Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 90: Spins on Surfaces at the Atomic Scale II

O 90.9: Talk

Thursday, March 20, 2025, 17:00–17:15, H11

Spin Excitations of High-Spin Fe(II) in Metal-Organic Chains on Metal and Superconductor — •Jung-Ching Liu^1,2, Chao Li², Outhmane Chahib², Xing Wang³, Simon Rothenbühler⁴, Robert Häner⁴, Silvio Decurtins⁴, Ulrich Aschauer⁵, Shi-Xia Liu⁴, Ernst Meyer², and Rémy Pawlak² — ¹Department of Physics, Technical University of Munich, James-Franck-Str.1, 85748 Garching, Germany — ²Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland — ³Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland — ⁴Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland — ⁵Department of Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer-Strasse 2A, 5020 Salzburg, Austria

Magnetic anisotropy induced by the substrate plays an important role in many-body interactions in metal-organic frameworks at surfaces. Investigated by STM at 1K, we present the study of magnetic signature at Fe atoms with high spin-state (S=2) using PTO as ligands. On Ag(111), we found long-range Fe-Fe coupling in addition to low-energy spin-flip excitations. Despite of the identical chain structure, such long-range superexchange through PTO is not observed on tunneling spectra on Pb(111) superconductor. We ascribe this distinct spin-spin coupling behavior to the depletion of electronic states around the Fermi level on Pb(111) as compare to Ag(111). We believe our study provides a route for fundamental studies in spin-spin and spin-substrate interactions with different lattice structures.

Keywords: metal-organic framework; scanning tunneling microscopy; superconductivity; long-range spin-spin coupling; spin-flip excitation