Evidence for spinarons in Co adatoms

• Published in: Nature physics 2024-01, Vol.20 (1), p.28-33
• Main Authors: Friedrich, Felix, Odobesko, Artem, Bouaziz, Juba, Lounis, Samir, Bode, Matthias
• Format: Article
• Language: English
• Subjects: 639/766/119/995; 639/925/357/995; Atomic; Bias; Classical and Continuum Physics; Cobalt; Complex Systems; Condensed Matter Physics; Conduction electrons; Electron spin; Electrons; Elementary excitations; Excitation; First principles; Hybrid systems; Kondo effect; Magnetic fields; Mathematical and Computational Physics; Molecular; Nanostructure; Noble metals; Optical and Plasma Physics; Physics; Physics and Astronomy; Scanning tunneling microscopy; Spectrum analysis; Temperature; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-023-02262-6

Cobalt atoms on the (111) surfaces of noble metals are considered to be prototypical systems for the Kondo effect in scanning tunnelling microscopy experiments. Recent first-principles calculations, however, suggest that the experimentally observed spectroscopic zero-bias anomaly can be interpreted in terms of excitations of the spin of the Co atom and the formation of a novel many-body state, namely, the spinaron, rather than from a Kondo resonance. The spinaron is a magnetic polaron that results from the interaction of spin excitations with conduction electrons. However, the experimental confirmation for the existence of spinarons remains elusive. Here we present experimental evidence for spinaronic states in Co atoms on the Cu(111) surface. Our spin-averaged and spin-polarized scanning tunnelling spectroscopy measurements in high magnetic fields allow us to discriminate between the different existing theoretical models and to invalidate the prevailing Kondo-based interpretation of the zero-bias anomaly. Our extended ab initio calculations instead suggest the presence of multiple spinaronic states. Thus, our work provides the foundation to explore the characteristics and consequences of these intriguing hybrid many-body states as well as their design in artificial nanostructures. Despite the theoretical prediction of spinaron quasiparticles in artificial nanostructures, experimental evidence has not yet been seen. Now it has been observed in a hybrid system comprising Co atoms on a Cu(111) surface.