157,305 research outputs found
Dynamical Josephson Effects in NbSe
The study of superconducting materials that also possess nontrivial
correlations or interactions remains an active frontier of condensed matter
physics. NbSe belongs to this class of superconductors and recent research
has focused on the two-dimensional properties of this layered material. Here an
investigation of the superconducting-to-normal-state transition in NbSe is
detailed, and found to be driven by dynamically-created vortices. Under the
application of RF radiation, these vortices allow for two novel Josephson
effects to be observed. The first is a coupling between Josephson currents and
charge density waves in phase-slip junctions. The second is the Josephson
detection of multi-band superconductivity, which is revealed in an anomalous
magnetic field and RF frequency response of the AC Josephson effect. Our
results shed light on the nature of superconductivity in this material,
unearthing exotic phenomena by exploiting nonequilibrium superconducting
effects in atomically-thin materials
Direct observation of voids in the vacancy excess region of ion bombarded silicon
The results reported in this letter indicate that the spatial separation of the vacancy and interstitial excesses which result from ion bombardment gives rise to stable voids upon annealing at 850 °C even for implants where the projected ion range is only of the order of a few thousand Ångstrom. Such voids have been observed directly by transmission electron microscopy. Furthermore, in cases where both voids and interstitial-based defects are present at different depths, it is found that Au has a strong preference for decorating void surfaces and hence Au can, indeed, be used as a selective detector of open volume defects in Si.One of the authors ~J.W.-L.!
acknowledges the Australian Research Council for financial
support
Identification of nanoindentation-induced phase changes in silicon by in situ electrical characterization
In situ electrical measurements during nanoindentation of Czochralski grown p-type crystalline silicon (100) have been performed using a conducting diamond Berkovich indenter tip. Through-tip current monitoring with a sensitivity of ∼10pA and extraction of current-voltage curves at various points on the complete load-unload cycle have been used to track the phase transformations of silicon during the loading and unloading cycle. Postindent current-voltage curves prove to be extremely sensitive to phase changes during indentation, as well as to the final phase composition within the indented volume. For example, differences in the final structure are detected by current-voltage measurements even in an unloading regime in which only amorphous silicon is expected to form. The electrical measurements are interpreted with the aid of previously reported transmission electron microscopy and Raman microspectroscopy measurements.This work was funded by the Australian Research Council
and WRiota Pty Ltd
Effect of oxygen concentration on nanoindentation-induced phase transformations in ion-implanted amorphous silicon
The effect of the local oxygen concentration in ion-implanted amorphous Si (a-Si) on nanoindentation-inducedphase transformations has been investigated. Implantation of oxygen into the a-Sifilms has been used to controllably introduce an approximately constant concentration of oxygen, ranging from ∼10¹⁸ to ∼10²¹ cm⁻³, over the depth range of the phase transformed zones. Nanoindentation was performed under conditions that ensure a phase transformed zone composed completely of Si-III/XII in the nominally oxygen-free a-Si. The effect of the local oxygen concentration has been investigated by analysis of the unloading curves, Raman microspectroscopy, and cross-sectional transmission electron microscopy (XTEM). The formation of Si-III/XII is suppressed with increasing oxygen concentration, favoring a greater volume of a-Si within the zones. The Raman microspectroscopy and XTEM verify that the volume of Si-III/XII decreases with increasing O concentration. With the smaller volumes of Si-III/XII, the pop-out normally observed on load versus penetration depth curves during unloading decreases in magnitude, becoming more kinklike and is barely discernable at high concentrations of oxygen. The probability of forming any high pressure phases is reduced from 1 to ∼0.1 for a concentration of 10²¹ cm⁻³. We suggest that the bonding of O with Si reduces the formation of Si-III/XII during unloading through a similar mechanism to that of oxygen-retarded solid phase crystallization of a-Si.This project is funded by the Australian Research Council
and WRiota Pty Ltd
Weak values and the Leggett-Garg inequality in solid-state qubits
An implementation of weak values is investigated in solid-state qubits. We
demonstrate that a weak value can be non-classical if and only if a
Leggett-Garg inequality can also be violated. Generalized weak values are
described, where post-selection on a range of weak measurement results.
Imposing classical weak values permits the derivation of Leggett-Garg
inequalities for bounded operators. Our analysis is presented in terms of
kicked quantum nondemolition measurements on a quantum double-dot charge qubit.Comment: 4 pages, 2 figure
SCRAM: Software configuration and management for the LHC Computing Grid project
Recently SCRAM (Software Configuration And Management) has been adopted by
the applications area of the LHC computing grid project as baseline
configuration management and build support infrastructure tool.
SCRAM is a software engineering tool, that supports the configuration
management and management processes for software development. It resolves the
issues of configuration definition, assembly break-down, build, project
organization, run-time environment, installation, distribution, deployment, and
source code distribution. It was designed with a focus on supporting a
distributed, multi-project development work-model.
We will describe the underlying technology, and the solutions SCRAM offers to
the above software engineering processes, while taking a users view of the
system under configuration management.Comment: Computing in High Energy and Nuclear Physics, La Jolla, California,
March 24-28, 2003 1 tar fil
Phase transformations induced by spherical indentation in ion-implanted amorphous silicon
The deformation behavior of ion-implanted (unrelaxed) and annealed ion-implanted (relaxed) amorphous silicon(a-Si) under spherical indentation at room temperature has been investigated. It has been found that the mode of deformation depends critically on both the preparation of the amorphous film and the scale of the mechanical deformation.Ex situmeasurements, such as Raman microspectroscopy and cross-sectional transmission electron microscopy, as well as in situ electrical measurements reveal the occurrence of phase transformations in all relaxed a-Si films. The preferred deformation mode of unrelaxed a-Si is plastic flow, only under certain high load conditions can this state of a-Si be forced to transform. In situ electrical measurements have revealed more detail of the transformation process during both loading and unloading. We have used ELASTICA simulations to obtain estimates of the depth of the metallic phase as a function of load, and good agreement is found with the experiment. On unloading, a clear change in electrical conductivity is observed to correlate with a “pop-out” event on load versus penetration curves
Explicit soliton-black hole correspondence for static configurations
We construct an explicit map that transforms static, generalized sine-Gordon
metrics to black hole type metrics. This, in particular, provides for a further
description of the Cadoni correspondence (which extends the
Gegenberg-Kunstatter correspondence) of soliton solutions and extremal black
hole solutions in 2D dilaton gravity.Comment: Submitted to Phys Rev D, 7 pages, no figure
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