Springe direkt zu Inhalt

Disputation Eva Rudisch

23.09.2021 | 10:00
Thema der Dissertation:
From single atoms to magnetic chains: Fe atoms on 2H-NbSe2
Abstract: This thesis investigates artificially constructed magnetic structures of magnetic Fe atoms on the quasi 2D superconductor NbSe2 by means of combined scanning tunneling microscopy and spectroscopy. The magnetic moments of the Fe atoms locally interact with the Cooper pair condensate and induce in-gap quasiparticle states - the so-called Yu-Shiba-Rusinov (YSR) states.
The peculiar properties of NbSe2 manifest in versatile features of the YSR states which we explore in detail. Capable of atomic manipulation we assemble customized structures - atomic dimers and extended chains - and investigate the hybridization within these structures.
We start by characterizing the pure substrate which exhibits an incommensurate
charge-density wave (CDW) that coexists with superconductivity at low temperatures.
Both correlated phases are driven by electron-phonon coupling yielding a highly anisotropic superconducting order parameter which appears as a peculiar quasiparticle peak distribution in differential conductance spectra around the superconducting gap.
Fe atoms adsorbed on the surface exhibit multiple YSR resonances with extended
wave functions due to the quasi-2D nature of the substrate. The CDW wave induces local variations of the density of states which affect the energy and symmetry of the YSR states which we systematically investigate.
We further study the influence of the CDW on the hybridization between the long-ranged YSR states within the versatile energetic landscape arising from the incommensurate CDW. We assemble various dimers and show that equal positions relative to the CDW are a prerequisite for substantial hybridization. Further, we detect signatures of the quantum spin nature in the coupling of atomic dimers. We go beyond dimers and stepwise assemble a dilute chain where the coupling between adjacent atoms is entirely mediated via the substrate. We track the formation of YSR bands which are identified by tunneling into their van Hove singularities. In longer chains, the incommensurate CDW induces band bending of the YSR bands.
As a last step we investigate chains consisting of densely packed Fe atoms in which direct exchange between d orbitals drives the formation of Fe2 molecules on the surface.

Zeit & Ort

23.09.2021 | 10:00

Hörsaal A - 1.3.14 *
(* Begrenzte Teilnehmerzahl unter Kontrolle der 3G Regeln – geimpft, genesen, getestet)
!!!Teilnehmer werden um 09:30 Uhr am Glastüreneingang zu Trakt 3 (Arnimallee 14, 14195 Berlin) abgeholt!!!