Observation of superconducting gap spectra of long-range proximity effect in Au/SrTiO3/SrRuO3/Sr2RuO4 tunnel junctions

M. S. Anwar, M. Kunieda, R. Ishiguro, S. R. Lee, L. A. B. Olde Olthof, J. W. A. Robinson, S. Yonezawa, T. W. Noh, and Y. Maeno
Phys. Rev. B 100, 024516 – Published 24 July 2019
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Abstract

We observe an unconventional superconducting minigap induced into a ferromagnet SrRuO3 from a spin-triplet superconductor Sr2RuO4 using an Au/SrTiO3/SrRuO3/Sr2RuO4 tunnel junction. Voltage bias differential conductance of the tunnel junctions exhibits V-shaped gap features around zero bias, corresponding to a decrease in the density of states with an opening of a superconducting minigap in SrRuO3. Observation of a minigap at the surface of a 15-nm-thick SrRuO3 layer confirms the spin-triplet nature of induced superconductivity. The shape and temperature dependence of the gap features in the differential conductance suggest that the even-frequency p-wave correlations dominate over odd-frequency s-wave correlations. Theoretical calculations support this p-wave scenario. Our work provides the density-of-states proof for an induced minigap in a ferromagnet, and it significantly advanced our understanding of the spin-triplet proximity effect between unconventional superconductors and ferromagnets.

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  • Received 3 March 2019
  • Revised 18 June 2019

DOI:https://doi.org/10.1103/PhysRevB.100.024516

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

M. S. Anwar1,2,*, M. Kunieda1, R. Ishiguro3,4, S. R. Lee5,6, L. A. B. Olde Olthof2, J. W. A. Robinson2, S. Yonezawa1, T. W. Noh5,6, and Y. Maeno1

  • 1Department of Physics, Kyoto University, Kyoto 606-8502, Japan
  • 2Department of Materials Science and Metallurgy, University of Cambridge, CB3 0FS Cambridge, United Kingdom
  • 3Department of Mathematical and Physical Sciences, Faculty of Science, Japan Women's University, Tokyo 112-8681, Japan
  • 4Department of Applied Physics, Faculty of Science, Tokyo University of Science, Tokyo 162-8601, Japan
  • 5Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Republic of Korea
  • 6Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Republic of Korea

  • *msa60@cam.ac.uk

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Issue

Vol. 100, Iss. 2 — 1 July 2019

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