Abstract
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.
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The data supporting the findings of this study are available from the corresponding authors upon request. Source data are provided with this paper.
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Acknowledgements
This research was supported by the DFG through SFB 1170 ‘ToCoTronics’ and the Würzburg-Dresden Cluster of Excellence ct.qmat, EXC2147, via project ID 390858490. M.B., A.O. and F.F. thank P. Sessi (Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany) for bringing this scientific topic to our attention. J.B. acknowledges support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant no. 856538, project ‘3D MAGiC’). S.L. acknowledges S. Brinker and A. Weismann for fruitful discussions.
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F.F., A.O., M.B. and S.L. conceived the experiments. F.F. and A.O. conducted the measurements and analysed the data. J.B. performed the first-principles simulations. S.L. and M.B. supervised the project. All authors discussed the results. F.F. and S.L. wrote the manuscript with input from all authors.
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Supplementary Figs. 1–7 and discussion.
Source data
Source Data Fig. 1
Data points used for the schematic of the field-induced splitting of magnetic resonances and excitations.
Source Data Fig. 2a
STM data of the Cu(111) surface with single adsorbed Co atoms (Fig. 2a).
Source Data Fig. 2
Unprocessed experimental data of magnetic-field-dependent splitting of the ZBA (Fig. 2b–h).
Source Data Fig. 3a
STM data of the Cu(111) surface decorated with Fe islands, Nc molecules and Co atoms.
Source Data Fig. 3
Unprocessed experimental data and fits of spin-resolved measurements on Co/Cu(111).
Source Data Fig. 4
Calculated orbital-resolved LDOS and theoretical inelastic tunnelling spectra.
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Friedrich, F., Odobesko, A., Bouaziz, J. et al. Evidence for spinarons in Co adatoms. Nat. Phys. 20, 28–33 (2024). https://doi.org/10.1038/s41567-023-02262-6
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DOI: https://doi.org/10.1038/s41567-023-02262-6
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