2,483 research outputs found
Gaussian Free Field in the background of correlated random clusters, formed by metallic nanoparticles
The effect of metallic nano-particles (MNPs) on the electrostatic potential
of a disordered 2D dielectric media is considered. The disorder in the media is
assumed to be white-noise Coulomb impurities with normal distribution. To
realize the correlations between the MNPs we have used the Ising model with an
artificial temperature that controls the number of MNPs as well as their
correlations. In the limit, one retrieves the Gaussian free
field (GFF), and in the finite temperature the problem is equivalent to a GFF
in iso-potential islands. The problem is argued to be equivalent to a
scale-invariant random surface with some critical exponents which vary with
and correspondingly are correlation-dependent. Two type of observables have
been considered: local and global quantities. We have observed that the MNPs
soften the random potential and reduce its statistical fluctuations. This
softening is observed in the local as well as the geometrical quantities. The
correlation function of the electrostatic and its total variance are observed
to be logarithmic just like the GFF, i.e. the roughness exponent remains zero
for all temperatures, whereas the proportionality constants scale with .
The fractal dimension of iso-potential lines (), the exponent of the
distribution function of the gyration radius (), and the loop lengths
(), and also the exponent of the loop Green function change in
terms of in a power-law fashion, with some critical exponents reported
in the text. Importantly we have observed that
, in which is the spin
correlation length in the Ising model
Timing performance of 30-nm-wide superconducting nanowire avalanche photodetectors
We investigated the timing jitter of superconducting nanowire avalanche
photodetectors (SNAPs, also referred to as cascade switching superconducting
single photon detectors) based on 30-nm-wide nanowires. At bias currents (IB)
near the switching current, SNAPs showed sub 35 ps FWHM Gaussian jitter similar
to standard 100 nm wide superconducting nanowire single-photon detectors. At
lower values of IB, the instrument response function (IRF) of the detectors
became wider, more asymmetric, and shifted to longer time delays. We could
reproduce the experimentally observed IRF time-shift in simulations based on an
electrothermal model, and explain the effect with a simple physical picture
Buckling instability for a charged and fluctuating semiflexible polymer
In this article we address the problem of Euler's buckling instability in a
charged semi-flexible polymer that is under the action of a compressive force.
We consider this instability as a phase transition and investigate the role of
thermal fluctuations in the buckling critical force. By performing molecular
dynamic simulations, we show that the critical force decreases when the
temperature increases. Repulsive electrostatic interaction in the finite
temperature is in competition with thermal fluctuations to increase the
buckling threshold
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