Séminaire virtuel : Katharina FRANKE (FU Berlin)

Quantum spins and hybridization in artificially-constructed chains of magnetic adatoms on superconducting 2H-NbSe 2
Mardi 8 Fevrier 2022, 11h

Prochain séminaire virtuel du GDR HOWDI : Mardi 8 Février 2022 à 11h.
Katharina FRANKE (Freie Universitaet, Berlin)
"Quantum spins and hybridization in artificially-constructed chains of magnetic adatoms on superconducting 2H-NbSe_2”

Résumé :

Magnetic adatom chains on superconducting substrates are promising platforms for topological superconductivity and Majorana zero modes. Signatures of these have been found in densely packed chains with direct exchange interaction among the adatoms. In contrast, the dilute limit of chains, where the atoms are sufficiently far spaced that direct hybridization of their d orbitals is negligible, but close enough for substrate-mediated interactions, has not been investigated previously. Engineering dilute adatom chains with substantial substrate-mediated interactions requires samples sustaining long-range Yu-Shiba-Rusinov (YSR) states. While these decay
quickly with 1/ 𝑘 𝑟 (with 𝑘 being the Fermi wave vector and 𝑟 the distance to the impurity) on three-dimensional superconductors, the decay of YSR states on two-dimensional superconductors is much slower, scaling with 1/√ 𝑘 𝑟 [1].
Here, we explore the well known quasi-two-dimensional superconductor 2H-NbSe 2 as a substrate for magnetic adatom structures. Individual Fe atoms induce Yu-Shiba-Rusinov states, which spatially extend over several nanometers with their energy and symmetry influenced by the crystal field and by the co-existing charge-density wave (CDW) [2]. When two Fe atoms are placed on equivalent adsorption sites at a distance of 1 nm, the YSR states are shifted in energy and split. While the splitting indicates hybridization of the YSR states, the strong shift can only be explained by RKKY coupling of quantum spins [3]. We deliberately increase the chain length by adding individual Fe atoms with the STM tip, up to a length of 51 atoms. In each step we track the evolution of the YSR states. We find signatures of YSR band formation consistent with ferromagnetic coupling of quantum spins [4].

[1] G. C. Ménard, et al., Nat. Phys. 11, 1013 (2015).
[2] E. Liebhaber et al., Nano Lett. 20, 339 (2020).
[3] E. Liebhaber, et al., arxiv2107.06361 (2021).
[4] J. F. Steiner, et al., arxiv2107.00031 (2021).

Informations de connection :

Sujet : GDR HOWDI SEMINAR - Katharina FRANKE - Quantum spins and hybridization in artificially-constructed chains of magnetic adatoms on superconducting 2H-NbSe2

8 févr. 2022 11:00 AM Paris

https://zoom.us/j/95506784928?pwd=aXV3MUdCUWJtdkZtRFJrS1IzaDFNZz09

meeting ID : 955 0678 4928

Code secret : uJ8QWP