120 research outputs found
Self-consistent theory of shot noise in nondegenerate ballistic conductors
A self-consistent theory of shot noise in ballistic two-terminal conductors
under the action of long-range Coulomb correlations is presented. Analytical
formulas for the electron distribution function and its fluctuation along the
conductor, which account for the Coulomb correlations, have been derived. Based
upon these formulas, the current-noise reduction factor has been obtained for
biases ranging from thermal to shot-noise limits as dependent on two
parameters: the ratio between the length of the sample and the Debye screening
length \lambda=d/L_D and the applied voltage qU/k_BT. The difference with the
formulas for a vacuum diode is discussed.Comment: 21 pages, 11 figs, minor change
Coherent patterns and self-induced diffraction of electrons on a thin nonlinear layer
Electron scattering on a thin layer where the potential depends
self-consistently on the wave function has been studied. When the amplitude of
the incident wave exceeds a certain threshold, a soliton-shaped brightening
(darkening) appears on the layer causing diffraction of the wave. Thus the
spontaneously formed transverse pattern can be viewed as a self-induced
nonlinear quantum screen. Attractive or repulsive nonlinearities result in
different phase shifts of the wave function on the screen, which give rise to
quite different diffraction patterns. Among others, the nonlinearity can cause
self-focusing of the incident wave into a ``beam'', splitting in two ``beams'',
single or double traces with suppressed reflection or transmission, etc.Comment: RevTex, 4 pages, epsf.sty to insert figures, to appear in Phys.Rev.
Quantum suppression of shot noise in field emitters
We have analyzed the shot noise of electron emission under strong applied
electric fields within the Landauer-Buttiker scheme. In contrast to the
previous studies of vacuum-tube emitters, we show that in new generation
electron emitters, scaled down to the nanometer dimensions, shot noise much
smaller than the Schottky noise is observable. Carbon nanotube field emitters
are among possible candidates to observe the effect of shot-noise suppression
caused by quantum partitioning.Comment: 5 pages, 1 fig, minor changes, published versio
Shot-noise spectroscopy of energy-resolved ballistic currents
We investigate the shot noise of nonequilibrium carriers injected into a
ballistic conductor and interacting via long-range Coulomb forces. Coulomb
interactions are shown to act as an energy analyzer of the profile of injected
electrons by means of the fluctuations of the potential barrier at the emitter
contact. We show that the details in the energy profile can be extracted from
shot-noise measurements in the Coulomb interaction regime, but cannot be
obtained from time-averaged quantities or shot-noise measurements in the
absence of interactions.Comment: 7 pages, 4 figure
Shot-noise suppression by Fermi and Coulomb correlations in ballistic conductors
We investigate the injection of degenerate Fermi-Dirac electrons into a
multimode ballistic conductor under the space-charge limited regime. The
nonequilibrium current fluctuations were found to be suppressed by both Coulomb
and Fermi correlations. We show that the Fermi shot-noise suppression factor is
limited below by the value 2kT/epsilon_F, where T is the temperature and
epsilon_F the Fermi energy of the injected electrons. The Coulomb noise
suppression factor may attain much lower values epsilon_F/2qU, because of its
dependence on the applied bias U >> kT/q. The asymptotic behaviour of the
overall shot-noise suppression factor in a high degenerate limit was found to
be kT/qU, independently of the material parameters.Comment: 8 pages, 4 figures, minor changes, published versio
Suppression of non-Poissonian shot noise by Coulomb correlations in ballistic conductors
We investigate the current injection into a ballistic conductor under the
space-charge limited regime, when the distribution function of injected
carriers is an arbitrary function of energy F_c(epsilon). The analysis of the
coupled kinetic and Poisson equations shows that the injected current
fluctuations may be essentially suppressed by Coulomb correlations, and the
suppression level is determined by the shape of F_c(epsilon). This is in
contrast to the time-averaged quantities: the mean current and the spatial
profiles are shown to be insensitive to F_c(epsilon) in the leading-order terms
at high biases. The asymptotic high-bias behavior for the energy resolved
shot-noise suppression has been found for an arbitrary (non-Poissonian)
injection, which may suggest a new field of investigation on the optimization
of the injected energy profile to achieve the desired noise-suppression level.Comment: extended version 4 -> 8 pages, examples and figure adde
Suppression of non-Poissonian shot noise by Coulomb correlations in ballistic conductors
We investigate the current injection into a ballistic conductor under the
space-charge limited regime, when the distribution function of injected
carriers is an arbitrary function of energy F_c(epsilon). The analysis of the
coupled kinetic and Poisson equations shows that the injected current
fluctuations may be essentially suppressed by Coulomb correlations, and the
suppression level is determined by the shape of F_c(epsilon). This is in
contrast to the time-averaged quantities: the mean current and the spatial
profiles are shown to be insensitive to F_c(epsilon) in the leading-order terms
at high biases. The asymptotic high-bias behavior for the energy resolved
shot-noise suppression has been found for an arbitrary (non-Poissonian)
injection, which may suggest a new field of investigation on the optimization
of the injected energy profile to achieve the desired noise-suppression level.Comment: extended version 4 -> 8 pages, examples and figure adde
Nonlinear statistics of quantum transport in chaotic cavities
Copyright © 2008 The American Physical Society.In the framework of the random matrix approach, we apply the theory of Selberg’s integral to problems of quantum transport in chaotic cavities. All the moments of transmission eigenvalues are calculated analytically up to the fourth order. As a result, we derive exact explicit expressions for the skewness and kurtosis of the conductance and transmitted charge as well as for the variance of the shot-noise power in chaotic cavities. The obtained results are generally valid at arbitrary numbers of propagating channels in the two attached leads. In the particular limit of large (and equal) channel numbers, the shot-noise variance attends the universal value 1∕64β that determines a universal Gaussian statistics of shot-noise fluctuations in this case.DFG and BRIEF
Statistics of quantum transport in chaotic cavities with broken time-reversal symmetry
The statistical properties of quantum transport through a chaotic cavity are
encoded in the traces \T={\rm Tr}(tt^\dag)^n, where is the transmission
matrix. Within the Random Matrix Theory approach, these traces are random
variables whose probability distribution depends on the symmetries of the
system. For the case of broken time-reversal symmetry, we present explicit
closed expressions for the average value and for the variance of \T for all
. In particular, this provides the charge cumulants \Q of all orders. We
also compute the moments of the conductance . All the
results obtained are exact, {\it i.e.} they are valid for arbitrary numbers of
open channels.Comment: 5 pages, 4 figures. v2-minor change
- …