6,452 research outputs found
Experimental Evidence for Crossed Andreev Reflection
We report on electronic transport properties of mesoscopic
superconductor-ferromagnet spin-valve structures. Two ferromagnetic iron leads
form planar tunnel contacts to a superconducting aluminum wire, where the
distance of the two contacts is of the order of the coherence length of the
aluminum. We observe a negative non-local resistance which can be explained by
crossed Andreev reflection, a process where an electron incident from one of
the leads gets reflected as a hole into the other, thereby creating a pair of
spatially separated, entangled particles.Comment: LT24 conference proceeding, 2 pages, 2 figure
A Ballistic Graphene Cooper Pair Splitter
We report an experimental study of Cooper pair splitting in an encapsulated
graphene based multiterminal junction in the ballistic transport regime. Our
device consists of two transverse junctions, namely the
superconductor/graphene/superconductor and the normal metal/graphene/normal
metal junctions. In this case, the electronic transport through one junction
can be tuned by an applied bias along the other. We observe clear signatures of
Cooper pair splitting in the local as well as nonlocal electronic transport
measurements. Our experimental data can be very well described by using a
modified Octavio-Tinkham-Blonder-Klapwijk model and a three-terminal beam
splitter model
Nonlinear thermoelectric effects in high-field superconductor-ferromagnet tunnel junctions
Thermoelectric effects result from the coupling of charge and heat transport,
and can be used for thermometry, cooling and harvesting of thermal energy. The
microscopic origin of thermoelectric effects is a broken electron-hole
symmetry, which is usually quite small in metal structures, and vanishes at low
temperatures. We report on a combined experimental and theoretical
investigation of thermoelectric effects in superconductor/ferromagnet hybrid
structures. We investigate the depencence of thermoelectric currents on the
thermal excitation, as well as on the presence of a dc bias voltage across the
junction. Large thermoelectric effects are observed in
superconductor/ferromagnet and superconductor/normal-metal hybrid structures.
The spin-independent signals observed under finite voltage bias are shown to be
reciprocal to the physics of superconductor/normal-metal microrefrigerators.
The spin-dependent thermoelectric signals in the linear regime are due to the
coupling of spin and heat transport, and can be used to design more efficient
refrigeratorsComment: 11 pages, submitted to Beilstein Journal of Nanotechnolog
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