Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 7: Electronic Structure of Surfaces: Magnetism and Spin Phenomena

O 7.6: Talk

Monday, March 20, 2017, 11:45–12:00, WIL C107

Proximity coupled Co chains on Pb(110) — Michael Ruby, Benjamin W. Heinrich, Yang Peng, Felix von Oppen, and •Katharina J. Franke — Fachbereich Physik, Freie Universität Berlin

Proximity-coupled ferromagnetic chains on a superconductor with strong spin-orbit coupling have been predicted as a nearly universal system for topological superconductivity and for hosting Majorana zero modes [1]. Experiments on Fe chains on Pb(110) indeed exhibit signatures of Majorana end states [2]. Here, we test the universality prediction by growing Co chains on a Pb(110) surface. Using Co-coated STM tips, we detect spin-polarized d-bands reflecting ferromagnetic coupling along the chain. The Yu-Shiba-Rusinov bands inside the superconducting energy gap also exhibit spin contrast. However, the rich subgap structure does not provide evidence of Majorana end states. In a simple model of tight-binding calculations, we ascribe the absence of Majorana end states to an even number of d-band crossings of the Fermi level. This is the crucial difference to the case of Fe chains.

[1] J. Li, et al., Phys. Rev. B 90, 235433 (2014).

[2] S. Nadj-Perge, et al., Science 346, 602 (2014).