56,190 research outputs found
Interplay between finite resources and local defect in an asymmetric simple exclusion process
When particle flux is regulated by multiple factors such as particle supply
and varying transport rate, it is important to identify the respective dominant
regimes. We extend the well-studied totally asymmetric simple exclusion model
to investigate the interplay between a controlled entrance and a local defect
site. The model mimics cellular transport phenomena where there is typically a
finite particle pool and non-uniform moving rates due to biochemical kinetics.
Our simulations reveal regions where, despite an increasing particle supply,
the current remains constant while particles redistribute in the system.
Exploiting a domain wall approach with mean-field approximation, we provide a
theoretical ground for our findings. The results in steady state current and
density profiles provide quantitative insights into the regulation of the
transcription and translation process in bacterial protein synthesis. We
investigate the totally asymmetric simple exclusion model with controlled
entrance and a defect site in the bulk to mimic the finite particle pool and
non-uniform moving rates in particle transport processes.Comment: 9 pages, 12 figures; v2: minor format changes; v3: major revision,
additional references; v4: minor format change to figures, additional
reference
Elimination of negative differential conductance in an asymmetric molecular transistor by an ac-voltage
We analyze resonant tunneling subject to a non-adiabatic time-dependent
bias-voltage through an asymmetric single molecular quantum dot with coupling
between the electronic and vibrational degrees of freedom using a {\em
Tien-Gordon-type} rate equation. Our results clearly exhibit the appearance of
photon-assisted satellites in the current-voltage characteristics and the
elimination of hot-phonon-induced negative differential conductance with
increasing ac driving amplitude for an asymmetric system. This can be ascribed
to an {\em ac-induced suppression} of unequilibrated (hot) phonons in an
asymmetric system.Comment: Accepted by Appl. Phys. Let
Finite-frequency current (shot) noise in coherent resonant tunneling through a coupled-quantum-dot interferometer
We examine the shot noise spectrum properties of coherent resonant tunneling
in coupled quantum dots in both series and parallel arrangements by means of
quantum rate equations and MacDonald's formula. Our results show that, for a
series-CQD with a relatively high dot-dot hopping ,
( denotes the dot-lead tunnel-coupling
strength), the noise spectrum exhibits a dip at the Rabi frequency, ,
in the case of noninteracting electrons, but the dip is supplanted by a peak in
the case of strong Coulomb repulsion; furthermore, it becomes a dip again for a
completely symmetric parallel-CQD by tuning enclosed magnetic-flux.Comment: 8 pages, 5 figure
Mesoscopic Kondo effect of a quantum dot embedded in an Aharonov-Bohm ring with intradot spin-flip scattering
We study the Kondo effect in a quantum dot embedded in a mesoscopic ring
taking into account intradot spin-flip scattering . Based on the finite-
slave-boson mean-field approach, we find that the Kondo peak in the density of
states is split into two peaks by this coherent spin-flip transition, which is
responsible for some interesting features of the Kondo-assisted persistent
current circulating the ring: (1) strong suppression and crossover to a sine
function form with increasing ; (2) appearance of a "hump" in the
-dependent behavior for odd parity. -induced reverse of the persistent
current direction is also observed for odd parity.Comment: 7 pages,6 figures, to be published by Europhys. Let
Positive current noise cross-correlations in capacitively coupled double quantum dots with ferromagnetic leads
We examine cross-correlations (CCs) in the tunneling currents through two
parallel interacting quantum dots coupled to four independent ferromagnetic
electrodes. We find that when either one of the two circuits is in the parallel
configuration with sufficiently strong polarization strength, a new mechanism
of dynamical spin blockade, i.e., a spin-dependent bunching of tunneling
events, governs transport through the system together with the inter-dot
Coulomb interaction, leading to a sign-reversal of the zero-frequency current
CC in the dynamical channel blockade regime, and to enhancement of positive
current CC in the dynamical channel anti-blockade regimes, in contrast to the
corresponding results for the case of paramagnetic leads.Comment: 9 pages, 3 figure
- …