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Stabilizing the magnetic moment of single holmium atoms by symmetry

Abstract

Single magnetic atoms, and assemblies of such atoms, on non-magnetic surfaces have recently attracted attention owing to their potential use in high-density magnetic data storage and as a platform for quantum computing1,2,3,4,5,6,7,8. A fundamental problem resulting from their quantum mechanical nature is that the localized magnetic moments of these atoms are easily destabilized by interactions with electrons, nuclear spins and lattice vibrations of the substrate3,4,5. Even when large magnetic fields are applied to stabilize the magnetic moment, the observed lifetimes remain rather short5,6 (less than a microsecond). Several routes for stabilizing the magnetic moment against fluctuations have been suggested, such as using thin insulating layers between the magnetic atom and the substrate to suppress the interactions with the substrate’s conduction electrons2,3,5, or coupling several magnetic moments together to reduce their quantum mechanical fluctuations7,8. Here we show that the magnetic moments of single holmium atoms on a highly conductive metallic substrate can reach lifetimes of the order of minutes. The necessary decoupling from the thermal bath of electrons, nuclear spins and lattice vibrations is achieved by a remarkable combination of several symmetries intrinsic to the system: time reversal symmetry, the internal symmetries of the total angular momentum and the point symmetry of the local environment of the magnetic atom.

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Figure 1: Magnetic sublevels of atoms with a total angular momentum J.
Figure 2: Magnetic behaviour of Ho atoms (J = 8) adsorbed on Pt(111).
Figure 3: Lifetimes of adsorbed Ho atoms as function of external parameters.

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Acknowledgements

We acknowledge funding by the German Science Foundation (DFG) grant number Wu 349/4-2, the DFG priority programme SPP 1538 Spin Caloric Transport and the DFG Collaborative Research Centre SFB 762 Functionality of Oxide Interfaces. The calculations were performed at the Rechenzentrum Garching of the Max Planck Society.

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Contributions

W.W. conceived the experiments, and T. Miyamachi, T.S., T. Märkl, A.S. and C.B. carried them out. The data were analysed by T. Miyamachi, T.S., T. Märkl, C.B., T.B. and W.W. Group theory of the crystal field was performed by T.S., T.B., C.B. and W.W. Master equations were analysed by C.K., S.A., M.M. and G.S. Ab initio calculations were performed by M.H., M.G., S.O., W.H., I.M. and A.E. The manuscript was written by T.B. and W.W. Figures were prepared by T. Miyamachi. All authors discussed the results and commented on the manuscript.

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Correspondence to Wulf Wulfhekel.

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The authors declare no competing financial interests.

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This file contains Supplementary Text and Data, Supplementary Figures 1-3, Supplementary Tables 1-2 and Supplementary References. (PDF 1146 kb)

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Miyamachi, T., Schuh, T., Märkl, T. et al. Stabilizing the magnetic moment of single holmium atoms by symmetry. Nature 503, 242–246 (2013). https://doi.org/10.1038/nature12759

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