395 research outputs found
Role of heating and current-induced forces in the stability of atomic wires
We investigate the role of local heating and forces on ions in the stability
of current-carrying aluminum wires. We find that heating increases with wire
length due to a red shift of the frequency spectrum. Nevertheless, the local
temperature of the wire is relatively low for a wide range of biases provided
good thermal contact exists between the wire and the bulk electrodes. On the
contrary, current-induced forces increase substantially as a function of bias
and reach bond-breaking values at about 1 V. These results suggest that local
heating promotes low-bias instabilities if dissipation into the bulk electrodes
is not efficient, while current-induced forces are mainly responsible for the
wire break-up at large biases. We compare these results to experimental
observations.Comment: 4 pages, 4 figure
Sequencing proteins with transverse ionic transport in nanochannels
{\it De novo} protein sequencing is essential for understanding cellular
processes that govern the function of living organisms and all
post-translational events and other sequence modifications that occur after a
protein has been constructed from its corresponding DNA code. By obtaining the
order of the amino acids that composes a given protein one can then determine
both its secondary and tertiary structures through structure prediction, which
is used to create models for protein aggregation diseases such as Alzheimer's
Disease. Mass spectrometry is the current technique of choice for {\it de novo}
sequencing. However, because some amino acids have the same mass the sequence
cannot be completely determined in many cases. Here, we propose a new technique
for {\it de novo} protein sequencing that involves translocating a polypeptide
through a synthetic nanochannel and measuring the ionic current of each amino
acid through an intersecting {\it perpendicular} nanochannel. To calculate the
transverse ionic current blockaded by a given amino acid we use a Monte Carlo
method along with Ramachandran plots to determine the available flow area,
modified by the local density of ions obtained from molecular dynamics and the
local flow velocity ratio derived from the Stokes equation. We find that the
distribution of ionic currents for each of the 20 proteinogenic amino acids
encoded by eukaryotic genes is statistically distinct, showing this technique's
potential for {\it de novo} protein sequencing.Comment: 12 pages (9 of main text, 3 of supporting information), 4 figures, 1
table in supporting informatio
Single-Base DNA Discrimination via Transverse Ionic Transport
We suggest to discriminate single DNA bases via transverse ionic transport,
namely by detecting the ionic current that flows in a channel while a
single-stranded DNA is driven through an intersecting nanochannel. Our all-atom
molecular dynamics simulations indeed show that the ionic currents of the four
bases are statistically distinct, thus offering another possible approach to
sequence DNA.Comment: 5 pages, 3 figure
Nonlinear current-induced forces in Si atomic wires
We report first-principles calculations of current-induced forces in Si
atomic wires as a function of bias and wire length. We find that these forces
are strongly nonlinear as a function of bias due to the competition between the
force originating from the scattering states and the force due to bound states.
We also find that the average force in the wire is larger the shorter the wire,
suggesting that atomic wires are more difficult to break under current flow
with increasing length. The last finding is in agreement with recent
experimental data.Comment: 4 figure
SPICE model of memristive devices with threshold
Although memristive devices with threshold voltages are the norm rather than
the exception in experimentally realizable systems, their SPICE programming is
not yet common. Here, we show how to implement such systems in the SPICE
environment. Specifically, we present SPICE models of a popular
voltage-controlled memristive system specified by five different parameters for
PSPICE and NGSPICE circuit simulators. We expect this implementation to find
widespread use in circuits design and testing
Shot Noise in Nanoscale Conductors From First Principles
We describe a field-theoretic approach to calculate quantum shot noise in
nanoscale conductors from first principles. Our starting point is the
second-quantization field operator to calculate shot noise in terms of single
quasi-particle wavefunctions obtained self-consistently within density
functional theory. The approach is valid in both linear and nonlinear response
and is particularly suitable in studying shot noise in atomic-scale conductors.
As an example we study shot noise in Si atomic wires between metal electrodes.
We find that shot noise is strongly nonlinear as a function of bias and it is
enhanced for one- and two-Si wires due to the large contribution from the metal
electrodes. For longer wires it shows an oscillatory behavior for even and odd
number of atoms with opposite trend with respect to the conductance, indicating
that current fluctuations persist with increasing wire length.Comment: 4 pages, 4 figure
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