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## "Topological Superconductivity Mediated by Skyrmionic Magnons", Kristian Mæland, Asle Sudbø, 2023

*Reviewed December 16, 2023*

*Citation:* Mæland, Kristian, and Asle Sudbø. "Topological Superconductivity Mediated by Skyrmionic Magnons." Physical Review Letters 130.15 (2023): 156002.

*Web:* https://arxiv.org/abs/2211.05129

*Tags:* Physical, Hardware, Majorana-fermions

In this paper, the authors propose a method for realizing topological superconductivity in a heterostructure
between a normal metal with a magnetic monolayer, mediated by a heavy metal. This has been subsequently clarified
and simplified in the paper

> Boström, Florinda Viñas, and Emil Vinas Boström. "Topological superconductivity in quantum wires mediated by helical magnons." arXiv preprint arXiv:2312.02655 (2023).

where the authors show that the same topological superconductivity can be induced in a quantum wire made out of a normal metal
(or slightly doped semiconductor) going through a helical magnet. They propose InAs for the wire and MnGe for the helical magnet.
The authors claim using numerical simulation that the superconducting gap should be large on the order of 1meV over an extended
region of chemical potentials.

The mechanism for this superconductivity is as follows. The presence of a skrymion below two electrons induces an attractive force between them,
because they both want to be near the skyrmion's core. Hence, Cooper pairs form not by phonon-induced superconductivity
but instead by skrymion-induced superconductivity. Upon writing out the Hamiltonian, one finds that its form
resembles the Kitaev chain Hamiltonian and hence the superconductor is topological. The groundwork for this paper
was laid out in

> Mæland, Kristian, and Asle Sudbø. "Quantum topological phase transitions in skyrmion crystals." Physical Review Research 4.3 (2022): L032025.

and the follow up work

> Sudbø, Asle, and Kristian Mæland. "Topological superconductivity mediated by magnons of a skyrmion crystal." Bulletin of the American Physical Society (2023).

showed that this sort of topological superconductivity can also appear at the interface
between a normal metal and a magnetic insulator.