Possible odd-frequency Amperean magnon-mediated superconductivity in topological insulator–ferromagnetic insulator bilayer

We study the magnon-mediated pairing between fermions on the surface of a topological insulator (TI) coupled to a ferromagnetic insulator with a tilted mean field magnetization. Tilting the magnetization toward the interfacial plane reduces the magnetic band gap and leads to a shift in the effective...

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Bibliographic Details
Published in:Physical review. B 2020-09, Vol.102 (12), p.1, Article 125429
Main Authors: Hugdal, Henning G., Sudbø, Asle
Format: Article
Language:English
Subjects:
Cooper pairs
Dependence
Eigenvectors
Fermions
Ferromagnetism
Magnetization
Magnons
P waves
Superconductivity
Topological insulators
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Summary:We study the magnon-mediated pairing between fermions on the surface of a topological insulator (TI) coupled to a ferromagnetic insulator with a tilted mean field magnetization. Tilting the magnetization toward the interfacial plane reduces the magnetic band gap and leads to a shift in the effective TI dispersions. We derive and solve the self-consistency equation for the superconducting gap in two different situations, where we neglect or include the frequency dependence of the magnon propagator. Neglecting the frequency dependence results in p-wave Amperean solutions. We also find that tilting the magnetization into the interface plane favors Cooper pairs with center-of-mass momenta parallel to the magnetization vector, increasing Tc compared to the out-of-plane case. Including the frequency dependence of the magnon propagator, and solving for a low number of Matsubara frequencies, we find that the eigenvectors of the Amperean solutions at the critical temperature are dominantly odd in frequency and even in momentum, thus opening the possibility for odd-frequency Amperean pairing.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.102.125429