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Séminaire « Axe matériaux 2D » de l’INSP

Magnetic nanostructures on superconductors studied by scanning tunneling microscope - Deung-Jang Choi - Mercredi 2 mai 2018 à 11 h

INSP - Sorbonne Université - 4 place Jussieu - 75005 Paris - Barre 22-32, 2e étage, salle 201

Deung-Jang Choi - Donostia International Physics Center (DIPC), San Sebastian

Abstract

Recently, the introduction of new impurity states in the superconducting gap has received a lot of attention. Indeed, the search of a new superconducting state dubbed topological superconductivity is strongly based in the combination of doping classical (s-wave) superconductors with magnetic impurities that arrange in a chiral fashion. Depending on the nature of the atomic species added to a superconductor, different effects can be achieved. Magnetic adatoms can be considered as impurities that weaken the binding of superconducting Cooper pairs leading to dirty superconductivity and to impurity levels in the gap : so-called Yu-Shiba-Rusinov (YSR) states. These YRS states are the results of weakening Cooper pairs by the localized magnetic moment of the impurity. By using scanning tunneling spectroscopy, resolving their origin and exploring basic properties of BCS superconductors, we found that the shape of YSR states reflects the shape of d atomic orbitals [1]. And aslo in this work, we present the first results of controlled single-atom manipulation to assemble a chain of Cr atoms on a Bi2Pd superconductor. The influence of the atoms on the superconducting electronic structure is revealed as well as the interactions at work. The interatomic distance between two Cr atoms is thoroughly explored revealing Cr-Cr interactions mediated by the superconductor [2]. Furthermore, we have extended our studies to spin chains of Cr on Bi2Pd, finding interesting solutions of YSR extended states, precursors of YSR bands.

References

[1] Choi, D.-J. et al. Mapping the orbital structure of impurity bound states in a superconductor. Nat. Commun. 8, 15175 (2017).
[2] Choi, D.-J. et al. Phys. Rev. Lett. 120, 167001 (2018)