2,621 research outputs found
Alumina fiber strength improvement
The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation
Spin-dependent transport in a quasiballistic quantum wire
We describe the transport properties of a 5 m long one-dimensional (1D)
quantum wire. Reduction of conductance plateaux due to the introduction of
weakly disorder scattering are observed. In an in-plane magnetic field, we
observe spin-splitting of the reduced conductance steps. Our experimental
results provide evidence that deviation from conductance quantisation is very
small for electrons with spin parallel and is about 1/3 for electrons with spin
anti-parallel. Moreover, in a high in-plane magnetic field, a spin-polarised 1D
channel shows a plateau-like structure close to which
strengthens with {\em increasing} temperatures. It is suggested that these
results arise from the combination of disorder and the electron-electron
interactions in the 1D electron gas.Comment: 4 pages, 5 figures, latex to be published in Phys. Rev. B (15/3/2000
Sensitivity of the magnetic state of a spin lattice on itinerant electron orbital phase
Spatially extended localized spins can interact via indirect exchange
interaction through Friedel oscillations in the Fermi sea. In arrays of
localized spins such interaction can lead to a magnetically ordered phase.
Without external magnetic field such a phase is well understood via a
"two-impurity" Kondo model. Here we employ non-equilibrium transport
spectroscopy to investigate the role of the orbital phase of conduction
electrons on the magnetic state of a spin lattice. We show experimentally, that
even tiniest perpendicular magnetic field can influence the magnitude of the
inter-spin magnetic exchange.Comment: To be published in PhysicaE EP2DS proceedin
Anomalous spin-dependent behaviour of one-dimensional subbands
We report a new electron interaction effect in GaAs/AlGaAs quantum wires.
Using DC-bias spectroscopy, we show that large and abrupt changes occur to the
energies of spin-down (lower energy) states as they populate. The effect is not
observed for spin-up energy states. At B=0, interactions have a pronounced
effect, in the form of the well-known 0.7 Structure. However, our new results
show that interactions strongly affect the energy spectrum at all magnetic
fields, from 0 to 16T, not just in the vicinity of the 0.7 Structure.Comment: 4 pages, 2 figure
Opto-mechanical micro-macro entanglement
We propose to create and detect opto-mechanical entanglement by storing one
component of an entangled state of light in a mechanical resonator and then
retrieving it. Using micro-macro entanglement of light as recently demonstrated
experimentally, one can then create opto-mechanical entangled states where the
components of the superposition are macroscopically different. We apply this
general approach to two-mode squeezed states where one mode has undergone a
large displacement. Based on an analysis of the relevant experimental
imperfections, the scheme appears feasible with current technology.Comment: 7 pages, 6 figures, to appear in PRL, submission coordinated with
Sekatski et al. who reported on similar result
Possible evidence of a spontaneous spin-polarization in mesoscopic 2D electron systems
We have experimentally studied the non-equilibrium transport in low-density
clean 2D electron systems at mesoscopic length scales. At zero magnetic field
(B), a double-peak structure in the non-linear conductance was observed close
to the Fermi energy in the localized regime. From the behavior of these peaks
at non-zero B, we could associate them to the opposite spin states of the
system, indicating a spontaneous spin polarization at B = 0. Detailed
temperature and disorder dependence of the structure shows that such a
splitting is a ground state property of the low-density 2D systems.Comment: 7 pages, 5 figure
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