ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT ttk.bme.hu>]

Meghívó

BME Elméleti Fizika Szeminárium,

ápr. 12. péntek 10h15,

1111 Budapest, Budafoki út 8., BME F III. magasföldszint 01.,
Elméleti Fizika Tanszék szemináriumi szoba

Lászlóffy András  (Wigner FK)
Topological band formation in magnetic chains on superconductors

In magnetic chains on superconductors, so-called Shiba bands are formed
within the superconducting gap of the host. Inside the Shiba bands, a
minigap can be induced around zero energy by forming a magnetic spin spiral
state or by a large spin-orbit coupling in the system. In the spirit of the
bulk-edge correspondence principle, if the band structure is topological,
zero energy bound states (Majorana states) can be found at both ends of
finite chains. To have a quantitative and realistic description of these
systems, we solve the Kohn—Sham—Dirac Bogoliubov-de Gennes equations within
the Korringa—Kohn—Rostoker multiple scattering theory [1,2]. With examples,
we show that physical quantities that are antisymmetric with respect to the
Fermi energy, e.g., the singlet order parameter, can be used to prove band
inversion of the system. Moreover, through the manipulation of the
magnitude of the magnetic moments, we explore the conditions for the
formation of topological phases in the chains and compare this to the
change of Shiba state energies in single adatoms. Finally, by adding a
non-magnetic overlayer between the superconductor and the chain, we explore
the topological properties of a large variety of systems in terms of
changing the crystallographic direction of the chain and the magnetic
configuration.

[1] B. Nyári, A. Lászlóffy, G. Csire, L. Szunyogh, B. Ujfalussy,
Topological superconductivity from first principles. I. Shiba band
structure and topological edge states of artificial spin chains, Physical
Review B 108, 134512 (2023)
[2] A. Lászlóffy, B. Nyári, G. Csire, L. Szunyogh, B. Ujfalussy,
Topological superconductivity from first principles. II. Effects from
manipulation of spin spirals: Topological fragmentation, braiding, and
quasi-Majorana bound states, Physical Review B 108, 134513 (2023)


Minden érdeklődőt szeretettel várunk.
Asbóth János,
 szemináriumi koordinátor