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Andreev reflection and subgap transport due to electron-magnon interactions in ferromagnet-superconductor junctions.

Research output: Contribution to journalJournal article

Published

Journal publication date10/11/2003
JournalInternational Journal of Modern Physics B
Journal number28
Volume17
Number of pages5
Pages5001-5005
Original languageEnglish

Abstract

We show that electron-magnon interactions at a ferromagnetic metal-superconductor interface lead to a new process of magnon-assisted Andreev reflection, which consists of the simultaneous injection of a Cooper pair from the superconductor and the emission of a magnon inside the ferromagnet. At low temperature this process represents an additional channel for subgap transport across an FS interface, which lifts restrictions on the current I resulting from the necessity to match spin-polarised current in the ferromagnet with spin-less current in the superconductor. We calculate I using the tunnelling Hamiltonian method and the nonequilibrium (Keldysh) Green functions technique. It is shown that the inelastic magnon-assisted Andreev process would manifest itself as a nonlinear addition to the I(V) characteristics which is asymmetric with respect to the sign of the bias voltage and is related to the local density of states of magnons at the interface.