Magnon-Cooparons in magnet-superconductor hybrids

TL;DR

This paper theoretically introduces magnon-cooparons, composite quasiparticles formed by magnons and spinful triplet Cooper pairs, enabling control and generation of spinful pairs in simple magnet-superconductor hybrids.

Contribution

It predicts the existence of magnon-cooparons and demonstrates their potential for controlling spinful triplet Cooper pairs in magnet-superconductor heterostructures.

Findings

Magnons induce a cloud of spinful triplet Cooper pairs in adjacent superconductors.

Magnon-cooparons have a large effective mass measurable experimentally.

Two magnetic wires can act as a controllable magnonic directional coupler via magnon-cooparons.

Abstract

Generation and detection of spinful Cooper pairs in conventional superconductors has been intensely pursued by designing increasingly complex magnet-superconductor hybrids. Here, we demonstrate theoretically that magnons with nonzero wavenumbers universally induce a cloud of spinful triplet Cooper pairs around them in an adjacent conventional superconductor. The resulting composite quasiparticle, termed magnon-cooparon, consists of a spin flip in the magnet screened by a cloud of the spinful superfluid condensate. Thus, it inherits a large effective mass, which can be measured experimentally. Furthermore, we demonstrate that two magnetic wires deposited on a superconductor serve as a controllable magnonic directional coupler mediated by the nonlocal and composite nature of magnon-cooparons. Our analysis predicts a quasiparticle that enables generation, control, and use of spinful triplet Cooper pairs in the simplest magnet-superconductor heterostructures.