Magnon-induced superconductivity in a topological insulator coupled to ferromagnetic and antiferromagnetic insulators

We study the effective interactions between Dirac fermions on the surface of a three-dimensional topological insulator due to the proximity coupling to the magnetic fluctuations in a ferromagnetic or antiferromagnetic insulator. Our results show that the magnetic fluctuations can mediate attractive...

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Bibliographic Details
Published in:Physical review. B 2018-05, Vol.97 (19), Article 195438
Main Authors: Hugdal, Henning G., Rex, Stefan, Nogueira, Flavio S., Sudbø, Asle
Format: Article
Language:English
Subjects:
Antiferromagnetism
Chemical potential
Coupling
Fermions
Ferromagnetism
Lattices (mathematics)
Magnetic variations
Magnons
Organic chemistry
Subgroups
Superconductivity
Topological insulators
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Summary:We study the effective interactions between Dirac fermions on the surface of a three-dimensional topological insulator due to the proximity coupling to the magnetic fluctuations in a ferromagnetic or antiferromagnetic insulator. Our results show that the magnetic fluctuations can mediate attractive interactions between Dirac fermions of both Amperean and BCS types. In the ferromagnetic case, we find pairing between fermions with parallel momenta, so-called Amperean pairing, whenever the effective Lagrangian for the magnetic fluctuations does not contain a quadratic term. The pairing interaction also increases with increasing Fermi momentum and is in agreement with previous studies in the limit of high chemical potential. If a quadratic term is present, the pairing is instead of BCS type above a certain chemical potential. In the antiferromagnetic case, BCS pairing occurs when the ferromagnetic coupling between magnons on the same sublattice exceeds the antiferromagnetic coupling between magnons on different sublattices. Outside this region in parameter space, we again find that Amperean pairing is realized.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.97.195438