Andreev bound states in superconductor/ferromagnet point contact Andreev reflection spectra

K. A. Yates, L. A. B. Olde Olthof, M. E. Vickers, D. Prabhakaran, M. Egilmez, J. W. A. Robinson, and L. F. Cohen
Phys. Rev. B 95, 094516 – Published 22 March 2017
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Abstract

As charge carriers traverse a single superconductor ferromagnet interface, they experience an additional spin-dependent phase angle that results in spin mixing and the formation of a bound state called the Andreev bound state. Here we explore whether point contact Andreev reflection can be used to detect the Andreev bound state and, within the limits of our experiment, we extract the resulting spin mixing angle. By examining spectra taken from La1.15Sr1.85Mn2O7Pb junctions, together with a compilation of literature data on highly spin polarized systems, we suggest that the existence of the Andreev bound state would resolve a number of long standing controversies in the literature of Andreev reflection, as well as defining a route to quantify the strength of spin mixing at superconductor-ferromagnet interfaces. Intriguingly, we find that for high transparency junctions, the spin mixing angle appears to take a relatively narrow range of values across all the samples studied. The ferromagnets we have chosen to study share a common property in terms of their spin arrangement, and our observations may point to the importance of this property in determining the spin mixing angle under these circumstances.

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  • Received 2 June 2016
  • Revised 9 December 2016

DOI:https://doi.org/10.1103/PhysRevB.95.094516

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

K. A. Yates1, L. A. B. Olde Olthof2,3, M. E. Vickers2, D. Prabhakaran4, M. Egilmez5, J. W. A. Robinson2, and L. F. Cohen1

  • 1Physics Department, The Blackett Laboratory, Imperial College London, SW7 2AZ, United Kingdom
  • 2Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
  • 3Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
  • 4Department of Physics, Clarendon Laboratory, University of Oxford, Park Road, Oxford OX1 3PU, United Kingdom
  • 5Department of Physics, American University of Sharjah, Sharjah 26666, United Arab Emirates

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Issue

Vol. 95, Iss. 9 — 1 March 2017

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