Speaker

Lieu

Moyen amphi (LPS) + ONLINE (Zoom)
Moyen amphi (LPS) + ONLINE (Zoom)

Date

19 Mai 2022
Expired!

Heure

11h00 - 12h00

B.BRAUNECKER: Subgap states and their topological classification at ferromagnetic and spiral-ordered magnetic chains in two-dimensional superconductors

	We investigate the topological classification of the subgap bands induced in a two-dimensional superconductor by a densely packed chain of magnetic moments with ferromagnetic or spiral alignments. By contrast with sparsely packed chains a consistent description requires that all wavelengths are taken into account for the scattering at the magnetic moments [1]. The wave functions for these bands are found to be composites of Yu-Shiba-Rusinov-type states and magnetic scattering states and have a significant spatial extension away from the chain.

We show [2] that this spatial structure prohibits a straightforward extraction of a Hamiltonian useful for the topological classification. To address the latter correctly, we construct a family of spatially varying topological Hamiltonians for the subgap bands adapted for the broken translational symmetry caused by the chain. The spatial dependence in particular captures the transition to the topologically trivial bulk phase when moving away from the chain by showing how this, necessarily discontinuous, transition can be understood from an alignment of zeros with poles of Green's functions. Through the latter, the topological Hamiltonians reflect a characteristic otherwise found primarily in strongly interacting systems.

[1] C. J. F. Carroll and B. Braunecker, Phys. Rev. B 104, 245133 (2021).
[2] C. J. F. Carroll and B. Braunecker, Phys. Rev. B 104, 245134 (2021).