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Protection of excited spin states by a superconducting energy gap

Nature Physics volume 9, pages 765–768 (2013)Cite this article

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Abstract

The latest concepts for quantum computing and data storage rely on the addressing and manipulation of single spins. A limitation for single atoms or molecules in contact with a metal surface is the short lifetime of excited spin states, typically picoseconds, due to the exchange of energy and angular momentum with the itinerant electrons of the substrate1,2,3,4. Here we show that paramagnetic molecules on a superconducting substrate exhibit excited spin states with a lifetime of τ≈10 ns. We ascribe this increase in lifetime by orders of magnitude to the depletion of electronic states around the Fermi level in the superconductor. This prohibits pathways of energy relaxation into the substrate and allows the magnetic molecule to be electrically pumped into higher spin states, making superconducting substrates prime candidates for spin manipulation. We further show that the proximity of the scanning tunnelling microscope tip modifies the magnetic anisotropy.

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Figure 1: Fe–OEP–Cl on Pb(111).
Figure 2: Long lived excited spin states probed by distance-dependent excitation spectra.
Figure 3: Changing the magnetic anisotropy with the STM tip.

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Acknowledgements

We thank P. Brouwer, F. von Oppen, N. Lorente and M. Ternes for fruitful discussions. Financial support by the Deutsche Forschungsgemeinschaft through Sfb 658 and by the focus area Nanoscale of Freie Universität Berlin is gratefully acknowledged.

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Author notes

  1. L. Braun

    Present address: Present address: Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany,

Authors and Affiliations

  1. Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

    B. W. Heinrich, L. Braun, J. I. Pascual & K. J. Franke

  2. CIC nanoGUNE, 20018 Donostia-San Sebastián, Spain

    J. I. Pascual

  3. Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain

    J. I. Pascual

Authors
  1. B. W. Heinrich
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  2. L. Braun
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  4. K. J. Franke
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Contributions

B.W.H., J.I.P. and K.J.F. designed the experiments. B.W.H. and L.B. performed the experiment. All authors discussed the data analysis and the results. B.W.H., J.I.P. and K.J.F. co-wrote the paper.

Corresponding author

Correspondence to B. W. Heinrich.

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The authors declare no competing financial interests.

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Heinrich, B., Braun, L., Pascual, J. et al. Protection of excited spin states by a superconducting energy gap. Nature Phys 9, 765–768 (2013). https://doi.org/10.1038/nphys2794

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