184 research outputs found
Transport Properties in Ferromagnetic Josephson Junction between Triplet Superconductors
Charge and spin Josephson currents in a ballistic
superconductor-ferromagnet-superconductor junction with spin-triplet pairing
symmetry are studied using the quasiclassical Eilenberger equation. The gap
vector of superconductors has an arbitrary relative angle with respect to
magnetization of the ferromagnetic layer. We clarify the effects of the
thickness of ferromagnetic layer and magnitude of the magnetization on the
Josephson charge and spin currents. We find that 0-\pi transition can occur
except for the case that the exchange field and d-vector are in nearly
perpendicular configuration. We also show how spin current flows due to
misorientation between the exchange field and d-vector.Comment: 6 pages, 8 figure
Nonequilibrium effects in tunnel Josephson junctions
We study nonequilibrium effects in current transport through voltage biased
tunnel junction with long diffusive superconducting leads at low applied
voltage, , and finite temperatures. Due to a small value of the
Josephson frequency, the quasiparticle spectrum adiabatically follows the time
evolution of the superconducting phase difference, which results in the
formation of oscillating bound states in the vicinity of the tunnel junction
(Andreev band). The quasiparticles trapped by the Andreev band generate higher
even harmonics of the Josephson ac current, and also, in the presence of
inelastic scattering, a non-equilibrium dc current, which may considerably
exceed the dc quasiparticle current given by the tunnel model. The distribution
of travelling quasiparticles also deviates from the equilibrium due to the
spectrum oscillations, which results in an additional contribution to the dc
current, proportional to .Comment: 11 pages, 7 figures, to be published in Phys. Rev.
Coherent Backscattering of Light in Atomic Systems: Application to Weak Localization in an Ensemble of Cold Alkali-Metal Atoms
Development of a theoretical treatment of multiple coherent light scattering in an ultracold atomic gas is reported. Specific application is made to coherent backscattering of a weak-radiation field from realistically modeled samples of ultracold atomic 85Rb. Comprehensive Monte Carlo simulations of the spatial, spectral, and polarization dependence of the backscattering line shape are made and compared with available experimental results
Spectral Dependence of Coherent Backscattering of Light in a Narrow-Resonance Atomic System
We report a combined theoretical and experimental study of the spectral and
polarization dependence of near resonant radiation coherently backscattered
from an ultracold gas of 85Rb atoms. Measurements in an approximately 6 MHz
range about the 5s^{2}S_{1/2}- 5p^{2}P_{3/2}, F=3 - F'=4 hyperfine transition
are compared with simulations based on a realistic model of the experimental
atomic density distribution. In the simulations, the influence of heating of
the atoms in the vapor, magnetization of the vapor, finite spectral bandwidth,
and other nonresonant hyperfine transitions are considered. Good agreement is
found between the simulations and measurements.Comment: 10 pages, 12 figur
Photo induced ionization dynamics of the nitrogen vacancy defect in diamond investigated by single shot charge state detection
The nitrogen-vacancy centre (NV) has drawn much attention for over a decade,
yet detailed knowledge of the photophysics needs to be established. Under
typical conditions, the NV can have two stable charge states, negative (NV-) or
neutral (NV0), with photo induced interconversion of these two states. Here, we
present detailed studies of the ionization dynamics of single NV centres in
bulk diamond at room temperature during illumination in dependence of the
excitation wavelength and power. We apply a recent method which allows us to
directly measure the charge state of a single NV centre, and observe its
temporal evolution. Results of this work are the steady state NV- population,
which was found to be always < 75% for 450 to 610 nm excitation wavelength, the
relative absorption cross-section of NV- for 540 to 610 nm, and the energy of
the NV- ground state of 2.6 eV below the conduction band. These results will
help to further understand the photo-physics of the NV centre.Comment: 9 pages, 7 figure
Measurement of Correlated Multiple Light Scattering in Utracold Atomic \u3csup\u3e85\u3c/sup\u3eRb
We report an experimental study of correlated multiple light scattering in an ultracold gas of 85Rb confined in a magneto-optic trap. Measurements are made of the polarization dependence of the spatial and spectral profile of light backscattered from the sample. The results show an interferometric enhancement sensitive to coherent multiple scattering in the atomic gas, and strong variations with the polarization of the incident and detected light. The spatial width and peak value of the enhancement are found to be dependent on the sample size. Comparison of all the measurements with realistic quantum Monte Carlo simulations yields a very good agreeme
On the action principle for a system of differential equations
We consider the problem of constructing an action functional for physical
systems whose classical equations of motion cannot be directly identified with
Euler-Lagrange equations for an action principle. Two ways of action principle
construction are presented. From simple consideration, we derive necessary and
sufficient conditions for the existence of a multiplier matrix which can endow
a prescribed set of second-order differential equations with the structure of
Euler-Lagrange equations. An explicit form of the action is constructed in case
if such a multiplier exists. If a given set of differential equations cannot be
derived from an action principle, one can reformulate such a set in an
equivalent first-order form which can always be treated as the Euler-Lagrange
equations of a certain action. We construct such an action explicitly. There
exists an ambiguity (not reduced to a total time derivative) in associating a
Lagrange function with a given set of equations. We present a complete
description of this ambiguity. The general procedure is illustrated by several
examples.Comment: 10 page
Odd spin-triplet superconductivity in a multilayered superconductor-ferromagnet Josephson junction
We study the dc Josephson effect in a diffusive multilayered SF'FF'S
structure, where S is a superconductor and F,F' are different ferromagnets. We
assume that the exchange energies in the F' and F layers are different (
and , respectively) and the middle F layer consists of two layers with
parallel or antiparallel magnetization vectors . The vectors in the left
and right F' layers are generally not collinear to those in the F layer. In the
limit of a weak proximity effect we use a linearized Usadel equation. Solving
this equation, we calculate the Josephson critical current for arbitrary
temperatures, arbitrary thicknesses of the F' and F layers ( and
) in the case of parallel and antiparallel orientations in the F
layer. The part of the critical current formed by the short-range
(SRC) singlet and S=0 triplet condensate components decays on a short length
, whereas the part due to the long-range
triplet component (LRTC) decreases with increasing on the
length . Our results are in agreement with the
experiment \cite{Birge}.Comment: 13 pages, 6 figures; some references updated and adde
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