1,709 research outputs found
Universal conductance fluctuations and low temperature 1/f noise in mesoscopic AuFe spin glasses
We report on intrinsic time-dependent conductance fluctuations observed in
mesoscopic AuFe spin glass wires. These dynamical fluctuations have a 1/f-like
spectrum and appear below the measured spin glass freezing temperature of our
samples. The dependence of the fluctuation amplitude on temperature, magnetic
field, voltage and Fe concentration allows a consistent interpretation in terms
of quantum interference effects which are sensitive to the slowly fluctuating
spin configuration.Comment: 4 pages, 4 figure
Interference and Interaction in Multiwall Carbon Nanotubes
We report equilibrium electric resistance R and tunneling spectroscopy dI/dV
measurements obtained on single multiwall nanotubes contacted by four metallic
Au fingers from above. At low temperature quantum interference phenomena
dominate the magnetoresistance. The phase-coherence and elastic-scattering
lengths are deduced. Because the latter is of order of the circumference of the
nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV
spectrum which is in good agreement with the density-of-states (DOS) due to the
one-dimensional subbands expected for a perfect single-wall tube. As a function
of temperature T the resistance increases on decreasing T and saturates at
approx. 1-10 K for all measured nanotubes. R(T) cannot be related to the
energy-dependent DOS of graphene but is mainly caused by interaction and
interference effects. On a relatively small voltage scale of order 10 meV, a
pseudogap is observed in dI/dV which agrees with Luttinger-Liquid theories for
nanotubes. Because we have used quantum diffusion based on Fermi-Liquid as well
as Luttinger-Liquid theory in trying to understand our results, a large
fraction of this paper is devoted to a careful discussion of all our results.Comment: 14 pages (twocolumn), 8 figure
Decoherence and single electron charging in an electronic Mach-Zehnder interferometer
We investigate the temperature and voltage dependence of the quantum
interference in an electronic Mach-Zehnder interferometer using edge channels
in the integer quantum-Hall-regime. The amplitude of the interference fringes
is significantly smaller than expected from theory; nevertheless the functional
dependence of the visibility on temperature and bias voltage agrees very well
with theoretical predictions. Superimposed on the Aharonov-Bohm (AB)
oscillations, a conductance oscillation with six times smaller period is
observed. The latter depends only on gate voltage and not on the AB-phase, and
may be related to single electron charging.Comment: 4 pages, 6 figures, discussion of charging effect change
Employment Changes Play Major Role in Access to Employer Health Coverage
Highlights findings on the factors that drive short-term changes in employer-sponsored health insurance coverage, including the rising cost of health insurance and changes in employment rates and availability of better jobs during macroeconomic cycles
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