1,047 research outputs found
Kondo Temperature in Multilevel Quantum Dots
We develop a general method to evaluate the Kondo temperature in a multilevel
quantum dot that is weakly coupled to conducting leads. Our theory reveals that
the Kondo temperature is strongly enhanced when the intradot energy-level
spacing is comparable to or smaller than the charging energy. We propose an
experiment to test our result, which consists of measuring the size-dependence
of the Kondo temperature.Comment: 4 pages, 1 figure and supplementary material. Revised and improved
version, to appear in Phys. Rev. Let
Increasing Stability of Crew Schedules in Airlines
In airline traffic disruptions occur frequently and cannot be totally avoided.
They may lead to infeasible aircraft and crew schedules during the day of operations, due to absence of resources or violation of crew rules. The process
of finding new schedules in such cases is called recovery or disruption management. The short-term recovery actions usually imply additional costs meaning that the total operational costs of a crew schedule can be significantly higher than the original planned costs. It is generally desirable to construct the schedule already in the planning phase in such a way that not just the planned costs, but the total operational costs are minimized. The goal is thus to construct schedules which remain feasible or can be recovered without high costs in cases of disturbances. This approach is generally called robust scheduling
Magnetization reversal and nonexponential relaxation via instabilities of internal spin waves in nanomagnets
A magnetic particle with atomic spins ordered in an unstable direction is an
example of a false vacuum that decays via excitation of internal spin waves.
Coupled evolution of the particle's magnetization (or the vacuum state) and
spin waves, considered in the time-dependent vacuum frame, leads to a peculiar
relaxation that is very fast at the beginning but slows down to a
nonexponential long tail at the end. The two main scenarios are linear and
exponential spin-wave instabilities. For the former, the longitudinal and
transverse relaxation rates have been obtained analytically. Numerical
simulations show that the particle's magnetization strongly decreases in the
middle of reversal and then recovers.Comment: 6 EPL pages, 4 figure
Evidence for spin-flip scattering and local moments in dilute fluorinated graphene
The issue of whether local magnetic moments can be formed by introducing
adatoms into graphene is of intense research interest because it opens the
window to fundamental studies of magnetism in graphene, as well as of its
potential spintronics applications. To investigate this question we measure, by
exploiting the well-established weak localization physics, the phase coherence
length L_phi in dilute fluorinated graphene. L_phi reveals an unusual
saturation below ~ 10 K, which cannot be explained by non-magnetic origins. The
corresponding phase breaking rate increases with decreasing carrier density and
increases with increasing fluorine density. These results provide strong
evidence for spin-flip scattering and points to the existence of adatom-induced
local magnetic moment in fluorinated graphene. Our results will stimulate
further investigations of magnetism and spintronics applications in
adatom-engineered graphene.Comment: 9 pages, 4 figures, and supplementary materials; Phys. Rev. Lett. in
pres
Crossover from thermal to quantum creep in layered antiferromagnetic superconductor
The influence of the antiferromagnetic order on the superconductor in the
mixed state results in creation of spin-flop domains along the cores of the
vortex lines. It is shown that this phenomenon makes possible crossover from
quantum creep regime to thermal one, and vice versa, at constant temperature.
To do this one needs to simply change the intensity or the direction of applied
magnetic field in the basal plane of layered structure.Comment: 9 pages, Latex(elsart.cls), 2 figures. to be published in Physica C
vol 340 nr 2/
Quantum Dynamics of a Nanomagnet driven by Spin-Polarized Current
A quantum theory of magnetization dynamics of a nanomagnet as a sequence of
scatterings of each electron spin with the macrospin state of the magnetization
results in each encounter a probability distribution of the magnetization
recoil state associated with each outgoing state of the electron. The quantum
trajectory of the magnetization contains the average motion tending in the
large spin limit to the semi-classical results of spin transfer torque and the
fluctuations giving rise to a quantum magnetization noise and an additional
noise traceable to the current noise.Comment: 4 pages, 4 figure
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