Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 26: Superconductivity - Heterostructures, Andreev Scattering, Proximity Effect, Coexistence
TT 26.2: Vortrag
Dienstag, 8. März 2005, 10:30–10:45, TU H3027
Experimental evidence for crossed Andreev reflections — •Detlef Beckmann1, Heiko B. Weber1, and Hilbert v. Löhneysen2,3 — 1Forschungszentrum Karlsruhe, Institut für Nanotechnologie — 2Forschungszentrum Karlsruhe, Institut für Festkörperphysik — 3Physikalisches Institut, Universität Karlsruhe
In our recent work [1], we have shown experimentally that electronic subgap transport in a superconducting non-local spin-valve can be described by the superposition of crossed Andreev reflection, i.e. the splitting of a Cooper pair into two different leads, and electron cotunneling, i.e. the transmission of an electron through the superconducting gap. Here, we report on experiments which allow us to discriminate both processes. We have extended our investigation from metallic point contacts to planar tunnel junctions, and replaced the non-local voltage detection (i.e. outside the current path) by a local detection scheme (along the current path). We observe a negative resistance which allows us to give a lower bound to the contribution due to crossed Andreev reflections alone.
[1] D. Beckmann et al., PRL 93 (2004) 197003