793 research outputs found
A Numerical Framework for Isotropic and Anisotropic Flexible Flapping Wing Aerodynamics and Aeroelasticity
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83616/1/AIAA-2010-5082-968.pd
Computational Modeling of Spanwise Flexibility Effects on Flapping Wing Aerodynamics
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76845/1/AIAA-2009-1270-256.pd
Kondo effect in coupled quantum dots under magnetic fields
The Kondo effect in coupled quantum dots is investigated theoretically under
magnetic fields. We show that the magnetoconductance (MC) illustrates peak
structures of the Kondo resonant spectra. When the dot-dot tunneling coupling
is smaller than the dot-lead coupling (level broadening), the
Kondo resonant levels appear at the Fermi level (). The Zeeman splitting
of the levels weakens the Kondo effect, which results in a negative MC. When
is larger than , the Kondo resonances form bonding and
anti-bonding levels, located below and above , respectively. We observe a
positive MC since the Zeeman splitting increases the overlap between the levels
at . In the presence of the antiferromagnetic spin coupling between the
dots, the sign of MC can change as a function of the gate voltage.Comment: 6 pages, 3 figure
Electron Transport through T-Shaped Double-Dots System
Correlation effects on electron transport through a system of T-shaped
double-dots are investigated, for which only one of the dots is directly
connected to the leads. We evaluate the local density of states and the
conductance by means of the non-crossing approximation at finite temperatures
as well as the slave-boson mean field approximation at zero temperature. It is
found that the dot which is not directly connected to the leads considerably
influences the conductance, making its behavior quite different from the case
of a single-dot system. In particular, we find a novel phenomenon in the Kondo
regime with a small inter-dot coupling, i.e.
Fano-like suppression of the Kondo-mediated conductance, when two dot levels
coincide with each other energetically.Comment: 6 pages,7 figure
Kondo resonant spectra in coupled quantum dots
The Kondo effect in coupled quantum dots is investigated from the viewpoint
of transmission spectroscopy using the slave-boson formalism of the Anderson
model. The antiferromagnetic spin-spin coupling between the dots is taken
into account. Conductance through the dots connected in a series is
characterized by the competition between the dot-dot tunneling coupling
and the level broadening in the dots (dot-lead coupling). When
, the Kondo resonance is formed between each dot and lead,
which is replaced by a spin-singlet state in the dots at low gate voltages. The
gate voltage dependence of has a sharp peak of in height in the
crossover region between the Kondo and spin-singlet states. The sharp peak of
survives when the energy levels are different between the dots. When , the "molecular levels" between the Kondo resonant states appear;
the Kondo resonant peaks are located below and above the Fermi level in the
leads at low gate voltages. The gate voltage dependence of has a broad
peak, which is robust against . The broad peak splits into two peaks when
the energy levels are different, reflecting the formation of the asymmetric
molecular levels between the Kondo resonant states.Comment: 21 pages, 8 figures, to appear in Phys. Rev.
Practical implementation of a quantum backtracking algorithm
In previous work, Montanaro presented a method to obtain quantum speedups for
backtracking algorithms, a general meta-algorithm to solve constraint
satisfaction problems (CSPs). In this work, we derive a space efficient
implementation of this method. Assume that we want to solve a CSP with
constraints on variables and that the union of the domains in which these
variables take their value is of cardinality . Then, we show that the
implementation of Montanaro's backtracking algorithm can be done by using data qubits. We detail an implementation of the predicate associated
to the CSP with an additional register of qubits. We explicit our
implementation for graph coloring and SAT problems, and present simulation
results. Finally, we discuss the impact of the usage of static and dynamic
variable ordering heuristics in the quantum setting.Comment: 18 pages, 10 figure
Smc5/6: a link between DNA repair and unidirectional replication?
Of the three structural maintenance of chromosome (SMC) complexes, two directly regulate chromosome dynamics. The third, Smc5/6, functions mainly in homologous recombination and in completing DNA replication. The literature suggests that Smc5/6 coordinates DNA repair, in part through post-translational modification of uncharacterized target proteins that can dictate their subcellular localization, and that Smc5/6 also functions to establish DNA-damage-dependent cohesion. A nucleolar-specific Smc5/6 function has been proposed because Smc5/6 yeast mutants display penetrant phenotypes of ribosomal DNA (rDNA) instability. rDNA repeats are replicated unidirectionally. Here, we propose that unidirectional replication, combined with global Smc5/6 functions, can explain the apparent rDNA specificity
Non-equilibrium Kondo effect in asymmetrically coupled quantum dot
The quantum dot asymmetrically coupled to the external leads has been
analysed theoretically by means of the equation of motion (EOM) technique and
the non-crossing approximation (NCA). The system has been described by the
single impurity Anderson model. To calculate the conductance across the device
the non-equilibrium Green's function technique has been used. The obtained
results show the importance of the asymmetry of the coupling for the appearance
of the Kondo peak at nonzero voltages and qualitatively explain recent
experiments.Comment: 7 pages, 6 figures, Physical Review B (accepted for publication
Transport in Coupled Quantum Dots: Kondo Effect Versus Anti-Ferromagnetic Correlation
The interplay between the Kondo effect and the inter-dot magnetic interaction
in a coupled-dot system is studied. An exact result for the transport
properties at zero temperature is obtained by diagonalizing a cluster, composed
by the double-dot and its vicinity, which is connected to leads. It is shown
that the system goes continuously from the Kondo regime to an
anti-ferromagnetic state as the inter-dot interaction is increased. The
conductance, the charge at the dots and the spin-spin correlation are obtained
as a function of the gate potential.Comment: 4 pages, 3 postscript figures. Submitted to PR
- …