dual
Maxwell Chern-Simons model in 1+1 dimensions obtained by the dimensional
reduction of the 2+1 model. Both topological and nontopological self-dual
solutions are found in this case. A la BPS dyons here the Bogomol'ny bound on
the energy is expressed in terms of two conserved quantities. We discuss the
underlying supersymmetry. Nonrelativistic limit of this model is also
considered and static, nonrelativistic self-dual soliton solutions are
obtained.Comment: 18 pages RevTex, 2 figures included, to appear in Phys. Rev.
Influence of Al doping on the critical fields and gap values in magnesium diboride single crystals
The lower () and upper () critical fields of
MgAlB single crystals (for , 0.1 and )
have been deduced from specific heat and local magnetization measurements,
respectively. We show that and are both decreasing with
increasing doping content. The corresponding anisotropy parameter
value also decreases from
in pure MgB samples down to for whereas
remains on the order of 1 in
all samples. The small and large gap values have been obtained by fitting the
temperature dependence of the zero field electronic contribution to the
specific heat to the two gap model for the three Al concentrations. Very
similar values have also been obtained by point contact spectroscopy
measurements. The evolution of those gaps with Al concentration suggests that
both band filling and interband scattering effects are present
Energy-efficiency improvements for optical access
This article discusses novel approaches to improve energy efficiency of different optical access technologies, including time division multiplexing passive optical network (TDM-PON), time and wavelength division multiplexing PON (TWDM-PON), point-to-point (PTP) access network, wavelength division multiplexing PON (WDM-PON), and orthogonal frequency division multiple access PON (OFDMA-PON). These approaches include cyclic sleep mode, energy-efficient bit interleaving protocol, power reduction at component level, or frequency band selection. Depending on the target optical access technology, one or a combination of different approaches can be applied
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