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Theme 3 colloquium: 'Investigating superconducting and magnetic surfaces by spin-polarized scanning tunneling' (Lecture)

Tuesday 5 April 2022Add to my calendar
from 16:00
HG00.307 & online
prof. Matthias Bode (Julius-Maximilians-Universität Würzburg, Germany)

In the past 15 years the interaction of magnetic matter with highly spin-orbit–coupled and superconducting substrates has been intensively investigated. For example, “exotic” spin structures, such as skyrmions or 3Q-spin spirals, unimaginable two decades ago, are nowadays routinely prepared and characterized with atomic resolution.
Recently, my research group could show, that another, rarely considered Dzyaloshinskii-Moriya-enhanced RKKY coupling needs to be added to the already existing zoo of magnetic interactions. This DM-RKKY results in a chiral coupling between adjacent one-dimensional transition metal oxide chains via conduction electrons of an Ir- or Pt-substrate. Some data even provide evidence for the existence of antiferromagnetic skyrmions. I will also report on a long outstanding study of the coverage-dependent domain structure of Gd(0001) films grown on W(110). While most data are in good agreement with existing models and bear little surprises, a more detailed look revealed some unexpected spin structures which indicate that the film–vacuum interface also leads to a substantial DM interaction which – under special circumstances– may significantly influence the surface spin structure of this material.

I will also briefly comment on the recent hunt for Majorana states which may, e.g., appear as zero-bias modes in vortices of topological insulators which are proximity-coupled to a superconductor. However, these topologically non-trivial states can easily be confused with other trivial excitations, such as Caroli–de Gennes–Matricon (CdGM) states. To define a base line which may help to separate conventional from topological behavior, we studied vortices in the trivial elemental type-II superconductor Nb. We find a magnetic vortices on the Nb(110) surface exhibit a striking bias dependence which is discussed in terms of the particular electronic structure in the vicinity of the Fermi level.

dr. Nadine Hauptmann