1,529 research outputs found
Casimir force calculations near the insulator-conductor transition in gold thin films
We present theoretical calculations of the Casimir force for Au thin films
near the insulator-conductor transition that has been observed experimentally.
The dielectric function of the Au thin films is described by the Drude-Smith
model. The parameters needed to model the dielectric function such as the
relaxation time, plasma frequency and the backscattering constant depend on the
thickness of the film. The Casimir force decreases as the film thickness
decreases until it reaches a minimum after which the force increases again. The
minimum of the force coincides with the critical film thickness where a
percolation conductor-insulator occurs.Comment: 5 figures, 1 tabl
Direct Experimental Evidence of the Statistical Nature of the Electron Gas in Superconducting Films
In an Nb film an alternate electrical current is partitioned at a Y-shaped
obstacle into two splitted beams. The intensity-fluctuation correlation of the
two beams (cross-correlation) and the intensity- fluctuation correlation of one
beam (auto-correlation) are measured within a low-frequency bandwidth as a
function of the incident beam intensity, at temperatures T above or below the
temperature Tc of the superconductive transition. The results of these
measurements reveal the statistical nature of the electron gas in the normal
film and in the superconducting film. The conceptual scheme of the present
experiment is a version of the Hanbury Brown and Twiss (HBT) experiment, here
adopted for a gas of particles in a solid
Progress towards Bell-type polarization experiment with thermal neutrons
Experimental tests of Bell-type inequalities distinguishing between quantum
mechanics and local realistic theories remain of considerable interest if
performed on massive particles, for which no conclusive result has yet been
obtained. Only two-particle experiments may specifically test the concept of
spatial nonlocality in quantum theory, whereas single-particle experiments may
generally test the concept of quantum noncontextuality. Here we have performed
the first Bell-type experiment with a beam of thermal-neutron pairs in the
singlet state of spin, as originally suggested by J. S. Bell. These
measurements confirm the quantum-theoretical predictions, in agreement with the
results of the well-known polarization experiments carried out on optical
photons years ago
Casimir torque between nanostructured plates
We investigate in detail the Casimir torque induced by quantum vacuum
fluctuations between two nanostructured plates. Our calculations are based on
the scattering approach and take into account the coupling between different
modes induced by the shape of the surface which are neglected in any sort of
proximity approximation or effective medium approach. We then present an
experimental setup aiming at measuring this torque.Comment: 7 pages, 7 figure
Corrosion Inhibition of AA2024-T3 by Vanadates
The speciation of vanadate solutions and the resultinginhibition of oxygen reduction and corrosion of AA2024-T3 wereinvestigated. 51V NMR is very useful for assessing vanadatespeciation. Clear metavanadate solutions contain nodecavanadate, which forms whenever the pH was decreased by theaddition of acid. Orange decavanadate solutions contain nomonovanadate, even when the pH is adjusted to high values.Monovanadate is a potent inhibitor in contrast to decavanadate. Inhibition by monovanadate seems to result from an adsorptionmechanism rather than reduction. Monovanadate effectivelyprotects S phase particles. Aging of high-pH decavanadatesolutions does not improve the inhibition performance or resultin complete depolymerization of the decavanadate
Rotational Excitation Spectroscopy with the STM through Molecular Resonances
We investigate the rotational properties of molecular hydrogen and its
isotopes physisorbed on the surfaces of graphene and hexagonal boron nitride
(-BN), grown on Ni(111), Ru(0001), and Rh(111), using rotational excitation
spectroscopy (RES) with the scanning tunneling microscope. The rotational
thresholds are in good agreement with transitions of freely
spinning para-H and ortho-D molecules. The line shape variations in RES
for H among the different surfaces can be traced back and naturally
explained by a resonance mediated tunneling mechanism. RES data for
H/-BN/Rh(111) suggests a local intrinsic gating on this surface due to
lateral variations in the surface potential. An RES inspection of H, HD,
and D mixtures finally points to a multi molecule excitation, since either
of the three rotational transitions are simultaneously
present, irrespective of where the spectra were recorded in the mixed
monolayer
Large temperature dependence of the Casimir force at the metal-insulator transition
The dependence of the Casimir force on material properties is important for
both future applications and to gain further insight on its fundamental
aspects. Here we derive a general theory of the Casimir force for
low-conducting compounds, or poor metals. For distances in the micrometer
range, a large variety of such materials is described by universal equations
containing a few parameters: the effective plasma frequency, dissipation rate
of the free carriers, and electric permittivity in the infrared range. This
theory can also describe inhomogeneous composite materials containing small
regions with different conductivity. The Casimir force for mechanical systems
involving samples made with compounds that have a metal-insulator transition
shows an abrupt large temperature dependence of the Casimir force within the
transition region, where metallic and dielectric phases coexist.Comment: 23 pages, 9 figure
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