585 research outputs found
Resistance noise in Bi_2Sr_2CaCu_2O
The resistance noise in a Bi_2Sr_2CaCu_2O thin film is found to
increase strongly in the underdoped regime. While the increase of the raw
resistance noise with decreasing temperature appears to roughly track the
previously reported pseudogap temperature for this material, standard noise
analysis rather suggests that the additional noise contribution is driven by
the proximity of the superconductor-insulator transition
Tuning the Correlation Decay in the Resistance Fluctuations of Multi-Species Networks
A new network model is proposed to describe the resistance noise
in disordered materials for a wide range of values ().
More precisely, we have considered the resistance fluctuations of a thin
resistor with granular structure in different stationary states: from nearly
equilibrium up to far from equilibrium conditions. This system has been
modelled as a network made by different species of resistors, distinguished by
their resistances, temperature coefficients and by the energies associated with
thermally activated processes of breaking and recovery. The correlation
behavior of the resistance fluctuations is analyzed as a function of the
temperature and applied current, in both the frequency and time domains. For
the noise frequency exponent, the model provides at low
currents, in the Ohmic regime, with decreasing inversely with the
temperature, and at high currents, in the non-Ohmic regime.
Since the threshold current associated with the onset of nonlinearity also
depends on the temperature, the proposed model qualitatively accounts for the
complicate behavior of versus temperature and current observed in many
experiments. Correspondingly, in the time domain, the auto-correlation function
of the resistance fluctuations displays a variety of behaviors which are tuned
by the external conditions.Comment: 26 pages, 16 figures, Submitted to JSTAT - Special issue SigmaPhi200
Low-frequency Current Fluctuations in Individual Semiconducting Single-Wall Carbon Nanotubes
We present a systematic study on low-frequency current fluctuations of
nano-devices consisting of one single semiconducting nanotube, which exhibit
significant 1/f-type noise. By examining devices with different switching
mechanisms, carrier types (electrons vs. holes), and channel lengths, we show
that the 1/f fluctuation level in semiconducting nanotubes is correlated to the
total number of transport carriers present in the system. However, the 1/f
noise level per carrier is not larger than that of most bulk conventional
semiconductors, e.g. Si. The pronounced noise level observed in nanotube
devices simply reflects on the small number of carriers involved in transport.
These results not only provide the basis to quantify the noise behavior in a
one-dimensional transport system, but also suggest a valuable way to
characterize low-dimensional nanostructures based on the 1/f fluctuation
phenomenon
Long-range potential fluctuations and 1/f noise in hydrogenated amorphous silicon
We present a microscopic theory of the low-frequency voltage noise (known as
"1/f" noise) in micrometer-thick films of hydrogenated amorphous silicon. This
theory traces the noise back to the long-range fluctuations of the Coulomb
potential produced by deep defects, thereby predicting the absolute noise
intensity as a function of the distribution of defect activation energies. The
predictions of this theory are in very good agreement with our own experiments
in terms of both the absolute intensity and the temperature dependence of the
noise spectra.Comment: 8 pages, 3 figures, several new parts and one new figure are added,
but no conceptual revision
Strong Suppression of Electrical Noise in Bilayer Graphene Nano Devices
Low-frequency 1/f noise is ubiquitous, and dominates the signal-to-noise
performance in nanodevices. Here we investigate the noise characteristics of
single-layer and bilayer graphene nano-devices, and uncover an unexpected 1/f
noise behavior for bilayer devices. Graphene is a single layer of graphite,
where carbon atoms form a 2D honeycomb lattice. Despite the similar
composition, bilayer graphene (two graphene monolayers stacked in the natural
graphite order) is a distinct 2D system with a different band structure and
electrical properties. In graphene monolayers, the 1/f noise is found to follow
Hooge's empirical relation with a noise parameter comparable to that of bulk
semiconductors. However, this 1/f noise is strongly suppressed in bilayer
graphene devices, and exhibits an unusual dependence on the carrier density,
different from most other materials. The unexpected noise behavior in graphene
bilayers is associated with its unique band structure that varies with the
charge distribution among the two layers, resulting in an effective screening
of potential fluctuations due to external impurity charges. The findings here
point to exciting opportunities for graphene bilayers in low-noise
applications
Point process model of 1/f noise versus a sum of Lorentzians
We present a simple point process model of noise, covering
different values of the exponent . The signal of the model consists of
pulses or events. The interpulse, interevent, interarrival, recurrence or
waiting times of the signal are described by the general Langevin equation with
the multiplicative noise and stochastically diffuse in some interval resulting
in the power-law distribution. Our model is free from the requirement of a wide
distribution of relaxation times and from the power-law forms of the pulses. It
contains only one relaxation rate and yields spectra in a wide
range of frequency. We obtain explicit expressions for the power spectra and
present numerical illustrations of the model. Further we analyze the relation
of the point process model of noise with the Bernamont-Surdin-McWhorter
model, representing the signals as a sum of the uncorrelated components. We
show that the point process model is complementary to the model based on the
sum of signals with a wide-range distribution of the relaxation times. In
contrast to the Gaussian distribution of the signal intensity of the sum of the
uncorrelated components, the point process exhibits asymptotically a power-law
distribution of the signal intensity. The developed multiplicative point
process model of noise may be used for modeling and analysis of
stochastic processes in different systems with the power-law distribution of
the intensity of pulsing signals.Comment: 23 pages, 10 figures, to be published in Phys. Rev.
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