1,763 research outputs found
Interplay of spin-discriminated Andreev bound states forming the 0- transition in Superconductor-Ferromagnet-Superconductor Junctions
The Josephson current in S-F-S junctions is described by taking into account
different reflection (transmission) amplitudes for quasiparticles with spin up
and down. We show that the 0- transition in the junctions can take place
at some temperature only for sufficiently strong spin-activity of the
interface. In particular, Andreev interface bound state energies in one spin
channel have to be all negative, while in the other one positive. Only one spin
channel contributes then to the zero-temperature Josephson current. At the
temperature of the 0- transition two spin channels substantially
compensate each other and can result in a pronounced minimum in the critical
current in tunnel junctions. The minimal critical current is quadratic in small
transparency and contains first and second harmonics of one and the same order.Comment: 5 pages, revtex, 2 ps-figure
How Large is the Intrinsic Flux Noise of a Magnetic Flux Quantum, of Half a Flux Quantum and of a Vortex-Free Superconductor?
This article addresses the question whether the magnetic flux of stationary
vortices or of half flux quanta generated by frustrated superconducting rings
is noisy. It is found that the flux noise generated intrinsically by a
superconductor is, in good approximation, not enhanced by stationary vortices.
Half flux quanta generated by -rings are characterized by considerably
larger noise.Comment: 11 pages, 3 figures. in: A. Bussmann-Holder, H. Keller (Eds.) High Tc
Superconductors and Related Transition Metal Oxides, Springer, 237-242; also
to be published in: Journal of Superconductivity (2007
Broadening of Andreev-Bound States in d_{x^2-y^2} superconductors
We investigate the broadening of the bound states at an interface of an
unconventional superconductor by bulk impurity scattering. We use the
quasiclassical theory and include impurity scattering in the Born and in the
unitarity limit. The broadening of bound states due to unitary scatterers is
shown to be substantially weaker than in the Born limit. We study various model
geometries and calculate the temperature dependence of the Josephson critical
current in the presence of these impurity-broadened bound states.Comment: 6 page including 7 figures, submitted to Phys. Rev.
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