6,136 research outputs found
Dephasing time in graphene due to interaction with flexural phonons
We investigate decoherence of an electron in graphene caused by
electron-flexural phonon interaction. We find out that flexural phonons can
produce dephasing rate comparable to the electron-electron one. The problem
appears to be quite special because there is a large interval of temperature
where the dephasing induced by phonons can not be obtain using the golden rule.
We evaluate this rate for a wide range of density () and temperature ()
and determine several asymptotic regions with temperature dependence crossing
over from to when
temperature increases. We also find to be a non-monotonous
function of . These distinctive features of the new contribution can provide
an effective way to identify flexural phonons in graphene through the
electronic transport by measuring the weak localization corrections in
magnetoresistance.Comment: 13 pages, 8 figure
Structure And Properties of Nanoparticles Formed under Conditions of Wire Electrical Explosion
Structure and properties of nanoparticles formed under conditions of wire
electrical explosion were studied. It was shown that the state of WEE power
particles can be characterized as a metastable state. It leads to an increased
stability of nanopowders at normal temperatures and an increased reactivity
during heating, which is revealed in the form of threshold phenomena.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Noise thermometry applied to thermoelectric measurements in InAs nanowires
We apply noise thermometry to characterize charge and thermoelectric
transport in single InAs nanowires (NWs) at a bath temperature of 4.2 K. Shot
noise measurements identify elastic diffusive transport in our NWs with
negligible electron-phonon interaction. This enables us to set up a measurement
of the diffusion thermopower. Unlike in previous approaches, we make use of a
primary electronic noise thermometry to calibrate a thermal bias across the NW.
In particular, this enables us to apply a contact heating scheme, which is much
more efficient in creating the thermal bias as compared to conventional
substrate heating. The measured thermoelectric Seebeck coefficient exhibits
strong mesoscopic fluctuations in dependence on the back-gate voltage that is
used to tune the NW carrier density. We analyze the transport and
thermoelectric data in terms of approximate Mott's thermopower relation and to
evaluate a gate-voltage to Fermi energy conversion factor
Local noise in a diffusive conductor
The control and measurement of local non-equilibrium configurations is of
utmost importance in applications on energy harvesting, thermoelectrics and
heat management in nano-electronics. This challenging task can be achieved with
the help of various local probes, prominent examples including superconducting
or quantum dot based tunnel junctions, classical and quantum resistors, and
Raman thermography. Beyond time-averaged properties, valuable information can
also be gained from spontaneous fluctuations of current (noise). From these
perspective, however, a fundamental constraint is set by current conservation,
which makes noise a characteristic of the whole conductor, rather than some
part of it. Here we demonstrate how to remove this obstacle and pick up a local
noise temperature of a current biased diffusive conductor with the help of a
miniature noise probe. This approach is virtually noninvasive and extends
primary local measurements towards strongly non-equilibrium regimes.Comment: minor revision, accepted in Scientific Report
Unbiased estimates of galaxy scaling relations from photometric redshift surveys
Many physical properties of galaxies correlate with one another, and these
correlations are often used to constrain galaxy formation models. Such
correlations include the color-magnitude relation, the luminosity-size
relation, the Fundamental Plane, etc. However, the transformation from
observable (e.g. angular size, apparent brightness) to physical quantity
(physical size, luminosity), is often distance-dependent. Noise in the distance
estimate will lead to biased estimates of these correlations, thus compromising
the ability of photometric redshift surveys to constrain galaxy formation
models. We describe two methods which can remove this bias. One is a
generalization of the V_max method, and the other is a maximum likelihood
approach. We illustrate their effectiveness by studying the size-luminosity
relation in a mock catalog, although both methods can be applied to other
scaling relations as well. We show that if one simply uses photometric
redshifts one obtains a biased relation; our methods correct for this bias and
recover the true relation
Biased Brownian motion in extreme corrugated tubes
Biased Brownian motion of point-size particles in a three-dimensional tube
with smoothly varying cross-section is investigated. In the fashion of our
recent work [Martens et al., PRE 83,051135] we employ an asymptotic analysis to
the stationary probability density in a geometric parameter of the tube
geometry. We demonstrate that the leading order term is equivalent to the
Fick-Jacobs approximation. Expression for the higher order corrections to the
probability density are derived. Using this expansion orders we obtain that in
the diffusion dominated regime the average particle current equals the
zeroth-order Fick-Jacobs result corrected by a factor including the corrugation
of the tube geometry. In particular we demonstrate that this estimate is more
accurate for extreme corrugated geometries compared to the common applied
method using the spatially dependent diffusion coefficient D(x,f). The analytic
findings are corroborated with the finite element calculation of a
sinusoidal-shaped tube.Comment: 10 pages, 4 figure
- …