Cooper-pair-mediated coherence between two normal metals

P. Cadden-Zimansky*, J. Wei, V. Chandrasekhar

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


Two electrons bound in a singlet state have long provided a conceptual and pedagogical framework for understanding the non-local nature of entangled quantum objects. As bound singlet electrons separated by a coherence length of up to several hundred nanometres occur naturally in conventional Bardeen-Cooper-Schrieffer superconductors in the form of Cooper pairs, recent theoretical investigations have focused on whether electrons in spatially separated normal-metal probes placed within a coherence length of each other on a superconductor can be quantum mechanically coupled by the singlet pairs. This coupling is predicted to occur through the non-local processes of elastic cotunnelling and crossed Andreev reflection. In crossed Andreev reflection, the constituent electrons of a Cooper pair are sent into different normal probes while retaining their mutual coherence. In elastic cotunnelling, a sub-gap electron approaching the superconductor from one normal probe undergoes coherent, long-range tunnelling to the second probe that is mediated by the Cooper pairs in the condensate. Here, we present experimental evidence for coherent, non-local coupling between electrons in two normal metals linked by a superconductor. The coupling is observed in non-local resistance oscillations that are periodic in an externally applied magnetic flux.

Original languageEnglish (US)
Pages (from-to)393-397
Number of pages5
JournalNature Physics
Issue number6
StatePublished - Jun 2009

ASJC Scopus subject areas

  • General Physics and Astronomy


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