47,402 research outputs found
Long-range triplet proximity effect in multiply connected ferromagnet-superconductor hybrids
Applying the linearized Usadel equations, we consider the nucleation of
superconductivity in multiply connected mesoscopic superconductor/ferromagnet
(S/F) hybrids such as a thin superconducting ring on a ferromagnet with a
uniform in-plane magnetization M and a spin-active S/F interface. We
demonstrate that the exchange field in F provokes a switching between
superconducting states with different vorticities which may increase the
critical temperature ( Tc ) of the superconductor in a magnetic field. We study
the interplay between oscillations in Tc due to the Little--Parks effect and
oscillations in Tc induced by the exchange field. Furthermore, we analyse the
influence of long-range spin-triplet correlations on the switching between
different vorticities.Comment: 11 pages, 7 figure
Oblique-incidence secondary emission from charged dielectrics
Secondary electron emission coefficients were measured on FEP-Teflon for normal and oblique incidence in the presence of a normal electric field. Such measurements require knowledge of the electrostatic environment surrounding the specimen, and they require calculation of particle trajectories such that particle impact parameters can be known. A simulation using a conformal mapping, a Green's integral, and a trajectory generator provides the necessary mathematical support for the measurements, which were made with normal fields of 1.5 and 2.7 kV/mm. When incidence is normal and energy exceeds the critical energy, the coefficient is given by (V sub 0/V) to the .58 power, and for oblique incidence this expression may be divided by the cosine of the angle. The parameter V sub 0 is a function of normal field
Decay of fidelity in terms of correlation functions
We consider, within the algebraic formalism, the time dependence of fidelity
for qubits encoded into an open physical system. We relate the decay of
fidelity to the evolution of correlation functions and, in the particular case
of a Markovian dynamics, to the spectral gap of the generator of the semigroup.
The results are applicable to the analysis of models of quantum memories.Comment: 9 pages, no figure
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